Always a pleasure to have a discussion with a well read person. I plan to test. The owner of the video/audio store here in town is a friend of mine, I think I'll see if he'll let me use his shop for an afternoon. About all I have is a DVM, which I mostly use for house and vehicles. Rather than kludge something up with it and my computer, a real scope and tone generator would be easier. I'm also going to do some spike testing with "real world" program.

Because the chamber is larger than in a lab or the Pi, my rod's longer than yours I'm going to slot the vent side rather than drill holes, due to laminar flow. It will have far less turbulence even than the bug screen.

Not to knock eminence, but I'd bet that the vent size is rather arbitrary. Just make it as big as the coil and gap allow, and see what happens. Reality in the mfg world. You have to design something marketable, and cannot take every factor into account.

You're on to something here, whether PSW likes it or not. If I can gain 3db with chunk of aluminum, or save a $130 driver, that's a bargain.