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[email protected] rdekleer@aol.com is offline
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Default AR3a/AS103a speakers and the Heathkit AR1500 receiver

A previous poster stated that the Heathkit AR1500 and AR3a are a poor
combination. This is true if you listen at any level other than quiet.

A couple of years after introduction, the AR1500's output amplifiers
were updated and the AR1500A was born. The AR1500A has specific
circuits that limit clipping and other distortion when it is driving
low imperance speakers at high levels. It is possible to modify the
AR1500's output amplifiers to include this improvement; you'd have to
go to a Heathkit users groups to obtain that information.

Driving AR3a's hard with an unmodified AR1500 produces a lot of
"clipped sine waves" that will blow the mid-range driver. If you don't
want to burnout the mid-range, but want to turn the volume up, add a 1
ohm resistor in series with each mid-range. This will change the
mid-range balance, but that's better than burning out the driver.

The AR3a was sold in kit form as the Heathkit AS103a.

Let me know if you have any questions.


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Jerry Jerry is offline
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Default AR3a/AS103a speakers and the Heathkit AR1500 receiver

wrote in message ...
A previous poster stated that the Heathkit AR1500 and AR3a are a poor
combination. This is true if you listen at any level other than quiet.


Rolf, I have an AR-3a and an AR1500 and they seem to work together fairly
well. I don't know about "quiet" as that is a relative term.

My den is quite small and my normal listening level is less than 1 watt, but
occasionally I'll listen at levels higher.

A couple of years after introduction, the AR1500's output amplifiers
were updated and the AR1500A was born. The AR1500A has specific
circuits that limit clipping and other distortion when it is driving
low imperance speakers at high levels. It is possible to modify the
AR1500's output amplifiers to include this improvement; you'd have to
go to a Heathkit users groups to obtain that information.


Rolf, any chance you have the schematic for the power amp on the "a"
version. If I could see the "a", I could document the differences.

I would think you'd really have to to be driving the speakers hard to get
anywhere near clipping. My guess is the heavy current drain forces the rail
voltages way down, and this allows even modest signals to clip. Only real
solution is to "beef up" the power supply.

Driving AR3a's hard with an unmodified AR1500 produces a lot of
"clipped sine waves" that will blow the mid-range driver. If you don't
want to burnout the mid-range, but want to turn the volume up, add a 1
ohm resistor in series with each mid-range. This will change the
mid-range balance, but that's better than burning out the driver.


Well, Rolf, I've done just the opposite. I've taken all the pots out of the
AR-3a circuit and this significantly INCREASES the sensitivity of the
mid-range and tweeter. (Frankly, I'm a little surprised that the mid is
most susceptible to clipping damage. People on the AR forum worry far more
about the tweeters.)

In any event, "clipping" is no longer an issue for me. I'm now bi-amping my
AR-3a's. My AR1500 drives only the woofers. I have a nice little 30 watt
Kenwood powering the mid-range and tweeter. The Kenwood has rail voltages
of 40 volts!

With the pots out AND the fundamentals greatly reduced, it's hard to get
peak voltages of 3 volts going to the mid-range and tweeter. I mean, at 3
volts I can barely stand the volume.

Now, there is no question that at the same time that I have 3 volt peaks in
the Kenwood, the peak voltages in the AR1500 are much, much higher. I can't
see any clipping, but even if there were some, the mid and tweeter are
totally isolated from that amp.

The AR3a was sold in kit form as the Heathkit AS103a.

Let me know if you have any questions.


Rolf, if you have an AR1500 and a set of AR-3a's, I'd strongly recommend you
try a bi-amping experiment. Not only will you protect your mids and
tweeters, but there is a significant tightening of the bass that results.

Regards,
Jerry
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Default AR3a/AS103a speakers and the Heathkit AR1500 receiver

Jerry wrote:
wrote in message ...
A previous poster stated that the Heathkit AR1500 and AR3a are a poor
combination. This is true if you listen at any level other than quiet.


Rolf, I have an AR-3a and an AR1500 and they seem to work together fairly
well. I don't know about "quiet" as that is a relative term.

My den is quite small and my normal listening level is less than 1 watt, but
occasionally I'll listen at levels higher.

A couple of years after introduction, the AR1500's output amplifiers
were updated and the AR1500A was born. The AR1500A has specific
circuits that limit clipping and other distortion when it is driving
low imperance speakers at high levels. It is possible to modify the
AR1500's output amplifiers to include this improvement; you'd have to
go to a Heathkit users groups to obtain that information.


Rolf, any chance you have the schematic for the power amp on the "a"
version. If I could see the "a", I could document the differences.

I would think you'd really have to to be driving the speakers hard to get
anywhere near clipping. My guess is the heavy current drain forces the rail
voltages way down, and this allows even modest signals to clip. Only real
solution is to "beef up" the power supply.

Driving AR3a's hard with an unmodified AR1500 produces a lot of
"clipped sine waves" that will blow the mid-range driver. If you don't
want to burnout the mid-range, but want to turn the volume up, add a 1
ohm resistor in series with each mid-range. This will change the
mid-range balance, but that's better than burning out the driver.


Well, Rolf, I've done just the opposite. I've taken all the pots out of the
AR-3a circuit and this significantly INCREASES the sensitivity of the
mid-range and tweeter. (Frankly, I'm a little surprised that the mid is
most susceptible to clipping damage. People on the AR forum worry far more
about the tweeters.)

In any event, "clipping" is no longer an issue for me. I'm now bi-amping my
AR-3a's. My AR1500 drives only the woofers. I have a nice little 30 watt
Kenwood powering the mid-range and tweeter. The Kenwood has rail voltages
of 40 volts!

With the pots out AND the fundamentals greatly reduced, it's hard to get
peak voltages of 3 volts going to the mid-range and tweeter. I mean, at 3
volts I can barely stand the volume.

Now, there is no question that at the same time that I have 3 volt peaks in
the Kenwood, the peak voltages in the AR1500 are much, much higher. I can't
see any clipping, but even if there were some, the mid and tweeter are
totally isolated from that amp.

The AR3a was sold in kit form as the Heathkit AS103a.

Let me know if you have any questions.


Rolf, if you have an AR1500 and a set of AR-3a's, I'd strongly recommend you
try a bi-amping experiment. Not only will you protect your mids and
tweeters, but there is a significant tightening of the bass that results.

Regards,
Jerry


October 5, 2005 update from Rolf:

Both versions of the AR1500's output amplifier have a current limiting
circuit to protect the amplifier's power transistors (Motorola MJ802's)
from burning out. For the original AR1500, the circuit limited the
current too soon when driving low impedance speaker like the AR3a. The
AR1500A added a modification (resistors and capacitors only) that
limited the response time of the current limiters. In effect, the new
current limit circuit let short high-current transients through (which
don't heat up the MJ802's enough to cause trouble) and only limited the
current for non-transients.

With the original AR1500 power amplifier, the too fast-acting current
limiting circuit introduced "harmonics" not in the original signal; at
high sound levels these harmonics have enough energy to burn-out the
mid-range drivers.

I have both versions of the AR1500, a pair of AR3a's (the kit version
Heathkit sold as AS103) and a pair of AS101's (the kit version of the
Altec Lansing Valencia). (The AR1500 and AR3a's were my dad's.) I
modified the power amplifier of the original AR1500 many years ago, and
unforunately no longer have the instructions.

The only problem I've had with the AR1500A was the need to replace the
front panel bulbs more frequently than I want to. I added silicone
grease into the bulbs' sockets, and the bulbs now last much longer (due
to better heat transfer away from the bulbs).

I also spray painted the inside of the AR1500A's cabinet flat black,
this reduces the internal heat of the receiver.
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Peter Wieck Peter Wieck is offline
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Default AR3a/AS103a speakers and the Heathkit AR1500 receiver

Jerry wrote:

My den is quite small and my normal listening level is less than 1 watt, but
occasionally I'll listen at levels higher.


Jerry:

There are a lot of misconception to do with "volume", and especially as
it relates to "watts".

At one watt average, with moderately dynamic source, you will need at
least a 100-watt amp to get clean peaks absolutely without clipping.
But you already know this. Put another way, a speaker with an 86dB @
1-watt SPL, a 30-watt amp simply will not cut it, even bi-amped at
anything above a very moderate volume. Agreed, mostly one listens at a
very moderate volume. But not always.

Components of the vintage of your Heath more-or-less send straight DC
into the speaker when driven to clipping. And depending on the source
(where, as it usually happens most of the signal is at the mid-range),
that could be a lot of the time and pretty rapidly fatal to your
speakers.

Again, put another way, it is (Very typical of vintage SS amps)
amplifiers of low power that burn speakers, not high power. Almost any
well-made speaker can handle normal signal at very high power, well
beyond their nominal ratings, for brief periods. Even the very best
conventional PM speakers will fry in short order when fed DC. I think
this is what the OP was trying to convey.

Those of us who dabble in tube equipment tend to ignore this simple
truth as output transformers will not pass DC, so clipping is much
softer and relatively harmless (to the speaker, that is). Also why
those of us who have high-powered amps (tube or SS) also tend to ignore
this as there is enough headroom in any case to minimize consequences
from clipping.

Bi-Amping, even as you have applied it will create some advantages if
very carefully managed. But the real-world difference between a 30 watt
amp and two 30-watt amps split is limited in this *particular*
application given that at any given moment about 75% of your signal
will be at/within the midrange, and if you include the tweeter, that
goes to about 90%, at least as it applies to the need for headroom. I
would very strongly suggest that you make it your mission in Audio to
beg, borrow or steal a well-made high-powered amplifier (200W/RMS/CH @
4 ohms or better) and re-evaluate your position.

Enjoy the results in any case.

Peter Wieck
Wyncote, PA
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Default AR3a/AS103a speakers and the Heathkit AR1500 receiver

Peter Wieck wrote:


Some misconceptions:

There are a lot of misconception to do with "volume", and especially as
it relates to "watts".

At one watt average, with moderately dynamic source, you will need at
least a 100-watt amp to get clean peaks absolutely without clipping.


A peak-to-average ratio of 20 dB: moderate??

Components of the vintage of your Heath more-or-less send straight DC
into the speaker when driven to clipping.


Some pathological cases do, the vast majority don't.

Again, put another way, it is (Very typical of vintage SS amps)
amplifiers of low power that burn speakers, not high power.


This has been pretty thoroughly debunked elsewhere, check
out Rane's application notes on apolifier clipping and tweeter
life.

Those of us who dabble in tube equipment tend to ignore this simple
truth as output transformers will not pass DC, so clipping is much
softer and relatively harmless


That tubes clip more softwly has almost nothing whatsoever to do
with the fact that the output transformers do not pass DC. The
clipping is software for two reasons:

1. The upper end gain transfer characteristics of the tube do not
change as abruptly when limiting is reached,

2. The conbination of the tube's HF bandwidth, the transformer's
HF bandwidth and the overall circuit's HF bandwidth can suppress
some of the higher harmonics resulting from clipping.


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Jerry Jerry is offline
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Default AR3a/AS103a speakers and the Heathkit AR1500 receiver

"Peter Wieck" wrote in message
...
Jerry wrote:

My den is quite small and my normal listening level is less than 1 watt,

but
occasionally I'll listen at levels higher.


Jerry:

There are a lot of misconception to do with "volume", and especially as
it relates to "watts".

At one watt average, with moderately dynamic source, you will need at
least a 100-watt amp to get clean peaks absolutely without clipping.
But you already know this. Put another way, a speaker with an 86dB @
1-watt SPL, a 30-watt amp simply will not cut it, even bi-amped at
anything above a very moderate volume. Agreed, mostly one listens at a
very moderate volume. But not always.


Peter, please remember that the 30 watt amp is driving strictly the mid and
tweeter. Further, this amp sees greatly reduced fundamentals, so the
voltage swings are NOTHING like what a single amp would experience. When
playing music at levels I can just barely stand (somewhere around 10 -20
watts), PEAK output voltages in this amp are LESS than 7 volts.

Now, one reason for that low output voltage is that I removed those blasted
pots from the AR xover circuit. This netted a huge gain in sensitivity on
just those drivers. So I must compensate by reducing volume or the
mid/tweeter will overpower the woofer. To give you a feel ... the average
voltage swings in the woofer amp are 5 times higher!

Based upon all of the above, there is just no way that peak output voltage
could ever get to the 40 volt rails in the mid/tweeter amp. Further, rail
drop will be minimal given the low current drain of the mid and tweeter.

Peter, please remember that I don't have the fundamentals going through that
30 watt amp and this significantly changes the game and the math.

Components of the vintage of your Heath more-or-less send straight DC
into the speaker when driven to clipping. And depending on the source
(where, as it usually happens most of the signal is at the mid-range),
that could be a lot of the time and pretty rapidly fatal to your
speakers.


