One of the better cell phone developments in the past year has been the proliferation of stereo Bluetooth. While previously it seemed that handset manufacturers were consciously avoiding the feature, a simultaneous push for music phones has, thankfully, made stereo Bluetooth a reality. And as the number of supported phones increases, manufacturers have started to introduce stereo Bluetooth headphones as well. One of Moto's latest entries in the space is the Motorola S9 Bluetooth Active Headphones. Made with the sports enthusiast in mind, these headphones feature a sleek, space-age design that wraps behind your head. For both calls and music, the sound quality was decent--and the fit was relatively comfortable. Priced in the $100 range, they're not exactly cheap, but they won't break the bank either.

Motorola emphasizes the word "active" when mentioning the S9, and by looking at the S9's design, it's clear why. Sleek and aerodynamic, the S9 weighs less then an ounce, which makes it one of the lightest stereo headphones we've seen. It also employs a simple, behind-the-head design that isn't clunky and doesn't look too conspicuous when worn. The rearmost portion of the headset, which holds the power button and charger jack, is the largest part of the S9 at almost an inch wide, but the ends connecting the earbuds taper to a slim diameter of .25 inch. We tested the red-and-blue version, but it also comes in a more subtle gray-and-black model as well. The S9 is water- and sweat-resistant, so you won't have to worry about wearing it during a hard workout.

Thanks to the practical design, we had no trouble slipping the headset on and off. Though the area with the power control and the charger jack is made of hard plastic, the ends are made of a rubberized material that bends easily. The ear hooks slipped easily on and off for us, but users with larger noggins may want to try the S9 before buying. On the whole, the fit is comfortable and the light weight made it barely noticeable, even for longer-wearing periods. The fit was quite secure as well. But the 0.5-inch earbuds did have a tendency to pinch if not positioned just-so. Indeed, it took us a few minutes of fiddling with the earbuds until they slipped comfortably into the ear. On the upside, the ear tips are made a flexible rubber and you get a choice of three sizes.

The controls on the headset were easy to understand and to use. As we mentioned previously, the power control is located on the bottom of the rear end of the headset, just next to the mini-USB charger port. It can be hard to locate when you're wearing the headset, but we can't imagine you'd be turning it on and off excessively. The charger jack is protected by a rubber flap, although the fit wasn't very secure. A small indicator LED sits between the power button and the charger port.

Moto smartly separated the phone and music controls on the S9. A Talk button and the volume control sits just near the left earbud. The former is easy to find and has a soft, tactile feel; the volume control is touch-sensitive and barely needs to be pressed. We haven't seen touch controls in very many headsets, but it's a feature we love on the S9. At times, they could be a bit too sensitive, but overall it was a very user-friendly experience. A music Play button sits near the right earbud and is also touch-sensitive.

We tested the Motorola S9 Bluetooth Active Headphones with the Motorola Razr V3xx. The pairing process took only a few seconds and the connection remained strong. Also, we were able to reconnect instantly after turning both devices off for a short period. Overall sound quality was quite good for all kinds of audio. We could hear callers plainly and there was plenty of volume, even in windy or noisy environments. Callers reported few problems on their ends and we had no trouble being understood by voice-automated calling systems. Our only complaint was that voices on our side sounded harsh and almost robotic at times. However, the effect wasn't constant, so we don't consider it a deal-breaker. Other calling features include voice dialing, call reject, and last-number redial.

Sound from the music player was better than the call sound. We loved the stereo experience and we were impressed by the volume range. Keep in mind that the sound wasn't the sharpest we've heard, but it's more than adequate for most uses. Conveniently, the music automatically pauses when you receive a call, and then resumes after you hang up. We also tested the headphones with streaming video clips and enjoyed solid audio quality. The S9 has a promised battery life of six hours on a single charge.