Pros: Big soundstage, good for monitoring
Cons: But not good for music listening. Very hard to drive.
This is the first time I give a lower than 5 star rate. The reason I say tha K812 is not good for music listening is because K812 seems to has it own way to illustrate music: it seems like K812 likes to confine every piece of music in a certain room with a stress of bass. This is good because that will ensure you hear something familiar every time you use K812. The strong signature is definitely for pros who do not want to waste time getting familiar with a headphone again and again. But for those who are not basshead or those who want to hear "music free in style", this strong signature is a big big big problem.
The sound is a bit dark, detailed but no way balanced. To much bass; imaging is good in a bad way (Clear, wonderful imaging, you can see everything but the singer seems to be in an awkward position: behind/is the drumer) treble sounds uncontrolled like hell if you don't drive it properly; sounds depressing as if I was listening via closeback phones
Bottom line: Remember these are monitor headphones. Don't waste you time if you are not a pro.