Even if this is the case, (and I doubt that because I measured the filter
caps and they are just fine), the mid and tweeter will never see the impact
of the clipped waves and resulting harmonics in the woofer amp. Further,
neither will the woofer as it's internal xover will reject those harmonics.

Peter don't forget that the Heath amp sees reduced harmonics as well. Now
this reduction is NOT as great as the reduction of fundamentals in the 30
watt amp, but still there is a significantly less harmonics "riding on
fundamentals" than what a single amp would see.

Again, put another way, it is (Very typical of vintage SS amps)
amplifiers of low power that burn speakers, not high power. Almost any
well-made speaker can handle normal signal at very high power, well
beyond their nominal ratings, for brief periods. Even the very best
conventional PM speakers will fry in short order when fed DC. I think
this is what the OP was trying to convey.


Peter, if we drove this 30 watt amp to the 40 volts rails, clipping would be
the least of our problems. Both the mid and the tweeter would be smoking
long, long before. With the fundamentals removed, the impact of stacking 40
volt rails on top of 40 volt rails in the Heath is equivalent to a 750 watt
amp. Now this is from the vantage point of the mids/tweeters. (The woofer
still sees the same 100 watt amp with but even it "goes further" without the
harmonics.)

Those of us who dabble in tube equipment tend to ignore this simple
truth as output transformers will not pass DC, so clipping is much
softer and relatively harmless (to the speaker, that is). Also why
those of us who have high-powered amps (tube or SS) also tend to ignore
this as there is enough headroom in any case to minimize consequences
from clipping.


Peter, you can ignore it, but the truth is that I have far, far more
headroom than you with your "brute" ss amp. You must pass fundamentals
with harmonics on top through that amp. Further, you still have the pots
"sucking up power" in your AR-3a's and this also contributes to a reduction
in headroom.

Bi-Amping, even as you have applied it will create some advantages if
very carefully managed. But the real-world difference between a 30 watt
amp and two 30-watt amps split is limited in this *particular*
application given that at any given moment about 75% of your signal
will be at/within the midrange, and if you include the tweeter, that
goes to about 90%, at least as it applies to the need for headroom. I
would very strongly suggest that you make it your mission in Audio to
beg, borrow or steal a well-made high-powered amplifier (200W/RMS/CH @
4 ohms or better) and re-evaluate your position.


Peter, are you saying that 75% of the signal STRENGTH is going to the
mids/tweeters? This is totally incorrect and I have a dual channel scope
to prove it. Less than 25% of the voltage swings are going to the
mid/tweeter amp. Then if we integrated the signals to compute power, once
again the real power is in the woofer amp ... BY A LOT! It's not even
close.

I have the equivalent of a 750 watt amp (@ 4 ohms - 375 watts @ 8 ohms).
Why in heavens name would I want a mere 200 watt amp. That would be going
backwards.

Regards,
Jerry
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Peter Wieck Peter Wieck is offline
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Default AR3a/AS103a speakers and the Heathkit AR1500 receiver

Jerry wrote:
I have the equivalent of a 750 watt amp (@ 4 ohms - 375 watts @ 8 ohms).
Why in heavens name would I want a mere 200 watt amp. That would be going
backwards.


Jerry:

Pulling the pots from the AR3(a) is about the first thing that should
be done, they were barely functional when-new. So we are 100% agreed
there. But per any of the several web-sites dedicated to these speakers
(Layne, Vintage, et.al.) this gives only about a 3dB gain (assuming
otherwise good pots) over the pots in the max (theoretically
straight-wire) position.

And, as to the "equivalent" of a 750 watt amp, _ALL_ I am suggesting is
that unless you have tried the brute-force amp and rejected it as being
unsatisfactory as compared to your present set-up, you REALLY SHOULD
try it. The results may well be revealing. At the very least they will
endorse your present position.

Yeah, a good part of the stuff I listen to regularly does have a 20dB
P/A, the room is fairly large, and I do like to run at a moderately
high volume... trumpets like that. And even the solo human voice with
an orchestral background likes that.

Peter Wieck
Wyncote, PA
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John Stone John Stone is offline
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Default AR3a/AS103a speakers and the Heathkit AR1500 receiver

On 10/6/06 10:47 PM, in article , "Jerry"
wrote:

Now, one reason for that low output voltage is that I removed those blasted
pots from the AR xover circuit. This netted a huge gain in sensitivity on
just those drivers. So I must compensate by reducing volume or the
mid/tweeter will overpower the woofer. To give you a feel ... the average
voltage swings in the woofer amp are 5 times higher!


I thought all your bi-amping adventures were done with the purpose of not
altering the original design of your AR3a's. Well, now that you're in there
changing things around, I'm wondering if you did anything to compensate for
the removal of those pots from the circuit. They place a 16 ohm load across
the mid and tweeter crossover circuits, and that load forms part of the
filter network. Did you put a fixed 16 ohm resistor in the circuit in their
place? If not, you've certainly altered the crossover responses and
consequently, the speaker response. (I can't wait to see whether you're
going to agree with this). I'm also trying to figure out how you got such a
huge gain in sensitivity by removing the pots. Turned all the way up, the
mid and tweeter are directly connected to the crossover outputs, so the pot
is out of the circuit other than presenting a parallel 16 ohm load. Unless
those were the world's most defective pots-and you would have easily been
able to tell from the intermittent operation-then I don't see where you're
picking up all the sensitivity from.
I'm also amazed at how much work you've gone through to deviate from the
original design intent of the AR3a's. If it was me, I would put them back to
stock and sell them. They still bring decent money. Then I would invest in
some real DIY loudspeaker building using the much more robust and better
performing loudspeaker components that are available today. You could then
tweak to your heart's desire without the worry of blowing fragile drivers
that are no longer available. You seem like the type that loves to
experiment. Why limit yourself to such old technology that will never reach
today's performance levels no matter what you do?
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Peter Wieck Peter Wieck is offline
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Default AR3a/AS103a speakers and the Heathkit AR1500 receiver

John Stone wrote:

I thought all your bi-amping adventures were done with the purpose of not
altering the original design of your AR3a's.


John, the various mod sites noted emphasize the need for a fixed
resistor in place of the pot, simply bypassing the adjustable function.
Yes, *maybe* get them out of the circuit, no, do not alter the overall
function of the circuit.

http://layneaudio.hypermart.net/AR3aXorig.gif shows the OEM crossover
arrangement. One may either bypass the wiper directly to the 0-ohms
position, or remove the pot inserting a 16-ohm resistor and tying the
correct leads at the 0-ohm position.

(above link courtesy Layne Audio)

Classic Speaker Pages:

http://www.classicspeakerpages.net/a...ar-3a/ar3a.htm

All sorts of information and suggestions.

Peter Wieck
Wyncote, PA
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Jerry Jerry is offline
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Default AR3a/AS103a speakers and the Heathkit AR1500 receiver

Peter Wieck wrote on 10/7/2006:

Jerry wrote:
I have the equivalent of a 750 watt amp (@ 4 ohms - 375 watts @ 8

ohms).
Why in heavens name would I want a mere 200 watt amp. That would be

going
backwards.


Jerry:

Pulling the pots from the AR3(a) is about the first thing that should
be done, they were barely functional when-new. So we are 100% agreed
there. But per any of the several web-sites dedicated to these speakers
(Layne, Vintage, et.al.) this gives only about a 3dB gain (assuming
otherwise good pots) over the pots in the max (theoretically
straight-wire) position.


Hmmm, 3db seems low, but could be right. I should have, but didn't measure
before and after. In any event, a 3db reduction in power is equivalant to
cutting the power to the mids/tweeters in HALF. That is, I now send half as
much power to the mids/tweeters and get the same SPL. This equates to a
terriffic gain in headroom and issures clipping in the mid/tweeter amp will
never happen.

Peter, you never told me you removed the pots from your AR-3a's!

You can't do this, Peter, and mainain the proper sound balance UNLESS you
compensate with fixed resistance in the xover. So, Peter, what mod did you
perform upon your 3a's?

And, as to the "equivalent" of a 750 watt amp, _ALL_ I am suggesting is
that unless you have tried the brute-force amp and rejected it as being
unsatisfactory as compared to your present set-up, you REALLY SHOULD
try it. The results may well be revealing. At the very least they will
endorse your present position.


Alas, I can't do this anymore. With the pots out, there is no way to power
my AR with a single amp and maintain any semblance of balance between the
energy sent to the woofer and that sent to the mids and tweeters. And I'm
NOT putting those pots back in the circuit. I itched for three days the
last time I opened those boxes.

Peter did you ever look at your audio signal on a scope to see the height of
the transients? I look fairly often and I've never seen peak voltages as
high as you describe.

Regards,
Jerry


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Default AR3a/AS103a speakers and the Heathkit AR1500 receiver

John Stone wrote on 10/7/2006:

I thought all your bi-amping adventures were done with the purpose of not
altering the original design of your AR3a's. Well, now that you're in

there
changing things around, I'm wondering if you did anything to compensate

for
the removal of those pots from the circuit. They place a 16 ohm load

across
the mid and tweeter crossover circuits, and that load forms part of the
filter network. Did you put a fixed 16 ohm resistor in the circuit in

their
place? If not, you've certainly altered the crossover responses and
consequently, the speaker response. (I can't wait to see whether you're
going to agree with this). I'm also trying to figure out how you got such

a
huge gain in sensitivity by removing the pots. Turned all the way up, the
mid and tweeter are directly connected to the crossover outputs, so the

pot
is out of the circuit other than presenting a parallel 16 ohm load. Unless
those were the world's most defective pots-and you would have easily been
able to tell from the intermittent operation-then I don't see where you're
picking up all the sensitivity from.


No, John! No pots and no fixed resistors. Pots are removed from the
circuit.

The real purpose of the pots was to balance the energy going to the more
sensitive drivers (mid and tweeters) in relationship to the energy going to
the woofers. In short, they were "padding" to bring all the drivers in
balance, plus they allowed some minor tweaking.

Now most folks have long set the tweeter pot to max as is recommended
everywhere. Further, removing the tweeter pot was even suggested by Chuck
McShane. See:

http://www.classicspeakerpages.net/ar/ar-9/3and9.txt

So, John, this leaves just the mid pot and it has a dramatic impact on the
balance of music ... no question about it. Any adjustments to this pot
dramatically impact the balance of high vs low frequencies. I don't think
anyone would argue this as a simple test of moving the pot form end to end
results in dramatically different sound.

Your question is how can I remove this pot and still maintain the proper
balance.

Well, for me, John, the pot is redundant. I still have total control over
the balance of energy going to the woofers vs the energy going to the
mids/tweeters ... only instead of pots, I use volume controls. Yes, the
volume controls on the amps that independently power each half of the
speaker.

I think you'll agree, John, that over time it's far, far easier to maintain
low power volume controls than it is to maintain the high power pots in the
speakers.

As for the improvement in sensitivity, all I can say it's significant and
very noticable. That 16 ohms still draws current that produces no sound.
If we assume that the impedance of the driver over it's frequency range
averages 4 ohms. Then if the pot is set to max increase, approx 25% of the
current going through the driver is also flowing through the pot and ...
producing zero sound.

On top of this, I never had the mid pot set to max. That would be way too
"bright" and in my room would NOT be balanced. So when I removed the pots
the padding that was going on, is no longer happening. So to balance the
speakers, I send significantly less power to the mids and tweeters and my
guess is the actual current flowing through them is very similar to what it
was when the pots were in the circuits.

John, when I removed the pots, I never claimed any change in sound with the
minor exception that my left speaker no longer loses mid-range completely
any more.

I'm also amazed at how much work you've gone through to deviate from the
original design intent of the AR3a's. If it was me, I would put them back

to
stock and sell them. They still bring decent money. Then I would invest in
some real DIY loudspeaker building using the much more robust and better
performing loudspeaker components that are available today. You could then
tweak to your heart's desire without the worry of blowing fragile drivers
that are no longer available. You seem like the type that loves to
experiment. Why limit yourself to such old technology that will never

reach
today's performance levels no matter what you do?


John, I don't believe that I have changed the intent of the AR3a's. I think
they sound terrific and I believe that any amp will drive them better with
the complex xover network split.

Further these drivers are somewhat unusual. AR made both the mid and
tweeter because they could NOT find drivers of comparable quality. The
woofer they purchased, but they specified all parameters so that it matched
the closed cabinet.

Regards,
Jerry

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Default AR3a/AS103a speakers and the Heathkit AR1500 receiver

Peter Wieck wrote on 8/7/2006:

John Stone wrote:

I thought all your bi-amping adventures were done with the purpose of

not
altering the original design of your AR3a's.


