The "wireless" portion of wireless sound bars typically only refers to the sub-woofer and/or rear surround speakers. And then, wireless only refers to not having to run speaker-wire connections to each speaker, however, each speaker (or their common amplifier) will still require AC power for their built-in amplifiers.

The sound bar is connected to both AC power and the audio line level (or digital audio) outputs of the television. It then amplifies the front/center channels which the internal speakers of the sound bar output, and sends the sub-woofer/rear channel signal to the wireless speakers via a RF (radio frequency) signal. Some don't use rear speakers but instead create "virtual" rear speakers that appear to come from behind.

While direct wiring of rear speakers from a home theater receiver provides the best sound quality, there are situations, such as a home built on a slab foundation with a raised ceiling, where wireless rears provide an economical alternative.