Ok I will tell you what part of the gear that I use to test the mics is a burr brown 1k oscillator its a chip that is encased in epoxy. It has one of the lowest distortions available for a 1k oscillator and I couple that with a Mylar driver that is mounted in a machined housing. But its not something off the shelf. I use a 4.7k resistor in almost all of my mics and it works provided you have approximately 10k or so load impedance and a 9 volt supply.
Thanks for this Chris. Now everything is clear.
I will say that you are probably the only builder to systematically tests their gear. I have only recently started testing (PC with EMU 1212m soundcard, RMAA program), and it is certainly more tricky than I imagined.
Richard (and anyone else), do you know of free/inexpensive software/gear to measure acoustic frequency response/impulse response of speakers & mikes?
Electrical stuff is easy
with RMAA and other stuff.
The nearest I know of is Professor Angelo Farina's Aurora plugins to Audition. Not exactly free but the Audition license is the main expense.
I use MARS, a programme by CRC, (Canada) for impulse responses and my own klunky DOS software for frequency response and signal processing to get a quasi anechoic measurement.
For commercial stuff, I like Clio; especially ClioQC for production testing. Their inexpensive measurement mikes are one of the few whose calibration I trust.