Pros: Great for recording
Cons: Not my first choice for listening
My first serious pair of headphones …
Having grown out of my previous AKG K-55 I was recommended those. I liked their sound and comfort better than with the smaller K171 Studio, so I spent the extra cash on them. My decision back then wasn't really well informed as I did not test many different headphones from different brands, but six years later my decision still holds up well.
As all the other classic AKGs, the K271 fits my head perfectly. It was very comfortable with the stock leather pads, however, since I retrofitted it with the new velours pads it has gotten even better. There's simply less heat building under the velours.
Soundwise, I like the way they combine detailled reproduction with some sort of laid-back quality, especially the bass register is somewhat "lean". This is great for recording in the studio because it results in little ear fatigue - at least for me. Actually listening to music is not my favorite occupation for the K271. I miss the bass somewhat and, depending on the amplification, I sometimes find the sound a little lifeless. Nevertheless it brings out details nicely and the soundstage is pretty good.
At 55Ω it is easy to drive in theory, but it seems to me that they still need a lot of power to sound good. They do get loud, but the difference in sound quality is eminent. Also, the K271 tends to drive weak headphone amps into clipping, which is not exactly the headphones' fault but sounds terrible nonetheless. On my JVC CD player they sound pretty enjoyable though.
Isolation is ok, at least for the low to medium volumes of the jazz ensembles I'm working with. It is really nothing in comparison to some cheap Superlux I know, but those also have a clamping force that gives me a headache after some time - with the K271 I never had that problem. Obviously, the stock pleather pads do a little better in that respect, but I simply don't want to miss the extra comfort of the velours.
Also, AKG has paid attention to the details: The automatic mute switch is great for "forgotten" headphones and the detachable cable saves maintenance costs. Having the choice between a straight and a coiled cable is also a nice idea. Anyway, if you take a Neutrik 1/4" plug, a Rean Tiny XLR, some nice Sommer or Mogami cable and perhaps a little heatshrink for protection, it is easy to solder a replacement that is equal or better to the original AKG part at a fraction of the cost.
All in all, the K271 Studio is a great tool for long recording sessions, however, it is not my favorite for listening, although it works well in that respect, too. My K240 Monitor has taken that part, but I bring the K271 and a headphone extension cord to every studio session I play.
A big pro: It's an AKG. Once you've figured out how the basic design works, they are pretty easy to maintain and parts are generally pretty affordable, making repairs easy.