In a less-than-usual repair situation (sangria spilled down a HF horn) I field-stripped a RAMSA tweeter. This is a rather nice cousin to the EV St350, a biradial small short horn on a dome tweeter diaphragm.
Removed the horn, removed the tweeter top plate revealing the diaphragm unit centered on the magnet. On lifting the diaphragm up I was very surprised to see a perfectly-shaped hunk of loose poly-fill material, not unlike quilt-batting, that sat on top of the magnet and filled the inside of the voice-coil/dome assembly! I assume this is there to supply some sort of damping for the tweeter. I've never seen this on any compression driver, and wonder if anyone else has seen this done anywhere?