A low-cost, lightweight, flat and very-high-efficiency loudspeaker system for low frequencies

The introduction of concepts such as Flat TV and 5.1 channel sound reproduction systems has led to a renewed interest in obtaining a high sound output from compact loudspeaker arrangements with a high efficiency. Compact relates here to both the volume of the cabinet into which the loudspeaker is mounted as well as the cone area of the loudspeaker. Normally, low-frequency sound reproduction with small transducers is quite inefficient. To increase the efficiency, we map the low-frequency region, say from 20 to 120 Hz, to a single tone and use a special transducer with a very high efficiency at that particular tone.