So I got another K550 from CT. This one is much more balanced and listenable than the 550 I had heard at the Headamp tables a few times. Those were thin, dry and bass light w/ the treble nasties. I thought they were doing the latest Shure trick by rolling off the bass to enhance fake detail and clarity. This pair is much more balanced, even a hair over neutral in the Bass, notes are more fleshed out and the signature is pretty clean and clear but the treble still has some issues. Female vocals and strings seem to carry harmonics into the fatigue zone either by peak and/or ringing. There is a hint of a unrefined signature and tbh seems to remind me a bit of the HFI580 which was my favorite Ultrasone, especially modded. I'm going to compare them now. I would listen to the 550 loud and over extended time unless the treble were resolved one way or another. It's just too splashy up top.
Hmm, the HFI580 (modded using AKG pads ironically) is even more refined and smoother sounding, they have a shout somewhere in the midrange but the treble is much more forgiving. The midrange signature is on the leaner side compared to the K550 , no doubt from the pads I'm using, but the overall signature is cleaner and better than the K500. Bass is much bigger than the 500 but actually just as detailed, textured and resolving of information on the track. No surprise as they were designed as Bass monitors for percussion. These simply have some of the best quality bass you can get for around $100 that I've ever heard if you don't mind the emphasis.
If I had to pick a driver to work with, the 50mm HFI580 would be it. If I had to pick a luxurious, and gorgeous housing it would be the K550. Hate to say it, but the AKG actually looks like a classier knock off of the Beats Pro done in black. Looks good.