[Gib]

Hi,
I've inherited my father's old 10" Tannoys (in the Tannoy vented
enclosures). They still sound good, but I've noticed that there is an
imbalance between the two speakers. One sounds a bit louder, (it
could be just a difference in the treble range) and swapping the
source leads, or swapping the speaker leads makes no difference. The
effect is confirmed with mono source - the sound does not seem to come
from the midpoint of the speakers. I don't have access to proper
testing gear, but I do have a multimeter and a basic understanding of
electronics.

I'm wondering what sort of testing sequence I can follow. I have
checked that the two voice coils on the lower output unit are intact,
with DC resistances of about 8.2 and 4.4 ohms on the tweeter and bass
respectively, so it isn't an obvious driver issue (I would have heard
the loss of sound quality in any case). Now I'm thinking about the
crossover unit. Can I perform simple ohmmeter tests on the crossover,
or will any deterioration only show up in AC? I guess the next
question is should I just go ahead and replace some crossover
components (capacitors) since these are now about 40 year old.

Thanks for any suggestions.

Gib

[Harry Lavo]

"Gib" wrote in message
...
Hi,
I've inherited my father's old 10" Tannoys (in the Tannoy vented
enclosures). They still sound good, but I've noticed that there is an
imbalance between the two speakers. One sounds a bit louder, (it
could be just a difference in the treble range) and swapping the
source leads, or swapping the speaker leads makes no difference. The
effect is confirmed with mono source - the sound does not seem to come
from the midpoint of the speakers. I don't have access to proper
testing gear, but I do have a multimeter and a basic understanding of
electronics.

I'm wondering what sort of testing sequence I can follow. I have
checked that the two voice coils on the lower output unit are intact,
with DC resistances of about 8.2 and 4.4 ohms on the tweeter and bass
respectively, so it isn't an obvious driver issue (I would have heard
the loss of sound quality in any case). Now I'm thinking about the
crossover unit. Can I perform simple ohmmeter tests on the crossover,
or will any deterioration only show up in AC? I guess the next
question is should I just go ahead and replace some crossover
components (capacitors) since these are now about 40 year old.

Thanks for any suggestions.

Gib

I'd leave the electronics alone for now, and buy either a test CD (from
Stereophile or Radio Shack) or test LP and use your ears and the test disk
to record/track frequency response (they all have such a test, intended for
just such purpose, on them). My suspicion is that you will find a high
frequency rolloff in one, most likely due to a "dead" horn tweeter (which
will be in the middle of the speaker). Once you have detemined if this is
the case or not, you can figure out what to do next.

[Gib]

Hi Harry,
Meanwhile I had a look at the crossover box, and noticed some
deformation of the plastic consistent with heating. Upon opening it
up I found that the two resistors on the edge of the PCB (5 and 10
ohms) have been very hot. Right next to these resistors on the other
side is a capacitor, 3.3 uF from the Tannoy circuit diagram.
Interestingly the crossover shown on Troels Gravesen's site
www.troelsgravesen.dk/Tannoy_IIILZ.htm has 3.3 uF electrolytics, but
these capacitors in my crossover are not electrolytic. In any case
the one next to the resistors shows signs of having been exposed to
high temperatures, and it could well have suffered. By the way, I'm
confident that the tweeter is not dead - the speaker sounds
reasonable, not totally deficient in treble. So I will replace the
3.3 uF capacitor, and while I'm at it I'm inclined to replace the 25
uF and 8 uF electrolytics. I have to decide whether to stick with
electrolytics or to go with a more expensive option (if one is
available).

The test CD or LP, by the way, is an excellent idea.

Cheers
Gib

[Bill Noble[_2_]]

You can replace all of those capacitors with non-electrolytics, these are
not large values - but the replacements will be physically larger. If you
select 50 volt capacitors you will have plenty of voltage margin. There are
claims that different dielectric materials affect sound quality - I don't
know how this plays out in crossover networks though. Capacitors are
cheap - so it may be worth some experimenting - try polypropelene, mylar,
maybe a oil type motor run capacitor - see if you hear a difference, and use
what you like

"Gib" wrote in message
...
Hi Harry,
Meanwhile I had a look at the crossover box, and noticed some
deformation of the plastic consistent with heating. Upon opening it
up I found that the two resistors on the edge of the PCB (5 and 10
ohms) have been very hot. Right next to these resistors on the other
side is a capacitor, 3.3 uF from the Tannoy circuit diagram.
Interestingly the crossover shown on Troels Gravesen's site
www.troelsgravesen.dk/Tannoy_IIILZ.htm has 3.3 uF electrolytics, but
these capacitors in my crossover are not electrolytic. In any case
the one next to the resistors shows signs of having been exposed to
high temperatures, and it could well have suffered. By the way, I'm
confident that the tweeter is not dead - the speaker sounds
reasonable, not totally deficient in treble. So I will replace the
3.3 uF capacitor, and while I'm at it I'm inclined to replace the 25
uF and 8 uF electrolytics. I have to decide whether to stick with
electrolytics or to go with a more expensive option (if one is
available).

