The RS 170 features 2.4-2.8 GHz Kleer carrier frequency wireless technology that offers lossless, CD-quality, 16-bit/44.1-kHz resolution. The system mostly worked flawlessly, but the sound occasionally cut out when I was across the room from the transmitter and seated in front of my computer. I experienced no other interruptions anywhere else in the room or my apartment.
Accessories include a 3.5mm-male-to-3.5mm-male analog cable, a female-3.5mm-to-stereo-male-RCA cable, and a 3.5mm-to-6.3mm adapter plug. Sennheiser also sells extra sets of RS 170 headphones without the transmitter/charger base; you can use up to four with one home transmitter base (for $119.95 each).
The RS 170 comes with a two-year warranty, and proof of purchase or sales receipt from an authorized dealer is required for warranty claims.
I didn't feel like I had to go easy on judging the RS 170s' sound quality because they're wireless headphones: they're very good-sounding, closed-back headphones, period. The RS 170's electronics don't add any background noise or hiss, but the sound occasionally cut out when I was across the room from the transmitter and seated in front of my computer. Sennheiser claims the headphones have a 260 foot "line-of sight" range, and the RS 170 even worked outside my apartment, about 20 feet from my front door.
Most stereo headphones with surround simulation modes tend to sound hollow or processed, but the RS 170 suffers no such problems. The Surround Sound Simulator feature spreads the stereo image wider than plain stereo, so it's less stuck inside my head. The Dynamic Bass Boost also works well, adding more fullness to the sound of the bass without overdoing it.
The RS 170 played fairly loud, actually a little louder than Sennheiser's top-of-the-linewith Eminem's "Live From New York City" DVD. Putting the maximum volume question aside, the RS 220 produced deeper bass and better sound overall. Most battery-powered headphones face the same loudness limitation compared with wired headphones, so if you want to play movies, games, or music really loud, I recommend buying a wired set of headphones instead.
As a closed-back-design model, the RS 170 sounds more "contained" and less expansive than Sennheiser's open-back Sennheiser RS 180 ($329.95). The RS 180 makes the traffic scenes in Fight Club's dingy city environment seem to come from off in the distance, while switching over to the RS 170 reduces the spaciousness and brings the sounds closer. Even so, the RS 170's sound quality is still very clear and easy to aurally digest over the course of a long movie. Switching between the two headphones, I did notice that the RS 180 has a richer sound balance and makes deeper and better-defined bass than the RS 170.
One significant advantage of the RS 170 is that its sound will only be heard by the person wearing the headphones. That makes it ideal to wear in bed -- where it won't disturb anyone nearby. Comparatively, the RS 180 and RS 220 will be audible to others.
Though the Sennheiser RS 170 is one of the least expensive wireless Sennheisers, I enthusiastically recommend it (even to persnickety audiophiles) for its wide stereo image projection and impressive maximum volume levels. It may not be the best-sounding set of wireless headphones from Sennheiser, but the RS 170 is very much worth the price for budget-minded shoppers.