Although piezo elements had already been available, the very first SDSV pads, particularly those (or most) built in 1981, used a speaker to generate the electric pulse for the brain.
While a speaker normaly converts alternating magnitism into mechanical oscillation, it cann also act vicy versa: Converting mechanical pulses into (electro-)magnetic pulses. The advantage of the piezos ist that they respond more exact. You have less trouble with cross talk and better dynamic response. And they are cheap and lighter. They can easily be glued on the plywood instead of intricately screwing them underneath the playing surface. Here is an original sketch ow Dave Simmons adviced his technicians how to convert SDSV pads to piezo trigger:
How can I see if my SDSV pads have a speaker or a piezo inside?
These indicators point to speakers inside:
- You have a Simmons logo under the riot shield playing surface
- The tom mount is die cast and made by Pearl
- The acrylic shells are hand made (the edges are less sharp) or even solid wood
These indicators point to a piezo inside:
- The tom mount is made of plastic
- The acrylic shells are series production