I have some speaker systems and I want to test their frequency
response. I'm not a sound engineer or anything and I don't really
know much about audio. But I assumed I could do this in the
following way.

I found a test clip on the net which has several frequencies in the
audible range 20 Hz - 20 kHz, each playing for 2 seconds. I open it
in Nero Wave Editor and it shows that it has the same level from
start to finish.

Then I take my mic and place it close to a speaker, I mute the
other speaker and playback this file, recording with the
microphone. I then save the recording uncompressed and open it in
Nero Wave Editor to see how loud/quiet each frequency is.

My understanding is that the recording should be as close as
possible to the test file that I use as input.

I did this with two different speaker sets and you can see the
results below:

http://img224.echo.cx/my.php?image=t...esponse7xo.png
http://img224.echo.cx/my.php?image=o...esponse8hv.png

Original test file (downloaded recording):

http://img156.echo.cx/my.php?image=testclip7ci.png

Is this lousy frequency response or what? Am I doing something
wrong with my testing method?

On 28 Jun 2005 13:40:54 GMT, "Pink_isn't_well"
wrote:

I have some speaker systems and I want to test their frequency
response. I'm not a sound engineer or anything and I don't really
know much about audio. But I assumed I could do this in the
following way.

I found a test clip on the net which has several frequencies in the
audible range 20 Hz - 20 kHz, each playing for 2 seconds. I open it
in Nero Wave Editor and it shows that it has the same level from
start to finish.

Then I take my mic and place it close to a speaker, I mute the
other speaker and playback this file, recording with the
microphone. I then save the recording uncompressed and open it in
Nero Wave Editor to see how loud/quiet each frequency is.

My understanding is that the recording should be as close as
possible to the test file that I use as input.

I did this with two different speaker sets and you can see the
results below:

http://img224.echo.cx/my.php?image=t...esponse7xo.png
http://img224.echo.cx/my.php?image=o...esponse8hv.png

Original test file (downloaded recording):

http://img156.echo.cx/my.php?image=testclip7ci.png

Is this lousy frequency response or what? Am I doing something
wrong with my testing method?

What you are trying to do here is really difficult, even for experts
with many years of experience. You are suffering from a few specific
problems. First trying to do it in a normal room instead of an
anechoic chamber; I know you are trying to mitigate the effects by
close miking, but that doesn't help - a speaker is not designed to be
flay close up. Then you are using tones; this is virtually impossible
with speakers. You need to use filtered noise, perhaps a third of an
octave wide. This is to provide some averaging of the residue of the
room's effects. Lastly, you have overdriven the sound card with the
mic signal, causing clipping.

I'm sorry to have to tell you this, but unless you are prepared to get
really serious, give up with this plan.

d

Pearce Consulting
http://www.pearce.uk.com

(Don Pearce) wrote on Tue, 28 Jun 2005
14:03:54 GMT in rec.audio.tech:

I'm sorry to have to tell you this, but unless you are prepared
to get really serious, give up with this plan.


So there is absolutely no way I can get an idea of my speakers' FR
without spending thousands and moving them to some sort of
professional chamber?

Pink_isn't_well wrote:
(Don Pearce) wrote on Tue, 28 Jun 2005
14:03:54 GMT in rec.audio.tech:

I'm sorry to have to tell you this, but unless you are prepared
to get really serious, give up with this plan.

So there is absolutely no way I can get an idea of my speakers' FR
without spending thousands and moving them to some sort of
professional chamber?

Well, not THOUSANDS, but around about a kilobuck if you want
reliable, consistent, repeatable results. Do a web search for
something called ClioWin, which is a purpose-built measurement
system for Windows including a very reasonable microphone.

There are other packages which can be had cheaper, but require
more care and knowledge using them.

"Pink_isn't_well" wrote in message
...

Is this lousy frequency response or what?

Can't say; it depends on the frequency response of the microphone you're
using.

Tim

Pink_isn't_well wrote:
I have some speaker systems and I want to test their
frequency
response. I'm not a sound engineer or anything and I don't
really
know much about audio. But I assumed I could do this in
the
following way.

