My new HD 600s are my first open-back headphones, having used the closed-back HD 380 Pros for many years. The 380s have great detail, nice bass, and flat response, and I still love them, but wanted a pair of open-backs too.
So far, the 600s appear to have a similarly flat response, excellent bass, and have been a complete joy to wear for long periods. I found my ears tiring after a while with the closed-back 380s, but the 600's allow my ears to breath, allowing for longer listening sessions without fatigue. I use them only in my studio, so leakage isn't an issue for me. I almost opted for the HD 650's, but the 600's are tried and true and still fetch a high price, so Sennheiser obviously did something right with these. I'd highly recommend them to anyone needing a realistic representation of their sound, with added comfort.
To be honest, I didn't know what I'd think about the straight cable, though, having had the HD 380's coiled cable for so long. The cable on the 600 appears durable, but is supple and soft to the touch, not stiff, and I've found that I actually like it better than the coiled cable, which tended to pull on me (and it is heavy). So for you coiled-cable users out there, don't let that deter you. I've adjusted quite nicely, and actually think I prefer it now, even the double sided connections, vs the single side on the 380s.
