The recable job was done by (I think) Purrin. I'm pretty sure it's copper (Probably Vampire Wire? It's red shielding and I know that was a Vampire Wire thing, and the adapter has a Vampire plug) and it's a 2x3pin XLR balanced cable that's 5 feet long.
For Sale or Trade: Sennheiser HD650 - Page 3
But someone please buy them. I haven't used either of them in much too long and I want to find these a good home. I've found a way to avoid the roommate issues, so I can use open headphones, but the HD650 sounds too close to my ZMF (The HD650 is noticeably better, but I don't want to risk chipping the paint so I've kept them in the box) and the SA5000 doesn't fit with my music tastes anymore.
SA5000 sold! I'm now on the fence about selling the HD650, but they do sound quite similar to my ZMF, so they might be going still. I'd love to trade it for a nicer Grado or something with lots of PRaT because I have my bases covered other than that with the ZMF and now the W1000X.