The Tannoy CMS 503 PI BACKCAN is a dedicated pre-installation back enclosure designed specifically for the Tannoy CMS 503 PI series of in-ceiling loudspeakers. Its primary function is to provide a sealed, rigid, and acoustically optimized cabinet within the ceiling void, which is critical for the loudspeaker to perform as designed by the manufacturer. Installed during the construction phase before drywall is applied, it creates an isolated environment that prevents the speaker's driver from interacting with the lossy and unpredictable airspace of the ceiling plenum. This isolation stops acoustic short-circuiting, resulting in tighter, more accurate bass response and ensuring the speaker delivers its full sonic potential with consistent, predictable performance.

Constructed from durable, acoustically inert materials, the back can is engineered for secure mounting between ceiling joists. It features a robust design with integrated brackets or a flange system that attaches firmly to the framing, providing a stable, vibration-free platform for the speaker baffle. By creating a defined internal volume matched to the driver's parameters, it also protects the speaker components from dust, insulation fibers, and moisture. The paintable grille and baffle of the main CMS 503 PI 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 503 PI speakers is fully realized in the final acoustic environment.