AtlasIED Q4612 12 inch Q Series 3 Cubic ft Enclosure SquareThis 12" Q Series enclosure has a unique acoustical fiber board permanently affixed to the inner walls of the enclosure which effectively eliminates the "hangover" and vibration normally associated with large metal enclosures. To achieve additional rigidity, unique ribs are formed on the back side of the enclosure. In addition, the inner walls are lined with 1 1 2" (38mm) thick fiberglass with a 1 1 2 lb. cu. ft. density to control unwanted resonances