• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Speaker Measurement Thread

ken kantor said:
Pete,

1- What do you mean by RTA? If you are wanting to average out noise, that implies synchronous, time-domain sampling. Neither REW nor TrueRTA can do that. Holm probably can. (When I looked at REW a while back, it had no windowing capabilities, which was a very serious limitation.)

2- I think the MXL uses vanilla USB audio drivers.

-k
Click to expand...

Hi Ken,

First concerning windowing, I use LAUD for my main measurement system - it has windowing. I do think that REW now has windowing also but since that is not my main interest I did not look for it. My intent for this system is to do in room measurements in order to see the influence of the room. The RTA feature is new in REW, and there is an option for PN Pink Noise, the averaging works since the mic noise is uncorrelated.

The MXL uses the "default" USB audio drivers in XP - probably from MS.
 
Last edited:
If it is using the default drivers then there should be no problem with them.

I have not looked at this pre, but can you do a loop back test with it?
 
"I use LAUD for my main measurement system - it has windowing."

Great, you are all set. I hear that's an excellent program.


"...the averaging works since the mic noise is uncorrelated."

That is only true if one uses vector averaging, ie- synchronous sampling with phase info. If scalar averaging is used there will be no increase in S/N ratio. In other words, one can't apply averaging to a filter-based RTA to gain any noise advantage, because only absolute magnitude information is available. I can run 1000 averages on TrueRTA, yet the S/N ratio of the measurement won't change at all. The curves might get smoother, but the mic or room noise won't drop.

-k
 
Last edited:
ken kantor said:
"I use LAUD for my main measurement system - it has windowing."

Great, you are all set. I hear that's an excellent program.


"...the averaging works since the mic noise is uncorrelated."

That is only true if one uses vector averaging, ie- synchronous sampling with phase info. If scalar averaging is used there will be no increase in S/N ratio. In other words, one can't apply averaging to a filter-based RTA to gain any noise advantage, because only absolute magnitude information is available. I can run 1000 averages on TrueRTA, yet the S/N ratio of the measurement won't change at all. The curves might get smoother, but the mic or room noise won't drop.

-k
Click to expand...

What you are citing is the strict definition; there are many exceptions that provide a significant improvement but perhaps not ideal:
http://en.wikipedia.org/wiki/Signal_averaging

One of my specialties is communications systems and signal processing.

http://en.wikipedia.org/wiki/Flicker_noise

http://en.wikipedia.org/wiki/Burst_noise
 
Last edited:
I have a TASCAM US-144 and Behringer ECM8000 mic. Have been using REW software to try and measure speaker response. But as Ken Kantor pointed out there is no way to Window the measurement and eliminate the room effects on the FR measurement.

I've seen Zilch use CLIO in the Zilch Lab, but don't want to invest a couple hundred in software.

Is there a good and free software available for a hobbyist like me? How about the HOLMmpulse software mentioned earlier? Is this software easy to use?
 
I find it rather interesting that people point out the lack of windowing as a disadvantage of REW. The intent
of REW is to analyze the room effects, therefore it would be wrong to window them out. It will also produce
files for programming some of the more advanced room EQ systems such as the Behringer:
http://www.bhphotovideo.com/c/product/280608-REG/Behringer_DEQ2496_DEQ2496_Digital_EQ.html

There are several free programs with windowing, but I have no experience with them. Speaker Workshop, Holm
which is getting a lot of attention here:
http://www.diyaudio.com/forums/mult...lse-measuring-frequency-impulse-response.html

and there are others, ARTA:
http://www.fesb.hr/~mateljan/arta/
 
juniorJBL said:
If it is using the default drivers then there should be no problem with them.

I have not looked at this pre, but can you do a loop back test with it?
Click to expand...

My XP system is reasonably clean, computers are one of my specialties, however perhaps the default drivers
from MS are sub standard - would not be anything new.

Can't easily do a loopback since the only input is balanced XLR with phantom power. I measured the freq
response with a very flat HP signal generator and it was very tight from 20 to 20K; IIRC less than .25 dB down.
 
Pete B said:
My XP system is reasonably clean, computers are one of my specialties, however perhaps the default drivers
from MS are sub standard - would not be anything new.

Can't easily do a loopback since the only input is balanced XLR with phantom power. I measured the freq
response with a very flat HP signal generator and it was very tight from 20 to 20K; IIRC less than .25 dB down.
Click to expand...

Yeah I'm in the computer field as well.

I just asked because my speaker tester uses the default usb audio drivers and I have not had an issue. Just trying to help locate the problem.

