This is one of my reference music for deep bass power! My experience a AKG headphone must run 15 .. 20 hours for a good sound (but not 500 hours), later till 50 .. 70 hours it will be "shine"
The K712 is hand-crafted in Vienna (Austria), pre-selected transducers, 3 dB improved low end performance, soft genuine leather headband, open back dynamic headphones, sensitivy 105dB/V, 10 Hz - 39.800 Hz, 62 Ohms, max. input power 200 mW, cable 3m 99.9% OFC (from the cover).
Enclosed accessories: Additional coiled cable, black velvet lookig carring bag, adapter 1/8" to 1/4".
In the long time test (I heard quite a few of my CDs "up and down" in the meantime) the K712 revealed a fatigue-free listening. All images were played back in great detail. The bass seems "the right place" and is not bloated (what with the D7000 occasionally occurs). The K712 affords no noticeable weaknesses. Otherwise error in the images are very probably noticeably - yes finally, that must be the meaning of Studio Headphones (the main purpose of the K712 Pro).
In my compareson tests, mostly I play short sequences of a few bars again alternating with the two headphones. For me the K712 ranks about the Q701 (both - original or K712 pads).
A comparison test K712 with the K701 (with original pads) coming soon.
PS: You must seen all my test are subjektiv - for your own opinion you should compare this headphones self. Less subjetive tests are ABX blind-tests with more persons - but this are hard to do with headphones.
Please excuse my not so perfect english - my native language is german.