The test CD or LP, by the way, is an excellent idea.

Cheers
Gib

[Gib]

Thanks Bill. In fact the range of capacitors available here (NZ) is
very limited, and they're not cheap. The best source here in Auckland
doesn't have 25 uF @50v, the closest is 2*10 uF + 4.7 uF, all at 160v
(i.e. big), and I have to buy a 5-pack of each size. I was able to
get 3.3 and 8 (actually 8.2) in non-electrolytic, some sort of poly.
My interim plan is to replace the 25 with an electrolytic, and order a
non-electrolytic replacement from overseas if necessary. Is there any
advantage to using a bipolar electrolytic?

Cheers
Gib

On Oct 12, 4:12=A0am, "Bill Noble" wrote:
You can replace all of those capacitors with non-electrolytics, these are
not large values - but the replacements will be physically larger. =A0If =
you
select 50 volt capacitors you will have plenty of voltage margin. =A0Ther=
e are
claims that different dielectric materials affect sound quality - I don't
know how this plays out in crossover networks though. =A0Capacitors are
cheap - so it may be worth some experimenting - try polypropelene, mylar,
maybe a oil type motor run capacitor - see if you hear a difference, and =
use
what you like

"Gib" wrote in message

...

Hi Harry,
Meanwhile I had a look at the crossover box, and noticed some
deformation of the plastic consistent with heating. =A0Upon opening it
up I found that the two resistors on the edge of the PCB (5 and 10
ohms) have been very hot. =A0Right next to these resistors on the other
side is a capacitor, 3.3 uF from the Tannoy circuit diagram.
Interestingly the crossover shown on Troels Gravesen's site
www.troelsgravesen.dk/Tannoy_IIILZ.htmhas 3.3 uF electrolytics, but
these capacitors in my crossover are not electrolytic. =A0In any case
the one next to the resistors shows signs of having been exposed to
high temperatures, and it could well have suffered. =A0By the way, I'm
confident that the tweeter is not dead - the speaker sounds
reasonable, not totally deficient in treble. =A0So I will replace the
3.3 uF capacitor, and while I'm at it I'm inclined to replace the 25
uF and 8 uF electrolytics. =A0I have to decide whether to stick with
electrolytics or to go with a more expensive option (if one is
available).

The test CD or LP, by the way, is an excellent idea.

Cheers
Gib

[Harry Lavo]

"Gib" wrote in message
...
Hi Harry,
Meanwhile I had a look at the crossover box, and noticed some
deformation of the plastic consistent with heating. Upon opening it
up I found that the two resistors on the edge of the PCB (5 and 10
ohms) have been very hot. Right next to these resistors on the other
side is a capacitor, 3.3 uF from the Tannoy circuit diagram.
Interestingly the crossover shown on Troels Gravesen's site
www.troelsgravesen.dk/Tannoy_IIILZ.htm has 3.3 uF electrolytics, but
these capacitors in my crossover are not electrolytic. In any case
the one next to the resistors shows signs of having been exposed to
high temperatures, and it could well have suffered. By the way, I'm
confident that the tweeter is not dead - the speaker sounds
reasonable, not totally deficient in treble. So I will replace the
3.3 uF capacitor, and while I'm at it I'm inclined to replace the 25
uF and 8 uF electrolytics. I have to decide whether to stick with
electrolytics or to go with a more expensive option (if one is
available).

The test CD or LP, by the way, is an excellent idea.

Cheers
Gib

Sounds like you are right on it. Do those things, and if it still sounds
funny, go to the test disk.

[g]

On Oct 11, 9:35=A0pm, Gib wrote:
Thanks Bill. =A0In fact the range of capacitors available here (NZ) is
very limited, and they're not cheap. =A0The best source here in Auckland
doesn't have 25 uF @50v, the closest is 2*10 uF + 4.7 uF, all at 160v
(i.e. big), and I have to buy a 5-pack of each size. =A0I was able to
get 3.3 and 8 (actually 8.2) in non-electrolytic, some sort of poly.
My interim plan is to replace the 25 with an electrolytic, and order a
non-electrolytic replacement from overseas if necessary. =A0Is there any
advantage to using a bipolar electrolytic?

