Just got my K550 today. Test running for the first few hours.
Setup: Sony NWZ-X1060 LOD + GoVibe Martini/FiiO E11
Crappy short review I must say, please excuse me lol.

Gorgeous packing. But that's all. No accessories others than the 6.35mm adapter is included. I'd be very much happier if they could include a carrying case for it (It's AKG though, I didn't expect much. *Looking at K702*).

First impression, solidly built and light weight. The isolation is alright, leakage is minor. Earpad is a comfortable but not recommended for long period of usage, it'll "suffocate" your ear lol. Headband is very nicely built, the metal headband and cushion feels great and the adjusting mechanism is as good as it can be, clicks better than the HD800. The specification and description kind of indicates that the K550 can be a portable headphone, doesn't required amping, can be driven straight out of portable media players, but what the hell, the cable's thickness and the size of the can definitely suggested the otherwise. There is no way in hell I will consider this anything close to the words "PORTABLE".

Sound quality? A little bit warmer than K701, but not as warm as DT880, somewhere in between I'm guessing. Clarification is above average but nothing impressive. I do notice the high losing control at times though when it's paired up with Martini, and the treble can be too aggressive and ear-piercing. Soundstage is very awesome despite being a closed-headphone, comparable to K701/DT880, but no where as good as HD800.

Presence of bass is somewhat better than in K701, but weaker than DT880. Definitely not a strong point of K550, but still, the quality is alright. Pairing up with E11 makes the headphone even more warmer and bass boost increases the presence nicely, some treble roll-off but a justified trade-off for certain genre of music or song, ie R&B, trance etc.

Overall..The K550 is mediocre at best, not necessary bad but I'd say it's alright for what it is, being a closed-headphone and whatnot, but..imo the retail price doesn't justify it (250GBP).
I picked mine up at 195GBP, I think that's what it actually worths. A passable substitute to K701 at the very least, so I'm happy with it.

This post has been edited by awyongcarl: Mar 24 2012, 04:03 AM