OK. Got these in today. They sound like flashier HD800s with more slightly bass and also more 6k peakage, but with technicalities (speed, clarity, resolution, etc.) between HD650 and HD800. Overall treble is slightly less and HD800. There is also an apparent midrange suckout. Upper mids and treble are not even, so cymbals, high-hats, snares sound really odd and different depending upon recording. Because of the peaks, these cause me hearing damage at normal listening levels (low volume is OK.)
Measurements can be found at the usual places.