Wireless speakers are very similar to traditional (wired) loudspeakers, but they transmit audio signals using radio frequency (RF) waves rather than over audio cables.
Wireless speakers are composed of two units: a main speaker unit combining the loudspeaker itself with an RF receiver, and an RF transmitter unit. The transmitter connects to the audio output of any audio devices such as hi-fi equipment, televisions, computers, mp3 players, etc. An RCA plug is normally used to achieve this. The receiver is positioned where the listener wants the sound to be, providing the freedom to move the wireless speakers around without the need of using cables. The receiver/speaker unit generally contains an amplifier to boost the audio signal to the loudspeaker; it is powered either by batteries or by an AC electric outlet. Batteries may last for three to four hours; some wireless speakers operate on rechargeable batteries.
The signal frequency range used by wireless speakers is generally the same as that used by cordless telephones — 900 MHz. The RF signal can traverse walls and floors/ceilings. Most manufacturers claim the signal transmits over a range of 150 to 300 feet. Many wireless speakers feature variable transmission frequencies (channels) that can be set using a tuning knob to overcome potential RF interference with other nearby wireless devices such as cordless phones or baby monitors.
Different types of wireless speakers are designed for specific needs: Stereo speakers can deliver both Left and Right stereo channels in a single speaker. Speakers designed specifically for outdoor use have a robust casing; manufacturers claim these are weatherproof. Home theatres utilize a specialized set of speakers in which only the rear speaker/s are wireless, while the front speakers are wired.
Wireless speakers receive considerable criticism from high-end audiophiles because of the potential for RF interference with other signal sources like cordless phones as well as for the relatively low sound quality some models deliver. Despite the criticism, wireless speakers have gained popularity with consumers and a growing number of models are actively marketed.