Well I think it is the first Sony headphone that I really like (note that I've not tried the crazy expensive R10) with a proper tonality, I mean not digitized like most of Sony headphones.
It reminds me to the Audeze LCD-2 on the bass performance, not as good as them but also with a great sub-bass and impact.
Mids are similar to the Focal Spirit Classic, a touch warm but less "grainy" and treble extension is like you have from a very good open headphone, it never sound like a closed headphone in this section, maybe the little vents help on this.