All Sonos Subs must be ‘bonded’ to another Sonos speaker. They can not be used as stand alone devices.

Airgetlam, Thank you for info,

which Sonos speaker will work best with Sub 3?

Depends on the use case. The music involved, the space involved, whether you’re connecting it to a single speaker or a stereo pair, and ultimately what your personal preferences are. There isn’t a single answer, just a spread of possibilities. Although it really shines with a Sonos Five, IMHO….but you’ll get equally valid opinions across the board.