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
Dekoni Audio Balanced 4.4mm Pentacon Cable for Sennheiser HD600 Series Headphones - 1.2M Length | Dekoni Audio
Amazon.com: 2.5mm Balanced Headphone Cable Compatible with Sennheiser HD600 Cable, HD 660S2, HD 660 S, HD 650, HD6XX, HD58X / 5N OCC Silver Plated Braided Cable for M17, M15, M11 Pro, K3,