Sennheiser RS 4-9 Wireless Headphone

• Lightweight wireless headphone with transmitter
• Volume control on headset
• Self-adjusting headband
• Three switchable transmission channels for simultaneous operation of multiple headsets
• Stereo adapters and nickel-metal-hydride accuplug battery included

The heart of the system is, of course, the headphone receiver, a sturdy plastic band lined with an adjustable cushioning band. The 4-inch padded earcups rest against and not over your ears, joined to the headband in pivot sockets that permit easy angling to fit your head. The other piece central to the RS 4-9 is the FM (frequency modulation) transmitter, a tiny device that you hook up to both an AC outlet and your sound source, and then essentially forget about.

The headset runs on a single "accuplug" rechargeable battery, not the sort of thing you pick up at your local convenience store. The RS 4-9 comes with one, but be careful: It only runs for 3 hours at a spell, and if you let it run completely flat you won't be able to recharge it. The battery comes charged and fitted in the headset's right earpiece, just above the conveniently placed volume/on/off switch. However, Sennheiser strongly recommends 24 hours' charging time before first use, so after you've checked to hear that the RS 4-9 works, be sure to put that battery right into the charger! The transmitter offers two charging slots in case you want to stock up.

The transmitter comes with an input cable that plugs into any stereo analog miniplug or 0.25-inch headphone jack, so you can easily feed it audio from your tuner, CD player, DVD player, cassette deck, minidisc, television--you name it, as long as you have a headphone jack on either the source or on your receiver, preamp, or integrated amplifier. We'd prefer a choice between using headphone outputs or RCA jacks, but in an either/or situation we feel the headphone connection offered here is most conducive to simple setups.

Sennheiser recommends not exceeding 100 meters (328 feet) in listening range, and we occasionally experienced interference--similar to FM radio static--at shorter distances, depending on the room. Metal parts, such as those in concrete construction or wall coverings, will reflect radio waves, whereas the audio signal passes unobstructed through wood, plaster, and (apparently) people. Different channels (1 to 3) permit use of multiple headsets in the same house.

Battery and transmission issues aside, setting up and enjoying the RS 4-9 really is quite simple, requiring very little effort to plug in, set the transmission channel, and crank up the tunes. Don't crank the level too high, though--your ears will thank you for it later.

FM wireless transmission should sound about like good FM radio--it's the same process, after all--and, like radio, reception will vary in different regional areas and buildings. The sound from Sennheiser's earcup drivers is good: clean, clear, and evenly balanced.

The headphones are deficient in the frequency extremes (low bass and high treble), but the emphasis here is on convenience and comfort, and in these the RS 4-9 has much to offer. --Michael Mikesell

Pros:

• Good sonic performance
• Convenient wireless portability
• Comfortable
• Self-adjusting headband
• Easy to set up and operate
• Rechargeable battery included
• 0.25-inch and minijack-to-male-RCA adapters included for transmitter hookup

Cons:

• Slightly muted high and low frequencies
• Battery dies if exhausted or not recharged
• Does not accept standard batteries