Although I have had issues with the Fast track pro and to many usb devices plugged in. Maybe this is an issue?

BTW is it a Intel chipset or AMD. Might be able to find updated drivers for the chipset from the manufacture.
 
Last edited:
Pete B said:
I find it rather interesting that people point out the lack of windowing as a disadvantage of REW. The intent
of REW is to analyze the room effects, therefore it would be wrong to window them out.
Click to expand...

Hello Pete,

No doubt....I've been misusing REW to try and measure freq. response on speakers without room interference. Will check out the HOLM software.
 
Last edited:
Pete B said:
What you are citing is the strict definition; there are many exceptions that provide a significant improvement but perhaps not ideal:
http://en.wikipedia.org/wiki/Signal_averaging

One of my specialties is communications systems and signal processing.

http://en.wikipedia.org/wiki/Flicker_noise

http://en.wikipedia.org/wiki/Burst_noise
Click to expand...

Pete, I know and respect your background. Just trying to make things clear for all readers here. The first sentence of your first citation says it all:

"Signal averaging is a signal processing technique applied in the time domain..."

The operative words here are, "time domain." Noise mitigation via signal averaging cannot be done in the frequency domain.

-k
 
Last edited:
Pete B said:
I find it rather interesting that people point out the lack of windowing as a disadvantage of REW. The intent
of REW is to analyze the room effects, therefore it would be wrong to window them out. It will also produce
files for programming some of the more advanced room EQ systems such as the Behringer:
http://www.bhphotovideo.com/c/product/280608-REG/Behringer_DEQ2496_DEQ2496_Digital_EQ.html

There are several free programs with windowing, but I have no experience with them. Speaker Workshop, Holm
which is getting a lot of attention here:
http://www.diyaudio.com/forums/mult...lse-measuring-frequency-impulse-response.html

and there are others, ARTA:
http://www.fesb.hr/~mateljan/arta/
Click to expand...

Pete,

To my way of thinking, a room doesn't have a single, stable response. The room response varies substantially with integration time. The easiest way to see this is to measure a room with pink noise, then measure it with a chirp, then with a slowly swept sine. Same room, but very different response curves will result. Using something like REW to investigate room response means accepting an integration time and window that someone else has arbitrarily decided is correct. It's like those old, rack-mount "auto eq" boxes that flattened out the 1/3-octave pink noise bands... universally unlistenable results.

Plus, if you can't window things, you can't easily isolate which room features are causing which response aberrations.

-k
 
Last edited:
Last edited:
How to's and setup

Would any member posting here be willing to help with writing up some How To's and Setup for the members that would like to try measurements?:scratch2:
 
I got the MicMate Pro today, hooked it up and was able to see the "Record Meter" moving in HOLMImpulse. So I ran a test thru my computer speakers and got a graph, but I really have no idea of what all the various settings are supposed to be set to.

A "HOLMImpulse for Total Idiots" thread would sure be nice, I just hate to clog up this forum with literally 1000 questions. The thread on DIY seems to be more for people who are already adept at running measurement software, and the user manual skips over the mundane things that I guess people taking measurements take for granted.

Wear earplugs. Even the blast from my computer speakers caused my tinnitus to flare up
 
I fired up the ART USB Dual Pre this evening and got the same slam-dunk result with HOLMImpulse as with the Fast Track Pro. The ART seems to have the same features and functionality for half the cost, but I'm in no position to evaluate either of them for native noise, etc.. There is a local expert on these matters whom I will approach regarding that. ;)

http://www.audiokarma.org/forums/showthread.php?t=279240

As to the "Measurements for Dummies" thing, I'm not up to speed yet with HOLMImpulse myself here yet, but it's easy to use and also getting good reviews by some of the big boys, so I'll work more on that part.

[It's also free.... :thmbsp: ]
 
Last edited:
Jeffery

We are working towards this and hopefully can have that for people to read sometime soon. :yes:

Zilch

Thanks for your help here as well. Very much appreciated.:yes:
 
juniorJBL said:
Jeffery

We are working towards this and hopefully can have that for people to read sometime soon. :yes:

Zilch

Thanks for your help here as well. Very much appreciated.:yes:
Click to expand...

Much appreciated! I was impressed with how easily the USB mic pre was to get running, and was happy that my soundcard played nice as well. That gets the major hardware hurdles handled, hopefully. I also had an Audyssey mic (ACM1?) with a mini phono plug, but I wanted to use the ECM8000 for something. The MicMate Pro now has a slot for it carved in the foam cradle in the case with the ECM8000.
 
You must log in or register to reply here.
Back
Top Bottom