John, the various mod sites noted emphasize the need for a fixed
resistor in place of the pot, simply bypassing the adjustable function.
Yes, *maybe* get them out of the circuit, no, do not alter the overall
function of the circuit.

http://layneaudio.hypermart.net/AR3aXorig.gif shows the OEM crossover
arrangement. One may either bypass the wiper directly to the 0-ohms
position, or remove the pot inserting a 16-ohm resistor and tying the
correct leads at the 0-ohm position.


Peter, if I were going to do this, I'd just solder the lead going to the
driver to the top of the pot. This by passes the wiper (which by now is
heavily corroded), but it leaves that 16 ohm wire resistor encased in
ceramic in the circuit. Current is still flowing through that resistor and
I like the fact that while it's inside the box surrounded by all that
insulation, that it's encased in ceramic.

That's NOT what I did, however. Pots are completely out of my xovers. All
I really did was move the function of the pots back to the volume controls
on the individual amps.

Under a single amp, I don't think "soldering to the top of the pot" would
actually work, Peter. I mean that balance would be way off ... far too
bright!

Regards,
Jerry

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Default AR3a/AS103a speakers and the Heathkit AR1500 receiver

Jerry wrote:

Peter, if I were going to do this, I'd just solder the lead going to the
driver to the top of the pot. This by passes the wiper (which by now is
heavily corroded), but it leaves that 16 ohm wire resistor encased in
ceramic in the circuit. Current is still flowing through that resistor and
I like the fact that while it's inside the box surrounded by all that
insulation, that it's encased in ceramic.

That's NOT what I did, however. Pots are completely out of my xovers. All
I really did was move the function of the pots back to the volume controls
on the individual amps.

Under a single amp, I don't think "soldering to the top of the pot" would
actually work, Peter. I mean that balance would be way off ... far too
bright!


YIKES!.... Yikes....

Before I completely misunderstand what you did, how did you remove the
3-wire pot from the circuit? OK. Pot is gone, what got connected where?
Did you just lump the three wires together?

I am (admittedly) boggling at the "far too bright" comment as well,
especially as connected to the comment "move the function back to the
volume controls". What does the crossover look like when you are done
with your mods? Did you replace the various caps?

Peter Wieck
Wyncote, PA
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Default AR3a/AS103a speakers and the Heathkit AR1500 receiver

On 10/7/06 8:40 PM, in article , "Jerry"
wrote:

John Stone wrote on 10/7/2006:
Well, now that you're in
there changing things around, I'm wondering if you did anything to compensate
for the removal of those pots.


No, John! No pots and no fixed resistors. Pots are removed from the
circuit.


Oh boy!

The real purpose of the pots was to balance the energy going to the more
sensitive drivers (mid and tweeters) in relationship to the energy going to
the woofers. In short, they were "padding" to bring all the drivers in
balance, plus they allowed some minor tweaking.

Now most folks have long set the tweeter pot to max as is recommended
everywhere. Further, removing the tweeter pot was even suggested by Chuck
McShane. See:

http://www.classicspeakerpages.net/ar/ar-9/3and9.txt
Yes, I read that. It wasn't Chuck McShane that wrote this, it was his nephew
writing what he BELIEVES Chuck McShane said. Hardly authoritative. The
context of this post is totally missing, and the meaning of the word
"remove" is misleading at best. He could easily have meant removing the L
pad aspect of the pots as opposed to removing the pots completely. I find it
hard to believe Chuck McShane would have recommended just pulling them out.


So, John, this leaves just the mid pot and it has a dramatic impact on the
balance of music ... no question about it. Any adjustments to this pot
dramatically impact the balance of high vs low frequencies. I don't think
anyone would argue this as a simple test of moving the pot form end to end
results in dramatically different sound.

Your question is how can I remove this pot and still maintain the proper
balance.


No, my question is NOT how you can remove the pot and still maintain the
proper balance. It's how you can remove the pot and still maintain the
proper crossover frequency.


Well, for me, John, the pot is redundant.

Obviously. You do like to make up your own rules, independent of facts or
reality.

I still have total control over
the balance of energy going to the woofers vs the energy going to the
mids/tweeters ... only instead of pots, I use volume controls. Yes, the
volume controls on the amps that independently power each half of the
speaker.


I fully understand what you are doing here. It doesn't take rocket science
to figure it out.

I think you'll agree, John, that over time it's far, far easier to maintain
low power volume controls than it is to maintain the high power pots in the
speakers.


But you say you've left the midrange pots in, so you still have to maintain
those. So you really haven't solved the maintenance problem at all. The big
issue with the pots is having to take apart the speakers to get to them.
Once you're in there, cleaning them is no big deal. All you've done is
eliminate the need to clean one of them, which you could have done anyway
just by jumpering the wiper to the high side of the pot.

As for the improvement in sensitivity, all I can say it's significant and
very noticable. That 16 ohms still draws current that produces no sound.
If we assume that the impedance of the driver over it's frequency range
averages 4 ohms. Then if the pot is set to max increase, approx 25% of the
current going through the driver is also flowing through the pot and ...
producing zero sound.


Jerry, your ignorance of even basic loudspeaker design principles is
appalling. If I didn't know better, I'd swear you were joking. The tweeter
network in the AR3a consists of a single series element; i.e., a 6uf cap
feeding a load consisting of a tweeter and a 16 ohm tapped resistor. For all
intents and purposes, when you run the tweeter pot at full, you simply have
a tweeter and a 16 ohm resistor in parallel. The crossover frequency is
determined by the value of the series cap AND the impedance of the load.
Removing that 16 ohm resistor alters the load (increases the impedance),
which in turn alters the crossover frequency, moving it downward. I'm quite
sure what you've done IS significant, just as I am quite sure what you have
done has completely changed the intended tonal balance of your speakers.
What I'm not sure of is how much you've increased the risk of blowing your
tweeters. But let's just say that those are quite fragile and you've
definitely moved things in the wrong direction regarding the chances of
surviving your "improvement". If you still don't get this, here's a link
that demonstrates, in simple terms, the relationship between load impedance
and crossover frequency:

http://www.carstereo.com/help/Articles.cfm?id=1

So to balance the
speakers, I send significantly less power to the mids and tweeters and my
guess is the actual current flowing through them is very similar to what it
was when the pots were in the circuits.


Well the only part of this statement I agree with is that you are guessing.
How do you dissipate less power through the drivers while keeping the
current flow the same? Sorry Jerry, but you cannot change the relationship
between SPL and power dissipation through the drivers. If you are getting
more output from a driver, it is simply because you are putting more signal
into it. End of story.


John, when I removed the pots, I never claimed any change in sound with the
minor exception that my left speaker no longer loses mid-range completely
any more.

Now I'm really confused. I thought you said you didn't remove the midrange
pots..

John, I don't believe that I have changed the intent of the AR3a's. I think
they sound terrific and I believe that any amp will drive them better with
the complex xover network split.


There's that belief system again. Never let the facts get in the way of what
you believe. You have come to the conclusion that ANY amp will drive them
better with split x-over based on what? Using what even you admit is a
pretty marginal amp for those speakers? Many here have told you from their
own experience that using a single amp of adequate power and stability for
these speakers will get as much out of them as they are capable of giving.

Which brings up another question: If using separate amps gave such a huge
improvement, why didn't AR suggest it in the first place? The same exact
thing you have done could have been done back in 1968
when they were introduced. Yet nowhere in the owner's manual or the
literature is any such arrangement suggested. Why not? Are you saying that
the designers never thought of it, or were totally unaware of the
capabilities of their own speakers? Strange that they could be so
brilliant in designing the speakers, yet so ignorant of their true
capabilities.

Further these drivers are somewhat unusual. AR made both the mid and
tweeter because they could NOT find drivers of comparable quality. The
woofer they purchased, but they specified all parameters so that it matched
the closed cabinet.

Yes, and all of that happened back in 1968. What does any of this have to do
with my suggestion of looking at what is going on today in DIY using
up-to-date driver technology?
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Default AR3a/AS103a speakers and the Heathkit AR1500 receiver

Peter Wieck wrote 10/8/2006:
Jerry wrote:


Under a single amp, I don't think "soldering to the top of the pot"

would
actually work, Peter. I mean that balance would be way off ... far too
bright!


YIKES!.... Yikes....

Before I completely misunderstand what you did, how did you remove the
3-wire pot from the circuit? OK. Pot is gone, what got connected where?
Did you just lump the three wires together?

I am (admittedly) boggling at the "far too bright" comment as well,
especially as connected to the comment "move the function back to the
volume controls". What does the crossover look like when you are done
with your mods? Did you replace the various caps?

Peter Wieck
Wyncote, PA


Ok, my "mod" (and I don't really think of it as a mod as there was
essentially zero change in sound) was to remove the pots from the circuit.
The pots are still in place, just doing nothing and dissipating zero energy.

To implement this, all I did was cut the lead on the pots going to the
drivers and the leads at the top of the pot. Twisted these together and
soldered. Put on a wire connector and sandwiched between mounds of
fiberglass (or whatever that itchy stuff is).

The yellow wires are still connected to the pots and from the pots on to the
drivers. Everything else is exactly as it was. All the reactive components
are intact.

Peter, I did not change the caps. They looked good so I measured and they
were fine. I expected to see some pretty excessive leakage, but that was
fine as well.

Next, I ran some tests to see if the current going to the drivers was
consistent with the xovers and again it's clear the xovers are performing
their job well. For these tests, I sent full signals to each half. And
while voltage was applied to the speakers, the xovers effectively "blocked"
frequencies not intended for their respective drivers.

So, xovers are doing their job, drivers are doing their job and all I have
to do is send the appropriate energy to each half of the speaker. Peter,
this adjustment is so coarse and impacts so many frequencies that it's
pretty hard to be much off. In short, if the balance isn't correct, human
voice sounds awful and so do instruments.

Under bi-amping the volume controls perform essentially the same function
that was performed by the pots ... to balance energy between the drivers.

Regards,
Jerry


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Default AR3a/AS103a speakers and the Heathkit AR1500 receiver

John Stone wrote 10/8/2006: On 10/7/06 8:40 PM, in article
, "Jerry"

Jerry wrote:

Now most folks have long set the tweeter pot to max as is recommended
everywhere. Further, removing the tweeter pot was even suggested by

Chuck
McShane. See:

http://www.classicspeakerpages.net/ar/ar-9/3and9.txt

Yes, I read that. It wasn't Chuck McShane that wrote this, it was his

nephew
writing what he BELIEVES Chuck McShane said. Hardly authoritative. The
context of this post is totally missing, and the meaning of the word
"remove" is misleading at best. He could easily have meant removing the L
pad aspect of the pots as opposed to removing the pots completely. I find

it
hard to believe Chuck McShane would have recommended just pulling them

out.

Well, John, it was published in the AR library and someone would have
complained vehemently if it was totally wrong. I think this is the part
that is most convincing:

"Even wide open, the pot reduces tweeter output by about 1db."

So, if the tweeter pot is set to max and the pot opens up, the net change in
the tweeter is 1 db. However, if the wiper in the pot is corroded the
reduction can be far, far more substantial than 1 db.


So, John, this leaves just the mid pot and it has a dramatic impact on

the
balance of music ... no question about it. Any adjustments to this pot
dramatically impact the balance of high vs low frequencies. I don't

think
anyone would argue this as a simple test of moving the pot form end to

end
results in dramatically different sound.

Your question is how can I remove this pot and still maintain the proper
balance.


No, my question is NOT how you can remove the pot and still maintain the
proper balance. It's how you can remove the pot and still maintain the
proper crossover frequency.


John, xover frequency is determined primarily by the reactive components.
The coils and caps are all still there. The xover for the mid-range is
really a band pass and I have tested the xover to see whether it was in fact
working.

I did this by applying a full frequency signal to the mid/tweeter (did
exactly the same for the woofer). So a full frequency and full strength
voltage was applied to the mid/tweeter and I measured the current actually
going to the drivers. In short, the xovers were performing perfectly.
That is, they were "blocking" (little or no current) was flowing for the
frequencies NOT intended for the respective drivers.

Lastly, John, as you stated in your other post, the net resistance of the 16
ohm pot and the mid-range driver (with the pot at max) is still pretty close
to the resistance of the mid-range driver. So, we really can't be that far
different from the original design.


Well, for me, John, the pot is redundant.


Obviously. You do like to make up your own rules, independent of facts or
reality.


Not my rules. Function of the pots is to balance energy going to the
respective drivers to adjust for room conditions and RECORDINGS. I can
perform exactly the same function with the volume controls.

With a single amp, John, you have no where near the control over sound that
I have. And with harmonics riding on fundamentals, you have no where near
the headroom that I have.

As an aside, John, a totally flat response on AR-3a's is achieved with the
pots at max AND a slight increase in the treble volume control.

I think you'll agree, John, that over time it's far, far easier to

maintain
low power volume controls than it is to maintain the high power pots in

the
speakers.


