Amazon.com: gotor 4.4mm Balanced Replacement Cable for Sennheiser HD 650 HD 660s HD 600 HD 6XX HD 25 HD 580 HD 58x 7N Silver Plated Copper (1.2m(3.9Feet)) : Electronics
Dual Senn. 2-pin headphone cable for HD Series (600, 6XX, 58x & more) – Hart Audio Cables
Geekria Apollo Silver-Plated Upgrade Audio Cable Compatible with Sennh
SENNHEISER HD 650 Modified Stock Cable - HD 600, HD 660 S, HD 6XX, HD – Corpse Cable