I've recently built a pair of speakers using Jordan JX92s'. I'm
considering boosting the low end using a resistor/inductor network.
Before doing this I'd like to measure the frequency response of the
speakers in their cabinets.

I was considering generating white noise on my pc and recording it to
CD. Then play this through the speakers and record back onto my PC to
analyse the frequency response.
Is this a good way to analyse speakers?

I need to get a mic for the job, either with a flat response or with a
known response so I can adjust my frequency response readings
accordingly.
What type of mic do I need, where could I get one in the UK (online
sources)?

Thanks in advance
Ivan

Behringer makes one, but I'm not sure how good it is. ECM something...

--

____________________________________

Brandon Anderson
Lighting, Sound, and Video

http://www.bdanderson.com/


"Ivan" wrote in message
om...
I've recently built a pair of speakers using Jordan JX92s'. I'm
considering boosting the low end using a resistor/inductor network.
Before doing this I'd like to measure the frequency response of the
speakers in their cabinets.

I was considering generating white noise on my pc and recording it to
CD. Then play this through the speakers and record back onto my PC to
analyse the frequency response.
Is this a good way to analyse speakers?

I need to get a mic for the job, either with a flat response or with a
known response so I can adjust my frequency response readings
accordingly.
What type of mic do I need, where could I get one in the UK (online
sources)?

Thanks in advance
Ivan

Behringer makes one, but I'm not sure how good it is. ECM something...

--

____________________________________

Brandon Anderson
Lighting, Sound, and Video

http://www.bdanderson.com/


"Ivan" wrote in message
om...
I've recently built a pair of speakers using Jordan JX92s'. I'm
considering boosting the low end using a resistor/inductor network.
Before doing this I'd like to measure the frequency response of the
speakers in their cabinets.

I was considering generating white noise on my pc and recording it to
CD. Then play this through the speakers and record back onto my PC to
analyse the frequency response.
Is this a good way to analyse speakers?

I need to get a mic for the job, either with a flat response or with a
known response so I can adjust my frequency response readings
accordingly.
What type of mic do I need, where could I get one in the UK (online
sources)?

Thanks in advance
Ivan

(Ivan) wrote in
om:


I was considering generating white noise on my pc and recording it to
CD. Then play this through the speakers and record back onto my PC to
analyse the frequency response.
Is this a good way to analyse speakers?

Definitely not. Try the software at either of these places:
http://www.etfacoustic.com/Index.html
http://www.speakerworkshop.com/ (freeware)

I need to get a mic for the job, either with a flat response or with a
known response so I can adjust my frequency response readings
accordingly.
What type of mic do I need, where could I get one in the UK (online
sources)?

http://www.etfacoustic.com/Index.html
Behringer ECM8000 (cheap, available almost anywhere, probably good enough)

(Ivan) wrote in
om:


I was considering generating white noise on my pc and recording it to
CD. Then play this through the speakers and record back onto my PC to
analyse the frequency response.
Is this a good way to analyse speakers?

Definitely not. Try the software at either of these places:
http://www.etfacoustic.com/Index.html
http://www.speakerworkshop.com/ (freeware)

I need to get a mic for the job, either with a flat response or with a
known response so I can adjust my frequency response readings
accordingly.
What type of mic do I need, where could I get one in the UK (online
sources)?

http://www.etfacoustic.com/Index.html
Behringer ECM8000 (cheap, available almost anywhere, probably good enough)

Ivan,

Is this a good way to analyse speakers?

Only if you do it outdoors far away from any buildings or other surfaces. Or
in a genuine anechoic chamber. Otherwise the room will contribute FAR more
than the speakers to what you measure.

What type of mic do I need

A high quality, omnidirectional condenser mike.

--Ethan

Ivan,

Is this a good way to analyse speakers?

Only if you do it outdoors far away from any buildings or other surfaces. Or
in a genuine anechoic chamber. Otherwise the room will contribute FAR more
than the speakers to what you measure.

What type of mic do I need

A high quality, omnidirectional condenser mike.