But you say you've left the midrange pots in, so you still have to

maintain
those. So you really haven't solved the maintenance problem at all. The

big
issue with the pots is having to take apart the speakers to get to them.
Once you're in there, cleaning them is no big deal. All you've done is
eliminate the need to clean one of them, which you could have done anyway
just by jumpering the wiper to the high side of the pot.


Neither pot is in the circuit (both pots are physically attached to the
speakers, but doing nothing and dissipating zero power.) From my first post
in this thread:

"Well, Rolf, I've done just the opposite. I've taken all the pots out of
the AR-3a circuit ...."

From this point on, I'll only take the speakers apart upon component failure

.... NOT for cleaning those blasted pots.

As for the improvement in sensitivity, all I can say it's significant

and
very noticable. That 16 ohms still draws current that produces no

sound.
If we assume that the impedance of the driver over it's frequency range
averages 4 ohms. Then if the pot is set to max increase, approx 25% of

the
current going through the driver is also flowing through the pot and

....
producing zero sound.


Jerry, your ignorance of even basic loudspeaker design principles is
appalling. If I didn't know better, I'd swear you were joking. The tweeter
network in the AR3a consists of a single series element; i.e., a 6uf cap
feeding a load consisting of a tweeter and a 16 ohm tapped resistor. For

all
intents and purposes, when you run the tweeter pot at full, you simply

have
a tweeter and a 16 ohm resistor in parallel. The crossover frequency is
determined by the value of the series cap AND the impedance of the load.
Removing that 16 ohm resistor alters the load (increases the impedance),
which in turn alters the crossover frequency, moving it downward. I'm

quite
sure what you've done IS significant,


My ignorance, huh? John, you spouted a lot of "facts", but not a single
number. Are you lazy, John, or perhaps you don't know how to do the math.

Let's just see how significant.

DC resistance of tweeter is approx. 3.2 ohms

So with the 16 ohm pot full across - net resistance = 2.67 ohms or a
difference of .53 ohms

Real, real significant, John ... huh??

Now, let's look at the total network near the xover frequency

I @ 2 v I @ 2 v
Hz Z for Cap Z w/o pot Z with pot w/o pot with pot
% diff
3,000 8.8 ohms 12.0 11.5 .166
..145 12.8%
4,000 6.6 ohms 9.8 9.3 .203
..179 11.9%
5,000 5.3 ohms 8.5 8.0 .235
..522 11.1%
6,000 4.4 ohms 7.6 7.1 .656
..588 10.4%

Real significant, John! Maximum difference in current going through the
tweeter is 2.2% over this entire range. WOW!! Tell us, John, do you
think there is a human anywhere ... that could actually hear this
difference?

Perhaps your arguments would have some weight, John, if you backed them up
with the math.

But let's just say that those are quite fragile and you've
definitely moved things in the wrong direction regarding the chances of
surviving your "improvement". If you still don't get this, here's a link
that demonstrates, in simple terms, the relationship between load

impedance
and crossover frequency:

http://www.carstereo.com/help/Articles.cfm?id=1


What in heck are you talking about?? What wrong direction? 0.5% more
current at 6000 Hz than at 3000 Hz!! Who cares??

Now, if you are talking about sensitivity in total .... YES, for the same
voltage we get approx. 11% more current going through the tweeters. We must
absolutely reduce the voltage in the mid/tweeter amp or the sound would be
too bright.

What in heavens name does that have to do with "fragile"?

So to balance the
speakers, I send significantly less power to the mids and tweeters and

my
guess is the actual current flowing through them is very similar to what

it
was when the pots were in the circuits.


Well the only part of this statement I agree with is that you are

guessing.
How do you dissipate less power through the drivers while keeping the
current flow the same? Sorry Jerry, but you cannot change the relationship
between SPL and power dissipation through the drivers. If you are getting
more output from a driver, it is simply because you are putting more

signal
into it. End of story.


Total nonsense, John. We are NOT talking about SPL out of the drivers.
We are talking about SPL out of the speakers.

I get more output for the same voltage for two reasons:

1. I'm NOT wasting current flowing through the 16 ohms pot like you do
(approx. 11%)

2. Actual waste on the mid-range is much, much higher, because I never set
the mid pot to max. In that case the amount of current the mid driver
actually sees is greatly reduced. This is really a waste of voltage and
headroom. Even though voltage can be significant the current will be low
due the voltage divider function that the pot performs.


John, when I removed the pots, I never claimed any change in sound with

the
minor exception that my left speaker no longer loses mid-range

completely
any more.


Now I'm really confused. I thought you said you didn't remove the midrange
pots..


Confused I guess you are, because I've been consistent. I've always said I
removed ALL pots.

John, I don't believe that I have changed the intent of the AR3a's. I

think
they sound terrific and I believe that any amp will drive them better

with
the complex xover network split.


There's that belief system again. Never let the facts get in the way of

what
you believe.


John, this is getting a little tiring. You have never quote a single fact
.... just total supposition.

Here is my charts and my graphs and facts :

http://www.classicspeakerpages.net/d...ng_type=search

You have come to the conclusion that ANY amp will drive them
better with split x-over based on what? Using what even you admit is a
pretty marginal amp for those speakers? Many here have told you from their
own experience that using a single amp of adequate power and stability for
these speakers will get as much out of them as they are capable of giving.


Look over the impedance charts, John. Then let's see your facts. Your
charts. Your experiments ... or do we have an empty bag?

As for my amps, after looking over the facts ... I believe I have far, far
more voltage headroom than anyone with a single amp.

Which brings up another question: If using separate amps gave such a huge
improvement, why didn't AR suggest it in the first place?


I don't believe at the time that the AR's were developed, people were even
experimenting with bi-amping for home use. As time went on and AR continued
to develop speakers, they started experimenting with bi-amping.
"Satisfactory results were obtained when bi-amping the AR-90" according to
AR (see reference on the AR forum).

The same exact
thing you have done could have been done back in 1968
when they were introduced. Yet nowhere in the owner's manual or the
literature is any such arrangement suggested. Why not? Are you saying that
the designers never thought of it, or were totally unaware of the
capabilities of their own speakers? Strange that they could be so
brilliant in designing the speakers, yet so ignorant of their true
capabilities.


I don't believe back in 1968 ANYBODY was thinking about bi-amping for home
use, but please share a reference showing that I am wrong. Quote any
article from 1968 or earlier recommending bi-amping in the home.

Further these drivers are somewhat unusual. AR made both the mid and
tweeter because they could NOT find drivers of comparable quality. The
woofer they purchased, but they specified all parameters so that it

matched
the closed cabinet.

Yes, and all of that happened back in 1968. What does any of this have to

do
with my suggestion of looking at what is going on today in DIY using
up-to-date driver technology?


I'm not so certain there are comparable drivers available today. It seems
that "quality" anything is harder to find. Just look at the products
offered today in terms of receiver and speaker systems.

Regards,
Jerry
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Jerry wrote:

To implement this, all I did was cut the lead on the pots going to the
drivers and the leads at the top of the pot. Twisted these together and
soldered. Put on a wire connector and sandwiched between mounds of
fiberglass (or whatever that itchy stuff is).

The yellow wires are still connected to the pots and from the pots on to the
drivers. Everything else is exactly as it was. All the reactive components
are intact.


OK, on the schematic (OEM), there is still 16 ohms in parallel with
each driver to ground, and 32 ohms across both drivers. If I read you
correctly, you have removed the green wire & the output wire from the
tweet-pot, joined them, and left them separated from the pot. The pot
is now out-of-circuit altogether.

On the Mid side (again, if I read you correctly), you have removed the
choke wire and the wire to the mid from the pot, joined those and left
them separate from the pot. Now that pot is also out-of-circuit, as
well as delivering maximum brightness to the mid. So, not only is the
resistor gone across the drivers, but also across the pair. This will
increase the impedance of the speaker overall, and, of course, the
tweet and the mid. It will also send _ALL_ of the energy across the two
drivers, dissipating none of it across the two TWENTY-FIVE WATT, 16 ohm
fixed resistors (elements of the pots) as they are now out-of-circuit.
You are correct (more-or-less) in that it will not affect the frequency
performance of the crossover, but it will change its function.

Is this correct? On mine, I have soldered the output wire to the 'high
side', but I have left the fixed elements of the pots in place
electrically. This gains the 1dB - 3dB that the pot-in-place wastes,
and with replacement of the caps with 'tighter' caps, makes the speaker
a good deal clearer, at least to me. But there could be _A LOT_ of
power going into those beasts, I question the wisdom of pulling the
pots out of the circuit entirely.

Peter Wieck
Wyncote, PA
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Default AR3a/AS103a speakers and the Heathkit AR1500 receiver

On 10/9/06 6:38 PM, in article , "Jerry"
wrote:

John Stone wrote 10/8/2006: On 10/7/06 8:40 PM, in article
, "Jerry"


Yes, I read that. It wasn't Chuck McShane that wrote this, it was his

nephew
writing what he BELIEVES Chuck McShane said. Hardly authoritative. The
context of this post is totally missing, and the meaning of the word
"remove" is misleading at best. He could easily have meant removing the L
pad aspect of the pots as opposed to removing the pots completely. I find

it
hard to believe Chuck McShane would have recommended just pulling them

out.

Well, John, it was published in the AR library and someone would have
complained vehemently if it was totally wrong.


Jerry, AR is long gone. The "AR library", as you put it, is nothing more
than a loose collection of posts and articles from DIY folks and others with
an interest in and nostalgia for the speakers. There's nothing official
about it and while there's lots of good stuff there, there's also some
really questionable stuff. Nobody polices it for accuracy, so it should not
all be taken as bible.

I think this is the part
that is most convincing:

"Even wide open, the pot reduces tweeter output by about 1db."

So, if the tweeter pot is set to max and the pot opens up, the net change in
the tweeter is 1 db. However, if the wiper in the pot is corroded the
reduction can be far, far more substantial than 1 db.


What a novel interpretation! Jerry, the term "wide open" is common
terminology to describe a pot being set to maximum, not a pot that is
electrically open. The 1dB simply refers to the insertion loss of the pot,
operating properly in circuit, at full setting.

No, my question is NOT how you can remove the pot and still maintain the
proper balance. It's how you can remove the pot and still maintain the
proper crossover frequency.


John, xover frequency is determined primarily by the reactive components.


Any filter network's turnover frequency is calculated through the values of
source impedance, the value of reactive components, and the impedance of the
load. Don't believe me? Then substitute a 100 ohm resistor for the tweeter
and run a sweep of the crossover. I'm sure you'll you'll see a pretty huge
change.

The coils and caps are all still there. The xover for the mid-range is
really a band pass and I have tested the xover to see whether it was in fact
working.


I did this by applying a full frequency signal to the mid/tweeter (did
exactly the same for the woofer). So a full frequency and full strength
voltage was applied to the mid/tweeter and I measured the current actually
going to the drivers. In short, the xovers were performing perfectly.
That is, they were "blocking" (little or no current) was flowing for the
frequencies NOT intended for the respective drivers.


I have read this paragraph over and over, and for the life of me, I can't
figure out what you are talking about. What kind of "full frequency and full
strength voltage" are you referring to? How do you accurately measure the
crossover response with a "full frequency" signal? Do you have a spectrum
analyzer? The simplest way to accurately measure the response is to run a
sine sweep and plot the voltage/frequency curve using an rms voltmeter at
the driver terminals. Do it with and without the pot in place an you'll get
an exact picture of what is happening.
You also keep using the term "current". How, and why are you are measuring
current (amps)?

Lastly, John, as you stated in your other post, the net resistance of the 16
ohm pot and the mid-range driver (with the pot at max) is still pretty close
to the resistance of the mid-range driver.


??? I never stated any such thing. Please provide a quote, and please show
me where I ever used the term "resistance" in reference to the drivers.


Not my rules. Function of the pots is to balance energy going to the
respective drivers to adjust for room conditions and RECORDINGS. I can
perform exactly the same function with the volume controls.


No you can't. You pulled out 2 pots and substituted them with 1 amplifier
gain control, driving the entire mid/tweeter section. You have removed one
of the pots' key functions, which was to allow shelving of the mid and
tweeter levels individually.

With a single amp, John, you have no where near the control over sound that
I have. And with harmonics riding on fundamentals, you have no where near
the headroom that I have.

I have no idea what this means.

As an aside, John, a totally flat response on AR-3a's is achieved with the
pots at max AND a slight increase in the treble volume control.


