Thanks for the update.
It's often assumed that the K701 and K702 are the same. After all, AKG claims they use the same driver, along with the Q701. However, to many listeners and pretty much all avid AKG fans, they are definitely different sounding headphones.
The K701, if you're a fan, is an awesome headphone. But it lacks in several areas, which the K702 makes up for in most people's opinions, including my own. The K701 really lacked in the bass department, and it's vocals could be recessed. It was something you tried to live with, if you were a fan of the headphones, but they got me looking for something "improved." I didn't want to give up the K70x sound, but I didn't want to live with those limitations if I didn't have to.
Happily, the K702 improves over the K701 in 4 distinct areas (IMO): it offers deeper, more impactful bass. Keep in mind, it's still a bass-light headphone! That is, the bass goes very deep, but has little impact. However, the K702's bass is enough that the headphone is no longer "lacking." In addition, it brings the vocals more forward again to match up with the rest of the instruments, so again, it's no longer glaringly lacking in any department.
Personally, I also felt that the K702's pads were way more comfortable, (less fuzzy/scratchy, and more firm), and the pair I owned had a nicer headclamp setting, as opposed to my K701's looser clamp, which allowed them to slip off whenever I tried to lie down. I think this again had to do with the firmness of the pads.
In comparison to the HD650:
The HD650 had definitely better bass, and in my case a perfect fit. But I simply enjoyed the clearer, more airy and spacious sound of the K702 by far. I owned both the HD600 and 650 for many years, and used them with many amps. But I never could get beyond their laid back, 'veiled-like' sound. Sure, they do everything perfect. But over time, they simply made most of my music sound boring. Whereas the clarity and articulation of the K701 + 2 sound alive, sparkly, and exciting, without being harsh.
In comparison to the DT880 / 600:
Again, the DT880 had much more impactful bass, though it did not extend as deep in my listening tests. For a while I thought I would just keep it and sell my K702. But where the DT880 fell short, IMO, to the K702 was in two places. First, instruments sounded great on the DT880, but they simply sounded more clear and natural to me, and more separated, on the K702. Second, of course, was soundstage. Both the DT880 and the HD650 have great soundstage! But the K701 + 2 have AWESOME soundstage.
This was a really tough choice for me. (As opposed to the HD650, which I simply didn't like as much as either of these). For a while I thought of keeping both the DT880 / 600 and the K702. But that just sounded like a lot of inconvenience. I'm really just a one woman, one headphone kind of guy. So I sacrificed the bass impact I wanted, in exchange for the clarity and soundstage I love, and kept the K702.
It may help to keep in mind that I listen primarily to Vocal Trance when listening to headphones, and I use a tube amp. (The Glow Audio Amp One). So, things like instrument separation, speed (so the presentation doesn't get muddy, as it often can with Trance), clarity and especially soundstage are critically important to me. Also, since Vocal Trance has enough bass on its own, missing a little of it doesn't bother me so much, as it would with for example classical music.
