These are typically part of the Ensemble satellite/subwoofer speaker system designed for home stereo or small home-theater setups.
What’s in the picture
* 2 large rectangular speakers (rear) – These are the bass modules (subwoofer cabinets).
* 2 small speakers (front) – These are satellite speakers that handle the mid and high frequencies.
This design splits the sound:
* Bass → handled by the large modules
* Mid/High frequencies → handled by the small satellites