Pros: Good mids, and decent treble
Cons: Subpar build quality for a 300$ pair of headphones
Well, the K550s don't sound bad by any means, however, the sound signature isn't really for me. I like a little less mid focus and a bit more bass. Less neutral and more fun, really.
Now the build quality of the K550s are not superb by any means. Firstly, the headband cushion was peeling off in the corner right out of the box. Which was really disappointing. The construction of these headphones felt flimsy, even though it is built of aluminum. The M50s have much better build quality than the K550s.
It's really love or hate for me. The comfort isn't great either. My ears touch the drivers which causes them to hurt my ears after only an hour of use.