Hope this helps if you are thinking about buying these...
Sub bass - Present all the way to the limit of hearing and snappy when EQ - Similar to Denon D2000, Not perfect but very good... On some songs the sub bass of these is just awesome...
Mid bass - Little bit loose at times but I have heard a lot worse in the price bracket, good but not great.
Lower mids - Actually really good I think even at twice the price, the imaging and rich sound of the lower mids is one of the best I have heard at £100-£150.
Upper mids - Too recessed but they still sound good with EQ... I think this headphone would be even better if 3Khz and up were a bit brighter and more detailed. Still good for the money and fits well with the rest of the sound.
Lower treble - Again this is recessed but to me this is better than sibilance. Some grain and sibilance but not bad, no more sibilance than is present in the recording, I am pretty picky about sibilance so this is a compliment. I would like the treble on these to be a bit more refined / smoother as well as a few DB brighter.
Upper treble - Again a bit recessed along with everything over about 3 khz but the quality is pretty good and better than excessive brightness. You can get better headphones for treble for the same money, but you cannot get such a well rounded overall sound.
Soundstage - Not huge but pretty good for a closed headphone, I like the presentation, sounds less hollow than M50 and has a nice 3D effect at times. I have never thought to myself that they sound excessively small or closed in. I usually think this about closed headphones, M50, CAL etc.
Imaging / Seperation / Speed - Another area where they punch above their price I think... Its pretty damn good.... Seperation and imaging sound better than you would expect for this price I think.... Not as good as something like HD-650 but they are 3x the price and not very good for the genres that these excel at. Compared to most headphones in this price range they are excellent. These sound pretty fast to me and keep up with most music..
Overall - Good especially for modern genres such as electronic music, hip hop etc. Although you could get better if you listen to only metal, rock or classical for example, as an all rounder though... excellent value in my opinion. They Could have a bit more / better quality treble but I prefer this to excessive brightness and sibilance, slightly peaky at 7-11Khz, and I would prefer if the sound above about 2khz was a bit more refined and smoother. I think if you prefer a darker sound and like modern genres, especially anything electronic and bass if you can pick them up for £100-£150 there is not a better headphone at the price. Personally I think they perform better than the ATH-M50 which is a popular headphone at similar price.
If these could tighten up the bass slightly (especially in active mode), make the treble a bit brighter and more refined and have the passive mode sound quality in active mode then these would be excellent 5 stars. As they are I give them 4 1/2 stars.