Help measuring frequency response for a speaker system

[Pink_isn't_well]

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=t3000freqresponse7xo.png
http://img224.echo.cx/my.php?image=oldspeakersfreqresponse8hv.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?

[Don Pearce]

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=t3000freqresponse7xo.png
>http://img224.echo.cx/my.php?image=oldspeakersfreqresponse8hv.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

[Tim Martin]

"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

[Arny Krueger]

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=t3000freqresponse7xo.png
>
http://img224.echo.cx/my.php?image=oldspeakersfreqresponse8hv.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 software:

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-Mini-Mic-Preamp-i11840.music

If you want better measurement software:

http://www.etfacoustic.com/

[[email protected]]

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?

[Pink_isn't_well]

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]

(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?

[[email protected]]

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.

[[email protected]]

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.

[Richard Crowley]

> 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.

[Pink_isn't_well]

"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/consumer/20041013/2-1_hifi_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.

[Pink_isn't_well]

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?

[Richard Crowley]

"Pink_isn't_well" wrote ...
> "Richard Crowley" wrote :
>> 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/consumer/20041013/2-1_hifi_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.

If you are really concerned enough about audio quality to go to the
trouble of trying to run frequency response curves, you likely will
not be sataisfied with ANY of those speakers that are sold to the
computer crowd. They're OK for playing games or listening to
internet radio, etc. but I wouldn't trust them for any kind of
qualitative audio mixing, processing etc.

I'd think that the minimum for any kind of quality would be some of
the powered monitors sold for the home recording crowd. Something
like M-Audio or Behringer or Roland, etc. This kind of stuff....
http://www.musiciansfriend.com/srs7/g=rec/search?c=4901

If you aren't doing serious audio processing, but just curious about
your computer speakers, maybe you'd be happier not knowing. :-)

[MZ]

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?

[Richard Crowley]

"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".

[[email protected]]

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?

[Mr.T]

> 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.

[Tim Martin]

"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

[Pink_isn't_well]

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?

[Richard Crowley]

"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.

[Michael Conzo]

" > 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.

[Ron Capik]

Pink_isn't_well wrote:

> Michael Conzo > wrote on Fri, 01 Jul
> 2005 04:06:46 GMT in rec.audio.tech:
>
> > Sounds mostly like he wants to have some 'fancy looking
> > pictures' to prove/disprove whatever his theory might be.
>
> No. You could've read the previous postings before you write this,
> couldn't you?

Ummm, Usenet, ...free advice, ...you get what you paid for.
~quityourbitchin~

Later...

Ron Capik <<< cynic in training >>>
--

[Pink_isn't_well]

Ron Capik > wrote on Fri, 01 Jul 2005
13:37:28 GMT in rec.audio.tech:

> Ummm, Usenet, ...free advice, ...you get what you paid for.
>

I've gotten lots of good advice here already.

[Richard Crowley]

"Pink_isn't_well" wrote ...
> Michael Conzo wrote :
>> Sounds mostly like he wants to have some 'fancy looking
>> pictures' to prove/disprove whatever his theory might be.
>
> No. You could've read the previous postings before you write this,
> couldn't you?

OK, then what ARE you trying to do? I didn't think Mr. Conzo's
characterization was that far from the mark. Sounds like all you need
is some way to balance your subwoofer, (and you never responded
to the obvious questions about setting the subwoofer level).

But then you got off on trying to actually measure the frequency
response without knowing what a huge can of worms it is and
how far in over your head you are.

If it were me, I would just play some pink noise and tune the
subwoofer level in-situ by ear. That is ultimately what counts,
after all.

[Pink_isn't_well]

"Richard Crowley" > wrote on Fri, 01 Jul
2005 16:07:17 GMT in rec.audio.opinion:

> If it were me, I would just play some pink noise and tune the
> subwoofer level in-situ by ear. That is ultimately what counts,
> after all.
>

Yeah, you're very smart. The problem is that bass level is too high
even with the subwoofer turned off.

