Trounce,
I must disagree 99% with Geek. I'm a "sibilance sensitive" guy myself and my HD-600's are permanently stuffed in the closet in favor of the 770's. The 600's may be more neutral and measure flatter, but they are also boring, bland, unemotional and completely uninteresting to me. I can't wear them for more than an hour because my lack of involvement in the music is distracting. I sit there thinking, "Boy, I really should be enjoying this more than I am." With the 770's I feel "connected" with the musicians. They are dynamic and exciting without being overwhelming, painful or tiring.
My 770's were a bit sharp when new, more "hashy" than sibilant though. I let them play continuously for 3 or 4 days and tried them again and the treble had smoothed considerably.
The frequency plot Geek mentioned reinforces my experience that these are not excessively sibilant phones. I've done some trial and error with an equalizer and have found that the danger zone for excessive sibilance is between 2500 and 6000 hz. Exaggerated levels from 6000 hz and up tends to emphasize the "tsshh tsshhh" of cymbals and make things like triangles and piccolos slice through the mix more, but don't have a dramatic effect on sibilance (if you define sibilance as the S's of DEATH). If you look at the curve for the DT 770 you will see that the headphone is actually recessed in the 2500-6000 hz danger zone, with a an elevated treble from ~7500 hz up.
As for Geek's proclamation that they are unacceptable with sub $500 equipment , I have found them to be an excellent match with the MG Head OTL which is priced significantly below $500.
These are not "perfect" headphones, but they are VERY enjoyable. You WILL tap your toes, bob your head and shake your booty while wearing these. You will NOT bleed from your ears.
I do agree with Geek about one thing: "The HD600s blow"
