This is a reply to an earlier post of who this crazy microphone guy is that nobody has ever heard of. Hopefully what follows is in line with the spirit of this forum.
I started building microphone capsules pretty much as a hobby - it was a neat thing to do. I posted progress over at the prodigy-pro forum (mostly DIY'ers over there), and there was some interest in other people purchasing these capsules. So I made approximately 120 or 130 capsules over the period of around two years. They have some features quite different than Neumann capsules (they are easy to identify as not original - not the least of which is a lack of a serial number), and each batch had some improvement over the previous ones. The latest ones sound pretty good, but there is a lot of scatter in the sound. I don't think too many of them sounded bad - those I would have weeded out during testing. Most sounded 'ok' to 'that's nice', but I only recall two of the capsules that I said 'wow' to - they compared quite well to a PVC M7 that I have. I did not keep them, although I probably should have.
That Neumann M7 is sick (the dreaded cracking problem), but with just the right amount of condensation, it works, sounds great, then the mic shorts out after half a minute of beauty. That is the standard that I try to aim for, but I find it a hard to get there.
I'm not really set up to have them tuned 'just so', and I don't have a test chamber for them, I make them and see if they sound good on my voice and usually a guitar before I send them out. I also don't have a particularly good clean-room area, so the occasional capsule gets some dust trapped beneath the diaphragm. I replace those if I don't catch them during assembly or testing.
I still have a couple of capsules that I use as my main recording microphones.
My first capsules were manually machined, and took about six hours to do the machining. The latest machining program takes a total of ten minutes on the lathe, around fifteen minutes on the mill, about fifteen minutes of cleaning and deburring, and around fifteen minutes to put the diaphragm on.
I've also designed a single-sided capsule that is very similar, though not identical to the Sony C37 capsule. I like its sound, but it does require care in the noise level of the amplifier in the microphone body. I built probably about thirty or so of these. I built a bright version and a dark version.
I haven't been building any capsules for several months now, it really is a second job. My day job (designing electronic engine management systems) is getting quite crazy these days. Having two jobs can be a bit stressful. Lately I've been working on reverberation software on DSP chips, and doing some tech work on various mixing boards around town.