I compared my K712 Pro with my mod Q701 (with the same pads as K712 Pro use). It's only a little difference - but I prefer the K712 pro.
The K712 have a bit more (fuller) bass as my Q701 with the pads from the K712 - but its very hard to catch, the music sample must be right.
The K712 plays the "creaking" ("knarzen" in german) of the chello a little but more succinctly as the Q701 (with both implementations of pads tested).
These differences are very small - I will test them on an other day again to confirm my own impression.
My used test samples for this: "AUDIOphile Pearls Volume 1" http://www.musik-sammler.de/media/817284
Compareing K712 <--> Q701 (with K712 Pads)
K712 - bass is a bit deeper, a bit more resolved, free.
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).
Roger Waters, Amused To Death, Tr. 12 "Three Wishes"
K712 vs. Q701 with flat (K712 like) Pads
The hiss of the basin (brass) appears a bit more terse and a bit better resolved with the K712.
The deep roar of the Three Wishes comes with a bit more pressure at the K712.
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).
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