--Ethan

"Ethan Winer" ethanw at ethanwiner dot com wrote in message
...
Ivan,

Is this a good way to analyse speakers?

Only if you do it outdoors far away from any buildings or other surfaces.
Or
in a genuine anechoic chamber. Otherwise the room will contribute FAR more
than the speakers to what you measure.

Which is why there are computer-aided methods of
measurement that eliminate the room effects.

What type of mic do I need

A high quality, omnidirectional condenser mike.

With a KNOWN (i.e. measured against calibrated standard)
freuency response. Else you have no idea whether you are
measuring the mic or the speakers (or room).

"Ethan Winer" ethanw at ethanwiner dot com wrote in message
...
Ivan,

Is this a good way to analyse speakers?

Only if you do it outdoors far away from any buildings or other surfaces.
Or
in a genuine anechoic chamber. Otherwise the room will contribute FAR more
than the speakers to what you measure.

Which is why there are computer-aided methods of
measurement that eliminate the room effects.

What type of mic do I need

A high quality, omnidirectional condenser mike.

With a KNOWN (i.e. measured against calibrated standard)
freuency response. Else you have no idea whether you are
measuring the mic or the speakers (or room).

Richard,

Which is why there are computer-aided methods of measurement that
eliminate the room effects.

Thanks, yes, good point. I've never actually used such a system, but someone
(probably in this group) explained it a while ago. By measuring only the
first few instants the test sounds are generated, the damaging reflections
that occur a few milliseconds later are ignored.

With a KNOWN (i.e. measured against calibrated standard)

That was implied with "high quality," but you are again correct. Even a
really great mike will deviate at least a little from flat. And that's fine
as long as the true response is known. For measuring I use an AKG C-451 with
a CK-22 omni capsule, and the top end on that capcsule does indeed vary a
little.

--Ethan

Richard,

Which is why there are computer-aided methods of measurement that
eliminate the room effects.

Thanks, yes, good point. I've never actually used such a system, but someone
(probably in this group) explained it a while ago. By measuring only the
first few instants the test sounds are generated, the damaging reflections
that occur a few milliseconds later are ignored.

With a KNOWN (i.e. measured against calibrated standard)

That was implied with "high quality," but you are again correct. Even a
really great mike will deviate at least a little from flat. And that's fine
as long as the true response is known. For measuring I use an AKG C-451 with
a CK-22 omni capsule, and the top end on that capcsule does indeed vary a
little.

--Ethan

Richard,

Which is why there are computer-aided methods of measurement that
eliminate the room effects.

Thanks, yes, good point. I've never actually used such a system, but someone
(probably in this group) explained it a while ago. By measuring only the
first few instants the test sounds are generated, the damaging reflections
that occur a few milliseconds later are ignored.

With a KNOWN (i.e. measured against calibrated standard)

That was implied with "high quality," but you are again correct. Even a
really great mike will deviate at least a little from flat. And that's fine
as long as the true response is known. For measuring I use an AKG C-451 with
a CK-22 omni capsule, and the top end on that capcsule does indeed vary a
little.

--Ethan

"Ethan Winer" ethanw at ethanwiner dot com wrote in message ...
Richard,

Which is why there are computer-aided methods of measurement that
eliminate the room effects.

Thanks, yes, good point. I've never actually used such a system, but someone
(probably in this group) explained it a while ago. By measuring only the
first few instants the test sounds are generated, the damaging reflections
that occur a few milliseconds later are ignored.

Actually, it's not "the first few instants," is the amount of time
between the arrivale of the direct signal and the arrival of the
first reflection. If, for example, the distance between the speaker
and the nearest reflecting surface is 5 feet, that gives you 10
mS of data to use.

With a KNOWN (i.e. measured against calibrated standard)

That was implied with "high quality," but you are again correct.
Even a really great mike will deviate at least a little from flat.
And that's fine as long as the true response is known. For measuring
I use an AKG C-451 with a CK-22 omni capsule, and the top end on
that capcsule does indeed vary a little.

