Driver membranes are simply mylar ( or other specific plastic type ) atomized with titanium or whatever coating they feel like adding, such as gold in this instance. Diaphragms are certainly not made out of titanium. Neodymium is a specific magnet type within the driver construction that drives the voice coil which is attached to the diaphragm, so nothing at all to do with diaphragms. been eyeing those 2400s myself, so tempting.
There was a pretty good deal posted in here from one of the sponsors. Here is the place.
http://www.head-fi.org/t/671580/peachbudz-introduction
check back in one of the Ultrasone threads if you do get these and let us know what you think. Be sure to run them in a fair bit also.