Anybody who has actually measured AR3a's as opposed to just reading the AR
literature will tell you this isn't true. Here's an actual real world
measurement of the 3a's:

http://murphyblaster.com/content.php?f=AR3a.html

These measurements are backed up in a post on 8/7 by Dick Pierce to you
regarding the frequency response of the AR3a:

"No, the reason for this is that Roy Allison and Ed Villchur at AR
decided on a balance that resulted in an overall downward trend
in the speaker's response toward the high end. That was their
choice, for whatever reasons. The midrange efficiency is about
2 db less than the woofer, and the tweeter is another 2-3 dB
less efficient than that. That's what the people of AR designed
it to be." (end quote)

A "slight increase" in the treble control will not achieve a totally flat
response as is clear from the actual response measurements.

...

Jerry, your ignorance of even basic loudspeaker design principles is
appalling. If I didn't know better, I'd swear you were joking. The tweeter
network in the AR3a consists of a single series element; i.e., a 6uf cap
feeding a load consisting of a tweeter and a 16 ohm tapped resistor. For

all
intents and purposes, when you run the tweeter pot at full, you simply

have
a tweeter and a 16 ohm resistor in parallel. The crossover frequency is
determined by the value of the series cap AND the impedance of the load.
Removing that 16 ohm resistor alters the load (increases the impedance),
which in turn alters the crossover frequency, moving it downward. I'm

quite
sure what you've done IS significant,


My ignorance, huh? John, you spouted a lot of "facts", but not a single
number. Are you lazy, John, or perhaps you don't know how to do the math.

Let's just see how significant.

DC resistance of tweeter is approx. 3.2 ohms

So with the 16 ohm pot full across - net resistance = 2.67 ohms or a
difference of .53 ohms


Sorry Jerry, but yes, your ignorance, or perhaps just lack of attention to
detail, as again demonstrated above. DC resistance is utterly meaningless to
this discussion, as the last time I checked, tweeters required AC to produce
sound. Yet you use resistance interchangeably with impedance as if they were
one and the same. The "nominal" impedance of a tweeter with 3.2ohm dcr is 4
ohms. If you take that nominal impedance in parallel with the 16 ohm pot
(the pot will have an impedance close to 16 ohms given that it is largely
non-inductive) the 2 in parallel yield a resulting impedance of 3.2 ohms.
With the pot totally out, you shift the impedance up by a minimum of 20%.

Real, real significant, John ... huh??


Um, yeah, I'd say by any measure a 20% shift is significant. And in a
previous post, you yourself said so:
As for the improvement in sensitivity, all I can say it's significant
and very noticable.


Those are YOUR words, Jerry. So which is it? Significant or not? 20% is way
beyond the impedance tolerance AR specified for the drivers alone, so the
crossover is indeed operating into a significantly different load than
intended, with the resultant shift in xover response as previously stated.
More importantly 20% is the MINIMUM shift. In reality, the tweeter (and
midrange) impedance curve is nowhere near flat, and deviates considerably
with frequency. Given that these drivers use no ferrofluid they will exhibit
a fairly high Q at mechanical resonance ( which I'd estimate around 300Hz
for the mid and 3kHz for the tweeter), yielding an impedance peak at
resonance perhaps double the nominal value. The driver impedance also rises
gradually with increased frequency, due to the voice coil inductance. So the
pots were there for 2 reasons: provide level adjustment, and to provide a
measure of impedance stabilization for the crossover. By removing them, you
have changed things a whole bunch.

Tell us, John, do you
think there is a human anywhere ... that could actually hear this
difference?

You said you could hear it yourself, so I'd assume others could as well.

Perhaps your arguments would have some weight, John, if you backed them up
with the math.


There's plenty of "math" above. And it least its based on correct parameters
(impedance rather than resistance), which makes your "math" less than
useful.


But let's just say that those are quite fragile and you've
definitely moved things in the wrong direction regarding the chances of
surviving your "improvement". If you still don't get this, here's a link
that demonstrates, in simple terms, the relationship between load

impedance
and crossover frequency:

http://www.carstereo.com/help/Articles.cfm?id=1


What in heck are you talking about?? What wrong direction? 0.5% more
current at 6000 Hz than at 3000 Hz!! Who cares??

Now, if you are talking about sensitivity in total .... YES, for the same
voltage we get approx. 11% more current going through the tweeters. We must
absolutely reduce the voltage in the mid/tweeter amp or the sound would be
too bright.

What in heavens name does that have to do with "fragile"?


Pushing down the crossover frequency puts more strain on the tweeter. Like
it or not, those tweeters were notorious for marginal power handling
ability. A.75in voice coil on a paper former with no ferrofluid cannot take
much power without burning out.

John, this is getting a little tiring. You have never quote a single fact
... just total supposition.


Jerry, you're the one making all the claims. It's up to you, not me, to back
your claims with facts. I and others smarter than me have provided plenty of
opposing facts, all of which you have chosen to ignore. And you think you're
tired?

Here is my charts and my graphs and facts :

http://www.classicspeakerpages.net/d...forum=3&topic_
id=10658&mesg_id=10658&listing_type=search


Nothing more than the same old stuff you've been saying here for the past
few months. I've read it all and there's nothing further to learn from it.

You have come to the conclusion that ANY amp will drive them
better with split x-over based on what? Using what even you admit is a
pretty marginal amp for those speakers? Many here have told you from their
own experience that using a single amp of adequate power and stability for
these speakers will get as much out of them as they are capable of giving.


Look over the impedance charts, John. Then let's see your facts. Your
charts. Your experiments ... or do we have an empty bag?


Jerry, as others here have told you countless times, nothing is to be gained
in your configuration compared to a single amp, as long as the driving
amplifier has adequately low output impedance and sufficient undistorted
power to drive the speakers to the desired level. Virtually all competent
amplifiers act as voltage sources, and within the limit of their power
output capability, perform largely independent of the load they see. The
AR3a designers knew this and designed the speakers accordingly. You have
never provided a shred of proof that your configuration solves any problem
that couldn't be solved with a single more powerful amplifier. To now
extend this argument to ALL amplifiers, regardless of power, is absurd and
based totally on unsubstantiated generalizations about power amplifier
behavior. Yes, by using 2 amps, you can now adjust the mid and tweeter
outputs to levels above the woofer, but that was never the intent of the
original design.

As for my amps, after looking over the facts ... I believe I have far, far
more voltage headroom than anyone with a single amp.


I know what you believe. Now, please explain the basis of this belief. Let's
see your experiments or charts showing your "biamp" configuration with
ancient low powered amplifiers of dubious quality having far more headroom
than a single 250 watt/ch amplifier with total stability down to 2 ohms.
Your claim, your proof.

Which brings up another question: If using separate amps gave such a huge
improvement, why didn't AR suggest it in the first place?


I don't believe at the time that the AR's were developed, people were even
experimenting with bi-amping for home use.

I don't believe back in 1968 ANYBODY was thinking about bi-amping for home
use, but please share a reference showing that I am wrong. Quote any
article from 1968 or earlier recommending bi-amping in the home.


Having lived during that era, I can assure you that biamping was indeed
being done in home systems well before 1968. Ever hear of the Marantz 3?
It's an electronic crossover from the '50s. In fact, even Heathkit offered
one called the XO-1 which also dates back well before 1968. There were
others.


I'm not so certain there are comparable drivers available today.

There aren't. Nobody buying a high quality driver today would accept the
performance compromises in power handling, sensitivity, or frequency
response.

It seems
that "quality" anything is harder to find. Just look at the products
offered today in terms of receiver and speaker systems.


Please look a little more closely. You will find plenty of examples of very
high quality loudspeakers that will outperform the AR3a by a wide margin.
Contrary to what you seem to believe, advances in loudspeakers did not end
in 1968.

Jerry, the last word is all yours. I won't be posting any further responses
to this thread in the hope that it dies the merciful death it so deserves.
Enjoy your speakers.
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Default AR3a/AS103a speakers and the Heathkit AR1500 receiver

Peter Wieck wrote on 10/9/2006:
Jerry wrote:

To implement this, all I did was cut the lead on the pots going to the
drivers and the leads at the top of the pot. Twisted these together and
soldered. Put on a wire connector and sandwiched between mounds of
fiberglass (or whatever that itchy stuff is).

The yellow wires are still connected to the pots and from the pots on to

the
drivers. Everything else is exactly as it was. All the reactive

components
are intact.


OK, on the schematic (OEM), there is still 16 ohms in parallel with
each driver to ground, and 32 ohms across both drivers. If I read you
correctly, you have removed the green wire & the output wire from the
tweet-pot, joined them, and left them separated from the pot. The pot
is now out-of-circuit altogether.


Peter, that is exactly correct. Only one wire (yellow wire) is connected to
the pot and pot acts as a terminal strip. The other two terminals on the
pot are connected to NOTHING!

On the Mid side (again, if I read you correctly), you have removed the
choke wire and the wire to the mid from the pot, joined those and left
them separate from the pot. Now that pot is also out-of-circuit, as
well as delivering maximum brightness to the mid. So, not only is the
resistor gone across the drivers, but also across the pair. This will
increase the impedance of the speaker overall, and, of course, the
tweet and the mid.


Yes, it does increase the effective impedance of those individual drivers.

Let's assume the DC resistance of the drivers is around 3.2 ohms (by
themselves). So with the 16 ohms in parallel, the effective resistance
would be 2.67 ohms. Pot causes the impedance to be .53 ohms LOWER.

Notice, that with the pot across the drivers the impedance is lower in total
(some would argue 2.76 ohms is a 'tough' load for any amp), so the speakers
draw more current. The sound output (SPL), however, is also lower!

It will also send _ALL_ of the energy across the two
drivers, dissipating none of it across the two TWENTY-FIVE WATT, 16 ohm
fixed resistors (elements of the pots) as they are now out-of-circuit.
You are correct (more-or-less) in that it will not affect the frequency
performance of the crossover, but it will change its function.


Peter, you are correct again! With zero dissipation, the drivers become
more sensitive so we must reduce the energy (actually voltage) applied to
them. Reducing voltage is trivial as all I do is set the volume control
LOWER. Failing to do this results in way, way too much emphasis in the high
frequencies.

With lower voltage being applied, the headroom (difference between signal
voltage and rails) INCREASES. That is, it becomes far, far more difficult
to get into clipping on this amp. Then when we significantly reduce the
fundamental frequencies, it's just about impossible to reach clipping in
that amp. Impossible, of course, UNLESS we "fry" the drivers by over
driving.

Is this correct? On mine, I have soldered the output wire to the 'high
side', but I have left the fixed elements of the pots in place
electrically. This gains the 1dB - 3dB that the pot-in-place wastes,
and with replacement of the caps with 'tighter' caps, makes the speaker
a good deal clearer, at least to me. But there could be _A LOT_ of
power going into those beasts, I question the wisdom of pulling the
pots out of the circuit entirely.

Peter Wieck
Wyncote, PA


Peter, what you have done is equivalent to setting the pots to Max Increase.
This is the correct position for the pots (you also need just a slight
increase in the treble control), if you want a totally FLAT response. AR
did NOT recommend this setting back in 1968, because at that time all the
record companies were enhancing high frequencies to compensate for the poor
audio equipment in the general market.

Peter, you have accomplished something else, however, which is very good.
Specifically, you have totally by-passed the pot wiper!! That wiper because
of age and dissimilar metals corrodes and that corrosion reduces effective
energy sent to the drivers.

You cannot do what I did, Peter, without testing the resulting balance.
That is, with the pots out the drivers become so sensitive and that
sensitivity is over such a broad band, that you would have a very difficult
time bringing the sound back into balance. You could NOT do it with tone
controls. You'd have to have a minimum 7 band EQ and even then I have my
doubts.

Now, with a separate amp powering those drivers, it's trivial maintaining
the balance.

Peter, this is why I've been trying to get you to try your tube amps on the
mid/tweeter. There may be a problem with your tube amps, however.

If I'm not mistaken, your tube amps don't tie the shielding on the audio
inputs to chassis ground. If I am correct, you cannot use them with an ss
amp on the woofers without bring out adding a new terminal on the speakers.
In short, I think you are out of luck.

Regards,
Jerry

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Default AR3a/AS103a speakers and the Heathkit AR1500 receiver

John Stone wrote on 10/11/2006:


John, xover frequency is determined primarily by the reactive

components.

Any filter network's turnover frequency is calculated through the values

of
source impedance, the value of reactive components, and the impedance of

the
load. Don't believe me? Then substitute a 100 ohm resistor for the tweeter
and run a sweep of the crossover. I'm sure you'll you'll see a pretty huge
change.


OK, but in this case (16 ohms across 3.2 ohms) the xover frequency is
primarily determined by the reactive components.

I did this by applying a full frequency signal to the mid/tweeter (did
exactly the same for the woofer). So a full frequency and full strength
voltage was applied to the mid/tweeter and I measured the current

actually
going to the drivers. In short, the xovers were performing perfectly.
That is, they were "blocking" (little or no current) was flowing for the
frequencies NOT intended for the respective drivers.


