Wireless headphones definitely seem a luxury, but to listeners tired of the tripwire tangle of a headphone cord across the carpet -- or who simply want to hear their tunes as they wander from room to room -- they might sound more like a necessity.

These devices come in two parts, the headphones and a transmitter that plugs into the stereo and broadcasts using either infrared or radio-frequency (RF) signals. Infrared, the same technology used in remote controls, requires a line of sight between your head and the transmitter and can lead to excess static if you move around (and sometimes if you don't).

Costlier, more versatile RF enables you to leave the room and still hear the music. It demands careful tuning and can suffer from static of its own. We did not, however, hear any interference from a cordless phone or a WiFi router.

The headphones need batteries, either standard-size units or proprietary rechargeables that are replenished when you drop the phones into the cradle on each transmitter. With moderate use, expect weeks between battery changes or recharges -- with one exception among the seven models tested.

We started with two Sony infrared models, the $60 MDR-IF240RK Wireless Stereo Headphone System and the $300 MDR-DS3000 Infrared Wireless Dolby Digital Headphones. Both include AA rechargeables.

Once each set's transmitter was properly positioned and we sat still, each generally sounded as good as regular wired headphones up to about 20 feet.

Sony's Dolby Digital headphones were easier to lock into the transmitter's signal, more comfortable to wear and delivered better sound, especially with movies -- a key benefit of its simulated surround sound. Is all that worth five times the cost of Sony's other system? Good question.

Koss joins Sony's cheaper model in the entry-level price bracket with two lightweight, $60 infrared models, the HB60 and HB70. The HB60 takes the form of a pair of small discs that you clip over your ears, while the HB70 comes in a standard headphone style. Both use AAA batteries, stored in the HB60's belt clip and in the earpieces of the HB70.

The two Koss models, however, felt a bit cheap and uncomfortable, especially at first, and the small transmitter took a bit more tweaking than Sony's.

A pricier Koss model, the $130 JR50, left the opposite impression. This RF set provided outstanding coverage without any hiss or fade, even three floors away from the transmitter; its large headphones are padded to close out external noise and are comfortable except for a sharp head band.

Sennheiser's $110 RS 120, an RF pair of headphones that run on AAA batteries, mixed high-end features with weak design choices. Its clever cradle all but guaranteed that the headphone's recharging contacts would land in the right spot whereas other cradles needed careful positioning. But in day-to-day use, it was too easy to mistake the RS 120's tuning wheel for the volume control next to it on the right earphone.

The RS 120 also suffered from a bit more static than the Koss JR50. But when things worked right, it offered the best sound overall; its deep, full sound field was terrific for movies.

A second Sennheiser model, the $210 RS 65, adds a simulated surround-sound mode without actually beating the performance of its cheaper sibling. It includes two removable, proprietary batteries instead of just one, so you can recharge one while the other plays on -- a good idea as it drained that unit within two days of moderate use.

For the best sound close to the source, the Sennheiser RS 120 edges out the Koss JR50, but otherwise that model is the way to go. On a low budget? Sony's MDR-IF240RK has few flaws for the price. But first consider buying a nice long headphone extension cord and tucking it under the rug.

Cordless headphones (from left, the Sennheiser RS 65, the Koss HB60 and JR50, and the Sony MDR-DS3000) let you rock while you roam.