Hi. Here's my short review of Ultrasone HFI-580. I'm not a professional writer and English isn't my native language, so bear that in mind.
My sound card: Asus Xonar D1
Music I listen to: trance (uplifting, progressive, tech), house (progressive, tech). Sometimes I also listen to hard trance, drum & bass and dubstep.
Dr. Bass-yl and Mr. Let's Hyde the Lows
During the first week I was overwhelmed with the amount of bass and its superb quality. Then they gradually got loose and lost much of their bass. It totally killed the pleasure of listening to bass-heavy tracks like Cosmic Gate - Ultra Curve or Nitrous Oxide - Magenta, which went from 'this is like an EARTHQUAKE' to 'this is nothing special, I'd rather do something else that listen to this'. It also killed the pleasure of listening to rather bass-light tracks like Aly & Fila - Khepera (Leon Bolier remix), at least to an extent. Very strangely, sometimes (like 1 in 30 cases) they sounded just like they should, and the bass was insane. I don't need 'moody' headphones - they need to be consistent! Some time later, I bought them again, and had the very same issue as with the previous cans - except that those were loose from the very beginning, and have never gotten to 'change their mood', as I returned them a few days later.
I had the exact same problem with AKG K81 DJ. The first week - the bass was great. Then they got loose, which killed much of the bass and most of the pleasure of listening to music. A couple of years later I bought another pair, and it was loose from the get-go and, of course, didn't provide enough bass to my liking. Am I cursed or what?
Problem with hissing
The inconsistent quantity of bass is the only reason that I'm giving these the lowest possible rating. If the bass were consistently powerful, I'd give these 4,5/5. Why only 4,5/5? They have a hissing problem, which made singers sound as if they had a lisp; this also made listening to e.g. the beginning of Cosmic Gate - London Rain (Back 2 Back 4 redub) physically painful. On the other hand, that's probably the only track with which there was such a problem. I strongly prefer music without vocals, so that was never a major issue.
They were as comfortable as one could reasonably expect from bass-heavy headphones; my issue was that the clamp was very often too weak to provide enough bass - see above. Shame on you, Ultrasone, for such a poor design. Before you ask: yes, I tried using a rubber band on the first pair. For 2 days. It made them looser than before, which I found comical.
They have a very long cord, which to me was comfortable - I could walk around the room without worrying about the headphones falling off my head. However, it's a double-edged sword - if you're looking for portable headphones, the length of HFI-580's cord is going to be a major issue.
Definitely the least important topic, but they look decent. No issues here.
If you want consistent powerful bass, do not buy these, as you may as well have the same problems as I and some other people (search for the thread 'Ultrasone HFI-580 too loose?' - the HFI-780 model is also mentioned there, so watch out for that one as well) had. It is scandalous that you should pay over $100 for something so flawed.