I have read this paragraph over and over, and for the life of me, I can't
figure out what you are talking about. What kind of "full frequency and

full
strength voltage" are you referring to? How do you accurately measure the
crossover response with a "full frequency" signal? Do you have a spectrum
analyzer?


I have a dual trace scope and a 20Hz to 200KHz sine and square wave
generator. With this I can monitor voltage while I'm watching current
flowing in the drivers.

The simplest way to accurately measure the response is to run a
sine sweep and plot the voltage/frequency curve using an rms voltmeter at
the driver terminals. Do it with and without the pot in place an you'll

get
an exact picture of what is happening.
You also keep using the term "current". How, and why are you are measuring
current (amps)?


John, this is really trivial. I put a .4 ohm resistor in series with the
mid/tweeter half of the speaker and watch the voltage drop across it. So as
I'm scanning the frequency spectrum and watching the voltage, I can
simultaneously watch the actual current flowing.

Not my rules. Function of the pots is to balance energy going to the
respective drivers to adjust for room conditions and RECORDINGS. I can
perform exactly the same function with the volume controls.


No you can't. You pulled out 2 pots and substituted them with 1 amplifier
gain control, driving the entire mid/tweeter section. You have removed one
of the pots' key functions, which was to allow shelving of the mid and
tweeter levels individually.


True, accept I always set the tweeter pot to max increase. Actually to
achieve a totally FLAT response both pots should be set to MAX and there
should be a slight increase in treble control.

So for me the only real control was over the mid range (which I set fairly
close to max as well). I still have control over the tweeter using my
treble tone control. If I need more I simply turn it up. If I need less, I
turn it down.

With a single amp, John, you have no where near the control over sound

that
I have. And with harmonics riding on fundamentals, you have no where

near
the headroom that I have.

I have no idea what this means.

As an aside, John, a totally flat response on AR-3a's is achieved with

the
pots at max AND a slight increase in the treble volume control.


Anybody who has actually measured AR3a's as opposed to just reading the AR
literature will tell you this isn't true. Here's an actual real world
measurement of the 3a's:

http://murphyblaster.com/content.php?f=AR3a.html

These measurements are backed up in a post on 8/7 by Dick Pierce to you
regarding the frequency response of the AR3a:


We have asbolutley no idea how the pots were set in this dude's experiments.
Nor do we know how well or what he did when he "restored" his AR-3a's. I
can't believe anyone takes this guy's stuff seriously.

And on top of all that, he mentions a problem in the mid-highs that the pots
would actually help correct.

I much prefer the folks at AR who really knew how to test speakers.
Further, I don't consider this advertising literatu

http://www.classicspeakerpages.net/a...ember_1968.jpg

"No, the reason for this is that Roy Allison and Ed Villchur at AR
decided on a balance that resulted in an overall downward trend
in the speaker's response toward the high end. That was their
choice, for whatever reasons.


Urban legend. Simply not true. Per Ken Kantor:

"Quantifying the high frequency response of a speaker, any speaker, is a
much more complex subject than (almost) anyone wants to think about. Short
sounds can evoke a perceptually different response than longer tones.
Distance from the speaker can have a profound effect, as can placement,
listening position and room acoustics. Even more subtly, the whole idea that
there is one uniquely "correct" frequency response is unjustifiable, as
comforting as it may be. (I believe it to be a residue of the Logical
Positivism that arose in the 1960's as an over-reaction to the magical
thinking of 1950's High End subjectivism. Kind of like now...)

To this day, there is little agreement even between very experienced
professionals about how to properly characterize what "flat" response is. AR
had their methods, (which evolved over the years.) Within the limitations of
those methodologies, AR always tried to make accurate speakers, at least
near the top of their line. "

Further, if you read the other reference, you can see that AR recommended
that folks set the pots at mid point to correct for what the record
companies were doing in 1968.

The midrange efficiency is about
2 db less than the woofer, and the tweeter is another 2-3 dB
less efficient than that. That's what the people of AR designed
it to be." (end quote)

A "slight increase" in the treble control will not achieve a totally flat
response as is clear from the actual response measurements.


So you are saying that the pots should be at flat and we need a more than a
slight increase in treble?? OK, so?

Jerry, your ignorance of even basic loudspeaker design principles is
appalling. If I didn't know better, I'd swear you were joking. The

tweeter
network in the AR3a consists of a single series element; i.e., a 6uf

cap
feeding a load consisting of a tweeter and a 16 ohm tapped resistor.

For
all
intents and purposes, when you run the tweeter pot at full, you simply

have
a tweeter and a 16 ohm resistor in parallel. The crossover frequency is
determined by the value of the series cap AND the impedance of the

load.
Removing that 16 ohm resistor alters the load (increases the

impedance),
which in turn alters the crossover frequency, moving it downward. I'm

quite
sure what you've done IS significant,


My ignorance, huh? John, you spouted a lot of "facts", but not a single
number. Are you lazy, John, or perhaps you don't know how to do the

math.

Let's just see how significant.

DC resistance of tweeter is approx. 3.2 ohms

So with the 16 ohm pot full across - net resistance = 2.67 ohms or a
difference of .53 ohms


Sorry Jerry, but yes, your ignorance, or perhaps just lack of attention to
detail, as again demonstrated above. DC resistance is utterly meaningless

to
this discussion, as the last time I checked, tweeters required AC to

produce
sound. Yet you use resistance interchangeably with impedance as if they

were
one and the same. The "nominal" impedance of a tweeter with 3.2ohm dcr is

4
ohms.


Yep, the reactive component combined with the resistive componet yields an
"effective" Z. Z= 3.2 +jwL

But the resistance components will respond exactly as I stated. There is no
reactive component in the pot.

If you take that nominal impedance in parallel with the 16 ohm pot
(the pot will have an impedance close to 16 ohms given that it is largely
non-inductive) the 2 in parallel yield a resulting impedance of 3.2 ohms.
With the pot totally out, you shift the impedance up by a minimum of 20%.

Real, real significant, John ... huh??


Um, yeah, I'd say by any measure a 20% shift is significant. And in a
previous post, you yourself said so:


John, what are you talking about?? Now whose ignorance is showing?

With the pots out, naturally LESS current flows ... all of the time. So
what?? The end result of that is the speakers have increased in
sensitivity.

Your issue was that we have significantly altered the xover frequency. That
is, taking the pots out causes current to flow MORE at some frequencies than
at others. That is we have a frequency altering impact.

(This is awful trying to create any tables in Usenet, but let's try again
and I'll even use your numbers.) Here we show the current flowing through
the high frequency driver under both conditions:

Z Z I @ 2 v I @ 2 v
Hz Z for Cap w/o pot with pot w/o pot with pot % diff
3,000 8.8 ohms 12.8 12.0 .156 .132 14.7%
4,000 6.6 ohms 10.6 9.8 .188 .163 13.5%
5,000 5.3 ohms 9.3 8.5 .215 .188 12.5%
6,000 4.4 ohms 8.4 7.6 .238 .210 11.6%

John, if we look at the last column, we see that the difference in current
varies by 3% between 3000Hz and 6000Hz

As for the improvement in sensitivity, all I can say it's significant
and very noticable.


Those are YOUR words, Jerry. So which is it? Significant or not? 20% is

way
beyond the impedance tolerance AR specified for the drivers alone, so the
crossover is indeed operating into a significantly different load than
intended, with the resultant shift in xover response as previously stated.


Yes, the speakers (not drivers) are more sensitive and it is significant.
The change in xover frequency is INSIGNIFICANT! See the table above and
show us your proof that this is incorrect (I even used your numbers for
impedance).

More importantly 20% is the MINIMUM shift.


Minimum shift in what? Current doesn't change by 20%. From my table
there is 14.7% more current at 3000 Hz and 11.6% more current flowing at
6,000 for the same applied voltage. Over the frequency range of where the
tweeter operates, my guess is the average increase in current through the
driver will be around 10%.

And, YES, that will make the driver put out more SPL.

In reality, the tweeter (and
midrange) impedance curve is nowhere near flat, and deviates considerably
with frequency. Given that these drivers use no ferrofluid they will

exhibit
a fairly high Q at mechanical resonance ( which I'd estimate around 300Hz
for the mid and 3kHz for the tweeter), yielding an impedance peak at
resonance perhaps double the nominal value. The driver impedance also

rises
gradually with increased frequency, due to the voice coil inductance. So

the
pots were there for 2 reasons: provide level adjustment, and to provide a
measure of impedance stabilization for the crossover. By removing them,

you
have changed things a whole bunch.


John, I don't agree with your conclusion at all. I even calculated the
current flow through the tweeter at 3000Hz both ways. At 3000 Hz there is a
14.7% difference .... @ 4000 hz the difference is 13.5% .... @ 5000 hz the
difference is 12.5% ... @ 6000 hz 11.6%

What the pots did is "pad" the output of these drivers to bring them closer
in line with the woofer. With the pots gone the output is higher.

Tell us, John, do you
think there is a human anywhere ... that could actually hear this
difference?

You said you could hear it yourself, so I'd assume others could as well.

Perhaps your arguments would have some weight, John, if you backed them

up
with the math.


There's plenty of "math" above. And it least its based on correct

parameters
(impedance rather than resistance), which makes your "math" less than
useful.


I re-did the math using your numbers (even though I don't agree with them)
and the result is still the same. No significant change in frequency
dependent current.

Pushing down the crossover frequency puts more strain on the tweeter. Like
it or not, those tweeters were notorious for marginal power handling
ability. A.75in voice coil on a paper former with no ferrofluid cannot

take
much power without burning out.


John, your argument bears weight if I removed the pots and single amped. I
don't! I adjust the voltage delivered to the mid/tweeter section with my
voilume controls. This half of the AR-3a's are NOW more sensitive, so I
send LESS voltage. The speakers simply require less voltage and that's part
of where I get more headroom.

Double check my math if you like, John, but there is simply is NO
significant change in frequency dependent current flowing. There is a
change that varies by 3% over the range of 3000 to 6000 hz. I don't
consider that significant and I don't believe there is a human on this earth
that can hear that difference.

Jerry, as others here have told you countless times, nothing is to be

gained
in your configuration compared to a single amp, as long as the driving
amplifier has adequately low output impedance and sufficient undistorted
power to drive the speakers to the desired level.


It's possible that no such amplifier exists. Some could better than others,
but the AR-3a has a very complex impedance map. I don't know if any
amplifier can perform over the entire range ... as well as an amp over a
much narrower, easier and better behave impedance range.

Further, the amp driving the mid/tweeter is operating at a completely
different level in terms of both voltage and current. In addition, it isn't
burdened at all with fundamentals. Whenever we mix fundamentals with
harmonics we create the opportunity for IM distortion. When these
frequencies are NOT mixed that opportunity is greatly reduced.

Virtually all competent
amplifiers act as voltage sources, and within the limit of their power
output capability, perform largely independent of the load they see.


I don't believe that for a minute. One requires enormous "faith" to assume
the simply because an amp can produce a nice wave form open loop, it will
perform the same when driving a dynamic speaker system. I believe that much
is going on inside an amp under continually varying loads and very complex
music signals. I believe they are anything, but pure voltage sources.

The AR3a designers knew this and designed the speakers accordingly. You

have
never provided a shred of proof that your configuration solves any problem
that couldn't be solved with a single more powerful amplifier. To now
extend this argument to ALL amplifiers, regardless of power, is absurd and
based totally on unsubstantiated generalizations about power amplifier
behavior. Yes, by using 2 amps, you can now adjust the mid and tweeter
outputs to levels above the woofer, but that was never the intent of the
original design.


I've demonstrated that the impedance seen by two amps is radically different
than the impedance seen by a single amp. The impedance seen by two amps is
much, much more stable. In an single map with widely varying impedance by
frequency, we'll see widely fluctuating current flows over the frequency
range ... at the same voltage. This "instability" just has to have
ramifications.

Each amp in a bi-amp of the AR-3a's just has a much, much easier job to do
and in my opinion, will always out perform a single amp. Now at the same
time that I say this, I want to go on the record that I don't believe this
is the case with every speaker system. I have bi-amped a fairly efficient
JBL system and while I can hear some minor difference, they are minor. I
believe the AR-3a benefits greatly from bi-amping because of the very
difficult frequency dependent load it presents to any single amp.

I've demonstrated that enormous headroom can be gained in the mid-tweeter
amp. Then others have argued that even if clipping occurs in the woofer
amp, the "harmful" harmonics are totally isolated from the mid-range and
tweeter.

As for adjusting the mid/tweeter above the woofer, I never claimed that as a
benefit. It's true I can, but I don't.

As for my amps, after looking over the facts ... I believe I have far,

far
more voltage headroom than anyone with a single amp.


