Abstract: The present invention constitutes a sound output unit for installation in a ceiling structure including an assembly for mounting a loudspeaker for use in conjunction with said output unit. The sound output unit comprises a polyhedral chamber or enclosure, a loudspeaker, an amplifier, and two sets of baffles. The polyhedral chamber is specially shaped in order to help reduce resonant vibrations. The loudspeaker is mounted in a large opening in the bottom plate of the enclosure so that it can radiate sound out from the enclosure into the area below the ceiling structure in which the unit has been installed. The amplifier is secured on the top of the loudspeaker inside the chamber and provides local power amplification. The baffles are mounted on the interior surfaces of the top and bottom plates of the enclosure and help reduce spurious sound reflections within the enclosure.