Sennheiser On-Ear 900MHz Wireless RF Headphones

This is the first product review I've written on Amazon, but I really felt the need, because I felt somewhat deceived by the huge amount of 5 star reviews for these headphones. Don't get me wrong, these are decent headphones. I am satisfied with them and I will not be returning them. But there are significant problems, the biggest of which is the ubiquitous hiss. Contrary to many of the other reviews, I found this hiss to be *quite* noticeable. I suppose that is just a fact of life with wireless headphones, but it really is quite annoying, particularly during quiet passages or when stretching the limits of the range. Speaking of range, it is true as other reviewers said that you can still get a "reasonable" signal at a remarkable distance (it beats my wi-fi network in terms of range). But I find that if I stray more than 15 feet or so from the base, I can notice a gradual reduction in quality, an increase in the volume of the hiss, and occasional whisps of static. I have fiddled with the channel setting and tuning knob quite extensively, and these issues still remain. I am probably a little pickier than the average person, but I do not consider myself an audiophile by any means -- so if *I'm* noticing the quality loss, it's pretty significant. Now the good news: When you are in the same room as the base and the music is loud enough to drown out the hiss, these headphones sound pretty darn good, at least to my untrained ears. All frequencies are filled out nicely (I did not find it lacking in bass at all) and I don't get that headache-y too-much-treble feeling that I get from extended listening on lousy earbuds. As other reviewers mentioned, it was a poor choice to put the volume knob and tuning knob right next to each other, but this is very manageable with practice. In summary, these ain't bad for wireless headphones -- but don't let all those 5-star reviews fool you into thinking you aren't going to pay a significant price for that freedom. Edit: Since writing the initial review, I figured out what the deal is with these. Whether as a side effect of FM transmission or by design, somewhere along the way this device is causing a pretty aggressive automatic gain control on the signal. A loud signal will cause the headphones to immediately adjust quieter, while they will adjust more gradually to a quiet signal, slowly bringing the level up. This more or less ruins music that has a lot of dynamics, though *most* modern music will sound more or less okay because of the way it is mastered. The AGC is also the cause of the infamous "hiss" that you hear when your signal is low (it keeps boosting the signal level until you hear noise). I find that keeping the input volume really high diminishes these problems somewhat, but of course then you have to be careful you aren't getting clipping. And it doesn't eliminate the problems altogether. It's a pity, because the headphones themselves sound great. But the automatic gain control really interferes with certain music, and as a result my review stays at 3 stars.