The acoustic suspension woofer

Woofer

Woofer is the term commonly used for a loudspeaker driver designed to produce low frequency sounds, typically from around 40 hertz up to about a kilohertz or higher. The name is from the onomatopoeic English word for a dog's bark, "woof"...

 is a type of loudspeaker

Loudspeaker

A loudspeaker is an electroacoustic transducer that produces sound in response to an electrical audio signal input. Non-electrical loudspeakers were developed as accessories to telephone systems, but electronic amplification by vacuum tube made loudspeakers more generally useful...

 that reduces bass distortion

Distortion

A distortion is the alteration of the original shape of an object, image, sound, waveform or other form of information or representation. Distortion is usually unwanted, and often many methods are employed to minimize it in practice...

 caused by non-linear, stiff mechanical

Machine

A machine manages power to accomplish a task, examples include, a mechanical system, a computing system, an electronic system, and a molecular machine. In common usage, the meaning is that of a device having parts that perform or assist in performing any type of work...

 suspensions in conventional loudspeakers. It was invented in 1954 by Edgar Villchur

Edgar Villchur

Edgar Marion Villchur was an American inventor, educator, and writer widely known for his 1954 invention of the acoustic suspension loudspeaker which revolutionized the field of high-fidelity equipment...

, and brought to commercial production by Villchur and Henry Kloss

Henry Kloss

Henry Kloss was a prominent American audio engineer and businessman who helped advance high fidelity loudspeaker and radio receiver technology beginning in the 1950s. Kloss was an undergraduate student in physics at Massachusetts Institute of Technology , but never received a degree...

 with the founding of Acoustic Research

Acoustic Research

Acoustic Research was a Cambridge, Massachusetts-based company that manufactured high-end audio equipment. The brand is now owned by Audiovox. Acoustic Research was well known for the AR-3 series of speaker systems, which used the 12-inch acoustic suspension woofer of the AR-1 with newly designed...

 in Cambridge Mass.

Description

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

Diaphragm (acoustics)

In the field of acoustics, a diaphragm is a transducer intended to faithfully inter-convert mechanical motion and sound. It is commonly constructed of a thin membrane or sheet of various materials. The varying air pressure of the sound waves imparts vibrations onto the diaphragm which can then be...

, 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

Bass reflex

A Bass reflex system is a type of loudspeaker enclosure that uses the sound from the rear side of the diaphragm to increase the efficiency of the system at low frequencies as compared to a typical closed box loudspeaker or an infinite baffle mounting.A reflex port is the distinctive feature of a...

cabinet design has improved, speakers with ported enclosures have become more common, especially in home theater and mid-level stereo systems.