Cheers
Gib

On Oct 12, 4:12=3DA0am, "Bill Noble" wrote:

You can replace all of those capacitors with non-electrolytics, these a=
re
not large values - but the replacements will be physically larger. =3DA=
0If =3D
you
select 50 volt capacitors you will have plenty of voltage margin. =3DA0=
Ther=3D
e are
claims that different dielectric materials affect sound quality - I don=
't
know how this plays out in crossover networks though. =3DA0Capacitors a=
re
cheap - so it may be worth some experimenting - try polypropelene, myla=
r,
maybe a oil type motor run capacitor - see if you hear a difference, an=
d =3D
use
what you like

"Gib" wrote in message

...

Hi Harry,
Meanwhile I had a look at the crossover box, and noticed some
deformation of the plastic consistent with heating. =3DA0Upon opening=
it
up I found that the two resistors on the edge of the PCB (5 and 10
ohms) have been very hot. =3DA0Right next to these resistors on the o=
ther
side is a capacitor, 3.3 uF from the Tannoy circuit diagram.
Interestingly the crossover shown on Troels Gravesen's site
www.troelsgravesen.dk/Tannoy_IIILZ.htmhas3.3 uF electrolytics, but
these capacitors in my crossover are not electrolytic. =3DA0In any ca=
se
the one next to the resistors shows signs of having been exposed to
high temperatures, and it could well have suffered. =3DA0By the way, =
I'm
confident that the tweeter is not dead - the speaker sounds
reasonable, not totally deficient in treble. =3DA0So I will replace t=
he
3.3 uF capacitor, and while I'm at it I'm inclined to replace the 25
uF and 8 uF electrolytics. =3DA0I have to decide whether to stick wit=
h
electrolytics or to go with a more expensive option (if one is
available).

The test CD or LP, by the way, is an excellent idea.

Cheers
Gib

A polarized cap will NOT work. They must be bipolar. You can also wire
polarized caps back to back to form one. I would suggest getting a
cheap cap tester and measure all the caps, and resistors. Substitution
other caps for electrolytics can cause problems. the thing was
designed using electrolytics, so changing values may be required to
get the orginal sound.

This should be in rec.audio.tech.

greg

[[email protected]]

On Oct 10, 7:32=A0pm, Gib wrote:
Hi,
I've inherited my father's old 10" Tannoys (in the Tannoy vented
enclosures). =A0They still sound good, but I've noticed that there is an
imbalance between the two speakers. =A0One sounds a bit louder, (it
could be just a difference in the treble range) and swapping the
source leads, or swapping the speaker leads makes no difference. =A0The
effect is confirmed with mono source - the sound does not seem to come
from the midpoint of the speakers. =A0I don't have access to proper
testing gear, but I do have a multimeter and a basic understanding of
electronics.

I'm wondering what sort of testing sequence I can follow. =A0I have
checked that the two voice coils on the lower output unit are intact,
with DC resistances of about 8.2 and 4.4 ohms on the tweeter and bass
respectively, so it isn't an obvious driver issue (I would have heard
the loss of sound quality in any case). =A0Now I'm thinking about the
crossover unit. =A0Can I perform simple ohmmeter tests on the crossover,
or will any deterioration only show up in AC? =A0I guess the next
question is should I just go ahead and replace some crossover
components (capacitors) since these are now about 40 year old.

Thanks for any suggestions.

Gib

Sort of a distillation of other advice given he

a) Rebuild your crossovers. Replace _all_ the resistors and _all_ the
capacitors. The caps should be non-polarized, and if you use
electrolytics spend the few extra bucks to get high-temperature units
at 50V or better. Use good resistors as well, rated at-or-better than
what you take out for wattage. If there are controls on the
crossovers, clean them thoroughly. Given the age of these units, all
of the above should be done as a matter of course and won't cost you
very much either.

b) Only then will the test disc do you much good. With what is in
there now your perceived defect could be about anything up to and
including a bad driver - but not for sure.

c) Heed the advice on polarized caps. You can put caps back-to-back
(tied on the negative side, positive side out), but to get 25uF, you
will have to put two 50uF caps back-to-back (in reality given the
tolerances for electrolytics, 47uF (standard size) caps will do fine.

d) The attached website might help: http://www.mouser.com/contact-australia=
/

Peter Wieck
Melrose Park, PA