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  #1   Report Post  
Fabio Berutti
 
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Default Loudspeaker testing hardware?

Dear RATs,

a question posed by Mr. Turner about my new LS is now puzzling me: what kind
of stuff is needed to test a loudspeaker? Is it possible to do it with some
VERY cheap microphone and the sound card included in any PC? I don't want
to spend a lot of $ in Bruel&Kjaer professional testing equipments....

Ciao

Fabio


  #3   Report Post  
Patrick Turner
 
Posts: n/a
Default



Fabio Berutti wrote:

Dear RATs,

a question posed by Mr. Turner about my new LS is now puzzling me: what kind
of stuff is needed to test a loudspeaker? Is it possible to do it with some
VERY cheap microphone and the sound card included in any PC? I don't want
to spend a lot of $ in Bruel&Kjaer professional testing equipments....

Ciao

Fabio


I am presently using an electret mic insert purchased from
Hi Q products in Melbourne for aud $1.20 each.
I bought 10, and all gave the same flat response as per their spec sheets for
that model of electret mic.
I fitted the insert into the end of a 12 mm copper pipe 300 mm long full of
wool.
Its clamped to a mic stand.
The response is only flat from about 20 Hz to 8 kHz, and then rolls off at 6 dB
/ octave.
So I placed an RC emphasis circuit in the mic amp, and made the recovered signal
flat to 15 kHz,
and after measuring many speakers, it must be about right enough to tell me if
there
are drastic problems.

The test signal is pink noise, or white noise eq'd by 3 dB / octave across the
band.

My home brew tunable 3 decade range bandpass filter for measuring bands has a Q
of about 12
at any F chosen, so if centred on 1 kHz,
the poles are at 41 Hz each side of 1 kHz.
The filter and noise source and mic amp are in the one box
and use opamps to achieve what I want.

There are calibrated mikes out there which may cost $100, and would probably be
better,
as would the use of a PC and program to analyse AF, 'Speclab' comes to mind.
I do it the old fashioned way with a book and pencil with several takes in the
room.
These can be averaged, and a resultant response line drawn.
The PC will be a lot faster.
The results always seem to co-relate to what I hear.
Drivers can be tested separately, then together, and the response of each driver
plotted.
When the phase of a driver is reversed, the results show up in the response.

Its real shoe string budget stuff what I have done, but its a lot better than
nothing at all.

I have my eye on better gear, but the bills keep me poor, and I have to save up
more.

Even with better gear, the room effects still give +/- 3 dB graph undulations.
Don't ever test with pure sine waves; you get a crazy +/- 12 dB variation with
maybe 50 peaks and troughs, and a totally meaningless outcome.

The more carpets and cushions, large bags of chopped foam in the room,
the flatter your measurements will be. And the better the music will be.

Its not as good as an anechoic chamber.

If most music cannot be improved by adjusting the amplifier tone controls,
then the speakers might be about right.
I said might be. The pink noise room test will find the
harder to hear other problems.

Patrick Turner.



  #4   Report Post  
Patrick Turner
 
Posts: n/a
Default



"François Yves Le Gal" wrote:

On Tue, 15 Feb 2005 13:49:01 GMT, "Fabio Berutti"
wrote:

Is it possible to do it with some
VERY cheap microphone and the sound card included in any PC?


You may consider using an affordable electret testing microphone, such as
the Behringer ECM8000 together with a suitable preamp and phantom power (you
can consider using a small mixer from Behringer).

ECM8000 http://www.behringer.com/ECM8000/index.cfm?lang=ENG

If you want to go for real cheap, you may build your own measuring mike from
a Panasonic capsule.

Most soundcards are OK.

On the software side, you may use Audua Speaker Workshop (freeware), which
is an excellent entry level solution.

http://www.audua.com/


I downloaded this but I cannot get it to set itself up.
It tries to use acrobat to open it, then comes up with a notice
"document does not start with '%PDF' ".

Another dead end?

Patrick Turner.


