Yeah I dunno, but from David's review of the HD650:
CABLE: The quality of the HD650's stock cable is not too bad considering the price of the headphone. Some have remarked that its internal design is a downgrade from the HD600's stock cable. However, Sennheiser makes the cable easily removable. This makes it easy to install an aftermarket cable replacement. I use the Moon Audio Silver Dragon when in balanced mode. I think the HD650 scales especially well in balanced mode; it opens up the soundstage a bit.