My First Impression: These cans seemed to have no soundstage, no separation, no treble, and stuck in the mud bass. The vocals seemed to be behind the rest of the music and was muffled at times or hard to hear. I have to say I was very unimpressed with these headphones out of the box. I was running these with my Onkyo TX-NR3007 integrated headphone amp. So out of the box as of sound, yuck!
The build quality is amazing though. They are built like a tank. I did not find them heavy at all when they were on my head. Like others on this forum, I found the headphones to be comfortable and the headband did not dig into my scalp. I could barely feel it for the first hour. The pleather pads fit right over my ears and the stock cable is stiff and long, but a good quality cable.
Burn-In period 20 hours: The sound got a lot better. The soundstage began to open up but not as wide as my Grado Rs2i's. I could feel the vocals starting to move forward, the treble began to brighten, and the bass stood out the most as it became tight and punchy. Not a overall loud base, like the Beats By Dre, but more tight and natural sounding.
Burn-In 40 hours: Okay, yuck has turned into... hmmm interesting. I am really starting to dig this sound. The instruments sound real and the bass again is becoming more robust while keeping its tightness. I never heard Eminem's "Mockingbird" sound so good. Usually with the cans I have had in the past (Soul SL300, Beats Detox Pro, and Shure SE-325, the bass overrides all the other sounds including the vocals. On the Grade RS2i's, you don't hear the bass as robust as it is on the He-400's. You do not get that punch either on the Grado's. The soundstage again appears to getting wider and more prevalent.. I am really starting to like these and they are becoming my favorite headphone to listen to for long periods of time. I find the Grade RS2i's to still be very harsh and bright on the high end almost to the point where my teeth begin to clench. The HE-400's just have a more warm sound to them. Not as fatiguing.
I will do a more in-depth review at a later date or later today, if I get some time. I can't believe it, but someone was upgrading to the Schiit Lyr, and they sold me there Schiit Asgard 2 with about 25 hours of burn-in time on the unit. I have put another 15-16 hours on it and I will give you more information as I continue to listen to my cans on this amazing AMP.
Just a note... the paperwork that comes with the HE-400's suggests 150 hours of burn-in time to really get the best quality. I was never really a believer in burn-in until I purchased my Martin Logan speakers about 4 years ago. When I first got those, they were bright as heck, now... they sound magical. I am hoping that the HE-400's are going to be the same way.
Pro's: Really clear sound as they begin to break-in, The soundstage is pretty wide and continues to open up with break-in, Build Quality is A+++, Looks cool (I like the blue color), Warm sounding, Easy and fun to listen too, I am starting to love the bass and the mids.
Con's: The cable is stiff and the screw in's on the cans are small and hard to screw in with my fat whale hands. The treble just is not there yet... hoping it begins to brighten a bit more (I am starting to hear the stick hit the cymbals but still is in the background and you have to concentrate on hearing it), Nothing more as of yet.
To be continued.... As I will compare the Grado RS2i and the HE-400's using my new Asgard 2 amp. All I have to say now is... wow the Asgard 2 makes a difference for both sets of cans... and even the Shure SE-425's. WOW!!