  #5   Report Post  
Robert McLean
 
Posts: n/a
Default

Patrick :
I got the same crazy peaks and troughs you mention when using sine waves to
test speakers. I even got big fluctuations in readings if I stood within a
few feet of the speaker and moved my arms around. I thought these were
fluctuations caused by the room, so I gave up doing measurements.

So your pink noise and band pass filter method interests me. Do you feed
the pink noise through the filter then to the speaker, and measure the
result ? or do you put the filter on the output of the mic ?

By the way, since the original question was about equipment, what I use for
a microphone is the analogue output from a RadioShack 33-2055 digital sound
level meter. It has its own amplifier etc. Just connect an audio voltmeter
to the output. There is a mod on the web somewhere showing how to extend the
lower frequency response and remove the weighting to get a uniform frequency
response.

Thanks

"Patrick Turner" wrote in message
...


Fabio Berutti wrote:

Dear RATs,

a question posed by Mr. Turner about my new LS is now puzzling me: what
kind
of stuff is needed to test a loudspeaker? Is it possible to do it with
some
VERY cheap microphone and the sound card included in any PC? I don't
want
to spend a lot of $ in Bruel&Kjaer professional testing equipments....

Ciao

Fabio


I am presently using an electret mic insert purchased from
Hi Q products in Melbourne for aud $1.20 each.
I bought 10, and all gave the same flat response as per their spec sheets
for
that model of electret mic.
I fitted the insert into the end of a 12 mm copper pipe 300 mm long full
of
wool.
Its clamped to a mic stand.
The response is only flat from about 20 Hz to 8 kHz, and then rolls off at
6 dB
/ octave.
So I placed an RC emphasis circuit in the mic amp, and made the recovered
signal
flat to 15 kHz,
and after measuring many speakers, it must be about right enough to tell
me if
there
are drastic problems.

The test signal is pink noise, or white noise eq'd by 3 dB / octave across
the
band.

My home brew tunable 3 decade range bandpass filter for measuring bands
has a Q
of about 12
at any F chosen, so if centred on 1 kHz,
the poles are at 41 Hz each side of 1 kHz.
The filter and noise source and mic amp are in the one box
and use opamps to achieve what I want.

There are calibrated mikes out there which may cost $100, and would
probably be
better,
as would the use of a PC and program to analyse AF, 'Speclab' comes to
mind.
I do it the old fashioned way with a book and pencil with several takes in
the
room.
These can be averaged, and a resultant response line drawn.
The PC will be a lot faster.
The results always seem to co-relate to what I hear.
Drivers can be tested separately, then together, and the response of each
driver
plotted.
When the phase of a driver is reversed, the results show up in the
response.

Its real shoe string budget stuff what I have done, but its a lot better
than
nothing at all.

I have my eye on better gear, but the bills keep me poor, and I have to
save up
more.

Even with better gear, the room effects still give +/- 3 dB graph
undulations.
Don't ever test with pure sine waves; you get a crazy +/- 12 dB variation
with
maybe 50 peaks and troughs, and a totally meaningless outcome.

The more carpets and cushions, large bags of chopped foam in the room,
the flatter your measurements will be. And the better the music will be.

Its not as good as an anechoic chamber.

If most music cannot be improved by adjusting the amplifier tone controls,
then the speakers might be about right.
I said might be. The pink noise room test will find the
harder to hear other problems.

Patrick Turner.







  #6   Report Post  
Ruud Broens
 
Posts: n/a
Default


"François Yves Le Gal" wrote in message
...
: On Tue, 15 Feb 2005 13:49:01 GMT, "Fabio Berutti"
: wrote:
:
: Is it possible to do it with some
: VERY cheap microphone and the sound card included in any PC?
:
: You may consider using an affordable electret testing microphone, such as
: the Behringer ECM8000 together with a suitable preamp and phantom power (you
: can consider using a small mixer from Behringer).
:
: ECM8000 http://www.behringer.com/ECM8000/index.cfm?lang=ENG
:
: If you want to go for real cheap, you may build your own measuring mike from
: a Panasonic capsule.
:
: Most soundcards are OK.
:
: On the software side, you may use Audua Speaker Workshop (freeware), which
: is an excellent entry level solution.
:
: http://www.audua.com/

