[John Hall]

I need a pair of more-than-average sensitivity earphones for a body-less
electric practice guitar. It came with a pair by Creative Labs (IIRC),
but I've lost them. The built-in preamp does not put much out. A
separate amp is not suitable as I'm lending/selling this guitar to a
friend who intends using it on a long airline flight.

I thought some Sennheiser earbuds looked OK, but they are specified as
113dB at 1V RMS, which is not the same way other manufacturers specify
theirs, e.g. 106dB 1 mW.

How do we convert Sennheiser's numbers to the 'standard'?
(Being earbuds, I can't just try them in the store).

[Trevor Wilson]

"John Hall" wrote in message
news:YCpGg.14463$tP4.1362@clgrps12...
I need a pair of more-than-average sensitivity earphones for a body-less
electric practice guitar. It came with a pair by Creative Labs (IIRC), but
I've lost them. The built-in preamp does not put much out. A separate amp
is not suitable as I'm lending/selling this guitar to a friend who intends
using it on a long airline flight.

I thought some Sennheiser earbuds looked OK, but they are specified as
113dB at 1V RMS, which is not the same way other manufacturers specify
theirs, e.g. 106dB 1 mW.

How do we convert Sennheiser's numbers to the 'standard'?

**Find out the impedance. BTW: Sennheiser's specs are more honest and
useful, regardless of what other manufacturers may or may not do.


--
Trevor Wilson
www.rageaudio.com.au



--
Posted via a free Usenet account from http://www.teranews.com

[Laurence Payne]

On Mon, 21 Aug 2006 21:31:36 GMT, John Hall
wrote:

I need a pair of more-than-average sensitivity earphones for a body-less
electric practice guitar. It came with a pair by Creative Labs (IIRC),
but I've lost them. The built-in preamp does not put much out. A
separate amp is not suitable as I'm lending/selling this guitar to a
friend who intends using it on a long airline flight.

Is he going to be allowed to take that sort of thing on a flight now?

[John Hall]

Trevor Wilson wrote:

I thought some Sennheiser earbuds looked OK, but they are specified as
113dB at 1V RMS, which is not the same way other manufacturers specify
theirs, e.g. 106dB 1 mW.

How do we convert Sennheiser's numbers to the 'standard'?

**Find out the impedance. BTW: Sennheiser's specs are more honest and
useful, regardless of what other manufacturers may or may not do.

Later, I found a review of Sennheiser PX 100 which says that
Sennheiser's spec: 114dB/1V Eff at 32 ohms is equivalent to 99dB/1mW.

I don't yet understand how the Sennheiser spec is more useful to me,
when trying to compare their products against other brands.

[Arny Krueger]

"Laurence Payne" lpayne1NOSPAM@dslDOTpipexDOTcom wrote in
message news
On Mon, 21 Aug 2006 21:31:36 GMT, John Hall
wrote:

I need a pair of more-than-average sensitivity earphones
for a body-less electric practice guitar. It came with a
pair by Creative Labs (IIRC), but I've lost them. The
built-in preamp does not put much out. A separate amp is
not suitable as I'm lending/selling this guitar to a
friend who intends using it on a long airline flight.

Is he going to be allowed to take that sort of thing on a
flight now?

Indeed. I foresee a resurgence of book reading on airplane flights, at least
until someone figures out how to make a bomb using only a normal book as raw
material.

[Arny Krueger]

"John Hall" wrote in message
news:3XDGg.15641$tP4.11677@clgrps12
Trevor Wilson wrote:

I thought some Sennheiser earbuds looked OK, but they
are specified as 113dB at 1V RMS, which is not the same
way other manufacturers specify theirs, e.g. 106dB 1 mW.

How do we convert Sennheiser's numbers to the
'standard'?

**Find out the impedance. BTW: Sennheiser's specs are
more honest and useful, regardless of what other
manufacturers may or may not do.

Later, I found a review of Sennheiser PX 100 which says
that Sennheiser's spec: 114dB/1V Eff at 32 ohms is
equivalent to 99dB/1mW.
I don't yet understand how the Sennheiser spec is more
useful to me, when trying to compare their products
against other brands.

The added utility of the Senn spec may be that it is factual, while
competive specs may be more likely to be fantasy or science fiction. ;-)

[GregS]

In article 3XDGg.15641$tP4.11677@clgrps12, John Hall wrote:
Trevor Wilson wrote:

I thought some Sennheiser earbuds looked OK, but they are specified as
113dB at 1V RMS, which is not the same way other manufacturers specify
theirs, e.g. 106dB 1 mW.

How do we convert Sennheiser's numbers to the 'standard'?

