Hi, first post! I've been reading the forums a lot doing research however. My HD 600s arrived today, I was interested in the model for its reputation of being very neutral and sounding good with everything, as well as liking the Sennheiser sound signature in general. I demoed a pair and liked what I heard as well. My dac/amp won't be here for a week (went with e7+e9), but I wasn't about to leave these babies sitting around for that long, so I decided to get started burning them in the natural way.
Initally I pretty much thought they would spit poison at my ears for the heresy of listening to them unamped and not burned in. My previous cans are a pair of Sennheiser HD 280s and Grado SR 60is, so I was initially pleased to find that that these are more revealing than either, I went through the whole experience of hearing things I never knew were in my music, again. As I listened to a song or two from as many different albums as I could think of, I found that with every album I listen to it's as if I'm rolling a die, and the sound quality can end up anywhere from a 1-6. Two albums of the same genre can sound vastly different, two albums that I know for a fact sound great can as well. One rolls a 1, the other a 6 (I do get a lot of 2-5 as well). I understand it's natural during burnin and especially without an amp - I'm not upset, I just find it humorous. Bad teenpop could potentially sound amazing at this point (though I won't be finding out).
Then I put in Nils Lofgren's acoustic album, and it changed the die to a 12-sider which rolled a 12, I actually cried! It was so unexpected, so completely out of nowhere. In that moment I was sold, it absolutely blew away anything I've ever heard through a set of headphones. I'm shivering to think of what amplification and burnin will do. And I'm certain that the albums which don't currently sound good will come around, hehe.