Guys, trust me, it's not the amp or my DAC. I have a large headphone collection, several 600ohm cans, and I have power to spare. My DAC is a top of the line consumer DAC, IE not boutique. I also have mutliple DAC's and amps to try, it doesn't make a difference. It's not a power problem it's an echo problem.
It's difficult to put into words what is wrong. I hear it, I know it, how to describe it. I think it stems partly from sound leakage from the outside in, partly from reflections between the pad, my ear, and the side of my head, partly from a lack of dampening in the enclosure, and partly the relatively hard, echoey pleather earcups. The sound doesn't sound like the cups are on all the way, but they are. This results in phase distortion where some frequencies are completely unaffected, and others are heavily colored. Some vocalists come through clear like I'm used to, others the voice is a phantasm floating somewhere between my ears.
Some sounds are harsh, some are so harsh they are sibilant or resonant.
They don't sound right, I don't know a better way to put it. The drivers are probably awesome but they aren't making a direct and single path connection to my ear canal, the sound is taking side trips and phase cancelling or wave doubling on some frequencies.
I played around with the EQ a bit more last night and I found the sound was more natural with a 2-3db bump at 1k and 2k. So if anything it's not that they need a V shape, they need a ^ shape. And I'm not a big midrange guy either, I usually like a scooped sound but the response in many songs is just un-natural and conspicuously echoey like a room with bad acoustics. It's improved somewhat, especially in the upper mid range. They definitely are breaking in some with the highs becoming less like a laser ray and more like champagne bubbles against your nose. The detail is starting to come out as well. 2 songs on the 400's blew my mind last night and I can see their potential.
Bonnie prince Billy - I See a Darkness. I heard things I haven't noticed before in that song. His voice cracking and how loudly he was singing became much more natural and apparent and it added an emotional depth to the performance on top of what was already there. And the bass, I could hear the bass string whacking air out of the way. As a sometime bass player, this is something you hear when playing but never in a recording. There just isn't enough detail to resolve anything but the boom and the note.
The other one was surprising because it's not a song I would ever have thought of as challenging or hi fidelity. David Bowie's Space Oddity. I've heard that song probably a hundred times. It is usually a somewhat thin, dry guitar without much sonic complexity other than the psychadelic electric parts. Basically a folk song with a scifi glitz on it. But in the he400's, the sound field was so expanded, I could wrap my ears around each instrument, and tell everything about it's sound. It's like listening with a magnifying glass, you settle your ears on one instrument in the mix, and it's easier to see it's detail. I was particularly struck by the string section. I am not 100% on if it is a melotron or a real orchestra, but on the 400's it was as dry and isolated as a 100 year old cedar plank. I have never heard anything that was so other worldly and well defined in audible space. It was like the music equivalent of 3d glasses and seeing something pop out of the page for the first time.
Then my wife went to bed
And the headphones went up
And I went back to my 990's
Which still sound excellent, are easy to listen to, and give me a different experience.
I'm not going to make a hasty decision. My velour earpads will be here today. I might try putting some auralex foam on the outside of the earcup (I don't want to take them apart in case I decide to return) and see if I can help that sound echo.