I found a test clip on the net which has several
frequencies in the
audible range 20 Hz - 20 kHz, each playing for 2 seconds.
I open it
in Nero Wave Editor and it shows that it has the same
level from
start to finish.

Then I take my mic and place it close to a speaker, I mute
the
other speaker and playback this file, recording with the
microphone. I then save the recording uncompressed and
open it in
Nero Wave Editor to see how loud/quiet each frequency is.

My understanding is that the recording should be as close
as
possible to the test file that I use as input.

I did this with two different speaker sets and you can see
the
results below:


http://img224.echo.cx/my.php?image=t...esponse7xo.png

http://img224.echo.cx/my.php?image=o...esponse8hv.png

It may not be as bad as it seems. One problem is that the
amplitude scale is given in percentage, when frequency
response is usually plotted on a dB scale. For example, 50%
on your FR curve is only 6 dB down from the peak level, and
10% is only 20 dB down. +/- 10 dB frequency response is not
all that bad, but it shows up as 10% - 100% on your chart.

Original test file (downloaded recording):

http://img156.echo.cx/my.php?image=testclip7ci.png

Is this lousy frequency response or what?

Hard to say.

Am I doing something wrong with my testing method?

For sure. As Don Pearce says, measuring the FR of speakers
correctly is a tall order, and your methodology is very
simplistic. If you want to see a better job of FR testing,
try downloading this softwa

http://audio.rightmark.org/downloads/rmaa55.exe

You also need a better microphone. About the cheapest one I
can recommend is this one:

http://www.zzounds.com/item--BEHECM8000

To interface it to your PC, you need this mic preamp or
something like it:

http://www.music123.com/Rolls-MP13-M...p-i11840.music

If you want better measurement softwa

http://www.etfacoustic.com/

Pink_isn't_well wrote:
I have some speaker systems and I want to test their frequency
response.

Before we get into the specifics of your case, let me ask you,
in all seriousness, why do you want to do this? Let's assume
for the moment your methods are correct and your data is good.
What are you going to do with this data? How are you going to
act on it? That's real important in determining WHAT data you
need to get.

Do you want to know the frequency response becuas you're just
curious or because you need to make design changes? Very
different sorts of data are needed.

That being said, let's proceed...

I'm not a sound engineer or anything and I don't really
know much about audio. But I assumed I could do this in the
following way.

I found a test clip on the net which has several frequencies in the
audible range 20 Hz - 20 kHz, each playing for 2 seconds. I open it
in Nero Wave Editor and it shows that it has the same level from
start to finish.

First problem: "several frequencies." Do you mean stepped sine
waves? Narrow band pink noise? What? All of these have their
advantages and disadvantages and require appropriate techniques
to gather useful data.

Then I take my mic

Second problem, what kind of mic? This has a profound influence
over the usability of the results. For reliable results, just
any ol' microphone won't do. Different microphones that may be
suitable different vocal or musical applications are generally
highly unsuitable for measurement purposes.

and place it close to a speaker,

Third problem: depending upon what you mean by "close," your
results are going to be severely skewed by a number of proximity
effects that make such measurements suspect under a number of
conditions.

Fourth problem: under what acoustical conditions are you measuring?
The existance of noise plus the influence of nearby reflective
boundaries and room-reletaed resonance can have a tremendous
influsence over such measurements.

I mute the
other speaker and playback this file, recording with the
microphone. I then save the recording uncompressed and open it in
Nero Wave Editor to see how loud/quiet each frequency is.

Fifth problem: such a display yells you nothing about frequency
response. Assuming the data you recorded is useable, a linear
display of amplitude is next to useless. FOr example, take the
differenence beween the loudest possible signal and one half as
loud: that's 1/4 of the height of the graph and corresponds
to a level difference of 6db between those to levels. But that
smae 1/4 height difference could correspond to a difference
of 10 db, if it's netween 25% and 75%, or it could correspond
to a difference of 34 dB if that 1/4 height is between 1% and
51%!

My understanding is that the recording should be as close as
possible to the test file that I use as input.

No, not necessarily.

Is this lousy frequency response or what?