[Arny Krueger]

"Pink_isn't_well" > wrote in message

> "Richard Crowley" > wrote on
Fri,
> 01 Jul 2005 16:07:17 GMT in rec.audio.opinion:
>
>> If it were me, I would just play some pink noise and tune
the
>> subwoofer level in-situ by ear. That is ultimately what
>> counts, after all.
>>
>
> Yeah, you're very smart. The problem is that bass level is
too
> high even with the subwoofer turned off.

Sounds like room resonance problems.

Here's a potential solution: http://www.realtraps.com/

[Richard Crowley]

"Arny Krueger" > wrote in message
...
> "Pink_isn't_well" > wrote in message
>
>> "Richard Crowley" > wrote on
> Fri,
>> 01 Jul 2005 16:07:17 GMT in rec.audio.opinion:
>>
>>> If it were me, I would just play some pink noise and tune
> the
>>> subwoofer level in-situ by ear. That is ultimately what
>>> counts, after all.
>>>
>>
>> Yeah, you're very smart. The problem is that bass level is
> too
>> high even with the subwoofer turned off.
>
> Sounds like room resonance problems.
>
> Here's a potential solution: http://www.realtraps.com/

Or maybe the subwoofer level adjustment is broken.
Doesn't seem to have an actual hardware pot. Uses
some kind of remote control(?)

[Pink_isn't_well]

"Richard Crowley" > wrote on Fri, 01 Jul
2005 22:50:43 GMT in rec.audio.tech:

> Or maybe the subwoofer level adjustment is broken.
> Doesn't seem to have an actual hardware pot. Uses
> some kind of remote control(?)
>

Wired control. It works, if I turn it up the effect is even worse. I
guess they make them that way so they can give stronger effects with
games and movies.

[[email protected]]

Pink_isn't_well wrote:
> "Richard Crowley" > wrote on Fri, 01 Jul
> 2005 22:50:43 GMT in rec.audio.tech:
>
> > Or maybe the subwoofer level adjustment is broken.
> > Doesn't seem to have an actual hardware pot. Uses
> > some kind of remote control(?)
> >
>
> Wired control. It works, if I turn it up the effect is even worse. I
> guess they make them that way so they can give stronger effects with
> games and movies.

I don't know how many systems use compensation, but the one I have on
my computer obviously has some form of loudness or automatic control
of the bass driver, a 3 piece unit. The response depends on the volume.
I could never get it right by any adjustmet or positioning, always too
much
low bass, or I should say too much upper bass.

It sounds like it would be much easier if you were back in the 70's,
with all those spectrum analyzers that were available back then.
They came with a mic, and with pink noise or warble tones, you could
get a rough look at what your looking for. They are still there
on Ebay.

greg

[Arny Krueger]

> wrote in message
oups.com


> It sounds like it would be much easier if you were back in
the
> 70's, with all those spectrum analyzers that were
available
> back then.

Just because they aren't in the same form as they were then,
doesn't mean that they don't exist.

> They came with a mic, and with pink noise or warble tones,
you
> could get a rough look at what your looking for.

Modern stuff does more and has far higher resolution. Much
of it is computer-based.

[Carl Valle]

"Arny Krueger" > wrote in message
...
> > wrote in message
> oups.com
>
>
>> It sounds like it would be much easier if you were back in
> the
>> 70's, with all those spectrum analyzers that were
> available
>> back then.
>
> Just because they aren't in the same form as they were then,
> doesn't mean that they don't exist.
>
>> They came with a mic, and with pink noise or warble tones,
> you
>> could get a rough look at what your looking for.
>
> Modern stuff does more and has far higher resolution. Much
> of it is computer-based.
>
>

You won't need much resolution since the damn speakers have no midrange or
treble.
I can get pretty good generalized response curves off my old Audio Control
and its cheap measurement mic.

As far as te anechoic chamber, that is not actually required. You can make
measurements in the back yard and get fairly good cures for speaker design
problems such as box tuning and beaming. its a good way to measure free air
resonance also

[Arny Krueger]

"Carl Valle" > wrote in message
m
> "Arny Krueger" > wrote in message
> ...
>> > wrote in message
>>
oups.com
>>
>>
>>> It sounds like it would be much easier if you were back
in
>> the
>>> 70's, with all those spectrum analyzers that were
>> available
>>> back then.
>>
>> Just because they aren't in the same form as they were
then,
>> doesn't mean that they don't exist.
>>
>>> They came with a mic, and with pink noise or warble
tones,
>> you
>>> could get a rough look at what your looking for.
>>
>> Modern stuff does more and has far higher resolution.
Much
>> of it is computer-based.

