Good question ! I bought the 3's from a Head-fier and they were already "broken in" or almost. My XCs were shipped new. Hence when I first heard the 3 and I hear it now, the "evolution" is more subtle. Then and now, the 3 to me is a very neutral headphone with everything done right. Repeated hearings have not lead me to any epiphany like "wow, this is the first time I'm hearing this".
The XC is still being "burnt in". The music is turning from "what have I done" to "now I can hear the bass extending low, the top end is opening up etc etc."
Edited by deafanddumb - 2/3/14 at 4:24am