A wireless speaker is a loudspeaker that receive audio signals using radio frequency (RF) waves rather than over audio cables. This is generally achieved one of two ways. A variation of WiFi IEEE 802.11 is most popular for connecting wireless speakers to home entertainment and multi-channel receiver systems. Bluetooth is preferred for transmitting audio data from mobile devices.
When wireless speakers are operating over WiFi, it is usually as part of a system comprising two units: the main speaker unit combining the loudspeaker itself with an RF receiver, and an RF transmitter unit. The transmitter connects to the audio output of the source audio device, the RF receiver feeds the speaker. Bluetooth wireless speakers usually don’t include or require any additional hardware.
Typically, a wireless speaker will also be an “active” speaker, containing a built-in crossover, power amplification, and in some cases DSP or other processing.