40 hours of break-in, and I'm really loving these. Thought I'd share some thoughts for anyone else that comes along. I've listened to them some with two setups, no EQ:
(1) Clip+ with a mix of mostly FLACS and some high bit rate MP3s (generally v0 VBR or 320kbps)--no amp (have to get one)
(2) Secondary PC in the house where they have been breaking in with Asus Xonar D1 with mix of v0 VBR or 320kbps MP3s on Windows 7 with Media Monkey.
(I also have an Asus Xonar Essence STX on my primary PC that I'll use once they break in some more--save the best to last 
)
The HFI 580 certainly do a little better with the Xonar D1, but the Clip+ was fine for general listening given its price. No complaints there.
The strong point is obviously with EDM and other bass heavy music, which I listen to about half the time. No contest. The HFI 580s are great, an all around better headphone than my Sony MDR-V6s. When it comes to sub bass and mid-bass, the HFI-580s are like a good enthusiast level sub paired with mid level towers in a home audio setup; I know that they are hitting down pretty low (although I have not tried Bass I Love You yet). As others have pointed out, it's all there with a good tight sound with plenty of texture. For anyone who would consider themselves in the car audio subwoofer SQ group, the HFI 580 would be an excellent choice. Although I could see how those listeners that would belong in the car audio SPL subwoofer crowd might be disappointed. The bass seems to be running a little hot, but not massively enough for serious SPL bassheads.
With other genres where there is any mid-bass or lower, the HFI 580 really does a nice job of foregrounding the bass for those that want that. For instance, last week I watched the Godfather. Since I occasionally get into a classical kick, I decided to listen to Erich Kunzel and the Cincinnati Pops Orchestra Theme from the Godfather. The bass in that piece is so important for the tone, and the HFI 580 did a marvelous job of conveying the mood of the song.
I also noticed some comments on Amazon complaining a lot about sibiliance. There may be a little bit--I try to ignore it, because if you look for it, you'll start hearing it more if is there. But I think some of those comments were a result of one or more of the following three factors:
1) Not enough break-in. (I would imagine the highs will tame a touch more even than they have with more time).
2) Revealing nature of the headphones. The treble does have some good clarity, and poorly recorded EDM and rock is going to reveal itself. At the same time, I'm also hearing detail that was not there before.
3) The recessed mids, which stress the treble, particularly if listening to something that is bass light where the treble will call even more attention to itself.
Edited by cel4145 - 8/23/12 at 8:13pm
