Over on Facebook, Boris L. tagged me on a link to this instructable on making a steel can microphone. I don’t care much about steel-can microphones (though they are apparently a thing?), but I was curious about the actual pickup element inside. That pickup turned out to be this balanced-output piezo contact microphone, which comes in a kit form for reasonably little money.
The assembly instructions for it are online. As I’m reading, hanging around in the back of my head have been these pressure zone microphones (generic name boundary microphone) that I’ve performed with once, and have seen discussed several places. They’ve always struck me as kind of interesting to play with, but never enough to justify purchase.
You can probably see where I’m going here: the outdoor versions of these PZMs look a lot like contact pickups attached to sheets of rigid plastic, suspended in air via a cord framework. I can certainly build that.
I’m considering a couple of designs, but this is my thinking: since this element is a piezo, it works best with direct contact with a resonating body. That could be a sheet of rigid lightweight plastic, much larger than the pickup, to gather sound and resonate. Hang that sheet-plus-attached-pickup from a rigid outer frame, using some form of elastic suspension. Low-density foam might work, for example, like with a speaker. Then that can be hung anywhere.
That’s the simplest of the ideas I have, and makes sense in that sniff-test kind of way. It’d be large, but every mic of this type I’ve seen has been large, so that’s fine. Depending upon what happens, I could also poke around with hanging it on walls, as is the usual use for boundary/pressure-zone microphones.
So, yeah! I won’t get to it immediately, but when I do, I will of course post about it. Mostly, I’m hoping I don’t have to build some sort of multi-layer frame around the large plastic pickup plate. That’s one of the more complicated designs. I could do it, but the more complicated these things get, the worse they tend to sound.
If you have any design knowledge of these sorts of things, share some knowledge in comments! I haven’t seen other attempts at DIY PZMs using this approach, which kind of surprises me. That might mean it doesn’t work at all, but it might also just mean nobody else has thought of it. Piezo isn’t generally very well regarded outside of instrument contact pickup applications. Maybe it could turn out to be a thing.