Atlas Sound 4" Blind-Mount enclosure system ( U.S. Patent # 4,673,149 ) provides an easy and cost-effective alternative for secure loudspeaker installation in retrofit ceiling applications. All necessary hardware is provided including a unique support system with mounting ears that telescope out from inside the enclosure and adjust vertically to accommodate ceilings with a thickness of 1/2" (13mm) to 1 3/8" (35mm). Units feature CRS construction and include torsion-spring receptacles for quick mounting of torsion-spring grilles. (J-Nuts are also included on the return of the enclosure to accommodate surface-mounting grilles.) To allow cable access, enclosure backplates are manufactured with three 1/2" (13mm) conduit knockouts. Enclosure is also equipped with sound damping material to minimize metallic resonance. Models are supported by two mounting ears and will accommodate Atlas Sound torsion-spring grille Models T51-84 and T720-4BT which mount 4" (102mm) loudspeakers. BMT95-4-7 is a 7" (178mm) deep extra-depth version which includes high-density fiberglass fill finished in a textured black epoxy.