> You won't need much resolution since the damn speakers
have no
> midrange or treble.

That makes no sense at all. If speakers have response
problems, we need our ears and our test equipment to
determine what the problem is. Bad speakers aren't a
justification for having poor test equipment.

> I can get pretty good generalized response curves off my
old
> Audio Control and its cheap measurement mic.

You get something, but how accurate is it?

Here's an independent critical look at the Audio Control
RTA:

http://www.hometheaterhifi.com/volume_6_1/audiocontrolc101seequalizer.html

"For one thing, a simple spectrum analyzer cannot capture
information in the time domain, and therefore cannot
differentiate between direct sound and reflected sound. So,
what the spectrum analyzer shows is the average of the two.
Because of this, if adjusted solely by the RTA, an EQ alters
both the direct and indirect sound so that the two sum flat,
although neither may be so individually. Human hearing works
in a much more complex manner, so that although we may not
hear the two (direct and indirect sound) as distinctly
separate in most home environments, altering one to correct
the other won't always work very well. One of the best
examples of this is to get a dipolar speaker, which usually
has a horrible pink noise response due to a high ratio of
delayed, reflected sound from the rear wall.

"If you adjust an EQ to compensate for the RTA reading, you
often get sliders shoved all over the place, and a very
weird tonality. This is because the process of hearing
somewhat compensates for the environment, and takes much of
the comb filtering effects of reflected/direct sound
interaction which skew the tonality of continuous pink
noise, and puts it to use with impulsive signals to derive
spatial cues about the environment. That's why
bipolar/dipolar speakers tend to do such a great job
providing a "they are here" presentation. Tangent aside,
even though an equalizer can slightly compensate for room
problems, if the room's broken, you're best off fixing the
room.

"Secondly, a spectrum analyzer, especially a 10 band, 1
octave jobbie, has limited frequency resolution, looking
only across relatively broad sections. For instance, the
frequency response may vary 10 dB up and down, but so long
as it averages within that octave, appears perfectly flat on
the analyzer. The corollary is that an equalizer with
similar resolution cannot effectively compensate for narrow
band response peaks or dips caused either by loudspeaker
problems or extreme room modes.


> As far as the anechoic chamber, that is not actually
required. You can make
> measurements in the back yard and get fairly good
> cures for speaker design problems such as box tuning and
> beaming. its a good way to measure free air resonance
also.

Actually, a RTA is a very poor means for measuring woofer
free air resonance. A signal generator a resistor and a AC
voltmeter are the classic means which yields excellent
results. Since I have a highly accurate computer-based
speaker impedance-measuring facility, that's what I use.

The technology of acoustic measurements has made dramatic
improvements in performance and convenience in the last 5-10
years. The key component has been the computer with an
apporpriate audio interface.

[GregS]

In article >, "Arny Krueger" > wrote:
>"Carl Valle" > wrote in message
m
>> "Arny Krueger" > wrote in message
>> ...
>>> > wrote in message
>>>
oups.com
>>>
>>>
>>>> It sounds like it would be much easier if you were back
>in
>>> the
>>>> 70's, with all those spectrum analyzers that were
>>> available
>>>> back then.
>>>
>>> Just because they aren't in the same form as they were
>then,
>>> doesn't mean that they don't exist.
>>>
>>>> They came with a mic, and with pink noise or warble
>tones,
>>> you
>>>> could get a rough look at what your looking for.
>>>
>>> Modern stuff does more and has far higher resolution.
>Much
>>> of it is computer-based.
>
>> You won't need much resolution since the damn speakers
>have no
>> midrange or treble.
>
>That makes no sense at all. If speakers have response
>problems, we need our ears and our test equipment to
>determine what the problem is. Bad speakers aren't a
>justification for having poor test equipment.
>
>> I can get pretty good generalized response curves off my
>old
>> Audio Control and its cheap measurement mic.
>
>You get something, but how accurate is it?
>
>Here's an independent critical look at the Audio Control
>RTA:
>
>http://www.hometheaterhifi.com/volume_6_1/audiocontrolc101seequalizer.html
>
>"For one thing, a simple spectrum analyzer cannot capture
>information in the time domain, and therefore cannot
>differentiate between direct sound and reflected sound. So,
>what the spectrum analyzer shows is the average of the two.
>Because of this, if adjusted solely by the RTA, an EQ alters
>both the direct and indirect sound so that the two sum flat,
>although neither may be so individually. Human hearing works
>in a much more complex manner, so that although we may not
>hear the two (direct and indirect sound) as distinctly
>separate in most home environments, altering one to correct
>the other won't always work very well. One of the best
cut