It's worse than that: it's a useless frequency response. Because
of all the problems outlined above, your data is invalid. This
is not to say your speakers do or do not have a bad frequency
response: it's just that there is no way of knowing that from
the data you're presented.

Am I doing something wrong with my testing method?

Yes, regrettably, just about everything fundamental is wrong
with your method.

Start first with answering my first question: why do you want to
do this?

wrote on Tue, 28 Jun 2005 15:32:59 GMT in
rec.audio.tech:


Before we get into the specifics of your case, let me ask you,
in all seriousness, why do you want to do this?

Well, I got myself some speakers recently and they sounded like they
had too much bass. That's what I thought. I did find a review of them
on tomshardware which had a frequency response graph and it showed no
particular problem with the bass, it was roughly the same as the
treble. So I got curious and thought maybe I'll try something like
that myself and see what comes out. I knew that I wasn't going to get
the most accurate results, but I thought the results would be
interesting, particularly checking against other speakers I have
laying around here.

First problem: "several frequencies." Do you mean stepped sine
waves? Narrow band pink noise?

I used this: http://www.dogstar.dantimax.dk/testwavs/3stepoct.zip

Second problem, what kind of mic? This has a profound influence
over the usability of the results. For reliable results, just
any ol' microphone won't do.

Well, I knew of course that my mic is a cheap one, but I have to
admit that the recorded file sounded the same as what my ears were
telling me, and that's all that matters I guess. I used the same mic
on the other set of speakers, too.

and place it close to a speaker,

Third problem: depending upon what you mean by "close," your
results are going to be severely skewed by a number of proximity
effects that make such measurements suspect under a number of
conditions.

Why? What could those effects be?

Fourth problem: under what acoustical conditions are you
measuring? The existance of noise plus the influence of nearby
reflective boundaries and room-reletaed resonance can have a
tremendous influsence over such measurements.

Under my normal listening conditions, close to my computer. I did
turn off the AC though.

Fifth problem: such a display yells you nothing about frequency
response. Assuming the data you recorded is useable, a linear
display of amplitude is next to useless. FOr example, take the
differenence beween the loudest possible signal and one half as
loud: that's 1/4 of the height of the graph and corresponds
to a level difference of 6db between those to levels. But that
smae 1/4 height difference could correspond to a difference
of 10 db, if it's netween 25% and 75%, or it could correspond
to a difference of 34 dB if that 1/4 height is between 1% and
51%!

Ah, and this is one reason why I posted here, so I could get help.
What software would give more useful displays?

My understanding is that the recording should be as close as
possible to the test file that I use as input.

No, not necessarily.

Why?




Thanks for the reply, I'm not trying to say that my method is perfect
or anything, just to learn some stuff and maybe evaluate my speakers
(or my ears) better.

Pink_isn't_well wrote:
wrote on Tue, 28 Jun 2005 15:32:59 GMT in
rec.audio.tech:


Before we get into the specifics of your case, let me ask you,
in all seriousness, why do you want to do this?

Well, I got myself some speakers recently and they sounded like they
had too much bass. That's what I thought. I did find a review of them
on tomshardware which had a frequency response graph and it showed no
particular problem with the bass, it was roughly the same as the
treble. So I got curious and thought maybe I'll try something like
that myself and see what comes out. I knew that I wasn't going to get
the most accurate results, but I thought the results would be
interesting, particularly checking against other speakers I have
laying around here.

Fine, but you still need to address the question, what are you going
to do with the results?

Second problem, what kind of mic? This has a profound influence
over the usability of the results. For reliable results, just
any ol' microphone won't do.

Well, I knew of course that my mic is a cheap one, but I have to
admit that the recorded file sounded the same as what my ears were
telling me, and that's all that matters I guess. I used the same mic
on the other set of speakers, too.

But the mic is one of the most important links in the chain.

and place it close to a speaker,

Third problem: depending upon what you mean by "close," your
results are going to be severely skewed by a number of proximity
effects that make such measurements suspect under a number of
conditions.

Why? What could those effects be?

