Many years ago, I bought two Realistic (a Radio Shack store brand) PZM microphones on ebay. “PZM” stands for “pressure zone microphone”. They have a small electret capacitor (condenser) element situated very close to the the main body of the mic, a metal plate. The element being positioned in the “pressure zone”, yields a boost in low frequency response and a hemispheric pickup pattern. The microphones’ cables have a small inline AA battery box with an ON/STANDBY/OFF switch. The battery provides the polarizing voltage for the electret element. The box also has a cheap transformer, which probably doesn’t help the audio coming from the mic. The mic output was also fairly low.
I used these mics for stereo recording, drum recording, highlight mics for instruments on stage, and interviews.
After a while using the mics in their stock configuration, I built two of the circuit kits from http://uneeda-audio.com/ to allow the mics to be powered by phantom 48+-. I housed the circuit in aluminum enclosures with XLR inputs and outputs. I went ahead and put XLRM on the mic outputs, and XLMF on the stock battery boxes, so I could use them in the original configuration if I chose.
They are louder, cleaner, and don’t rely on a AA battery, which is nice.