It's actually interesting that you should mention this particular
unit, because I was asked by AKG about 10 years ago to evaluate
451/CK22's as a possible measurement microphone. While it was not
bad as a microphobe per se, there was simply to much unit-to-unit
variation between capsules, and the diaphragm itself was too large
to make an effective measurement tool without going through very
expensive calibration and measurement for each individual example
of the product. The construction of the capsule did not lend itself
to calibration by electrostatic actuation, which is the means B&K
uses for calibrating capsules, leaving it up to acoustic calibration
which for anything other than low frequencies, is VERY difficult and
expensive.

Electrostatic actuation is where the microphone diaphragm, without
it's shield, is placed in close proximity to a plate on which the
charge is varied over a wide range of frequencies. The results in
movement of the diaphragm as if it was being mived acoustically.
It provides a repeatable, accurate measurement of the mechanical
properties of the microphone. Now, it does not include effects such
as diffraction and such, but that is constant from sample to sample:
you only need to measure those effects once for a given capsule type.
It also assumes the the mic is being used for pressure response
measurement, which as long as the wavelength is longer than the
diaphrgan dimensions, is the same as the perpendicular and random
incidence response.

Another method is reciprocity caibration. The reciprocity principle
states in essence that if you take two samples of a transducer, using
one as a transmitter and the second as a receiver in close proximity,
the total response of the two is the sum of each units response. Thus,
if one is a standard capsule, whose response is well known, then by
using them in tandem in such a fashion you can measure the response
of the other. As in every such measurement, the limit to high frequency
measurement is the pjysical dimensions of the device. But the limit to
the low end is the time constant of any leaks in the system.

"Ethan Winer" ethanw at ethanwiner dot com wrote in message ...
Richard,

Which is why there are computer-aided methods of measurement that
eliminate the room effects.

Thanks, yes, good point. I've never actually used such a system, but someone
(probably in this group) explained it a while ago. By measuring only the
first few instants the test sounds are generated, the damaging reflections
that occur a few milliseconds later are ignored.

Actually, it's not "the first few instants," is the amount of time
between the arrivale of the direct signal and the arrival of the
first reflection. If, for example, the distance between the speaker
and the nearest reflecting surface is 5 feet, that gives you 10
mS of data to use.

With a KNOWN (i.e. measured against calibrated standard)

That was implied with "high quality," but you are again correct.
Even a really great mike will deviate at least a little from flat.
And that's fine as long as the true response is known. For measuring
I use an AKG C-451 with a CK-22 omni capsule, and the top end on
that capcsule does indeed vary a little.

It's actually interesting that you should mention this particular
unit, because I was asked by AKG about 10 years ago to evaluate
451/CK22's as a possible measurement microphone. While it was not
bad as a microphobe per se, there was simply to much unit-to-unit
variation between capsules, and the diaphragm itself was too large
to make an effective measurement tool without going through very
expensive calibration and measurement for each individual example
of the product. The construction of the capsule did not lend itself
to calibration by electrostatic actuation, which is the means B&K
uses for calibrating capsules, leaving it up to acoustic calibration
which for anything other than low frequencies, is VERY difficult and
expensive.

Electrostatic actuation is where the microphone diaphragm, without
it's shield, is placed in close proximity to a plate on which the
charge is varied over a wide range of frequencies. The results in
movement of the diaphragm as if it was being mived acoustically.
It provides a repeatable, accurate measurement of the mechanical
properties of the microphone. Now, it does not include effects such
as diffraction and such, but that is constant from sample to sample:
you only need to measure those effects once for a given capsule type.
It also assumes the the mic is being used for pressure response
measurement, which as long as the wavelength is longer than the
diaphrgan dimensions, is the same as the perpendicular and random
incidence response.

Another method is reciprocity caibration. The reciprocity principle
states in essence that if you take two samples of a transducer, using
one as a transmitter and the second as a receiver in close proximity,
the total response of the two is the sum of each units response. Thus,
if one is a standard capsule, whose response is well known, then by
using them in tandem in such a fashion you can measure the response
of the other. As in every such measurement, the limit to high frequency
measurement is the pjysical dimensions of the device. But the limit to
the low end is the time constant of any leaks in the system.

