Heres my Freq Graph for anyone interested.
Since this thread is for impressions i'm going say something controversial... & keep in mind this is my FIRST impressions of the HD800s.
I expected a (extra) large soundstage because its common in reviews "This is the largest soundstage in a headphone i've heard" well its not the larest i've heard, its defintly not HD668B extra large its more K712 large (this is going off memory), I'm speaking in terms of how far out the sound goes in it to its limit, But it has a lot of more "play" & movement of instruments from the imaging in the depth of the soundstage than those & many other i concider close in size.
Now that was first impression the more i listen to them the more its starting to open up, not get larger just getting more noticeably "airy" so a "false sense of expanse" i guess is how i would descirbe it.
When i was first told about the "holy grail" HD600 they never menchioned no soundstage & very warm mid sounding bass, so in my head the HD800s sounds exactly how i picture the HD600 would sound at the time. Don't get me wrong i was never dissapointed in the HD600 (or HD660s just the HD650/XX), I just expected much more & i'm glad I found the HD800s because that expectation has been meet in full now.
That out of the way, I find everything impressive from the light, fast but just punchy bass to the highs that just go up, but never hit the peaks. Weridly i find the mids a bit hidden for a Sennheiser headphone but they are there, Guess its just a bit of getting used to since they are new.
I actually only bought it to game with.... But looks like im going to be using it for everything now!