Couple of words about metal music + AKG K712 PRO. (Summary on impressions on metal + almost 60 cans is here http://www.head-fi.org/t/715478/headphones-for-metal-music-ultimate-solution)
AKG K712 PRO
Initially I had an idea to listen 712 in comparison with 812, but at the first test it became clear that there is no sense in such a test. 812 and 712 are animals of obviously different levela (a top top level and a top middle level) and different character (ultra-bright with an average soundstage and darkish with a wide scene). Next I tried to compare 712 to Denons D600, again it made no sense, at fast switch from cans to cans it was too obvious, that D600 have very "non-flat" character. As a result I listened 712 in parallel with Senns 650. And in my opinion result are not in favor of 650, objectively, without discounts for a personal taste.
The character of cans a bit darkish, cool (as a matter of a fact I expected something brighter), fast and accurate. Relative darkness doesn't affect resolution, detail level is quite high. Mids are natural and have cold spirit. Soundstage is wide, not such a stadium as Senns 800 have, but scene is much wider than average, cans are airy . Headphones have enough bass for heavy genres, often there was a wish to get more slam, but generally we have enough of low frequencies. It seems reasonable to assume, that increase of bass pressure would lead to problems with a soundstage air
Symphonic: Natural niche for 712. Very broad soundstage, moderately sparkling treble, cool mids, adequate bass and flat overal balance.
Power: Space, speed. Compact and quite sufficient bass. Bit of brightness for fun.
Industrial: Accurate and cold. Nice infrabass extention. Quantity of a bass - good or great? Perhaps Ultrasone 2900 Industrial interpretation is better, but if you to compare to any other middle level colleague - it's perfect.
Sludge, Stoner: There is no such a hard requirements to quantity of a bass as on Doom. Great mids, wide soundstage and easy sound flow make gestalt response with genre.
Black: Perfect - accurate, quick, with great bass control. It would be possible to add some punch on low frequencies, but then "air" would dissipate perhaps.
Progressive: It is predictably great. Vast soundstage, cool, technically perfect.
Doom: There is no enough bass concentration (surprisingly just a little).
Death: Somewhat strange, but even more sharp transients, than 712 have, would be welcomed here and it would be great to add some bite at treble.
Grindcore: Here we seriously lack the bass slam, a wide sounstage becomes an obstacle for great Grindcore performance.
Overall, in my opinion, 712 today are the best cans for heavy genres on the middle level.