The Tannoy CMS 801 PI 8 OHM BACKCAN is a dedicated pre-installation enclosure designed specifically for the Tannoy CMS 801 PI series of in-ceiling loudspeakers. Its primary function is to provide a sealed, acoustically optimized cabinet within the ceiling void, which is essential for the loudspeaker to perform as designed. When installed during construction before drywall is applied, it creates a rigid, airtight environment that isolates the driver from the lossy and unpredictable conditions of the ceiling plenum. This prevents acoustic short-circuiting, where sound waves from the rear of the driver cancel those from the front, resulting in weak and distorted bass. The back can ensures the speaker delivers its full potential, with tight, accurate low-frequency response and consistent performance.

Constructed from durable, acoustically inert materials, the back can is engineered for secure mounting between ceiling joists. It features integrated brackets or a flange system that attaches firmly to the framing, providing a stable, vibration-free platform for the speaker baffle. The 8-ohm designation indicates it is impedance-matched to the compatible CMS 801 PI speaker models. By creating a defined internal volume, it also protects the speaker components from dust, insulation fibers, and moisture. The paintable grille and baffle of the main speaker assembly then mount flush to this solid foundation, resulting in a professional, finished appearance. This accessory is a critical component for high-fidelity in-ceiling installations, ensuring that the premium performance of the CMS 801 PI speakers is fully realized in the final acoustic environment.