[ericj]

It's not often that we can, as consumers, buy a brand new headphone driver and have full specs for it.

Parts Express is carrying two such devices, made by Peerless/Tymphani. One big:

https://www.parts-express.com/peerless-hpd-50n25pr00-32-2-headphone-driver-diaphragm--264-1510

One less big:

https://www.parts-express.com/peerless-hpd-40n16pet00-32-1-1-2-headphone-driver-diaphragm--264-1508

Anybody ever mess with these? The big one looks like it has a pretty reasonable response curve.