Man of Honour
I think most of the tuning is done via the ear pads, the 65th Anniversary and 712 have memory foam pads which increase the bass by quite a bit. However, they do lose some of the airiness that you get with the Q701's and even more so with the 702's.
Makes sense and this is probably in part why the X1 sound so meaty as well as they too are memory foam pads with thick velour on top.
I need to know how much soundstage is affected though!