"Ethan Winer" ethanw at ethanwiner dot com wrote in message ...
Richard,

Which is why there are computer-aided methods of measurement that
eliminate the room effects.

Thanks, yes, good point. I've never actually used such a system, but someone
(probably in this group) explained it a while ago. By measuring only the
first few instants the test sounds are generated, the damaging reflections
that occur a few milliseconds later are ignored.

Actually, it's not "the first few instants," is the amount of time
between the arrivale of the direct signal and the arrival of the
first reflection. If, for example, the distance between the speaker
and the nearest reflecting surface is 5 feet, that gives you 10
mS of data to use.

With a KNOWN (i.e. measured against calibrated standard)

That was implied with "high quality," but you are again correct.
Even a really great mike will deviate at least a little from flat.
And that's fine as long as the true response is known. For measuring
I use an AKG C-451 with a CK-22 omni capsule, and the top end on
that capcsule does indeed vary a little.

It's actually interesting that you should mention this particular
unit, because I was asked by AKG about 10 years ago to evaluate
451/CK22's as a possible measurement microphone. While it was not
bad as a microphobe per se, there was simply to much unit-to-unit
variation between capsules, and the diaphragm itself was too large
to make an effective measurement tool without going through very
expensive calibration and measurement for each individual example
of the product. The construction of the capsule did not lend itself
to calibration by electrostatic actuation, which is the means B&K
uses for calibrating capsules, leaving it up to acoustic calibration
which for anything other than low frequencies, is VERY difficult and
expensive.

Electrostatic actuation is where the microphone diaphragm, without
it's shield, is placed in close proximity to a plate on which the
charge is varied over a wide range of frequencies. The results in
movement of the diaphragm as if it was being mived acoustically.
It provides a repeatable, accurate measurement of the mechanical
properties of the microphone. Now, it does not include effects such
as diffraction and such, but that is constant from sample to sample:
you only need to measure those effects once for a given capsule type.
It also assumes the the mic is being used for pressure response
measurement, which as long as the wavelength is longer than the
diaphrgan dimensions, is the same as the perpendicular and random
incidence response.

Another method is reciprocity caibration. The reciprocity principle
states in essence that if you take two samples of a transducer, using
one as a transmitter and the second as a receiver in close proximity,
the total response of the two is the sum of each units response. Thus,
if one is a standard capsule, whose response is well known, then by
using them in tandem in such a fashion you can measure the response
of the other. As in every such measurement, the limit to high frequency
measurement is the pjysical dimensions of the device. But the limit to
the low end is the time constant of any leaks in the system.

Dick,

I was asked by AKG about 10 years ago to evaluate 451/CK22's as a possible
measurement microphone.

I got mine many years ago, in the late 1970s as I recall. I know there are
better measuring mikes these days, having smaller diaphragms and other
advantages. Fortunately nothing I do is critical.

Electrostatic actuation is ... Another method is reciprocity caibration.

Fascinating. I had heard of the reciprocal method, but never electrostatic.
I assume reciprocal works only with dynamic elements, and not condensers,
right?

Thanks.

--Ethan

Dick,

I was asked by AKG about 10 years ago to evaluate 451/CK22's as a possible
measurement microphone.

I got mine many years ago, in the late 1970s as I recall. I know there are
better measuring mikes these days, having smaller diaphragms and other
advantages. Fortunately nothing I do is critical.

Electrostatic actuation is ... Another method is reciprocity caibration.

Fascinating. I had heard of the reciprocal method, but never electrostatic.
I assume reciprocal works only with dynamic elements, and not condensers,
right?

Thanks.

--Ethan

Dick,

I was asked by AKG about 10 years ago to evaluate 451/CK22's as a possible
measurement microphone.

I got mine many years ago, in the late 1970s as I recall. I know there are
better measuring mikes these days, having smaller diaphragms and other
advantages. Fortunately nothing I do is critical.

Electrostatic actuation is ... Another method is reciprocity caibration.

