From my own experience i believe that burn in has different impact on different brands. The closest thing to objective changes after burn in that i noticed was with my first set of higher quality headphones, the Beyerdynamics. When they were fresh out of the box I plugged them straight in to my Ipod, and at full volume they produced a weak, very anemic sound which had me really disappointed and worried. After a few weeks of using them through a better amp and having left them playing around the clock, the Ipod could drive them just fine on volume mid-way with a full, richer sound.
I´ve tried burn in on different cans on the other hand, where i never heard a, at least for me, noticable change in sound quality och character.
I still use to leave new phones playing over night for a few days with pink noise, starting with lower volume that I gradually increase and after that I just use them as supposed to and enjoy the music.
Cheers Johan

















