Pros: Good craftsmanship, good looking, good sound isolation. Lifetime warranty.
Cons: SQ inadequate for serious listening to music.
Being a (non-professional) recording engineer -- my specialities are the recording of organ music and chamber music-- I required next to my Sennheiser HD 595 (excellent!!!) a pair of closed headphones. These would be useful in the case that the recording equipment lives in the same room as where the music is made.
Attracted by Koss'reputation and good reviews I decided for the Pro4AAT.
At first I conected the headphone to the output of my computer's sound board, and it became clear that this output is not capable of driving a high-impedance headphone. My audio amplifier solved that problem. But I found the SQ very disappointing. The lows are not convincing at all, the mids sound tinny and the highs are too dull, not sparkling. The overall sound lacks any presence.
In a few words: If you want to listen to music, with your headphone, and with your eyes closed; if you want the sensation that you are present in the cathedral or other environment where the music is made, do not go for this headphone. It was not made for you.