This is all very interesting. I suppose one could go on and on
about measuring speakers and also comparing this to listening
to speakers. I do know delayed sound is not as loud to
the ear,. Perhaps that sort of diminishes its importance in
measuring response.

I have used my trusty cheap BSR display unit with remarkable results
over time. I have come to trust its readings for the most part,
except for the lowest and highest frequency ranges. Even if its off,
its interesting to compare different responses of various
speakers.

greg

[Mr.T]

"Arny Krueger" > wrote in message
...
> The technology of acoustic measurements has made dramatic
> improvements in performance and convenience in the last 5-10
> years. The key component has been the computer with an
> apporpriate audio interface.

Whilst I agree with your other points, computer controlled measurement
systems have been used for over 30 years.
Obviously they have steadily improved, but I see no radical developments
that have only occurred in the last 5 years, or even 10.

Maybe you mean the cost is now within the range of many amateurs?
Unfortunately though, the concept of measurement uncertainty doesn't seem to
have trickled down along with the technology.

MrT.

[Richard Crowley]

"Mr.T" wrote ...
> Whilst I agree with your other points, computer controlled measurement
> systems have been used for over 30 years.
> Obviously they have steadily improved, but I see no radical developments
> that have only occurred in the last 5 years, or even 10.
>
> Maybe you mean the cost is now within the range of many amateurs?
> Unfortunately though, the concept of measurement uncertainty doesn't seem
> to
> have trickled down along with the technology.

And computer-aided trickery can go only so far to cheat the
physical/acoustical facts of life. (i.e. measurement environment,
etc.)

[Arny Krueger]

"Mr.T" <MrT@home> wrote in message

> "Arny Krueger" > wrote in message
> ...

>> The technology of acoustic measurements has made dramatic
>> improvements in performance and convenience in the last
5-10
>> years. The key component has been the computer with an
>> apporpriate audio interface.

> Whilst I agree with your other points, computer controlled
> measurement systems have been used for over 30 years.

Cars have been used for over 100 years, doesn't mean that
they haven't involved over that time.

> Obviously they have steadily improved, but I see no
radical
> developments that have only occurred in the last 5 years,
or
> even 10.

I'm speaking in the context of measurements by enthusiasts
and listeners.

> Maybe you mean the cost is now within the range of many
> amateurs?

Yes.

> Unfortunately though, the concept of measurement
> uncertainty doesn't seem to have trickled down along with
the
> technology.

What do you mean by that?

[Ben Bradley]

In rec.audio.tech and rec.audio.opinion, On Fri, 8 Jul 2005 06:21:30
-0400, "Arny Krueger" > wrote:

>"Mr.T" <MrT@home> wrote in message

>> "Arny Krueger" > wrote in message
>> ...
>
>>> The technology of acoustic measurements has made dramatic
>>> improvements in performance and convenience in the last
>5-10
>>> years. The key component has been the computer with an
>>> apporpriate audio interface.

>...

>> Maybe you mean the cost is now within the range of many
>> amateurs?
>
>Yes.
>
>> Unfortunately though, the concept of measurement
>> uncertainty doesn't seem to have trickled down along with
>the
>> technology.
>
>What do you mean by that?

