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It's not allowing me to access the link you posted.
Sorry, I mistakenly referenced a post in the moderators section.

Anyway, we do recommend West Caldwell labs as the place to go... Be sure that you use the mic in a vertical position when measuring. The calibration will be the most accurate that way..

brucek
 

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Well, the jist was that we had some discussion regarding the method of calibration that WCCL was using (pressure testing) and whether they compensated for baffle interaction of the microphone which would cause treble anomalies. WCCL does an excellent job and is very professional, but the concern was whether at high frequencies there might be inaccuracies because baffle step compensation wasn't considered. A basic explaination of baffle step with regard to speakers can be found here. It applies to microphones just as readily as speakers, so the small 0.5" baffle of a measurement mic could begin to have a problem at upper frequencies.

I'm no expert in this area, so someone else would have to explain it deeper for you.... :)

brucek
 

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Can we see a graph your soundcard calibration file?

Specifically show us a blow up of the 10Khz to upper range...

What microphone preamp are you using and did you include it in the soundcard calibration routine when testing? Is so, did you include the mic preamp or just the line-in?

brucek
 

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...... created the cal file by going line-out to line-in rather than from line-out to mic-in. Could that be a potential problem?

If I recalibrate the soundcard/pre using the mic-in, should I engage the phantom power button?
No, the line-out to line-in will be fine. If the soundcard cal file drops off quickly at 18K or is jagged, then that's as high as you should measure. If it tails off smoothly and slowly, then you can go higher. (read this thread through on mic preamp calibration methods).

I'd like to see the graph though.

Really though, when you start to get serious about measurements above 15KHz in speakers, you should get a professional calibration done on the microphone. The generic files we supply are fine for sub woofers and general mid range work, but you're trying to get up to 20KHz without a properly calibrated mic....

brucek
 

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The soundcard cal files look good, so that isn't contributing to the problem.

If I recalibrate the soundcard/pre using the mic-in, should I engage the phantom power button?
No, you don't engage the phantom power button. It is power for a microphone circuitry.
With a high quality card such as you have, I can tell you that the mic preamp will have a good response and won't be part of the problem. You can include it in the soundcard cal routine if you want, but I don't think it will be the source of the trouble.

The only thing left is the microphone calibration.

brucek
 

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It surprises me that either of these mics would roll-off early when the generic cal files show lifted response from about 10KHz on up.
Please explain? I don't see that in the generic files? The cal files all show negative values as you get to the extremes of bandwidth...

brucek
 
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