Couple of thoughts...
I've been using studio monitors for almost 30 years. I have many different phones that I use in my studio. Some are better for mixing and others for playback. Reference monitors (speakers) are essential for mixing, but I know we can't always have that as an option. The other posters are correct in that you really need something as flat and neutral as possible for mixing.
Headphones I use often in the studio:
Very neutral. Great for mixing.
Beyerdynamic DT 700 Pro (this is NOT the regular DT770)
Most comfortable for long sessions. They have a drop-off in the upper mids which you need to compensate for but that also means they are less fatiguing.
Equation Audio RP-21
They seem to have a bit of a bass boost, but still pretty neutral. Not very comfortable though. Some people have modded them with velour pads.
Headphones I've tried and don't like for studio use:
Sennheiser HD280 Pro
Not enough soundstage and imaging for me.
Sony V6 or 7506
Decent enough but there is a drop-off in the upper bass and a boost in the upper mids. Also, they cut off pretty abruptly at about 10K, so if you're not careful you can end up with some unwanted sibilance and hiss in your mix.
Here's some Frequency Response charts (top to bottom - Sony V6, Fostex T50-RP, Beyerdynamic DT 770 Pro)
I'm reviewing these right now. They do sound (and look) very much like the Sony V6 and are about 1/2 the price. But they are not as comfortable and while I am still burning them in they are sounding a bit brighter and more forward that the V6. Still a very good phone for approx. $50.
I have not heard these but most reviews are good. They seem to be a bit better the the Shure studio headphones. I am expecting to recieve a pair of the less expensive 6400 model for review soon, so I'll post some impressions here when I have tried them.
See if you can find a music equipment retailer nearby where you can try them out before buying. But I would recomment the Fostex and the Beyerdyamic.The AKG 701 is an industry standard too. I like them, but prefer the other two.
Edited by postrock - 8/1/12 at 8:08am