I was an early adopter of the X. My old pair are one of the first production runs. The new pair sounded very similar out of the box - maybe a tad less smooth but now with ~100 hours they are mellowing. The biggest difference I noticed is the break-in of the leather ear pads. The old pair are now very comfortable while the new pair are still a bit stiff on the head. BTW, I upgraded both with the new carbon fiber head band that IMO is a big improvement.