Also, there are offers combining MLSSA and some fair quality microphones
with calibrated response curves - just google around in eu :-)
Rudy


  #7   Report Post  
Choky
 
Posts: n/a
Default


"Fabio Berutti" wrote in message
...
| Dear RATs,
|
| a question posed by Mr. Turner about my new LS is now puzzling me: what
kind
| of stuff is needed to test a loudspeaker? Is it possible to do it with
some
| VERY cheap microphone and the sound card included in any PC? I don't want
| to spend a lot of $ in Bruel&Kjaer professional testing equipments....
|
| Ciao
|
| Fabio
|
|

do you mind few MB in your mail box?

--
--
.................................................. ........................
Choky
Prodanovic Aleksandar
YU

"don't use force, "don't use force,
use a larger hammer" use a larger tube
- Choky and IST"
- ZM
.................................................. ...........................


  #8   Report Post  
Ruud Broens
 
Posts: n/a
Default


"François Yves Le Gal" wrote in message
...
: On Tue, 15 Feb 2005 21:50:04 +0100, "Ruud Broens"
: wrote:
:
: Also, there are offers combining MLSSA and some fair quality microphones
: with calibrated response curves - just google around in eu :-)
:
: A solution around MLSSA costs more than 5,000 EUR...
:
Ok, cheaper solution:
http://www.speaker-online.de/messtechnik/
most expensive solution there, with the MBC550, preamp, software EURO 498,-

Rudy


  #10   Report Post  
Ruud Broens
 
Posts: n/a
Default


"François Yves Le Gal" wrote in message
...
: On Tue, 15 Feb 2005 22:41:30 +0100, "Ruud Broens"
: wrote:
:
: most expensive solution there, with the MBC550, preamp, software EURO 498,-
:
: That's much more in the hobbyist league.
: :-)
:
Well, it depends - take for instance us streetcar racing modded cars, owners
there may spend 30.000 to 50.000 USD - yet the car may be impounded after
a single 'race'... then all of a sudden audio seems like a very cheap hobby
:-)))
Rudy




  #11   Report Post  
Chris Hornbeck
 
Posts: n/a
Default

On Tue, 15 Feb 2005 13:49:01 GMT, "Fabio Berutti"
wrote:

a question posed by Mr. Turner about my new LS is now puzzling me: what kind
of stuff is needed to test a loudspeaker? Is it possible to do it with some
VERY cheap microphone and the sound card included in any PC? I don't want
to spend a lot of $ in Bruel&Kjaer professional testing equipments....


I can recommend WinAIRR, available from AudioXpress in the US for
about $50. Others have mentioned several suitable microphones.

Speaker testing at home is done in two bands; low frequencies
are tested with a microphone in the very-near-field. Above a
few hundred Hz, time-sampled measurements, using impulses, or
noise that's shaped to have the mathematical characteristics of
impulses, are manipulated by computer program to derive all
kinds of cool info.

Good fortune,

Chris Hornbeck
  #12   Report Post  
Patrick Turner
 
Posts: n/a
Default



"François Yves Le Gal" wrote:

On Wed, 16 Feb 2005 01:51:53 +1100, Patrick Turner
wrote:

Another dead end?


The program is distributed as a .zip archive. If your PC tries to launch
Acrobat, then you've got a serious configuration problem...

Have you got Winzip or similar installed ?


No, so do I try to download Winzip?

Patrick Turner.


  #13   Report Post  
Patrick Turner
 
Posts: n/a
Default



Robert McLean wrote:

Patrick :
I got the same crazy peaks and troughs you mention when using sine waves to
test speakers. I even got big fluctuations in readings if I stood within a
few feet of the speaker and moved my arms around. I thought these were
fluctuations caused by the room, so I gave up doing measurements.


Fixed tone sine waves radiate from the speaker and all the reflected waves from
the room
also appear at the microphone, and depending on their power and phase these will

tend to these will add to add or subtract to the amplitude recorded by the mic.

One can also use a wobbulator, where the F is varied fast enough prevent
reflected
waves from adding or subtracting to the centre F waves.
Pink noise contains all the bandwidth F over a period of time, with F and phase
changing at random rates.



