Received HE-400 in the mail today, have been unable to put them down ever since unboxing them. As a 6'3'' man these feel a tiny bit small, almost as if they were designed for an average sized Asian. The cables require tiny fingers to screw them in, the earpads are good 20% smaller than Q701's, the headband must extend all the way to fit me - but those issues aside, the sound is simply phenomenal. Q701s in comparison are shrill, bright, aggressively mid forward, and bass light.
HE-400 on other hand sound ruler flat and incredibly smooth to my ears.
Started off with some Steely Dan, Aphex Twin, Autechre, Rob Zombie, Adele, Judas Priest, Miles Davis - everything sounds just right - a bit more bass wouldn't hurt but they respond real well to EQ. No matter how loud I go, they still don't sound too bright or unpleasant. I notice a bit of tizzyness in the upper treble region in some songs but it doesn't ruin music for me.
If my initial impressions don't change in the next week or two I'll be selling Q701s and keeping HE-400s. I'm looking forward to a weekend with this great sounding piece of technology.
Bought them from HeadAmp, another big vouch for Justin even though it would have been nice if he shipped them a day or two earlier