Summary: I was looking for a pair of phones that had great low end response. These phones have great bass compared to a pair of shure srh240's I returned before getting these.. Very portable and GREAT for casual listening and it folds up for easy portability. Great pair if you are looking for good bass (no complaints about miss or highs). Only complaint is they squeeze your ears like crazy (so you have to stretch them).
Summary: The K81DJ's are a pretty decent set for the money. They serve good purpose for the hip-hop fan or a DJ. Bass has a lot of impact, but only rarely becomes boomy, could be a positive or negative aspect depending on what you are looking for. Mids are smooth, although recession and slight boxy-ness ruins them. Highs are decent, but with a slight lack in detail. Soundstage is acceptable, but there are cans with better. Portability is okay, isolation is killer.
Summary: These closed portables may sound good, but they're also one of the best-looking and -feeling Beyers. Although only medium-sized, this turns out to be one of their major virtues. - The K81DJ as a punchy, rich sound with a solid bass presence. Some have attempted various mods to tone down the bass, but tonal change is going to be very subtle at best. For this reason, the phones are best at pop genres, and less so with classical and instrumentals.
Summary: Great headphones for someone just starting into our hobby. It is even possible that you will not need to go any further than these great little phones what are possibly one of the best values today. I really enjoy them being closed and having the bass line it does. Their mid frequencies are patient AKG with pleasant extension on the high side. They appear very durable.
Summary: Given that there are not a lot of quality closed-back portable headphones available, the AKG K-81DJ's still stand out as an excellent set of headphones. They offer better than expected isolation, are reasonably comfortable (some tweaking with the headband is said to work wonders for those who find them annoying), and enough sonic quality to make them listenable for more then just travel.
Summary: I have yet to find a headphone that will survive my brutal habits. AKG offers a two-year warranty on its products but I've manage to make two pairs defective in only one year. I will not return the second pair due to a negative aspect of these headphones--the bass is just too much. When listening at a normal volume your ears hurt because of the sound and the headphones are very tight on your head. Unless you have a smaller head, you are most likely to feel discomfort.
Summary: I bought these a few years ago when I used to frequent Head-fi.org and have never regretted them. They offer excellent sound with strong bass and detailed highs. They are not bright, but not rolled off either. They bass impact is excellent for a small headphone (or even a large set). The cups offer excellent comfort and noise isolation (I actually used them as ear muffs on a flight from North America to Europe to cut down on the jet engine noise.
Pros: Clear Sound, Compact, Easy To Use, Isolation, Lightweight, Versatile
Summary: If the frequency range is important to you, DO NOT BUY THESE HEADPHONES.
If you're looking to use them for something like Centerpointe's Holosync cds, these will not work for you.
The advertised frequency range, when I bought these headphones, was 5-30,000 Hz. When the package arrived, the frequency range on the package reads 16-24,000 Hz.
Summary: Wow, the price here is a lot lower than I've been paying for these at other places. (Almost half). I found the headphones to be very comfortable, but I don't have a very large head. The sound is not flat -- I like the bias the phones have, though. They have a lot of clarity and a very nice sound. A bit extra on the low frequencies (but not too much) and a bit on the highs. As a drummer, this is perfect for me. Warm sound, but not fuzzy.
Summary: The K81 may be a huge step coming from KSC75/PP/PX100, but you soon detect its flaws, as properly described in the other reviews. However, I keep the K81 as portable workhorse and still feel quite content with this little redneck. Things aren't very audiophile, but you get a smooth and somewhat coherent presentation coupled with an almost tank-like indestructability. Allover, I wasn't too impressed by its main contenders HD25-1 and ES7, which cost almost 3 times as much.