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Speaker Measurement Thread

ken kantor said:
I'll tell ya, reading some of those ECM8000 links remind me of what an OCD crowd audio techies are!

-k
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I'm about to take a lot of measurements, and I want to get them right the first time. So yes, I am cautious because I don't like doing work over 2 and 3 times. But I'm sure you were not referring to me! And, part of the emphasis of this work is below 50 Hz where I'm seeing a lot of noise.

I'm certain that the noise is from the mic, the electronics noise is at least 20 - 30 dB down below the mic noise, if not more.
 
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+- 3mV

ken kantor said:
Hey, I've been wanting to ask another Minilyzer owner:

My ML1 has a strange glitch in its voltmeter amplitude response right around 315 Hz. Not a huge deviation, but noticeable. It's ruler flat just above, and just below, that frequency. It does this at all signal levels, very consistently. Checked it against various reference meters, etc.

Does yours show anything weird there?

-k
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Hey Ken, I just plugged mine into my HP 339 generator, it has switches for the frequency so I set it to 1K (ML read 985Hz) and adjusted the output to 2.000V, then switched it to 320Hz. It has not been calibrated in literally decades, so the frequency is a bit off, The Minilyzer said it was actually 315.6HZ! Level read 2.003V. Switching a lot of different frequencies did not read any further from 2.000 than that. I got the same thing when setting the 339's analog meter to zero, 775mV at all freqs, plus or minus a couple mV.
 
Pete B said:
I'm about to take a lot of measurements, and I want to get them right the first time. So yes, I am cautious because I don't like doing work over 2 and 3 times. But I'm sure you were not referring to me! And, part of the emphasis of this work is below 50 Hz where I'm seeing a lot of noise.

I'm certain that the noise is from the mic, the electronics noise is at least 20 - 30 dB down below the mic noise, if not more.
Click to expand...

Nah, I wasn't referring to you. More like the people who have dissected vast #'s of ECM9000's, traced their circuits, created timelines of their evolution, debated bias resistor alternatives ad infinitum, argued over who has the must ubiquitous compensation curve, etc. To what possible end?

Re: noise... I don't remember commenting on the mic's noise?

-k
 
4343 said:
Hey Ken, I just plugged mine into my HP 339 generator, it has switches for the frequency so I set it to 1K (ML read 985Hz) and adjusted the output to 2.000V, then switched it to 320Hz. It has not been calibrated in literally decades, so the frequency is a bit off, The Minilyzer said it was actually 315.6HZ! Level read 2.003V. Switching a lot of different frequencies did not read any further from 2.000 than that. I got the same thing when setting the 339's analog meter to zero, 775mV at all freqs, plus or minus a couple mV.
Click to expand...


Cool, thanks! I totally trust the Minilyzer's crystal-controlled counter when it comes to frequency.

-k
 
ken kantor said:
Nah, I wasn't referring to you. More like the people who have dissected vast #'s of ECM9000's, traced their circuits, created timelines of their evolution, debated bias resistor alternatives ad infinitum, argued over who has the must ubiquitous compensation curve, etc. To what possible end?

Re: noise... I don't remember commenting on the mic's noise?

-k
Click to expand...

OK, I see. I don't have the time to trace the circuits as you say, but I did put the ECM8000 design into LTSPICE for simulation. It does not drive both sides of the balanced output, when it seems from the design that it was intended to be true balanced.
 
Pete B said:
OK, I see. I don't have the time to trace the circuits as you say, but I did put the ECM8000 design into LTSPICE for simulation. It does not drive both sides of the balanced output, when it seems from the design that it was intended to be true balanced.
Click to expand...

The Great Firewall of Audiokarma has sanitized my gripes, but also some comments on other mics. Ah well, the Truth Will Out! Or Not!

So, re: the 8000, I have a few that are transformer coupled, but I don't know if they are older or newer ones. I lost track. All the 8000's I have, more than a dozen, are vastly better than I need them to be for what I do with them. Having never seen worse than a dB-ish of variation at above 15KHz, I never worried about the design differences. For the occasional reference or high SPL measurement, I use other mics.

Maybe this weekend, I will test various B's for overload with 48V.

-k

-k
 
Jeffery said:
I have an ECM8000 mic. If I bought this MicMate Pro, would I be able to take meaningful measurements with HOLMImpulse? I read the first several pages and it seemed like they were having a few issues back in the day.
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Sure, it would work fine, unless you wanted to do high SPL measurements, say >115dBrms. One might find this kind of level during loud, live situations, or when doing near-field driver testing. For typical testing or recording at >1M, the combo is good to go.

