Regardless of what has been said previously, the DT880 do not isolate. Sure, they isolate slightly more than some fully open designs do but if you need isolation they will not satisfy you. There is not much difference between a semi-open headphone and a fully open headphone in regards to isolation and leakage. In both cases the people around you can hear what you are listening to and you can hear what is going on around you. When you are listening to music the noises around you are hard to hear regardless of whether the headphone is isolating slightly more than a comparable fully open design would. And the noise that leaks out of these headphones isn't very loud so a slight difference in that quantity is essentially meaningless. We're talking about tiny drivers sitting next to your ears so even if you don't isolate them at all they will still sound quiet to someone standing a few feet from you. Very slightly decreasing that makes very little difference.
If you need isolation do not get open or semi-open headphones.
Edited by devhen - 10/3/13 at 2:11pm