I know what you believe. Now, please explain the basis of this belief.

Let's
see your experiments or charts showing your "biamp" configuration with
ancient low powered amplifiers of dubious quality having far more headroom
than a single 250 watt/ch amplifier with total stability down to 2 ohms.
Your claim, your proof.


First of all, I don't believe any claims of stable down to 2 ohms. I have
some pretty large 2 ohm resistors. Wanna burn out your amp?

Next, my typical voltage on the mid/tweeter amp is around 2 volts for fairly
loud music. My rails are at 40 volts. Now look at the the voltages of your
amp with fundamentals and see what your real headroom is.

Which brings up another question: If using separate amps gave such a

huge
improvement, why didn't AR suggest it in the first place?


I don't believe at the time that the AR's were developed, people were

even
experimenting with bi-amping for home use.

I don't believe back in 1968 ANYBODY was thinking about bi-amping for

home
use, but please share a reference showing that I am wrong. Quote any
article from 1968 or earlier recommending bi-amping in the home.


Having lived during that era, I can assure you that biamping was indeed
being done in home systems well before 1968. Ever hear of the Marantz 3?
It's an electronic crossover from the '50s. In fact, even Heathkit offered
one called the XO-1 which also dates back well before 1968. There were
others.


I never heard of any of this and was a Heathkit customer, so I can't imagine
it was very popular.

Regards,
Jerry


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Peter Wieck Peter Wieck is offline
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Default AR3a/AS103a speakers and the Heathkit AR1500 receiver

Jerry:

I keep a 10-band equalizer, but at the same time I question the value
of installing such a unit in other than extreme cases, especially to
replace a function that is both effective and already in place, the OEM
crossover. Also, keep in mind that that OEM crossover was developed
over some 20 years of production of this particular speaker and its
children. (3, 3a, LST, 11, 10pi) and does a pretty good job. Note also
that none of the aftermarket 'acquired wisdom' on these speakers
suggests that the pots should be removed from the circuit, a couple of
contributors even caution against it. Apart from all that, I used the
term "more-or-less" when I mentioned crossover function. There is some
marked effect on its response, making your balance yet more
"tetchy"(but not impossible).

Once again, I urge you to borrow, beg, steal a brute-force amp and try
it with the pots bypassed but the fixed elements LEFT IN PLACE. This
adds back the element of protection that the pots provided, brings back
the full response of the crossover to its original intention, and still
allows you to play with the overall response with your pre-amp tone
controls and/or an equalizer.

On a purely techical level, I also question your contention that by
simply turning down the Volume Control (and therefore reducing the
potential for clipping), you are increasing headroom to the mid/tweet.
You are increasing both the simple resistance across the voice-coil and
the overall impedance (of course). This means that you will require
_more_ energy out of the amplifier to make the same voltage at the
speakers (watts drop as nominal load increases for most solid-state
devices). So what you gain at one end, you lose at the other. However
in this case, the speaker VCs are now acting as the system fuse... Pre
Ferro-Fluid AR domes are not so good at that... allow me to rephrase:
they are very good at being fuses, and blowing.

Energy Dissipation: You may think that the most energy going into a
speaker goes into the woofer. Not really. Take a simple operatic piece,
one of my favorites: Handel's "Let the Bright Seraphim" and the
test-piece I used for my biamping experiments. Although there is _some_
bass on that piece (kettledrums, and so forth), even those elements are
mostly above the crossover point to the woofer. The P/A on that piece
is well over 10dB, approaching 20dB. So at some of the loudest
passages, at least 70% (probably more) of the total energy delivered to
the speakers is above the crossover point to the woofers. I am not
saying that you are going to clip, but I am saying that you are sending
a bunch of energy (heat) into those speakers with all the designed-in
protections removed, such as they were. Bi-amped or otherwise. Not that
I am arguing with your scope and other instruments, but just do a
simple band-pass reading of the amp(s) output and see where the
frequencies (and associated energy levels) are.

Just some thoughts. What you have done seems to work for you, but as
much as you have urged me to try things, I also urge you to do the
same. I also really hope you have fused your speakers, the AR factory
had quite a bit of literature on fusing, and specified quite-expensive
low-loss fuses, not the little glass-bits that most use.

Peter Wieck
Wyncote, PA
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[email protected] dpierce@cartchunk.org is offline
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Default AR3a/AS103a speakers and the Heathkit AR1500 receiver

Jerry wrote:
John Stone wrote on 10/11/2006:


John, xover frequency is determined primarily by the reactive

components.

Any filter network's turnover frequency is calculated through
the values of source impedance, the value of reactive
components, and the impedance of the
load. Don't believe me? Then substitute a 100 ohm resistor
for the tweeter and run a sweep of the crossover. I'm sure
you'll you'll see a pretty huge change.


OK, but in this case (16 ohms across 3.2 ohms) the xover frequency is
primarily determined by the reactive components.


False. Completely false, for several reasons.

First, especially in the case of the high-pass function for
the tweeter crossover and the low-pass function for the
midrange crossover, these are first-order networks, and
the crossover frequency is an equal function of BOTH
the series reactance AND the driver impedance.

Second, you keep making a simplifying assumption
that the drivers are essentially equivalent to these
3.2 ohm resistors, and the most assuredly ARE NOT.
Take, for instance, the fact that the tweeter impedance
shows a significant rise above it's DC resistance at the
fundamental mechanical resonance, which is around
2500 Hz. The impedance reaches, IIR, a high of about
9-10 ohms at that frequency. Under this circumstance,
the presence or absence of that 16 ohm shunt resistance
makes a SUBSTANTIAL difference in the response of
the crossover output below cutoff, and that has an
equally substantial effect on the amount of signal fed to
the tweeter below cutoff. This changes the frequency
response of the speaker as a whole, increases the
distortion output of the tweeter and reduces its overall
power handling.

More specifically, the impedance presented to the tweeter
crossover at about 2.5 kHz with and without the shunt
resistance of the pot is 6 ohms vs about 9.5 ohms.

Thirdly, you keep focusing on one VERY narrow aspect
of the crossover response, the "crossover frequency" while
ignoring totally the much BIGGER issue of the overall
crossover transfer function. IN just the case of the tweeter,
not only is the crosover frequency changed rather substantially
(assuming the "crossover frequency, you mean the -3dB re
passband level frequency, which is moved DOWN by a third
of an octave), but you have also substantially changed the
shape of the crossover response. Among other things, you
have introduced a substantial hump in the response around
2.5 kHz, leading to the problems outlined above.

No you can't. You pulled out 2 pots and substituted them with 1 amplifier
gain control, driving the entire mid/tweeter section. You have removed one
of the pots' key functions, which was to allow shelving of the mid and
tweeter levels individually.


True, accept I always set the tweeter pot to max increase. Actually to
achieve a totally FLAT response both pots should be set to MAX and there
should be a slight increase in treble control.

So for me the only real control was over the mid range (which I set fairly
close to max as well). I still have control over the tweeter using my
treble tone control. If I need more I simply turn it up. If I need less, I
turn it down.

With a single amp, John, you have no where near the control over sound

that
I have. And with harmonics riding on fundamentals, you have no where

near
the headroom that I have.

I have no idea what this means.

As an aside, John, a totally flat response on AR-3a's is achieved with

the
pots at max AND a slight increase in the treble volume control.


Anybody who has actually measured AR3a's as opposed to just reading the AR
literature will tell you this isn't true. Here's an actual real world
measurement of the 3a's:

http://murphyblaster.com/content.php?f=AR3a.html

These measurements are backed up in a post on 8/7 by Dick Pierce to you
regarding the frequency response of the AR3a:


We have asbolutley no idea how the pots were set in this dude's experiments.
Nor do we know how well or what he did when he "restored" his AR-3a's. I
can't believe anyone takes this guy's stuff seriously.

And on top of all that, he mentions a problem in the mid-highs that the pots
would actually help correct.

I much prefer the folks at AR who really knew how to test speakers.
Further, I don't consider this advertising literatu

http://www.classicspeakerpages.net/a...ember_1968.jpg

"No, the reason for this is that Roy Allison and Ed Villchur at AR
decided on a balance that resulted in an overall downward trend
in the speaker's response toward the high end. That was their
choice, for whatever reasons.


Urban legend. Simply not true. Per Ken Kantor:

"Quantifying the high frequency response of a speaker, any speaker, is a
much more complex subject than (almost) anyone wants to think about. Short
sounds can evoke a perceptually different response than longer tones.
Distance from the speaker can have a profound effect, as can placement,
listening position and room acoustics. Even more subtly, the whole idea that
there is one uniquely "correct" frequency response is unjustifiable, as
comforting as it may be. (I believe it to be a residue of the Logical
Positivism that arose in the 1960's as an over-reaction to the magical
thinking of 1950's High End subjectivism. Kind of like now...)

To this day, there is little agreement even between very experienced
professionals about how to properly characterize what "flat" response is. AR
had their methods, (which evolved over the years.) Within the limitations of
those methodologies, AR always tried to make accurate speakers, at least
near the top of their line. "


Nowhere in this quote does Mr. Kantor in any way refute what
I said, nor does Mr. Kantor sdtate or even infer that the AR3a's
had anechoically flat response. Indeed, the AR3a literature to
which you refer show clearly THEY DID NOT HAVE ANECHOICALLY
flat response and never did they claim that it did.

Further, if you read the other reference, you can see that AR
recommended that folks set the pots at mid point to correct
for what the record companies were doing in 1968.


The midrange efficiency is about
2 db less than the woofer, and the tweeter is another 2-3 dB
less efficient than that. That's what the people of AR designed
it to be." (end quote)

A "slight increase" in the treble control will not achieve a totally flat
response as is clear from the actual response measurements.


So you are saying that the pots should be at flat and we need a more than a
slight increase in treble?? OK, so?

Jerry, your ignorance of even basic loudspeaker design principles is
appalling. If I didn't know better, I'd swear you were joking. The

tweeter
network in the AR3a consists of a single series element; i.e., a 6uf

cap
feeding a load consisting of a tweeter and a 16 ohm tapped resistor.

For
all
intents and purposes, when you run the tweeter pot at full, you simply
have
a tweeter and a 16 ohm resistor in parallel. The crossover frequency is
determined by the value of the series cap AND the impedance of the

load.
Removing that 16 ohm resistor alters the load (increases the

impedance),
which in turn alters the crossover frequency, moving it downward. I'm
quite
sure what you've done IS significant,

My ignorance, huh? John, you spouted a lot of "facts", but not a single
number. Are you lazy, John, or perhaps you don't know how to do the

math.

Let's just see how significant.

DC resistance of tweeter is approx. 3.2 ohms

So with the 16 ohm pot full across - net resistance = 2.67 ohms or a
difference of .53 ohms


Sorry Jerry, but yes, your ignorance, or perhaps just lack of attention to
detail, as again demonstrated above. DC resistance is utterly meaningless

to
this discussion, as the last time I checked, tweeters required AC to

produce
sound. Yet you use resistance interchangeably with impedance as if they

were
one and the same. The "nominal" impedance of a tweeter with 3.2ohm dcr is

4
ohms.


Yep, the reactive component combined with the resistive componet yields an
"effective" Z. Z= 3.2 +jwL

But the resistance components will respond exactly as I stated. There is no
reactive component in the pot.


You utterly and completely failed or igored what he said.
The simply point is that the drivers DO NOT present a resistive
load equal to the DC resistance of the voice coils to the
crossover, and any conclusion based on this assumption
are simply incorrect.

With the pots out, naturally LESS current flows ... all of the time. So
what?? The end result of that is the speakers have increased in
sensitivity.


False, the SENSITIVITY, as defined by the loudspeaker industry
IS THE SAME.

Your issue was that we have significantly altered the xover
frequency.


No, his issues, and your problem, is that you have changed
THE CROSSOVER RESPONSE. The crossover frequency is
merely one aspect of that repsonse. You have chosen, at your
peril, to ignore the bigger issue.

is, taking the pots out causes current to flow MORE at
some frequencies than
at others. That is we have a frequency altering impact.


If you want to play in the realm of loudspeaker engineering,
how about using the proper terminology and concepts, please?

You HAVE change the transfer function of the network by what you
did. You HAVE altered the frequency response as a result. This
is true whether you want to admit it or know it or not.

Yes, the speakers (not drivers) are more sensitive and it is significant.
The change in xover frequency is INSIGNIFICANT!


THE CROSSOVER FREQUENCY IS NOT THE ISSUE! YOU HAVE
CHANGED THE OVERALL REPONSE OF THE CROSSOVER, EVEN
IF THE CROSSOVER FREQUENCY REMAINS THE SAME.

Minimum shift in what? Current doesn't change by 20%. From my table
there is 14.7% more current at 3000 Hz and 11.6% more current flowing at
6,000 for the same applied voltage. Over the frequency range of where the
tweeter operates, my guess is the average increase in current through the
driver will be around 10%.


