Just received my KEF M500 and M200. Checking out the M500 first. Out of the box>>> Whoa! Not blowing me away like the X1, but very nice with no burn-in what so ever. Great visceral bass, with a nice amount of sub bass. Mids aren't recessed at all, but treble is a bit bright (not harsh to my ears, but pushing close). I hope the highs tame a bit.
The headphone, itself, is smaller than it looks in the photos to me, but it fits like a Isotoner glove! Probably one of the most comfortable headphones (especially for a portable) I've ever worn. And the headphone and it's clam-shape hardshell case are like pieces of art. One of the most beautiful headphones I own (along with the X1). I would say the sound is not too warm or cool. A very full and neutral sounding headphone. Actually, right now, the sound kind of remind me of a fuller sounding CKN-70, with deeper bass, but with those almost harsh highs. Precision sound and timbre. Okay, I'm about to break open the M200 in a few, but a thumbs-up for the M500. The WS99 is wonderful portable, but the M500 leaves it in the dust already without burn-in. Very beautiful refined-sounding portable headphone with a gorgeous physical styling to match.