3.5mm OCC Audio Cable For Sennheiser HD25 HD25 Plus HD25 II HD25-1 II HD 25-C II | eBay
Sennheiser Replacement Cable for HD25-1 Headphones 523874 B&H
Amazon.com: NewFantasia Replacement Cable Compatible with Sennheiser HD25 / HD25-1 / HD25-1 / II HD25-13 / HD25-C Headphone, Remote Volume Control Mic Compatible with Samsung Galaxy Android : Electronics
Amazon.com: Black Earphone Cable Headphone Extra Cable for Sennheiser HD 25-sp HD 222 HD 224 HD 230 HD 250 HD 250 Linear II HD 414 HD 414 SL : Electronics
headphone Audio Cable For Sennheiser HD25 HD25-1 HD25-1 II HD25-C HD25-13 HD 25 HD420 HD600 HD650 For Sennheiser Headset Cable
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Sennheiser Replacement Cable for HD 25-1 Headphones (Steel)
Clearly, the HD25-1 II needs a $400 cable : r/headphones
Amazon.com: Geekria Apollo Single Crystal Copper Upgrade Audio Cable Compatible with Sennheiser HD25, HD25-1 II, HD25-C, 2.5mm Replacement Headphones Cord for Hi-Resolution Audiophile, HiFi Headset (5ft/1.5m) : Electronics