Pressure Zone Microphones - History and other information
Crown PZM-6D Pressure Zone Microphone
1983 Realistic Pressure Zone Microphone - YouTube
PZM!: The inexpensive mic that can do a lot! | Tape Op Magazine | Longform candid interviews with music producers and audio engineers covering mixing, mastering, recording and music production.
Crown PZM 30D Pressure Zone Microphone | Sweetwater