Fascinating. I had heard of the reciprocal method, but never electrostatic.
I assume reciprocal works only with dynamic elements, and not condensers,
right?

Thanks.

--Ethan

"Ethan Winer" ethanw at ethanwiner dot com wrote in message ...
Fascinating. I had heard of the reciprocal method, but never electrostatic.
I assume reciprocal works only with dynamic elements, and not condensers,
right?

Wrong. Any transducer that can produce sound can act as a microphone,
and vice versa. A condensor microphone works just fine as a little,
tiny speaker, just like a dynamic mike.

"Ethan Winer" ethanw at ethanwiner dot com wrote in message ...
Fascinating. I had heard of the reciprocal method, but never electrostatic.
I assume reciprocal works only with dynamic elements, and not condensers,
right?

Wrong. Any transducer that can produce sound can act as a microphone,
and vice versa. A condensor microphone works just fine as a little,
tiny speaker, just like a dynamic mike.

"Ethan Winer" ethanw at ethanwiner dot com wrote in message ...
Fascinating. I had heard of the reciprocal method, but never electrostatic.
I assume reciprocal works only with dynamic elements, and not condensers,
right?

Wrong. Any transducer that can produce sound can act as a microphone,
and vice versa. A condensor microphone works just fine as a little,
tiny speaker, just like a dynamic mike.

"Ethan Winer" ethanw at ethanwiner dot com wrote in message ...

Fascinating. I had heard of the reciprocal method, but never electrostatic.
I assume reciprocal works only with dynamic elements, and not condensers,
right?

It should work with any reciprocal transducer, and both dynamic and
condenser mics are.

"Ethan Winer" ethanw at ethanwiner dot com wrote in message ...

Fascinating. I had heard of the reciprocal method, but never electrostatic.
I assume reciprocal works only with dynamic elements, and not condensers,
right?

It should work with any reciprocal transducer, and both dynamic and
condenser mics are.

"Ethan Winer" ethanw at ethanwiner dot com wrote in message ...

Fascinating. I had heard of the reciprocal method, but never electrostatic.
I assume reciprocal works only with dynamic elements, and not condensers,
right?

It should work with any reciprocal transducer, and both dynamic and
condenser mics are.

Dick Pierce wrote:

Wrong. Any transducer that can produce sound can act as a microphone,
and vice versa. A condensor microphone works just fine as a little,
tiny speaker, just like a dynamic mike.

So Dick, you saying the typical condenser mike that has a Phantom powered preamp or impedance convertor or
such connected to the actual condenser element will work as a speaker transducer by hooking a signal up to its
XLR jacks? Did I understand you right?

Bob



-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
-----== Over 100,000 Newsgroups - 19 Different Servers! =-----

Dick Pierce wrote:

Wrong. Any transducer that can produce sound can act as a microphone,
and vice versa. A condensor microphone works just fine as a little,
tiny speaker, just like a dynamic mike.

So Dick, you saying the typical condenser mike that has a Phantom powered preamp or impedance convertor or
such connected to the actual condenser element will work as a speaker transducer by hooking a signal up to its
XLR jacks? Did I understand you right?

Bob



-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
-----== Over 100,000 Newsgroups - 19 Different Servers! =-----

Dick Pierce wrote:

Wrong. Any transducer that can produce sound can act as a microphone,
and vice versa. A condensor microphone works just fine as a little,
tiny speaker, just like a dynamic mike.

So Dick, you saying the typical condenser mike that has a Phantom powered preamp or impedance convertor or
such connected to the actual condenser element will work as a speaker transducer by hooking a signal up to its
XLR jacks? Did I understand you right?

Bob



-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
-----== Over 100,000 Newsgroups - 19 Different Servers! =-----

(Ivan) wrote in message . com...
I've recently built a pair of speakers using Jordan JX92s'. I'm
considering boosting the low end using a resistor/inductor network.
Before doing this I'd like to measure the frequency response of the
speakers in their cabinets.

I was considering generating white noise on my pc and recording it to
CD. Then play this through the speakers and record back onto my PC to
analyse the frequency response.
Is this a good way to analyse speakers?

