I have no chance to hear K712. But I have K550/551, K701, K340, had K601 and some other AKG. I have DT150 which is extensively compared in head-fi with K712.
According to all the things I read and my listening experiences I expect X2 to be on par in some ways (with K712), better to be on the bass, soundstage depth and imaging section. Only the mid-high and high section might be a stiff competition as I may expect slightly more presence and clarity on highs with K712. But I don't want to speculate more as I have not heard the K712.
As I said on the "one of the first paragraphs" on my review, X2 eradicated my entire AKG line and I became ice cold to them now (Except K340).
It's soo sweet sounding HP.
Is X2 accurate, neutral? We may discuss. In to some degree yes, in to some degree no. But it is technically superb and clarity surprised me. Also bass is very detailed after burn-in -although not on the tight category like the DT150 bass- but very very close to it. For an open headphone it is quite hard to achieve this quality/quantity bass.
In the beginning it was very bassy. Mids were recessed a little bit. Now all the frequencies are very leveled (especially after passing 200h). Although bass is still slightly more dominant part IMO. Highs are very smooth. Never harsh or grainy for my perception.
I am putting my DT150 (closed HP) and X2 on my top of the full sized list. They are both very very good HP's.
For build quality and comfort part I can't compare X2 to anything else, it's really awesome!
Hope this helps.
(On my part, I wish to hear K712 because I really heard great things about them, especially when properly amped)