-k
 
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Zilch I will do the same for your post above.

BTW: Thanks for the great links. :thmbsp:
 
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ken kantor said:
Sure, it would work fine, unless you wanted to do high SPL measurements, say >115dBrms. One might find this kind of level during loud, live situations, or when doing near-field driver testing. For typical testing or recording at >1M, the combo is good to go.

-k
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OK, I ordered it and have the latest version of the HOLM Impulse program.

I'm dumber than a box of rocks, I'm not certain what all the settings and values in the program mean and the threads where guys are using it seem to indicate they are familiar with using speaker measurement software. But the mic preamp was cheap and I had the mic, I can futz around for awhile and see if I can make heads or tales out of it.
 
I'm looking for a good free RTA program. SYNRTA is good however it has only very basic features.
Room EQ Wizard (REW) seems to be quite good and has a nice RTA. It seems a bit buggy with the
MXL MIC-MATE it might be a driver issue with the MIC-MATE - am looking into it. Are many here using REW?
http://www.hometheatershack.com/roomeq/

I've mentioned the issue of LF noise with these electret mics, and signal averaging is a good
way to improve the SNR, particularly with this being highly transient in nature. REW includes
averaging whereas SYNRTA does not.
 
Pete B said:
It seems a bit buggy with the
MXL MIC-MATE it might be a driver issue with the MIC-MATE - am looking into it.
Click to expand...

If it is a driver issue then it should be a problem with any software you use it with. can you do a loop back test with the MXL? Can you try to use windows sound recorder to see if you are getting the same problems?
 
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




Pete B said:
I'm looking for a good free RTA program. SYNRTA is good however it has only very basic features.
Room EQ Wizard (REW) seems to be quite good and has a nice RTA. It seems a bit buggy with the
MXL MIC-MATE it might be a driver issue with the MIC-MATE - am looking into it. Are many here using REW?
http://www.hometheatershack.com/roomeq/

I've mentioned the issue of LF noise with these electret mics, and signal averaging is a good
way to improve the SNR, particularly with this being highly transient in nature. REW includes
averaging whereas SYNRTA does not.
Click to expand...
 
Pete B said:
I'm looking for a good free RTA program. SYNRTA is good however it has only very basic features.
Room EQ Wizard (REW) seems to be quite good and has a nice RTA. It seems a bit buggy with the
MXL MIC-MATE it might be a driver issue with the MIC-MATE - am looking into it. Are many here using REW?
http://www.hometheatershack.com/roomeq/

I've mentioned the issue of LF noise with these electret mics, and signal averaging is a good
way to improve the SNR, particularly with this being highly transient in nature. REW includes
averaging whereas SYNRTA does not.
Click to expand...

Praxis does that and then some, and it is free. I have not figured it all out yet, but I am still working at it.

From: http://www.libinst.com/praxfaq.htm#Q3

How much does Praxis cost?
The Praxis software, usable in free/demo mode is...free! (download the software free). The Audpod interface/key is, however, needed for full access to all of Praxis' functions. For local pricing information, call your dealer - see: ordering information.

If I just download the software but don't buy the Audpod, will Praxis still be of any use to me?
When Praxis does not sense that the Audpod is connected, it runs in "Free (or demo) Mode". But Praxis' "Free Mode" does more than just show demos.

It provides a fully functional, and particularly fast and effective Thiele-Small (via impedance) measurement facility for woofers. You'll find that it outperforms programs and hardware costing hundreds of dollars. For free.

It provides a high resolution dual channel RTA spectrum analyzer (up to 1/48th octave) with a pink noise generator, averaging functions, and table readout of data.

It allows for handy display, printing and formatting of measured data from Praxis (and other measurement systems).

It is a handy display program for exchanging data curves (double click on compatible data files in Windows Explorer, and Praxis will open the data file document for display!)

These "Free Mode" capabilities are provided at no-cost for use by amateur or start-up speaker designers.​
 
lilmike said:
Praxis does that and then some, and it is free. I have not figured it all out yet, but I am still working at it.

From: http://www.libinst.com/praxfaq.htm#Q3
Click to expand...

My main measurement system is LAUD also by Bill Waslo, and I also have his IMP and followed his articles many years ago.

I have the free version of PRAXIS on one of the machines around here. I will download the most recent version and give the RTA feature a try.
Thanks for pointing out the RTA feature.

I do like REW because I'm measuring in room, and will probably do some work with bass EQ. This is the main intent of REW.
 
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