So your pink noise and band pass filter method interests me. Do you feed
the pink noise through the filter then to the speaker, and measure the
result ? or do you put the filter on the output of the mic ?


The pink noise is fed to the amp.
It sounds like a large waterfall, with rumble and hiss.

The microphone picks this up, and amplifies it, and passes
the signal through the bandpass filter.
The amount of energy for the band selected is then sent to a peak
detector with a long time constant, and this is sent to a logarithmic amp
to power a large scale analog meter with 0dB at the centre of the meter
and +/- 20 dB each side.
This way you can easily read across a 40 dB range of voltages.

Set for 1 kHz, the meter needle sways a bit, since the 1 kHz band undulates at
low frequency a little, but not badly enough to prevent getting a measurement
after a few seconds of watching the needle.




By the way, since the original question was about equipment, what I use for
a microphone is the analogue output from a RadioShack 33-2055 digital sound
level meter. It has its own amplifier etc. Just connect an audio voltmeter
to the output. There is a mod on the web somewhere showing how to extend the
lower frequency response and remove the weighting to get a uniform frequency
response.


The HF end of the band on those types of meters isn't too wonderful.
In fact I wonder how accurate they are at all.

I believe my set up to be more accurate than an SPL meter I could buy like that.

But it did take a week or two to get it going right.
I did it before I went on the net in 2000 so instead of hours at the PC each
day,
I was reading books and building and testing circuits.

Patrick Turner.



Thanks

"Patrick Turner" wrote in message
...


Fabio Berutti wrote:

Dear RATs,

a question posed by Mr. Turner about my new LS is now puzzling me: what
kind
of stuff is needed to test a loudspeaker? Is it possible to do it with
some
VERY cheap microphone and the sound card included in any PC? I don't
want
to spend a lot of $ in Bruel&Kjaer professional testing equipments....

Ciao

Fabio


I am presently using an electret mic insert purchased from
Hi Q products in Melbourne for aud $1.20 each.
I bought 10, and all gave the same flat response as per their spec sheets
for
that model of electret mic.
I fitted the insert into the end of a 12 mm copper pipe 300 mm long full
of
wool.
Its clamped to a mic stand.
The response is only flat from about 20 Hz to 8 kHz, and then rolls off at
6 dB
/ octave.
So I placed an RC emphasis circuit in the mic amp, and made the recovered
signal
flat to 15 kHz,
and after measuring many speakers, it must be about right enough to tell
me if
there
are drastic problems.

The test signal is pink noise, or white noise eq'd by 3 dB / octave across
the
band.

My home brew tunable 3 decade range bandpass filter for measuring bands
has a Q
of about 12
at any F chosen, so if centred on 1 kHz,
the poles are at 41 Hz each side of 1 kHz.
The filter and noise source and mic amp are in the one box
and use opamps to achieve what I want.

There are calibrated mikes out there which may cost $100, and would
probably be
better,
as would the use of a PC and program to analyse AF, 'Speclab' comes to
mind.
I do it the old fashioned way with a book and pencil with several takes in
the
room.
These can be averaged, and a resultant response line drawn.
The PC will be a lot faster.
The results always seem to co-relate to what I hear.
Drivers can be tested separately, then together, and the response of each
driver
plotted.
When the phase of a driver is reversed, the results show up in the
response.

Its real shoe string budget stuff what I have done, but its a lot better
than
nothing at all.

I have my eye on better gear, but the bills keep me poor, and I have to
save up
more.

Even with better gear, the room effects still give +/- 3 dB graph
undulations.
Don't ever test with pure sine waves; you get a crazy +/- 12 dB variation
with
maybe 50 peaks and troughs, and a totally meaningless outcome.

The more carpets and cushions, large bags of chopped foam in the room,
the flatter your measurements will be. And the better the music will be.

Its not as good as an anechoic chamber.

If most music cannot be improved by adjusting the amplifier tone controls,
then the speakers might be about right.
I said might be. The pink noise room test will find the
harder to hear other problems.

