I believe the internal of my cable is broken and was wondering which replacement cable is the newest to buy. I'm not necessarily looking for an expensive upgraded cable.
obviously the hd650 cable is what you need
or you could take a chance on this cheap cable:
The HD650 cable is the least expensive option - cheaper than HD600 cable - unless you want a 3.5mm plug.
The HD650 cable is thicker and has a 6.3mm plug.
http://en-us.sennheiser.com/high-quality-headphones-around-ear-audio-surround-hd-650#accessoriesThe HD600 cable is thinner and has the 3.5mm plug.
No idea why the 600 cable is twice the price of the 650 cable...