Acoustic Dampening Materials

A loudspeaker enclosure is a cabinet designed to transmit sound to the listener via mounted loudspeaker drive units. more...

Home
Car Alarms & Security
Car Amplifiers
Car Audio In-Dash Units
Car CD Changers
Car Electronics
Car Electronics Parts &...
Car GPS Devices
Car Installation Products
Acoustic Dampening Materials
Cables, Wiring, Kits
Capacitors
Circuit Breakers
Connectors, Terminals
Dashboard Installation Kits
Distribution Blocks
Fuses, Fuse Holders
Other Installation Products
Wire Harnesses
Car Portable Appliances
Car Radar, Laser Detectors
Car Signal Processors
Car Speakers & Speaker...
Car Subwoofers & Enclosures
Car Video & Navigation
Other Car Electronics
Wholesale Car Audio Lots

The major role of the enclosure is to prevent the out of phase sound waves from the rear of the speaker from combining with the 'in phase' sound waves from the front of the speaker. This results in interference patterns and cancellation, causing the efficiency of the speaker to be reduced, particularly in the low frequencies where the wavelengths are large enough that interference will affect the entire listening area.

History

Before the 1950s many manufacturers did not fully enclose their loudspeaker cabinets; the back of the cabinet was typically left open. This was done for several reasons, not least because electronics (then always hot tube equipment) could be placed inside and, if the enclosure were open, could be cooled by convection. Early on, it was observed that the enclosure had a strong effect on the bass response of the speaker. An engineer at Bell Labs even patented a primitive ported enclosure design. Since the rear of the loudspeaker radiates soundwaves 180 degrees out of phase from the front, there will be constructive and destructive interference for loudspeakers without enclosures, and below some frequencies, in open baffled loudspeakers. This causes loss of bass and comb filtering (ie, response peaks and dips in power regardless of the signal meant to be reproduced). Most of the enclosure types discussed in this article were invented to either wall off the out of phase sound from one side of the driver, or to modify it so that it could be used to enhance the sound produced from the other side.

Background

In some respects, the ideal mounting for a low frequency loudspeaker driver would be an inert flat panel of infinite size with infinite space behind it. This would entirely prevent the rear soundwaves from interference (ie, comb filter cancellations) with the soundwaves from the front. An "open baffle" loudspeaker is an approximation of this, since the driver is mounted on a panel, hopefully of size comparable to the lowest wavelength to be reproduced. In either case, the driver would have to have a relatively stiff suspension to provide the restoring force which might have been provided at low frequencies by a smaller enclosure, so only some drivers are suitable for this kind of mounting. However, for most purposes this is impractical and enclosures must use other techniques.

Most loudspeaker cabinets use some sort of structure (usually a box) to contain the out of phase sound energy. the box is characteristically made of wood or, more recently, plastic, both for reasons of ease of construction and appearance.

Read more at Wikipedia.org