Microphone Distortion Comparison

[TNT]

That word again. It's like there are two threads. In the one I'm reading a designer doing uncommon loudspeaker tests questioned the results of his tools, made a change, and discovered some widely adopted measurement microphones are seriously inadequate for IMD measurement. By changing a variable it was additionally discovered loudspeakers may have much better - near amplifier - IMD performance than was previously expected and went to the next step.
The other thread is a critique centred around demands for absolute measurement accuracy, 'improper' devices and lacking formalism without explaining how the interim step of using an SM58 invalidates the unexpected loudspeaker IMD discovery later confirmed and exceeded with the AKO.
Honestly don't see the point.

My idea was to merge the IMD properties AND straight FR in one and the same mic, the SM-58. Would't that be good? I just hocked on to your comment about calibration just previous...

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[IamJF]

My idea was to merge the IMD properties AND straight FR in one and the same mic,

That's easy - it's called "AKO Pacific 7052PH" in this test.
There are plenty others too of course, but the SM-58 it's not. And the supercheap electret mic's don't do it either. Mic W M215 is the cheapest which comes to my mind which could probably do it.

p.s.: "Calibration" of an SM58. How do YOU do it? You need a reference.
Frequency response changes with distance. It changes with temperature (big and thin plastic membrane is sensitive) and over time. You need to send it to a lab for calibration and still don't know the tolerances when you get it back and how much worse it got after a year. Save your money, buy a useful measurement mic.

 

[TNT]

I'm certain that there is a protocol and equipment for calibrating mics. There are shops to where you can send one and pay for the service.

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[IamJF]

I tried to explain why it's not a good idea. It's up to you to waste money ...

 

[rdf]

Cheap "measurement microphones" have to much noise for this measurement.

My initial thought as well however the Dayton EMM-6 floor was -50 dB at 2 kHz, or around 0.3%. The question mark is that limit should also appear as a limit on the REW THD sweeps available online. Maybe the Behringer and UMIK are better?

 

[IamJF]

Behringer an UMIK aren't better. Combine a cheap electret capsule with cheap electronics ... doesn't make a good mic.
You still can use them for frequency response measurements if they are calibrated but they simply have limits.

THD measurements work differently and can "reject" some noise when programmed correctly (cause they only show a narrow frequncy pin for k2, k3, ... and not the whole noise spectrum. THD and THD+N is a difference).
ALWAYS KNOW what you are measuring!

 

[IamJF]

May I add a link to my distortion measurements for reference:
https://www.diyaudio.com/community/...ement-microphones-actual-measurements.411218/

With an M215 distortion should be low enough to also be able to do proper IMD measurements.