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Old 30th August 2004, 10:05 AM   #1
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Default Measuring the frequency response of a mic?

Having bought a decent (at least for my ears) soundcard, I'm thinking about buying a mic to do SPL measurements. Not affording fancy stuff, I think I'll buy a $15 or so dynamic mic. I expect to see the 20Hz-20kHz super-dynamic ultra-professional spec on all the boxes, so I want to have an idea of how crap that will actually be. I think that when doing SPL measurements, if one knows the real frequency response of the mic, fairly exact results can be obtained. But, how to measure the FR of a mic without a speaker with a precisely known FR/radiation pattern? Is there some way of deriving the frequency response from the impedance plot? Well, that's presuming that the impedance of a mic CAN be measured as if it were a speaker. I don't know if I'm good enough with words in order to make my self understood, but maybe I'm making some sense.


PS: I ask the admins to excuse me if I'm not into the appropriate section, and move it to the right one
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Old 30th August 2004, 10:27 AM   #2
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You may want to look at this thread for general info, and there is another thread somewhere about calibration using high pressure air, I will see if I can find it...

edit: yup, here it is.

Oh, and I moved this to Loudspeakers, probably a little more appropriate
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Old 30th August 2004, 10:33 AM   #3
johnnyx is offline johnnyx  United Kingdom
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Dynamic mics are not at all suitable, they have a peaky response, especially vocal mics.

Calibrated Girardin mics can be obtained from Liberty instrunentshere , they are provided by Wadenhome Sound in Winona USA.

You need a precision reference mic with a known frequency response, and then plot the deviation of your mic to the precision reference. This will give you a calibration file. You need sensitivity (mV/Pascal) as well as frequency response.

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Old 30th August 2004, 10:57 AM   #4
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Hm, good calibrated mic from Liberty, that's pretty expensive I presume. I think I'll check the threads that pinkmouse has linked.
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Old 30th August 2004, 01:17 PM   #5
jomor is offline jomor  Greece
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I wouldnt go for a dynamic for measurements. If you want something cheap but really accurate, try the Behringer ecm8000 mic. Mics that are not rated for measurements but just for recordings do not have the flattest response on earth usually..

http://www.behringer.com/ECM8000/index.cfm?lang=ENG

http://www.partsexpress.com/pe/pshow...number=248-625

There is no official calibration file about this mic, but does have quite flat freq response so you probably wont need it. If you want something that will give you extremely accurate results ( which means the rest of hardware and software equipment has to be appropriate and the room has to be huge) you can try the Mitey Mike which goes down to 4Hz !

Otherwise the only way is a DIY mic and pre amp using the Panasonic WM-61 capsule.
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Old 30th August 2004, 01:26 PM   #6
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Quote:
Originally posted by jomor Otherwise the only way is a DIY mic and pre amp using the Panasonic WM-61 capsule. [/B]
Is this that MCE-2000 mic that Monacor sells? Surprinsingly Mocacor has a representative here in Romania, maybe I'm lucky today. Always mind about local availability when recommending something to someone living in such a great country like mine, not only price. Electronic products end here almost twice as expensive as in US, for instance. Ordering from the Internet is not an option either, you end up paying a few times the price of that product for the transportation. That's IF they accept payments from Romania. Thanks anyway.
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