I need to get a mic for the job, either with a flat response or with a
known response so I can adjust my frequency response readings
accordingly.
What type of mic do I need, where could I get one in the UK (online
sources)?

Thanks in advance
Ivan

I remember reading an artical, years ago, that said you could measure
speaker response without a microphone! Use one speaker as the source
and the other speaker as the microphone. Divide the resultant
frequency response (in dB) by 2. In other words, if the
speaker/"microphone" combination shows a peak 4 dB, it is 2 dB.

I have never tried this measuring technique, but it sounds somewhat
reasonable.

Bob Stanton

(Ivan) wrote in message . com...
I've recently built a pair of speakers using Jordan JX92s'. I'm
considering boosting the low end using a resistor/inductor network.
Before doing this I'd like to measure the frequency response of the
speakers in their cabinets.

I was considering generating white noise on my pc and recording it to
CD. Then play this through the speakers and record back onto my PC to
analyse the frequency response.
Is this a good way to analyse speakers?

I need to get a mic for the job, either with a flat response or with a
known response so I can adjust my frequency response readings
accordingly.
What type of mic do I need, where could I get one in the UK (online
sources)?

Thanks in advance
Ivan

I remember reading an artical, years ago, that said you could measure
speaker response without a microphone! Use one speaker as the source
and the other speaker as the microphone. Divide the resultant
frequency response (in dB) by 2. In other words, if the
speaker/"microphone" combination shows a peak 4 dB, it is 2 dB.

I have never tried this measuring technique, but it sounds somewhat
reasonable.

Bob Stanton

(Ivan) wrote in message . com...
I've recently built a pair of speakers using Jordan JX92s'. I'm
considering boosting the low end using a resistor/inductor network.
Before doing this I'd like to measure the frequency response of the
speakers in their cabinets.

I was considering generating white noise on my pc and recording it to
CD. Then play this through the speakers and record back onto my PC to
analyse the frequency response.
Is this a good way to analyse speakers?

I need to get a mic for the job, either with a flat response or with a
known response so I can adjust my frequency response readings
accordingly.
What type of mic do I need, where could I get one in the UK (online
sources)?

Thanks in advance
Ivan

I remember reading an artical, years ago, that said you could measure
speaker response without a microphone! Use one speaker as the source
and the other speaker as the microphone. Divide the resultant
frequency response (in dB) by 2. In other words, if the
speaker/"microphone" combination shows a peak 4 dB, it is 2 dB.

I have never tried this measuring technique, but it sounds somewhat
reasonable.

Bob Stanton

Dick and Svante,

Any transducer that can produce sound can act as a microphone

I was also considering the FET or tube preamp, which of course won't work in
reverse.

So you're saying if you remove the head preamp but leave the polarizing
voltage, you can send a pre-amped signal to the capsule and it will make
noise? Okay, that makes sense.

Thanks.

--Ethan

Dick and Svante,

Any transducer that can produce sound can act as a microphone

I was also considering the FET or tube preamp, which of course won't work in
reverse.

So you're saying if you remove the head preamp but leave the polarizing
voltage, you can send a pre-amped signal to the capsule and it will make
noise? Okay, that makes sense.

Thanks.

--Ethan

Dick and Svante,

Any transducer that can produce sound can act as a microphone

I was also considering the FET or tube preamp, which of course won't work in
reverse.

So you're saying if you remove the head preamp but leave the polarizing
voltage, you can send a pre-amped signal to the capsule and it will make
noise? Okay, that makes sense.

Thanks.

--Ethan

(Bob-Stanton) wrote in message . com...
I remember reading an artical, years ago, that said you could measure
speaker response without a microphone! Use one speaker as the source
and the other speaker as the microphone. Divide the resultant
frequency response (in dB) by 2. In other words, if the
speaker/"microphone" combination shows a peak 4 dB, it is 2 dB.

I have never tried this measuring technique, but it sounds somewhat
reasonable.

Within VERY narrow cnostraints, it is reasonable. Unfortunately
those constraints are too narrow to make it useful.

