Here are detailed instructions for building your own plate reverb:
Typically, the plate is a large sheet of steel suspended in a tubular steel frame. In theory, the plate simulates a large concert hall, or church, with a decay time of approximately five seconds at approximately 500 Hz. A driver attached to the plate excites it, and as the sound waves travel through it, the plate flexes. The plate’s motion is then picked up by one or two contact mics, and added to the dry signal at the mixer.
The project isn’t for the timid. But if you’re handy, and have a large sheet of steel lying around, an authentic plate reverb could add a distinctive touch to your recordings.