The acoustic suspension woofer is a type of loudspeaker that reduces bass distortion caused by non-linear, stiff mechanical suspensions in conventional loudspeakers. It was invented in 1954 by Edgar Villchur, and brought to commercial production by Villchur and Henry Kloss with the founding of Acoustic Research in Cambridge Mass.
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The acoustic-suspension woofer (sometimes known as “air suspension”) uses the elastic cushion of air within a sealed enclosure to provide the restoring force for the woofer diaphragm.
Unlike the stiff suspension of conventional speakers, the trapped air inside the sealed-loudspeaker enclosure provides a more linear restoring force for the woofer's diaphragm, enabling it to oscillate a greater distance (excursion) in a linear fashion. This is a requirement for clean reproduction of deep-bass tones by drivers with relatively small cones (e.g. smaller than 12-16 inches in diameter) not mounted in a horn or similar for increased coupling at low frequencies enclosure. Acoustic suspension cabinets are not entirely airtight. A small amount of airflow must be allowed so the speaker can adjust to changes in atmospheric pressure.
Acoustic suspension woofers were once very popular in hi-fi systems, due to their low distortion. However, as bass reflex cabinet design has improved, speakers with ported enclosures have become more common, especially in home theater and mid-level stereo systems.