What you're describing is, indeed, the reciprocity method. It works
for things like microphones because microphones are generally very
small and can be used up to an appropriately high frequency,
proportionaly to the reciprocal of the dimensions of the transducer.
Generally, when the wavelength reaches or exceeds 1/4 wavelength,
the method no longer works.

That suggests, for example, that for 1/2" laboratory microphone
capsules used in very close proximity (say, within 1/2" of each
other), the technique is usable up to 6500 Hz. For 1/4" capsules,
it's more like 13 kHz.

But for a speaker, with multiple drivers extending of a couple of
feet, you run into the problem that your limiting frequency is now
in the realm of less than 200 Hz. In addition, you must couple the
two speakers quite tightly, e.g., face to face with an airtight
gasket between them. Any energy leaking from the system will not
be accounted for in the reciprocal principle.

So, yes, it's THEORETICALLY possible, but hardly useful.

(Bob-Stanton) wrote in message . com...
I remember reading an artical, years ago, that said you could measure
speaker response without a microphone! Use one speaker as the source
and the other speaker as the microphone. Divide the resultant
frequency response (in dB) by 2. In other words, if the
speaker/"microphone" combination shows a peak 4 dB, it is 2 dB.

I have never tried this measuring technique, but it sounds somewhat
reasonable.

Within VERY narrow cnostraints, it is reasonable. Unfortunately
those constraints are too narrow to make it useful.

What you're describing is, indeed, the reciprocity method. It works
for things like microphones because microphones are generally very
small and can be used up to an appropriately high frequency,
proportionaly to the reciprocal of the dimensions of the transducer.
Generally, when the wavelength reaches or exceeds 1/4 wavelength,
the method no longer works.

That suggests, for example, that for 1/2" laboratory microphone
capsules used in very close proximity (say, within 1/2" of each
other), the technique is usable up to 6500 Hz. For 1/4" capsules,
it's more like 13 kHz.

But for a speaker, with multiple drivers extending of a couple of
feet, you run into the problem that your limiting frequency is now
in the realm of less than 200 Hz. In addition, you must couple the
two speakers quite tightly, e.g., face to face with an airtight
gasket between them. Any energy leaking from the system will not
be accounted for in the reciprocal principle.

So, yes, it's THEORETICALLY possible, but hardly useful.

(Bob-Stanton) wrote in message . com...
I remember reading an artical, years ago, that said you could measure
speaker response without a microphone! Use one speaker as the source
and the other speaker as the microphone. Divide the resultant
frequency response (in dB) by 2. In other words, if the
speaker/"microphone" combination shows a peak 4 dB, it is 2 dB.

I have never tried this measuring technique, but it sounds somewhat
reasonable.

Within VERY narrow cnostraints, it is reasonable. Unfortunately
those constraints are too narrow to make it useful.

What you're describing is, indeed, the reciprocity method. It works
for things like microphones because microphones are generally very
small and can be used up to an appropriately high frequency,
proportionaly to the reciprocal of the dimensions of the transducer.
Generally, when the wavelength reaches or exceeds 1/4 wavelength,
the method no longer works.

That suggests, for example, that for 1/2" laboratory microphone
capsules used in very close proximity (say, within 1/2" of each
other), the technique is usable up to 6500 Hz. For 1/4" capsules,
it's more like 13 kHz.

But for a speaker, with multiple drivers extending of a couple of
feet, you run into the problem that your limiting frequency is now
in the realm of less than 200 Hz. In addition, you must couple the
two speakers quite tightly, e.g., face to face with an airtight
gasket between them. Any energy leaking from the system will not
be accounted for in the reciprocal principle.

So, yes, it's THEORETICALLY possible, but hardly useful.

BOB URZ wrote in message ...
Dick Pierce wrote:

Wrong. Any transducer that can produce sound can act as a microphone,
and vice versa. A condensor microphone works just fine as a little,
tiny speaker, just like a dynamic mike.

So Dick, you saying the typical condenser mike that has a
Phantom powered preamp or impedance convertor or such
connected to the actual condenser element will work as a
speaker transducer by hooking a signal up to its
XLR jacks?

