When I use the 81' DJ's in an ipod they are good,
When I use them with CD player with legit (not burned) CD's it is very good, and the bass is amazing.
When I use them with a computer they are...epic, for the price. The bass is really good, feels like I have a fat sub on my head. The mids and highs are also very good.
While they do not have active noise cancellation, you can't hear shit when they are on your head. I got mine for like $65 and it was the best $65 I've ever spent. I bought them in June and I've already put hundreds of hours on them no joke.
check out head-fi.org
for headphone info. These people know headphones, like newschoolers knows skiing. I asked them what to get and they said 81 DJ's so I copped a pair and have never regretted it.
The music I listen to is mostly rap and techno with pounding bass) and then Linkin Park and they really good headphones.