I need to find a quiet pair of headphones but that sound just as good as the athm50s for a cheap price (200$-) and that have low impedance..
Edited by bobbert - 8/17/12 at 3:14am
What kind of ambient noise are we talking here? The M50's have pretty decent passive isolation. Moving to active noise cancelation isn't going to net you much more privacy honestly but it's dependent on what kind of noise it is.
IEM might be the way to go for you, if you're able to tolerate them. You'll get better isolation with them than a full size headphone. Better quality per dollar too. And you can wear a headphone on top of them to further increase passive isolation.