Patrick Turner.




  #14   Report Post  
Stewart Pinkerton
 
Posts: n/a
Default

On Tue, 15 Feb 2005 23:44:46 +0100, François Yves Le Gal
wrote:

On Tue, 15 Feb 2005 23:22:46 +0100, "Ruud Broens"
wrote:

then all of a sudden audio seems like a very cheap hobby


Hmmm. Some ultra-fi rigs cost more than a couple of luxury cars. Ongaku
anyone?


You can buy a couple of luxury cars for $28,000? Where?
--

Stewart Pinkerton | Music is Art - Audio is Engineering
  #15   Report Post  
Robert McLean
 
Posts: n/a
Default


"Patrick Turner" wrote in message
...

So your pink noise and band pass filter method interests me. Do you feed
the pink noise through the filter then to the speaker, and measure the
result ? or do you put the filter on the output of the mic ?


The pink noise is fed to the amp.
It sounds like a large waterfall, with rumble and hiss.

The microphone picks this up, and amplifies it, and passes
the signal through the bandpass filter.
The amount of energy for the band selected is then sent to a peak
detector with a long time constant, and this is sent to a logarithmic amp
to power a large scale analog meter with 0dB at the centre of the meter
and +/- 20 dB each side.
This way you can easily read across a 40 dB range of voltages.

Set for 1 kHz, the meter needle sways a bit, since the 1 kHz band
undulates at
low frequency a little, but not badly enough to prevent getting a
measurement
after a few seconds of watching the needle.


OK, understood. I will give this a try next time I am fooling around with
speakers.
Thanks.
Robert.




  #16   Report Post  
Fabio Berutti
 
Posts: n/a
Default

Hmmm... I suppose that my testing line-up will be the following:

- Chet Baker, "Broken Wings" on 180 grams vinyl
- Thorens TD126 MkIII
- Shure V15-VI
- homebrew tube preamp (EF86+ECC88)
- homebrew line amp (ECC81)
- homebrew power amp (EC86/2A3)
- mother-supplied microphones on the sides of my head
- inboard analog signal processor (sometimes called brain)
- 15yrs Barbancourt rum
- Swiss bitter chocolate
- European common cat if available (purring is a benchmark for 50Hz noise.
American cats are surely tuned to 60)
- 5kg hammer to smash the phone in case of incoming calls

Definitely not scientific, but more fun.

Anyway, I suppose that I'll do something, someday, with my PC sound card and
a mike. The answers I got were quite helpful, thanks to all.

Ciao

Fabio



"Fabio Berutti" ha scritto nel messaggio
...
Dear RATs,

a question posed by Mr. Turner about my new LS is now puzzling me: what
kind of stuff is needed to test a loudspeaker? Is it possible to do it
with some VERY cheap microphone and the sound card included in any PC? I
don't want to spend a lot of $ in Bruel&Kjaer professional testing
equipments....

Ciao

Fabio



  #17   Report Post  
Ruud Broens
 
Posts: n/a
Default


"Fabio Berutti" wrote in message
news : Hmmm... I suppose that my testing line-up will be the following:
:
: - Chet Baker, "Broken Wings" on 180 grams vinyl
: - Thorens TD126 MkIII
: - Shure V15-VI
: - homebrew tube preamp (EF86+ECC88)
: - homebrew line amp (ECC81)
: - homebrew power amp (EC86/2A3)
: - mother-supplied microphones on the sides of my head
: - inboard analog signal processor (sometimes called brain)
: - 15yrs Barbancourt rum
: - Swiss bitter chocolate
: - European common cat if available (purring is a benchmark for 50Hz noise.
: American cats are surely tuned to 60)
: - 5kg hammer to smash the phone in case of incoming calls
:
: Definitely not scientific, but more fun.
:
: Anyway, I suppose that I'll do something, someday, with my PC sound card and
: a mike. The answers I got were quite helpful, thanks to all.
:
: Ciao
:
: Fabio

Heh. Did you read about Sander's '0 feedback' - aware cat , on RAO ? ;-)
Rudy:


