I recently purchased the HE400, after asking for advice in the 400i thread, regarding if I should go for the i version or the regular 400's (after doing a lot of research, and being enthralled by "the legend of electronic musical bliss in two cans"). Some guys there told me to post how they worked out for me, so here we go:
I only received the non-i ones today (seemingly the 2. rev based on the white color of the magnet supports), and even if they obviously aren't broken in yet, I have formed an initial impression, using the relatively neutral Oppo ha2 amp. To jump to the conclusion straight away: I am very very happy about my choice. My goal was initially to get a new set for electronic music, which they seem to do excellently. As some of the weird electronic sounds my ears are subjected to can be extremely harsh due to loads of distortion and filter usage, the treble is an important factor when choosing hp's, to conserve my already diminishing hearing. The 400's strikes a good balance between clear and defined high frequencies and painfully sharp ones, and I experience very little listening fatigue. Hence I can listen to the music I love at higher levels than I otherwise would be able to. Far from every set I own manage to pull off this feat.
However, the main priority I had when choosing between the i version and these ones were the bass. In this department I am very pleased. They have this warm, energetic sub bass sound that never seems to bleed into the mids and "take over" the soundstage. Both breakbeats and electronic drum kits (808, 909 etc.) seems to be punchy and fulfilling, and basslines of all flavours and filters seem to thrive, coming out of the 400's. All this coming out from the original mix, from a neutral source, which is an important thing since I am no fan of having to EQ my sets to get an acceptable sound from them (tubes are ok in my book though). The electronic music I listen to is obviously dependent on lower frequencies, so the 400's really hits the nail on the head here. Mission accomplished!
Personally I also find the soundstage very good, with good separation in the mid/high frequency regions, and they feel "big" enough for me whenever I listen to grandiose soundscapes, often found in industrial and ambient music. They also feel very dynamic. Compared to my HD650's, these are obviously more "coloured", and while the 650's does a terrific job reproducing the mixtapes of the world, also ones containing electronic music, the 400's feel different in the sense that they are less analytical and up close, but rather a bit more pulled back, like when observing a canvas of art from a distance. I am also very fond of my ATH-M50's. These are perhaps even more "playful" and purely fun to listen to, but they really cant match the mids and lower highs of the 400's, and often dont do a very good job playing non-electronic music. They also dont have the same degree of sustained low frequency reproduction, but pulls of the "boom" factor in a good manner. In fact I would say that the 400's in many ways land somewhere between the 650's and the M50's, which is excellent for my needs.
I actually find that the 400's also play non-electronic music very well, contrary to what I thought beforehand, based on the comments of others here. Although the mids doesnt reach the level of my 650's or PS1000's, I would say they do more than fine. Distorted guitars are powerfully and precisely reproduced, and misc. acoustic instruments sound nice as well (but again, not "perfect" like with some other sets, and a tiny bit recessed at times). Industrial rock, with a mix of guitars and electronic instruments, seems very suited for these phones. If I find the 400's lacking for a particular kind of music, this doesnt matter anyhow, as they were never intended for being my "jack of all kinds" (thats what my 650's are for). Its worth mentioning that my Aune T1 amp (with the bright stock tube) made the 400's sound VERY different than with the Oppo, which is a good thing as I can try out different tubes to experience very different soundscapes.
The only negative point I can find is that the cable is way too stiff for its own good, but I guess thats easy enough to fix in due time. I'll take advice on this if provided (not willing to shell out 400 usd or something for this however). Comfort-wise I actually expected the cans to be way more uncomfortable, but I have used them for several hours today with no issues of head or ear fatigue (with default faux leather pads). They dont feel heavy on my head either, but then again I am an adult man with a reasonably strong neck.
Anyways. Since I am bound to writing this on the iPad, and have been for months now (which sucks), I think I will round up this "first impression" here. All in all, the hype I have been absorbing regarding the 400's holds true, and I havent regretted buying them for one nanosecond. My initial fear of these overlapping with some of my other hp's have been alleviated, and they will most certainly find their rightful place among my other low/mid/high tier phones, or should I rather say "beside" them. I havent tried the 400i's, but I honestly believe that I made the right choice in choosing this, based on the reviews and comments regarding the i's, more specifically that they are somewhat ironed out in their signature.
Lastly; glad to join you 400 guys here, and thank you all for your feedback regarding your experiences, since back when they were released. Cheers!