Has anyone updated Senn HD650 cable?

Are you thinking of upgrading to the Cardas replacements? I haven't convinced myself to pull the trigger on that one, but given the resolution level of the Sennheiser HD 580/600/650 series, I'd be surprised if you *didn't* hear an improvement. The Cardas is also supposed to be more rugged; George designed the cable for his daughter who's a DJ.

Once you get into that money, maybe you should look at http://www.headphone.com for their balanced headphone option

Yes, I did: Revelation Audio Labs cable. Some improvement was gained, like better resolution and increased dynamics. It's a much higher quality cable than what Sennheiser provides and worth the investment if you're a serious listener.

Yes, I tried the Cardas which was an improvement but found the Moon Audio Blue Dragon V2, and later, the Black Dragon significantly better. The Cardas, like many of their wiring has a lower midrange, upper bass hump. The Moon cables were more balanced and still more revealing.

...and the Sennheisers don't need the added warmth of the Cardas although it is an improvement in other ways.