Ok, my Q701 have over 150 hours in them now, about 100 of those hours playing bass heavy and extremely dynamic music on very high volumes...I thought I'd give some impressions again. First of all, I now definitely don't believe in burn-in. I hear no changes whatsoever in sound. There are changes most probably, but they're so minor its not worth mentioning them, and are probably only barely noticeable when A-B comparing a brand new and a burned in pair of headphones. The thing that has improved is comfort. With about 50 hours total on on my head, they're now extremely comfortable, almost non-existent clamping force and extremely light feel. However, I do feel that damn headband after an hour or so, so I have to adjust it, but its not a big deal. HD650's require adjusting every 20 minutes because of their tightness.
Now...about sound. As I said, no major changes compared to out of the box sound. However, now that I spent more time listening to them, I found a couple of things in general that I didn't notice at first:
1) I find them to be very sibilant and overly bright with almost all music. BUT, that brightness is only there when using them with Little Dot Mk5 amp, when plugging then directly into Xonar ST, there's no sibilance or brightness, but there's also much less sound stage, accuracy, instrument separation, worse imaging.... Little Dot just makes the sound better than straight out of ST, although overall not especially great. These headphones reveal nicely that Little Dot Mk5 is an entry level amp.
2) Not a good amp + hp combo if you ask me. Mk5 seems to have a very hard time running these headphones. High output impedance I guess. I find myself turning the knob to 100% with some recordings and still not getting the volume I'd like, while on HD650 I never ever go above 70% when listening to music.
3) I'd like more warmth and slightly more bass presence in everything apart from electronic music. Yes, sounds weird? I find them to have just the right amount of bass and great punch (almost on HD650 level) with trance, like Infected Mushroom for example, but I find them lacking bass impact in rock, pop, etc...and they lack some fullness with vocals, instrumentals, jazz, classical. They do indeed tend to sound thin, especially directly compared to HD650.
4)These headphones sound very good technically...very fast, accurate, clear, detailed (although not more detailed than HD650, its just an illusion because of excessive brightness)...but somewhat boring. Even less involving than HD650's, which I already consider boring, but at least you'd expect HD650's to be boring, because they're laid back and smooth, Q701's are not laid back or smooth. Its kind of weird, they manage to be somewhat fatiguing and very forward sounding, but at the same time not involving. However, their accuracy and clarity makes up for it.
5) Sound stage is weird. IMHO, HD650's have a much better sound stage for music. I don't know whether its due to my source and amp, but Q701's seem to have a very left-right sound stage. Wide, but without any feel of depth whatsoever. All the sound seems to come from the sides, and even from behind sometimes, no matter how far forward on my head I wear them. They also don't seem to have a very big soundstage when listening to music. Actually pretty small, smaller than HD650 or HD558, not much bigger than HD438, which are closed <100 dollar headphones. I really don't know why AKG 701 series has a reputation of having a great soundstage, thats by far the worst thing about them if you ask me.
But, everything I mentioned can probably be sorted with a more powerful slightly darker sounding SS amp with smaller output impedance.
Overall, great headphones for the price. They compare nicely with HD650's, even when we consider that Mk5 and HD650 are a match made in heaven sonically. I'd say they sound better than HD650's with vocals, some instrumental recordings, some jazz and some classical, trance, games, movies. With rock, pop, metal, etc. they're about equal, depends on recording... Oh and yes, some records that sounds like crap with Q701 sound decent on HD650.
Another thing that bothers me is something I expected to be the advantage of having both of these headphones. At first they sounded similar, but now they're worlds apart in their character. It takes time to get used to each of them. When listening to Q701 for an hour or two, and then putting on the HD650's, they sound very dark. When going from HD650 to Q701, they're unbearably bright for a few minutes. The point is, as my mood for music changes and I change the headphones, I first have to wait a few minutes for my ears to adapt to new sound, which is annoying.