STOP LOOKING AT THE NARROW ISSUE OF CURRENT AND
CROSSOVER FREQUENCY.

Try this: Jerry, youy're staring at a single tree. Are you aware
there's a bug forest that you have igored?

In reality, the tweeter (and
midrange) impedance curve is nowhere near flat, and deviates considerably
with frequency. Given that these drivers use no ferrofluid they will

exhibit
a fairly high Q at mechanical resonance ( which I'd estimate around 300Hz
for the mid and 3kHz for the tweeter), yielding an impedance peak at
resonance perhaps double the nominal value. The driver impedance also

rises
gradually with increased frequency, due to the voice coil inductance. So

the
pots were there for 2 reasons: provide level adjustment, and to provide a
measure of impedance stabilization for the crossover. By removing them,

you
have changed things a whole bunch.


John, I don't agree with your conclusion at all. I even calculated the
current flow through the tweeter at 3000Hz both ways. At 3000 Hz there is a
14.7% difference .... @ 4000 hz the difference is 13.5% .... @ 5000 hz the
difference is 12.5% ... @ 6000 hz 11.6%


Once again, you ignored what he said, and you ignored the physical
reality of what's going on with the drivers.

You failed completely to address his point:

"In reality, the tweeter (and midrange) impedance curve is
nowhere near flat, and deviates considerably with
frequency. Given that these drivers use no ferrofluid they will
exhibit a fairly high Q at mechanical resonance ( which I'd
estimate around 300Hz for the mid and 3kHz for the tweeter),
yielding an impedance peak at resonance perhaps double
the nominal value. The driver impedance also rises gradually
with increased frequency, due to the voice coil inductance.

Perhaps your arguments would have some weight, John,
if you backed them up with the math.


He did. You chose, perhaps conveniently, to ignore it.

It's possible that no such amplifier exists.


They do. They're quite common and affrodable. The Heath AR1500
most assuredly isn't one of them.

Some could better than others,


And almost all are better than what you're using, with all due
respect, but you've reduced your experiment to one based
on the lowest common denominator of 30 years ago. You
have an obvious problem with your am,plifier, and you've
done absolutely everything EXCEPT fix the problem: the
amplifier.

but the AR-3a has a very complex impedance map.


No, it most assuredly does not. It's impedance is low,
to be sure, but it is largely resistive in nature. Above its
low-frequency resonance of about 43 Hz, the impedance
is, in fact, quite tame.

The fact that YOU have decided to stick with an amplifier
that seems to be uniquely incapable of handling one of the
more common speakers of the era is no reason to assume
that the faults and warts or your AR1500 is generally applicable.

I don't know if any
amplifier can perform over the entire range


You should get out a lot more. THere are literally hundreds of
such that will do what you are trying to do with your ancient
AR1500 MUCH better than the AR1500 ever good on its best
day.

Further, the amp driving the mid/tweeter is operating at a completely
different level in terms of both voltage and current. In addition, it isn't
burdened at all with fundamentals. Whenever we mix fundamentals with
harmonics we create the opportunity for IM distortion.


When you mix fundamentals with harmonics AND they generate
intermodulation products, those products ARE AT THE SAME
FREQUENCIES AS THE FUNDAMENTAL AND HARMONICS.

When these
frequencies are NOT mixed that opportunity is greatly reduced.


But, even in your scheme, they are, because you have completely
failed to priovide a sufficiently sharp crossover to eliminate one
from the other. Further, the largest producer of distortion products
is the woofer, and it will produce them whether or not you've multi
amped or not.

Virtually all competent
amplifiers act as voltage sources, and within the limit of their power
output capability, perform largely independent of the load they see.


I don't believe that for a minute. One requires enormous "faith" to assume
the simply because an amp can produce a nice wave form open loop, it will
perform the same when driving a dynamic speaker system.


Uh, no. An audio amplifier without a load IS NOT 'OPEN LOOP."

Please learn what the terminology measn before you bandy it about
so.

I believe that much
is going on inside an amp under continually varying loads and very complex
music signals. I believe they are anything, but pure voltage sources.


My, god, Jerry, do you really NOT have any idea what "pure
voltage source" means. Are you at all familiar with the
concept of Thevenin equivalents?

Mr. Stone is talking about fundamental concepts of electrical
engineering which you are twisting into so much gobbledygook.

The impedance seen by two amps is much, much more stable.


No, the impedance is NOT more or less "stable." Please
define what "stable impedance" mean, in your view.

In an single map with widely varying impedance by
frequency, we'll see widely fluctuating current flows over the frequency
range ... at the same voltage. This "instability" just has to have
ramifications.


No, it does not. Your fundamental premise is highly flawed.

Each amp in a bi-amp of the AR-3a's just has a much, much easier job to do
and in my opinion, will always out perform a single amp.


That's your opinion, and you're entitled to it. But no matter
how strongly held, your opinion is still opinion and not
fact.

There have been a number of people involved in this
conversation, any one of whom has DECADES more
professionial experiuence than you have, yet you have
chosen to simply plow forward, ignoring facts, ignoring
reality, and stating your opinions as fact.

I
believe the AR-3a benefits greatly from bi-amping because of the very
difficult frequency dependent load it presents to any single amp.


NO, IT PRESENTS A DIFFICULT LOAD TO YOUR AR1500, WHICH
CAN'T GET OUT OF ITS OWN WAY.

If your amp is BUSTED, which you have provided ample evidence
that it is, the solution is to REPLACE THE AMP.

I've demonstrated that enormous headroom can be gained in the mid-tweeter
amp. Then others have argued that even if clipping occurs in the woofer
amp, the "harmful" harmonics are totally isolated from the mid-range and
tweeter.


No, you have misread, misconstrued, mirunderstood and
misrepresented that they are "totally" isolate. They most
assuredly ARE NOT, and your particular "solution" is about
as far from what you are claiming as one could imagine.

I know what you believe. Now, please explain the basis of this belief.

Let's
see your experiments or charts showing your "biamp" configuration with
ancient low powered amplifiers of dubious quality having far more headroom
than a single 250 watt/ch amplifier with total stability down to 2 ohms.
Your claim, your proof.


First of all, I don't believe any claims of stable down to 2 ohms. I have
some pretty large 2 ohm resistors.


The wide disparity between your beliefs and opinions and physical
reality have been noted a plenty elsewhere.

Wanna burn out your amp?


Bring it on. I have amplifiers here that are UNDCONDITIONALLY
stable into ANY load, resistive or reactive. ANY load.

Your AR1500 seems to have problems driving one of the more
common speakers of its era. Sorry about that, but the world has
LONG since moved on. Maybe you should, too.

Which brings up another question: If using separate amps gave such a

huge
improvement, why didn't AR suggest it in the first place?

I don't believe at the time that the AR's were developed, people were

even
experimenting with bi-amping for home use.

I don't believe back in 1968 ANYBODY was thinking about bi-amping for

home
use, but please share a reference showing that I am wrong. Quote any
article from 1968 or earlier recommending bi-amping in the home.


Having lived during that era, I can assure you that biamping was indeed
being done in home systems well before 1968. Ever hear of the Marantz 3?
It's an electronic crossover from the '50s. In fact, even Heathkit offered
one called the XO-1 which also dates back well before 1968. There were
others.


I never heard of any of this and was a Heathkit customer, so I can't imagine
it was very popular.


So, once again, YOUR opinon is the same as reality?

What about the Marantz 3, which was sold a decade before
your time frame? What about the Heat XO-1? What about
products from DeCoursey, Crown and others.

What about the AR1-W? which was late '50's/early '60's which
was SPECIFICALLY designed for multi-amped systems? A
VERY common high-end setup at the time was KLH-9's
with AR1W's using the McIntosh electronic crossovers.

The fact that you never heard of them doesn't mean they didn't
exist.

You are either unaware of or have deliberately chosen to
ignore an enormous body of act that contradicts your world
view. Unfortunately, no matter how much you might ignore
or be unaware of, the real worls is still out there, and your
continued tilting against it has done little but squander
any credibility you might have enjoyed.

I mean no insult by this, none whatseoevere, and only use it
necause it is a convenient metaphor, but Mr. Stone (who has
been in the loudspeaker business for a LONG time) myself
(who also enhoys a long and successful career in the business)
and other have been egaging in an excercise akin to teaching
a pig to sing: It's a long, frustrating and fruitless endeavor, and
it only serves to **** off the pig.

There is SO much to learn and know and enjoy about how
loudspeakers work, and you have done yourself a huge
disservice by staking out such a narrowly constructed,
poorly supported and largely technically incorrect position.
The facts and realities of loudspeaker physics are so much
more varied and nuanced and powerful than what your opinions
and what you are unaware of aloow you to experience.

If that satisfies you, then, well, fine, have at it. But while you are
sitting there with your AR1500 and your VERY narrowly limited
experience and view, the rest of the world has moved on. Decades
ago.
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Jerry Jerry is offline
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Default AR3a/AS103a speakers and the Heathkit AR1500 receiver

Peter Wieck wrote on 10/12/2006:

Jerry:

On a purely techical level, I also question your contention that by
simply turning down the Volume Control (and therefore reducing the
potential for clipping), you are increasing headroom to the mid/tweet.
You are increasing both the simple resistance across the voice-coil and
the overall impedance (of course). This means that you will require
_more_ energy out of the amplifier to make the same voltage at the
speakers (watts drop as nominal load increases for most solid-state
devices).


Peter, it's a little confusing (actually it can be a LOT confusing), even
though the impedance without the pots goes UP, the actual current flowing
through the driver goes UP. Please remember that the pots "steal current"
yet produce no sound.

So for exactly the same voltage (with and without pots), there is more
current flowing through the driver when the pots are completely removed.
Since Watts = I * I * R Power consumed in the driver is approx 25%
higher and it follows with more power we get more SPL.

So for the same voltage, we get approx 25% more SPL and this would make the
sound far, far too bright. So we must reduce the voltage coming out of the
amp by turning down the volume.

Lower voltage for the same sound gets us further away from the rail voltages
..... hence more headroom.

So what you gain at one end, you lose at the other.


There is NO losss only a gain in sensitivity of the speakers (the
sensitivity of the raw drivers, of course, remains unchanged).

However in this case, the speaker VCs are now acting as the system fuse...

Pre
Ferro-Fluid AR domes are not so good at that... allow me to rephrase:
they are very good at being fuses, and blowing.


Ok, for the same voltage we have approximately 25% more power dissipated in
the voice coil. Over driving is easier ... admittley, but that's why I use
a quality, low power amp (approx. 30 -35 watts). This amp has no where
near the power of the AR1500, but even at 30 watts, it could still easily
fry the mid and the tweeter. However to achieve that kind of power
requires the volume control to be way, way over on the right hand side. I
rarely advance beyond 9 o'clock.

Energy Dissipation: You may think that the most energy going into a
speaker goes into the woofer. Not really. Take a simple operatic piece,
one of my favorites: Handel's "Let the Bright Seraphim" and the
test-piece I used for my biamping experiments. Although there is _some_
bass on that piece (kettledrums, and so forth), even those elements are
mostly above the crossover point to the woofer. The P/A on that piece
is well over 10dB, approaching 20dB. So at some of the loudest
passages, at least 70% (probably more) of the total energy delivered to
the speakers is above the crossover point to the woofers.


Peter, I seriously doubt your numbers. It's more complicated than just the
ratio of frequencies. The low frequencies require far, far more power to
reproduce, so even though you don't hear much low frequency, what you do
hear requires plenty of power.

Peter, the only way to understand this better is to watch the current
flowing to the respective halves. You'd be surprised by how much current
goes to woofer ... even for instruments we consider "altos".

I am not
saying that you are going to clip, but I am saying that you are sending
a bunch of energy (heat) into those speakers with all the designed-in
protections removed, such as they were.


The pots really aren't protection, Peter. Yes, they siphon off 25% of the
current, but you can still over drive. Their real function is "padding" to
bring the SPL from the various drivers somewhat "in line".

Bi-amped or otherwise. Not that
I am arguing with your scope and other instruments, but just do a
simple band-pass reading of the amp(s) output and see where the
frequencies (and associated energy levels) are.


I have and the vast majority of energy goes to the woofer ... by a lot!

Just some thoughts. What you have done seems to work for you, but as
much as you have urged me to try things, I also urge you to do the
same. I also really hope you have fused your speakers, the AR factory
had quite a bit of literature on fusing, and specified quite-expensive
low-loss fuses, not the little glass-bits that most use.

Peter Wieck
Wyncote, PA


My amp has fuses, however, I doubt they'd protect the drivers. The AR
literature is OK, except I would have to reduce everything by approx. 12%.

Regards,
Jerry


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