Pros: Bass texture, incredibly smooth across all frequencies
Cons: Treble can be harsh at first; takes time to mellow out
When I first tried these headphones out of the box, I was a little disappointed at how the higher frequencies seemed to be more forward than the mids and bass. It wouldn't have been a huge deal, except that the treble was also completely unforgiving on sibilant tracks, which really put me off. The saving grace at the time was that the bass, while not having a huge presence, had a buttery smooth texture that made my mouth water. The clarity and precision of the low end also extended well into the upper midrange, making the k612's perfect for acoustic, classical, and jazz. The overall impression I was left with was somewhat reminiscent of a more neutral k240 signature with vastly improved separation and detail.
After three months
Wow. These cans have absolutely blown me away. The treble has settled down completely and now sits perfectly with the bass and mids. The entire spectrum is wonderfully blended without sounding messy or lost, and the imaging seems to have improved as well; the sense of space is more natural and the separation remains consistent without isolating instruments completely from one another.
Took about a week to break the headband and pads in, though for me nothing about the way these headphones sat was noticeably irritating. Structurally sound, with both metal and plastic parts. The cable is not detachable, which could be a deal-breaker for chronic cable destroyers.