The DS4000s use digital infrared-light technology to transmit sound from the base station/battery charger to the headphones. The headphones weigh 11 ounces, which is fairly light for a full-size, over-the-ear design, and thanks to their self-adjusting headband, the vinyl cover cushions exert minimal pressure against your ears. We found the DS4000s extremely comfortable over an evening of watching DVDs and listening to CDs. Sony claims seven hours between charges, and we made it through at least two movies in a row without any problems.
Sony opted for easy control options; there's a volume dial on the right earcup, and the headphones don't even have a power switch. They automatically turn on when you place them on your ears and turn off when you remove them. Connectivity chores are dead simple: just hook up the base station's optical digital cable (included) or your own set of stereo analog cables to the matching outputs on your A/V receiver. In fact, the DS4000s will work with any other A/V device with a line-level output (VCR, CD/DVD player, and many TVs), and--if you supply a standard minijack-to-RCA Y-cable--you should be able to connect to anything with a standard headphone output, too. Of course, we would've preferred the flexibility of stereo minijack and coaxial digital inputs on the DS4000 base station as well.
Our prime gripe with wireless headphones in general is that their electronics add background hiss, staticky noises, or random bursts of distortion to the sound. The DS4000s don't, however; they're the first wireless 'phones we've tested that consistently remained free of noise and hiss.
If you've seen the Hide and Seek DVD, you know the icky bloodbath episodes are chilling in their stillness. The DS4000s were, as they say, dead quiet, and dialogue was eerily natural. The sound never dropped out, even when we moved into the corners of the room, but we had to stay in line of sight of the transmitter/charger base. Sound quality was first rate--easily the best we've heard from wireless 'phones. The DS4000s are absolutely state of the art.
Ah, but are they are they in the same league as high-quality corded headphones? Not quite. Sennheiser's HD555s ($170) played a lot louder, had more powerful bass, and were more dynamically alive. The scene in Hide and Seek where Robert De Niro kicks down a door fell a little flat over the DS4000s--it was scarier over the HD 555s.
That said, if you're not an audio geek, you'll probably be perfectly satisfied with the DS4000s' sound. We cruised through The Day after Tomorrow DVD's wind, rain, snow, and tsunami special effects, and the sound kept us glued to the screen. CDs also fared well; acoustic jazz sounded sweet, though Queens of the Stone Age's hard-core edge was ever so slightly blunted by the DS4000s.
You can listen to DVDs and CDs in stereo or take advantage of the DS4000s' surround processing modes; they're compatible with Dolby Digital, Dolby Pro Logic II, and DTS. Furthermore, because the headphone base station has onboard surround decoding, you can connect any stereo or optical digital output--from a CD or DVD player, for instance--bypassing your A/V receiver completely. We felt the headphones' processing added a bit too much reverberation to the sound, but we're sure some folks will enjoy the more open sound. A compression switch located on the base station reduces DVDs' and CDs' dynamic range for late-night listening.
Bottom line: if you've been waiting for wireless phones that won't drive you crazy with hiss and dropouts, by all means, check out these Sonys.