I understood him to mean that high-quality measurement equipment is
now inexpensive, but many people who can afford it and will buy it
don't know how to effectively use it or interpret the results.

-----
http://www.mindspring.com/~benbradley

[George Middius]

Ben Bradley said to the Krooborg:

>>> Unfortunately though, the concept of measurement
>>> uncertainty doesn't seem to have trickled down
>>> along with the technology.

>>What do you mean by that?

> I understood him to mean that high-quality measurement equipment is
>now inexpensive, but many people who can afford it and will buy it
>don't know how to effectively use it or interpret the results.

Please spare Arnii your peacock's tail of superior knowledge. Arnii is a grunt's
grunt.

[Mr.T]

"Ben Bradley" > wrote in message
...
> >> Unfortunately though, the concept of measurement
> >> uncertainty doesn't seem to have trickled down along with
> >> the technology.
> >
> >What do you mean by that?
>
> I understood him to mean that high-quality measurement equipment is
> now inexpensive, but many people who can afford it and will buy it
> don't know how to effectively use it or interpret the results.

Yes. Access to a million dollar + lab is usually only for those with
measurement experience, understanding of proper procedures, calibration
requirements, and how to interpret the test results and uncertainty.

Having access to a computer, soundcard and microphone requires none of those
things. Yet many still think their results are beyond reproach.

MrT.

[Arny Krueger]

"Mr.T" <MrT@home> wrote in message

> "Ben Bradley" > wrote
in
> message ...
>>>> Unfortunately though, the concept of measurement
>>>> uncertainty doesn't seem to have trickled down along
with
>>>> the technology.
>>>
>>> What do you mean by that?
>>
>> I understood him to mean that high-quality measurement
>> equipment is now inexpensive, but many people who can
afford
>> it and will buy it don't know how to effectively use it
or
>> interpret the results.
>
> Yes. Access to a million dollar + lab is usually only for
> those with measurement experience, understanding of proper
> procedures, calibration requirements, and how to interpret
the
> test results and uncertainty.
>
> Having access to a computer, soundcard and microphone
requires
> none of those things. Yet many still think their results
are
> beyond reproach.

Chauvenism aside, the results one gets with intelligent
procedures, intelligent equipment choices, and the use of a
computer, soundcard and microphone does serve one's
technical interests a whole lot better than a 10-band audio
analyzer.

[[email protected]]

Arny Krueger wrote:
> > Having access to a computer, soundcard and microphone
> > requires none of those things. Yet many still think
> > their results are beyond reproach.
>
> Chauvenism aside, the results one gets with intelligent
> procedures, intelligent equipment choices, and the use of a
> computer, soundcard and microphone does serve one's
> technical interests a whole lot better than a 10-band audio
> analyzer.

So, you say that good technical measurements require the
following ingredients:

1. Intelligent procedures
2. Intelligent equipment choices

I would agree.

I would further point out that the majority of audio measurements
are done using, at most, only one of the two above.

Thus, having made "intelligent equipment choices" does NOT,
as suggested, automatically mean that the results are better
than some random 10-band real-time analyzer.

Case in point: a modern PC and sound card choice running FFT-
based software can easily show that a stable, very low distortion
sine wave has lots of sideband distortion and jitter, simply
because the person running it doesn't understand the issues
of window edge discontinuity and proper windowing techniques.
The very same signal, measured two different ways, could exhibit
itself as a pure, single-bin spike or something with wide, shallow
skirts that extend to the band edges, all because of differences
in procedures.

In the hands of someone who does NOT understand these sorts of
subtleties, I would argue, based not only on theory but on watching
people doing it, that they're probably better off with the
equivalent of a 1/3 or 1/2 octave real-time analyzer.

[Mr.T]

"Arny Krueger" > wrote in message
...
> Chauvenism aside,

An extreme interpretation.

> the results one gets with intelligent
> procedures, intelligent equipment choices, and the use of a
> computer, soundcard and microphone does serve one's
> technical interests a whole lot better than a 10-band audio
> analyzer.

The results one gets with either need to be interpreted properly and not
taken as gospel.
Some knowledge and experience is usually required.

MrT.