Flat panel sound radiator with fire protective back box

A fire protective flat panel radiator assembly for installation in a suspended ceiling grid is provided. The assembly includes a flat panel radiator having a frame that supports a sonic diaphragm, which is driven by a transducer to reproduce an audio program. A back box is mounted to the radiator and the back box covers and encloses the diaphragm and other fire susceptible components of the radiator. The back box is provided with a cut-out portion that is covered with an air pervious panel, which is resistant to fire hazards but that allows air flow in and out of the back box. In one embodiment, the radiator has a bridge and the back box is formed by a pair of shells mounted on each side of the bridge to enclose and protect the diaphragm. The result is a fire protected flat panel radiator assembly that meets the fire performance requirements for air handling plenums while retaining the sonic fidelity of a flat panel sound radiator without a fire protective back box.