Topic: Checking mic performance

[redbook]

Hi there,

I got some old damaged mics, and I think they lost part of they freq response.
I'd like the best way (if possible) to check the actual mic performance and compare it with the factory values and check the possible loss (maybe with Mathlab or something similar)

Does this make sense?

[redbook]

bump 

[kgreener]

would a service like this help you? 

http://www.cross-spectrum.com/measurement/mike_meas.html

[redbook]

yeah that would work but the idea is do do it myself accurately at home
is it possible?

[kgreener]

yeah that would work but the idea is do do it myself accurately at home
is it possible?

oh, now this i have no idea.  unless you have the proper equipment i think it's a stretch to think this can be done.  the measuring equipment alone will probably cost you way more than the mics themselves!

[Church-Audio]

yeah that would work but the idea is do do it myself accurately at home
is it possible?

In order to do this you have to have a known good microphone with the same acoustic characteristics as the mics you want to measure, with this you can get a baseline. In order to do this you must have a mic that is known to be in spec (almost impossible because of variances in manufacturing) I have spent $1000's on doing this, for my mics. Its something that is not easy to do.

The other method would be to buy a earthworks m30 or some higher quality measurement mic and measure your speakers, then use a data file to make them flat to your sound analyzer. Then you can subtract the speakers response from your mics. Only one problem with that method, You mics I am assuming are cardioid the M30 is omni. The response curves will not match.

So...... To make a long story short your better off sending them back to the people that make the mics. They will have the means of testing your mics and comparing them to the known good response curve, and seeing if they are in spec. Testing mics is part science, part voodoo. This is not something for the do it yourselfer. You can compare one mic against the other, but when performing these test the mics have to be in exactly the same position so that they can be compared, and you should also use a MONO source. The results will show the differences between the two mics, but this test will not help you with over all performance, because you have no reference point from witch to interpolate the results.

Complicated ain't it.

Chris Church

[TNJazz]

This might help a little.  Not for comparison of factory values, but at least to accurately measure the response?

http://audio.rightmark.org/products/rmaa.shtml

[Church-Audio]

This might help a little.  Not for comparison of factory values, but at least to accurately measure the response?

http://audio.rightmark.org/products/rmaa.shtml

The problem with using any software is you have to use a transducer to measure the response of the mic. This transducer response is not known in the environment its operating in, unless measurements are made of the speaker in question and subtracted from the measurements of the microphone in question. 

This is the only way to get accurate tests, the other issues are what do you use for a source sound file? do you use pink noise, white noise, or MLS what??? because all of these respond differently to the environment they are in. Not to mention at what distance do you measure the mic to get an accurate frequency response. And you have other issues try finding a single point source that is flat from 20hz to 20khz ( they dont exist ) So you must do what earthworks does, or other companies and use two transducers one for low frequencey response and with for mid high response they use a electric spark as a test source because an electric spark contains very sharp peek with all the frequencies in the spectrum they use a vandergraph generator to do this. The two speakers response's must then be stitched together. In order to have anything close to an accurate response of the mic.

You see measuring a loudspeaker is very easy in comparison to measuring a microphone, because I can take an earthworks m30 and point it 1 meter away from a speaker, and say in this room this is what this speaker is doing. If I want to measure the speaker and tell you what it does MINUS the room acoustics I can create a anaholic chamber and measure it. The problem with measuring microphones is at what distance do you measure it? what effect does the shape of the baffle on the transducer have in tricking the response of the microphone? I could go on and on with the difficulties in measuring mics its not easy. Most response curves you see from manufactures are highly dubious and I suspect smoothed out for appearance.

So if I did not have the equipment I have I would say rather then spending $1000's on gear just send the mics back to the company

Chris Church