**Find out the impedance. BTW: Sennheiser's specs are more honest and
useful, regardless of what other manufacturers may or may not do.

Later, I found a review of Sennheiser PX 100 which says that
Sennheiser's spec: 114dB/1V Eff at 32 ohms is equivalent to 99dB/1mW.

I don't yet understand how the Sennheiser spec is more useful to me,
when trying to compare their products against other brands.

Using watts is ridiculous.

greg

[[email protected]]

John Hall schreef:

I need a pair of more-than-average sensitivity earphones for a body-less
electric practice guitar. It came with a pair by Creative Labs (IIRC),
but I've lost them. The built-in preamp does not put much out. A
separate amp is not suitable as I'm lending/selling this guitar to a
friend who intends using it on a long airline flight.

I thought some Sennheiser earbuds looked OK, but they are specified as
113dB at 1V RMS, which is not the same way other manufacturers specify
theirs, e.g. 106dB 1 mW.

How do we convert Sennheiser's numbers to the 'standard'?
(Being earbuds, I can't just try them in the store).


In your case you need to look at the impedance of the headphones in
order to find a suitable headphone. Impedance is the resistance against
an AC current. So the lower the impedance the louder the output at a
constant (i/p) voltage. It goes as follows:

Power [in Watts] = Impedance [in Ohms] / ( Voltage [in
Volts] x Voltage)

The math will show that a signal of 0.775Vrms will produce one mW in a
600 Ohm load and 8mW in a 75 Ohm load. This is about 9dB difference,
almost twice as loud.

In order to convert the two different ways of describing the
sensitivity of the headphones, which in your case is not so important
to know, you need also to convert the dBs because dBs are relative to a
set measure and that differs for power and voltage. If you really want
to go there here are the formulas you need:

Air Pressu dBSPL = 20 log (SPL [Pa] / 0.2*10exp-4)

Voltage: dBu = 20 log (E [V] / 0.775)

Voltage: dBV = 20 log (E [V] / 1)

Power: dBm = 10 log (P [W] / 1.0*10exp-3)



SPL [Pa] = 10exp(dBspl / 20) * 0.2*10-4

E [V] = 10exp(dBu / 20) * 0.775

E [V] = 10exp(dBV / 20) * 1

P [W] = 10exp(dBu / 10) * 1.0*10exp-3

[[email protected]]

wrote:
In your case you need to look at the impedance of the headphones in
order to find a suitable headphone. Impedance is the resistance against
an AC current. So the lower the impedance the louder the output at a
constant (i/p) voltage. It goes as follows:

Power [in Watts] = Impedance [in Ohms] / ( Voltage [in
Volts] x Voltage)

Uhm, but that's not what your expression says. Simplifying
your text, your equation is:

P = Z / E^2

when what you mean to say is:

P = E^2 / Z

Then it works out as you claim.

The math will show that a signal of 0.775Vrms will
produce one mW in a 600 Ohm load and 8mW in a
75 Ohm load.

Actually, your math shows that:

P = 600 / 0.775^2 = 1000 Watts

which is surely not what you meant :-)

All the rest6 of you math, while quite possibly true, is
needlessly complex for the problem and largely
irrelevant to the poster's immediate problem.

Basically, what is needed is a common base of specification,
and without that, only knowledge of the effective impedance
will get us there.

[[email protected]]

schreef:

Uhm, but that's not what your expression says. Simplifying
your text, your equation is:

P = Z / E^2

when what you mean to say is:

P = E^2 / Z

You are quite right

All the rest6 of you math, while quite possibly true, is
needlessly complex for the problem and largely
irrelevant to the poster's immediate problem.

I was trying to show how irritating it is when manufacturers don't use
the same reference levels.

Basically, what is needed is a common base of specification,
and without that, only knowledge of the effective impedance
will get us there.

Again, true, but also in his case he doesn't need to comare the
sensitivities, it just doesn't matter. He just needs a lowZ headphone.

Thanks for the correction and sorry for the mistake

Henk

[[email protected]]

Oh yeah, if we want to keep it simple here consult the list at the
bottom of this page and select one with a low impedance:
http://www.rane.com/note100.html

[Mr.T]

wrote in message
ups.com...
Again, true, but also in his case he doesn't need to comare the
sensitivities, it just doesn't matter. He just needs a lowZ headphone.

Maybe, but even given an identical impedance (32 ohms being fairly common),
the sensitivity can still vary quite a lot.
With low output devices, the difference in sensitivity can make headphones
satisfactory, or virtually unusable IME.
And if one were to try 8 ohm headphones, you would usually find there is
insufficient drive current to be usable either.

So the answer in many cases is to get the *correct* impedance, and high
sensitivity. Or use a separate headphone amp.

MrT.