The Nady QH 660s are a pair of 'studio' headphones.  I bought two pairs of these a few years back when Musician's Friend had a buy one get one free sale.  I should have known that it was because they were very poorly designed!  Within only a few months, both pairs of headphones were broken as one ear had cut out beyond repair.  I planned to use these headphones in my home studio for monitoring during recording.  They certainly didn't have the best sound quality, but got the job done for a very short period of time as I needed a few extra pairs of headphones to go along with my good ones just in case.  The QH 660s have a strange design, as I didn't find them all that easy to wear and definitely aren't the most comfortable headphones around.  They do have some padding on the top and the ear pieces which helps to ease the burden a bit, but not by much.  The sound of the headphones a bit lack luster, as there isn't too much low end at all and they don't sound very full.  However, I was not too concerned with this since I just wanted to use them for play back and monitoring purposes.  Obviously, I don't even have to say that the Nady QH 660s are not suitable for mixing or any use beyond simple monitoring or listening.  I'm not sure if Nady even still manufactures these headphones, but judging from the fact that I got a buy one get one with these a few years ago, they were probably trying to get rid of the last ones that they had.  While they were incredibly cheap at the time, it definitely was not worth it since they broke quite promptly!  Definitely stay away from the Nady QH 660s as there are plenty of other headphones out there that are pretty cheap and will last a decent amount of time...