It's funny to remember that when I bought these I thought they were good headphones, at the time all I had was CX300 and the fact that they weren't muffled, had good separation and had nice crisp highs that bought out drums nicely seemed enough to win me over. They aren't uncomfortable either. Let's face it for the price you have nothing to lose, I got mine for £12.
But now, with some real headphones under my belt, they sound god awful. There is really nothing good about these. That's being unfair. There is no bloating or distorting across the spectrum and separation is actually very good. But the whole sound is artificial from the weedy almost non-existant bass through to the metalic, robotic mids. The treble does the best but who cares about a nice snappy drum track when the rest of the sound is so unnatural?
What has frustrated me the most is that nothing can save these. My girlfriend has an awful pair of low end Sony fart cannons, but I was able to open them up, add some dampening, tape up the vents and bring them under control a bit. With these phones nothing seemed to improve them and nothing bought any bass out of them. It's not an issue of a good driver in a cheap case with no dampening - it's a case of a bad driver.
Frustrated, I finally binned these. 
But if you have £12 to spend and you want something better than the stock buds on your DAP, they are certainly worth the asking price. My advice is to bite the bullet and up your budget.

I've owned these headphones for around a year now, when I first bought them they were a quantum leap forward in my headphone listening life. It felt like a big spend as I had to buy a desktop amp and a dac at the same time and it took a pay rise at the point where I was questioning the wisdom of it all to finally pull the trigger. I never looked back.
 
It is funny that the cost seemed so extreme to me now; once you delve into the audio enthusiasts world and see the prices some other headphones go for you realise that the HD650 is in fact a serious bargain, especially since many people (myself included) think it is a far better phone than many of those higher priced offerings.
 
The sound signature is one with bass emphasised yet superbly controlled and clear; I am definitely in the camp that thinks that a respectable boost in the bass region makes music sound more natural.  Perhaps this is because the majority of cheap music systems have speakers that put out uneven bass so producers make the decision to counteract that with reduced bass? Whatever the reason, the HD650 level of bass and mid-bass is spot on for making the music sound real and natural and live.
 
Laid back is another term often used to describe these headphones and for good reason. Some people call this a "veil" over the sound but I think that again, what they are reproducing is a very lifelike sound. In real life the source of all sound is not an inch of so from the ear like with headphones, everything does seem a little pushed back from us and since we are used to this I find that it adds to the natural feeling of the phones.
 
In terms of sound stage, well I used to think it was perfect, but since I got the AKG K702 I have to say I have found myself wishing the HD650 could be a little spacier. Everything else about the headphones sound sig, from the laid back presentation to the natural bass boost seems to be aiming for a realistic sounding reproduction of live sound so to have it all so close around the head is a little self defeating. That said, it is certainly big enough for analytical listening and beats other high end phones, like Grados, by a country mile.
 
Since everything about the sound engineering of these phones seems to be aimed towards making you forget you are wearing them it does seem an odd decision for the product designers to have added a clamp so tight you really cannot be unaware they are on your head. This is well counteracted by the softness of the very comfortable pads and I was very used to it but when I got my AKG K702 I did start becoming a bit less forgiving. When my other main headphones were the MS2i with flats the HD650 showed up favourably in the comfort stakes, but with the velour laden K702 with its self adjusting headband and super light clamp I definitely now feel the pressure on my temples of the HD650. I've read about people bending parts of the headband to relieve this. I've also seen pictures of snapped headbands as a result so am going to play it safe and live with it. It has slowly reduced over a year and I imagine will disappear completely in the future. This is a shame though as the sound of these phones is one I find extremely relaxing and this effect is negated by an unfortunate product design decision. 
 
This is the one minor bugbear regarding a high quality, great value package. Everything about them screams quality, from the classy timeless design to the velour pads and padded headband to the sound when you put them into action. While there are some genres other phones do better with (K702 certainly a better option for classical and electronica) there is no genre these do not do proud. So long as they don't break (and I do baby these headphones) I would not be surprised if I'm still putting these on my head in retirement.

I've owned these for the best part of a month now and have done some extensive listening with them both in extended listening sessions of several albums and of comparative listening sessions with with my HD650. I feel I am ready to comment on the qualities of these phones.
 
I had always intended to put these and the HD650 against each other and sell one, as I had thought it would be an indulgence to keep two expensive open circumaural home-listening phones. The problem I have found (and it's a good problem to have) is that the are fantastic companions. Any type of music the HD650 does not do so well with, the K702 shines with and where the K702 seems a bit too formal and cold, the HD650s warmth is a perfect tonic. I'm keeping both.
 
Formality is really the term I would use to describe these phones. They are polite, analytical and are certainly revealing of a track, with details not just presented but presented with a crispness and accuracy that is a joy to hear. Don't bother listening with anything but high quality encodings though, as it will show up the wrong kind of detail just as clearly.
 
The AKG K702 have less bass than most of my other phones, but still presents more low end than, say my Phonak PFE or MS2i with bowls rather than flats. The bass is of an exceptional quality, impact and speed. The mid range is beautiful and airy, especially where it comes to female vocals which sound sometimes unnervingly real and the treble is crisp, if a little cold.
 
The real star of the show when it comes to the K702 package is the sound stage. I was worried I would be put off by its size as many complain of it being unrealistic. Well, it's really not that big, but it does offer the space you need to really delve into a song, picking up on this and that instrument and then mentally stepping back to hear the whole track as one.
 
It's sound stage and level of detail really make these phones perfectly suited for my classical music and my jazz and my electronica and works very well with layered rock/alternative music such as Radiohead, Captain Beefheart and the Magic Band, Frank Zappa, the last two Joanna Newsom albums and that sort of thing. That isn't to say it doesn't do a great job of presenting rock, pop, reggea and simpler folk as well as it is certainly pleasant, but for these warmer and simpler types of music I find myself switching to the funner HD650 with its more intimate sound stage.
 
Comfort with the K702, for me, is a major plus. I understand a lot of people have big problems with the bumps on the bottom of the headband. Pressing them with my fingers I can feel they aren't comfortable, but I have plenty of hair and do not really feel them. The 3D form cut velour pads seem to have been designed for the shape of my skull and compared to the HD650 the lack of clamp is quite a relaxing experience. I can wear these for hours on end and often forget I am wearing them. 
 
If the AKG K702 were my only headphones, I might find their genre range a bit limiting, I might find myself wanting a bit more bass with my reggae and hiphop and a more intimate sound stage with my rock and folk. But as a part of a varied collection with the HD650 and MS2i as the other two main home phones I find I have a great set of options to cater for every mood and genre.
 
The AKG K702 has filled in some gaps for me; has given me a classical and jazz listening option that can seriously compete with speakers, a natural home for aphex twin and a sound stage that brings the best out of some of my more complex rock music as well. Add to this it's almost unnervingly realistic reproduction of female vocals and it really does justify its price.