http://recordinghacks.com/articles/how-to-build-a-microphone/
For decades condenser microphones have been the staple for high-quality recording and live sound assignments. Unfortunately, not everyone can afford to own a good one. Well that's about to change. I've written this article so that anyone who wants a great condenser mic (or those who just want more of them) can have their wish.
For around $20 (US) anyone can build an extremely accurate, life-like condenser microphone. DO NOT let the cost fool you, this mic's frighteningly good performance will blow your mind — and it's easy to build! -Joel Cameron
This microphone is largely based on a posting I found on the internet showing how to modify Realistic (Radio Shack) PZMs for better performance. I have simply finished the design so people can build a complete mic from scratch. After making a pair of these, I was shocked to find out how amazing they sound. In fact, these little buggers have become my first choice for capturing unhyped, totally natural stereo images, beating-out pairs of choice small and large-diaphragm condensers, and some nice ribbons too!
(Score: 1, Informative) by Anonymous Coward on Monday October 21 2019, @05:29PM
These old panasonic capsules are ~26dBA, a modern electret will have a self-noise of ~20dBA while ~15dBA is more typical for a true, externally polarized condenser.
EM258? [primomic.com] I've no idea if it's a drop-in replacement and I'd be looking for a better amplifier circuit too.