Burned in for 1 week. Using this product for 2.1 music listening. These headphones are a little and I mean a little veiled and sibulent. You can hear every bit of music that is a a available on sound tracks being played. Not bassy headphones but they do have bass and are very impressive with the mod that i corporated. The mid range and highs are now superb. With a sound stage forward, rear and side to side. Using an AUNE X7S with a NAD DAC 2 Wireless and Dell laptop running tidal at 24/96. I have heard more music then ever before in my library. The 660s pull you in. Some times I turn my head to make sure it's not an outside noise. They do have a good clamp on your head but it can be lessend by pulling the phone extender out all the way and bending the metal slider. BE VERY CAREFUL NOT TO BEND OUTWARDS TOO FAR or HARD AS THEY MAY BREAK. One hand on the phone bracket and other on the metal piece that comes out of the head band and use your thumbs to apply pressure on the bend in the metal band. Still debating whether I sell my 600's As the sound is a little more rich. Will update when finished testing and final choice. Waiting Dekoni hybrids ear pads as the defaults are a little hard for my liking. I have not heard planar mgnetics or eletrostatics but the 660s make me want to put them on and relax when I'm home from work and rock out when feeling up. They are an excellent all round headphone and play all genres of music. Do your research. Good luck and remember everyone hears differently. Find your sound?. Oh the metal screen did pop out of the plastic molding when I tried to take the back off. Make sure you poke the plastic through the small holes on the driver side and not the metal, if you want to take the back plate off.