No, I did NOT say that:

"Any transducer that can produce sound can act as a
microphone, and vice versa."

A "transducer" is the device in a microphone that converts
acoustical energy (really, mechanical energy) into electrical
energy. That device is quite reversable. So is any other such
transducer, such as dynamic microphone, a ribbon microphone,
a ceramic microphone, a speaker, even a magnetic phono cartridge.

The preamp, impedance converter and such is NOT part of the
transducer, but there to provide electrical-to-electrical
interfacing, gain and such. Since these are NOT part of the
transducer, they are not part of the definition encompassed
by the reciprocity principle.

BOB URZ wrote in message ...
Dick Pierce wrote:

Wrong. Any transducer that can produce sound can act as a microphone,
and vice versa. A condensor microphone works just fine as a little,
tiny speaker, just like a dynamic mike.

So Dick, you saying the typical condenser mike that has a
Phantom powered preamp or impedance convertor or such
connected to the actual condenser element will work as a
speaker transducer by hooking a signal up to its
XLR jacks?

No, I did NOT say that:

"Any transducer that can produce sound can act as a
microphone, and vice versa."

A "transducer" is the device in a microphone that converts
acoustical energy (really, mechanical energy) into electrical
energy. That device is quite reversable. So is any other such
transducer, such as dynamic microphone, a ribbon microphone,
a ceramic microphone, a speaker, even a magnetic phono cartridge.

The preamp, impedance converter and such is NOT part of the
transducer, but there to provide electrical-to-electrical
interfacing, gain and such. Since these are NOT part of the
transducer, they are not part of the definition encompassed
by the reciprocity principle.

BOB URZ wrote in message ...
Dick Pierce wrote:

Wrong. Any transducer that can produce sound can act as a microphone,
and vice versa. A condensor microphone works just fine as a little,
tiny speaker, just like a dynamic mike.

So Dick, you saying the typical condenser mike that has a
Phantom powered preamp or impedance convertor or such
connected to the actual condenser element will work as a
speaker transducer by hooking a signal up to its
XLR jacks?

No, I did NOT say that:

"Any transducer that can produce sound can act as a
microphone, and vice versa."

A "transducer" is the device in a microphone that converts
acoustical energy (really, mechanical energy) into electrical
energy. That device is quite reversable. So is any other such
transducer, such as dynamic microphone, a ribbon microphone,
a ceramic microphone, a speaker, even a magnetic phono cartridge.

The preamp, impedance converter and such is NOT part of the
transducer, but there to provide electrical-to-electrical
interfacing, gain and such. Since these are NOT part of the
transducer, they are not part of the definition encompassed
by the reciprocity principle.

(Dick Pierce) wrote in message . com...
BOB URZ wrote in message ...
Dick Pierce wrote:

Wrong. Any transducer that can produce sound can act as a microphone,
and vice versa. A condensor microphone works just fine as a little,
tiny speaker, just like a dynamic mike.

So Dick, you saying the typical condenser mike that has a
Phantom powered preamp or impedance convertor or such
connected to the actual condenser element will work as a
speaker transducer by hooking a signal up to its
XLR jacks?

No, I did NOT say that:

"Any transducer that can produce sound can act as a
microphone, and vice versa."

A "transducer" is the device in a microphone that converts
acoustical energy (really, mechanical energy) into electrical
energy. That device is quite reversable. So is any other such
transducer, such as dynamic microphone, a ribbon microphone,
a ceramic microphone, a speaker, even a magnetic phono cartridge.

The preamp, impedance converter and such is NOT part of the
transducer, but there to provide electrical-to-electrical
interfacing, gain and such. Since these are NOT part of the
transducer, they are not part of the definition encompassed
by the reciprocity principle.

You might want to add that the transducer must be reciprocal, which
most but not all are. In old telephones there was a transducer type
based on the resistance in carbon powder (I don't know the proper
english name for it, but a direct translation from swedish would be
"carbon-powder-microphone") that was NOT reciprocal, ie it would not
produce any sound if a signal was applied to it.