US Patent 7277552 Increased LF spectrum power density loudspeaker system

The power density of a bass-reflex enclosure is improved by providing transducers in pairs, with the members of each pair being oriented front to back with respect to one another. The transducers are mounted on the enclosure with at least one of the transducers being substantially perpendicular to a front face of the enclosure and having its backside partially rested in the second transducer of the pair. The gap between the transducers is wider on the side open to the surrounding environment through the front face. Directivity may be provided by incorporating a second pair of transducers.