  #18   Report Post  
Ruud Broens
 
Posts: n/a
Default


"Chris Morriss" wrote in message
...
: In message , François Yves
: Le Gal writes
: On Tue, 15 Feb 2005 21:50:04 +0100, "Ruud Broens"
: wrote:
:
: Also, there are offers combining MLSSA and some fair quality microphones
: with calibrated response curves - just google around in eu :-)
:
: A solution around MLSSA costs more than 5,000 EUR...
:
:
:
: MLSSA is grossly out of date and frighteningly expensive. (And runs
: under DOS!)
:
: Why not get a good quality sound card (like a DMX-6fire) and buy 'Sample
: Champion'? Better than MLSSA performance at a fraction of the price.
: --
: Chris Morriss

heh, that's the soundcard installed in this computer
I gave a link to a far cheaper solution, elsewhere in the thread.
cheers,
Rudy


  #19   Report Post  
Tom Schlangen
 
Posts: n/a
Default

Hi Fabio,

funny list of testing equippment :-) But i agree.

- European common cat if available (purring is a benchmark
for 50Hz noise.


We have 3 cats @ home and one or two of them sleeping in front
of the speakers while Mozart is playing is a sure sign that
all is okay.

During the breadboard stage of my 807PP, once a cat jumped
up and ran away as I switched the amp under construction on.
Surely enough, it showed at the scope that the circuit at
that time had stability problems at real speaker loads leading
to slight parasitic oscillations. Obviously, the cat noticed
that and didn?t like it :-)

Tom

--
  #20   Report Post  
Fabio Berutti
 
Posts: n/a
Default

I suppose that, being able to hear ultra-sounds up to 30 or 40K, our pets
can detect overtones due to instability or bad distortion products much
better than us.
In fact they are annoyed by many "technological" noises, particularly vacuum
cleaners or other small electric motors AFAIK: the bearings'whistle must be
like nails on the blackboard, for a cat.
There are dogs trained to spot drugs or explosives... maybe it is possible
to teach a cat to detect odd harmonics.

Ciao

Fabio


"Tom Schlangen" ha scritto nel messaggio
...
Hi Fabio,

funny list of testing equippment :-) But i agree.

- European common cat if available (purring is a benchmark
for 50Hz noise.


We have 3 cats @ home and one or two of them sleeping in front
of the speakers while Mozart is playing is a sure sign that
all is okay.

During the breadboard stage of my 807PP, once a cat jumped
up and ran away as I switched the amp under construction on.
Surely enough, it showed at the scope that the circuit at
that time had stability problems at real speaker loads leading
to slight parasitic oscillations. Obviously, the cat noticed
that and didn?t like it :-)

Tom

--





  #21   Report Post  
Patrick Turner
 
Posts: n/a
Default



Fabio Berutti wrote:

I suppose that, being able to hear ultra-sounds up to 30 or 40K, our pets
can detect overtones due to instability or bad distortion products much
better than us.
In fact they are annoyed by many "technological" noises, particularly vacuum
cleaners or other small electric motors AFAIK: the bearings'whistle must be
like nails on the blackboard, for a cat.
There are dogs trained to spot drugs or explosives... maybe it is possible
to teach a cat to detect odd harmonics.


One thing is for sure, cats sure don't need to be taught to detect odd dogs ;-)

Miao,

Patrick Turner.



Ciao

Fabio

"Tom Schlangen" ha scritto nel messaggio
...
Hi Fabio,

funny list of testing equippment :-) But i agree.

- European common cat if available (purring is a benchmark
for 50Hz noise.


We have 3 cats @ home and one or two of them sleeping in front
of the speakers while Mozart is playing is a sure sign that
all is okay.

During the breadboard stage of my 807PP, once a cat jumped
up and ran away as I switched the amp under construction on.
Surely enough, it showed at the scope that the circuit at
that time had stability problems at real speaker loads leading
to slight parasitic oscillations. Obviously, the cat noticed
that and didn?t like it :-)

Tom

--


  #22   Report Post  
The dumbest industriralized county on earth
 
Posts: n/a
Default

Get yourself a Rane RA 27 or RA 30 and get on with life.

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