Melodica-Me, I’m not sure it has to do with chamber pressure. It looks like the HP diaphragm extrudes towards the capsule: maybe it is supposed to mechanically transmit vibrations to the capsule? Or to exalt some vibration range? I’m just guessing…
In any case, Mr Kawamoto proved himself invaluable once again: I was able to order a couple of mike capsules from them, although it will take 2/3 weeks to have them shipped.
I’m thinking about adding a second capsule, in parallel to the existing one, at the other end (basses): once the parts arrive I’ll make some experimentation…
gl