A while ago I found a description of measuring microphone on Linkwitz site. Remembering his name from 20 year old publications, related to speaker design and evaluation of crossover networks, I was really intrigued by the fact that reasonably good measuring microphone could be done from $2 electret capsule. Next day I ordered a couple of WM-60A Panasonic capsules from Digi-Key. A few days later I build a microphone form arrived capsule. I used his modification, converting common source integrated amplifier into common drain follower. Then I buffered it by simple emitter follower and powered from 9V battery.
I send it to Laboratory of Electroacoustic of NIKFI, Moscow, and my friends measured frequency response of this homemade miracle in acoustic anechoic chamber. I don’t remember what kind of B&K measuring microphone was used to create calibrated field, but this was the same setup that they were using to measure frequency response of professional studio condenser microphones.
WM-60A frequency response
Don’t pay attention to small bump at 2 KHz, it is related to loudspeaker problem.
The second plot is just repeat of 0 deg measurement to double check.
My overall impression-not bad, not bad at all for $2 capsule.
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