They've existed for quite a long time. From someone I knew years ago they work well once you get the calibrated to your ears. But they're far from perfect so I'd be a bit nervous about using them to judge a 5.1 mix. Are you adjusting the real mix or compensating for how you're monitoring would be the question. Using cans for mixing is problematic enough with stereo, 5.1 would be a real issue I suspect.

Bob.

Best NOT to use headphones for DD5.1 editing.... They don't contain 6 speakers. They instead work out the surround sound and channel it electronically by varying frequencies/balances, so you're not getting TRUE 5.1 sound (although it sure sounds like it). Given this... it is quite easy to make a mistake or 4 with sounds levels and such. You need 6 TRUE channels in a proper configuration to get a good finished sound.

Whether it's Stereo or 5.1, if you want a bad mix, use headphones. You'll hear things so well, you're bound to get it wrong.

You'll hear things so well, you're bound to get it wrong.

Yes, Oh Yes!

I work with cans on a lot but not for mixing. I'm monitoring archival material that's already mixed, looking for problems like noise etc. For this purpose cans are ideal except you've got to know the importance of what you're hearing. I initially wasted a lot of time futzing around with things that became inaudible in a real listening environment.

Even with decent monitors it's easy to get it wrong when mixing. Given my level of inexperience I find I can get say the music sitting nicely with the dialogue but when played back through a TV the music goes from background to annoying drone that's too low to work. Moral to this, check mixes in several listening environments.

And here's a tip from a pro (not me):

If you want your mixes to sound loud, turn you monitors down when mixing.

Bob.