There are a number of such effects, depending upon the distance.
I'm hardly going to take the time to catalog and explain them all,
but consider, for example, close-miking a woofer, with the result
that there are significant differences in the distances to different
parts of the driver, with the result that cancellations occur at
some frequencies. These cancellations will not be present in the
far field.

Fourth problem: under what acoustical conditions are you
measuring? The existance of noise plus the influence of nearby
reflective boundaries and room-reletaed resonance can have a
tremendous influsence over such measurements.

Under my normal listening conditions, close to my computer. I did
turn off the AC though.

Fine, but did you attempt, at all, to account for the influence
of the room boundaries and such?

Fifth problem: such a display yells you nothing about frequency
response. Assuming the data you recorded is useable, a linear
display of amplitude is next to useless. FOr example, take the
differenence beween the loudest possible signal and one half as
loud: that's 1/4 of the height of the graph and corresponds
to a level difference of 6db between those to levels. But that
smae 1/4 height difference could correspond to a difference
of 10 db, if it's netween 25% and 75%, or it could correspond
to a difference of 34 dB if that 1/4 height is between 1% and
51%!

Ah, and this is one reason why I posted here, so I could get help.
What software would give more useful displays?

Software thatv is more suited to measuring frequency response.
what you picked is uttewrly unsuitable to the task, as you're
discovering. Check out some of the references given.

My understanding is that the recording should be as close as
possible to the test file that I use as input.

No, not necessarily.

Why?

Because of all the problems you have encountered. Because the
speaker may not have been designed that way, on purpose.
Because you may not be measuring on the preferred axis
of the system, at a sufficient distance, and more.

Well, I got myself some speakers recently and they sounded like
they had too much bass.

Do they have a volume control for the "sub-woofer" speaker?

That's what I thought. I did find a review of them on tomshardware
which had a frequency response graph and it showed no particular
problem with the bass, it was roughly the same as the treble.

Did you reveal what speakers you are talking about? I've never seen
reviews on TomsHardware for anything except plastic toy "computer"
speakers.

Nothing against plastic toy computer speakers, they have their place.
I use them myself. But they will never be something that one would
expect any kind of accurate frequency response from.

"Richard Crowley" wrote on Wed, 29 Jun
2005 17:58:49 GMT in rec.audio.tech:

Did you reveal what speakers you are talking about? I've never seen
reviews on TomsHardware for anything except plastic toy "computer"
speakers.


http://www6.tomshardware.com/consume..._audio-05.html

Well, yes, I'm talking about "toy" speakers (why would they be toy?).
Of course you can connect them to any kind of device, not just
computers.

wrote on Tue, 28 Jun 2005 15:32:59 GMT in
rec.audio.tech:

Fifth problem: such a display yells you nothing about frequency
response. Assuming the data you recorded is useable, a linear
display of amplitude is next to useless.

Any free software I can use to open my waves and have them on a dB
scale?

For a while, Cool Edit Pro was available as a demo version. Now that
they're no longer making it (I believe Adobe bought it out), you might have
to do some digging.

"Pink_isn't_well" wrote in message
...
wrote on Tue, 28 Jun 2005 15:32:59 GMT in
rec.audio.tech:

Fifth problem: such a display yells you nothing about frequency
response. Assuming the data you recorded is useable, a linear
display of amplitude is next to useless.

Any free software I can use to open my waves and have them on a dB
scale?

"Pink_isn't_well" wrote ...
Any free software I can use to open my waves and have them on a dB
scale?

Audacity? GoldWave? likely others?

But it doesn't really mean anything unless you are interested in the
combined frequency response of the speakers AND the microphone.

And even if you had a flat instrumentation mic, you can get any curve
you wish by moving the mic a fraction of an inch in any direction in
your "measurement environment".

Pink_isn't_well wrote:
wrote on Tue, 28 Jun 2005 15:32:59 GMT in
rec.audio.tech:

Fifth problem: such a display yells you nothing about frequency
response. Assuming the data you recorded is useable, a linear
display of amplitude is next to useless.

Any free software I can use to open my waves and have them on a dB
scale?

Why? The data you have is probably useless. Displaying useless
data in the proper format is still pretty useless.

