I'm still quite a newb when it comes to headphone testing and comparisons and my ears haven't been trained to hear frequency humps and what-not so my take is strictly layman. That being said, I bought a pair of QP55x's off of ebay several months ago because I wanted to try something open and something that had the "Grado" sound, but on the cheap.
They were a great bang for the buck, and besides have to get a 1/4 to 1/8 adapter, I was very pleased. They're extremely comfy and didn't leak as much as I thought. The cord was also pretty strange, but I liked not having foots of straight cord under my desk.
Soundwise, I was astounded by how much juice they needed. At the time, I had only a TBAAM connected to my Powerbook, but all the headphones I've tried (dt770, hd595, portapro, ksc75, hd201) were plenty loud at one or two bars of volume. The MB Quart's, however, could push 6-7. I really enjoyed their sound, very nice highs, I didn't get any sibilance or anything. I enjoyed them so much, that I went on to acquire my own Grado. They were Grado-gateway phones for me.
So after a bit, I landed a pair of SR225's and was astonished once again. To me, the Grado's had the same highs as the MB Quarts, but definitely had more mids and lows to go with it. However, with other phones like the dt770s and HD25s, so I still felt a lack in the lower range. I fixed this by getting flat pads which gave me the bass I wanted and also managed to make the Grado's much more comfortable to me.
Anyways, back on track, the QP55x's took a break for a while and I even put them up for sale a little while ago. When I saw this thread, I remembered them sitting in my closet and took them out for another try. I'm glad I did. I think the MB Quarts have more Grado-highs than my Grado's do with flat pads (if that's possible). Very clear and fluid, whereas the Grado's are more balanced and muddy in a good sense (less shrill). My stand is that I'll keep the MB Quart's around after-all. Although they can't touch the SR225's, they're a hell of a lot comfier for long sessions (although the band makes my hair look like a camel's back) and still have that sound I've grown to love. They're a high impedance-circumaural-budget-grado that shines with amping.
In short, if you don't want to shell out the dough for $200 plus headphones, or you want to try something Grado-esque, and you don't mind spending a little for an adapter and amp, or better yet, have them already, this is a great deal. I'm surprised these haven't been mentioned more, but I'm glad they're finally getting the respect they deserve.