Do you remember all the other problems we discussed? The issue
of the display format is probably the easiest to solve and the
least useful of the bunch. It's not going to make your data
any more valid.

And it's been revealed that the epseakers you're measuring are
so-called "computer speakers." Almost without exception, these
sorts of things range from plain awful to truly, miserably
dreadful. They aren't toys, they're worse than toys. The
designers of these things (and I've had the misfortune of working
with some of them) are required to shoehorn as much pizzazz and
sparkle and over-hyped specifications into the absolute cheapest
package possible, and about the LAST thing on their mind is
reasonable acoustic performance. A fair number of them are, in
fact, made in a number of far east companies whose main product
line is high-volume (as in millions) injection-molded products
ranging anywhere from plastic forks and spoons to telephone
cases. They know next to nothing about loudspeakers, only how
to make a whole bunch of anything at the lowest possible price.

One of my clients makes a computer-based system and has to supply
speakers with it. Their customer expects the speakers to be worth
on the order of $100-$150 a pair, and the client had a devil of
a time finding speakers at OEM pricing for any more tha $20 the
pair!

They're junk. They measure like junk, they sound, as you said,
like junk.

Why bother?

wrote in message
oups.com...
One of my clients makes a computer-based system and has to supply
speakers with it. Their customer expects the speakers to be worth
on the order of $100-$150 a pair, and the client had a devil of
a time finding speakers at OEM pricing for any more tha $20 the
pair!

Surely you told them they are looking in the wrong spot?
They should be checking out the cheaper near field monitors available from
the pro audio manufacturers.

MrT.

wrote on Thu, 30 Jun 2005 00:14:41 GMT in
rec.audio.tech:

They know next to nothing about loudspeakers, only how
to make a whole bunch of anything at the lowest possible price.


I see. Is this true even for the more expensive systems, ranging $300
- $500? Or just for the cheap systems like mine?

"Pink_isn't_well" wrote ...
dpierce wrote :
They know next to nothing about loudspeakers, only how
to make a whole bunch of anything at the lowest possible price.

I see. Is this true even for the more expensive systems, ranging $300
- $500? Or just for the cheap systems like mine?

Define "more expensive systems". As far as I have seen ANYTHING
intended for the "computer speaker market" suffers from this problem
regardless of selling price.

"Computer speakers" as a class are held in low regard in these circles.
I've never seen any that even aspired to having a decent frequency
response. Glitz, thump, and number of channels/speakers seems far
more important than audio quality.

Even historically prestigious names in audio history like Altec have
been sold off to the highest bidder and are now put on toy plastic
computer speakers. How the mighty have fallen. James B Lansing
just be spinning in his grave.

"Pink_isn't_well" wrote in message
...
wrote on Tue, 28 Jun 2005 15:32:59 GMT in
rec.audio.tech:

Fifth problem: such a display yells you nothing about frequency
response. Assuming the data you recorded is useable, a linear
display of amplitude is next to useless.

Any free software I can use to open my waves and have them on a dB
scale?

You may have got some suitable software with your sound card. Otherwise,
you can download Goldwave - it's not free, but you can use it first and
decide whether to pay later.

You can also use Goldwave to generate test signals. The test signal you are
using starts with a lot of LF sound, from 20Hz to 40Hz, which is below the
LF range of your speakers,

You will have a problem with the microphone ... most microphones are
designed to be less responsive to low frequencies below about 70Hz, and I
believe it's the LF region you are most concerned with..

You have another problem with the microphone, in that it won't have a flat
response in the mid-and HF region. Again, most microphones are deliberately
designed that way.

What you could try is measure your speakers, measure another pair which you
think sound normal, and compare the results. If your speakers are
over-responsive in part of the frequency range, this might help show where.

Anyway, it's well worth doing, because it's fun and educational..

Tim

" wrote:


Do you want to know the frequency response becuas you're just
curious or because you need to make design changes? Very
different sorts of data are needed.

Sounds mostly like he wants to have some 'fancy looking pictures' to
prove/disprove whatever his theory might be. His methodology however looks
to be pretty dodgy.