Enclosed Subwoofer Systems

A loudspeaker, speaker, or speaker system is an electromechanical transducer which converts an electrical signal into sound. more...

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The term loudspeaker is currently used for both individual devices and for complete systems consisting of one or more drivers (as the individual transducers are often called) in an enclosure, often with a crossover circuit. Their cost may range from pennies in a cheap radio to high-fidelity speaker systems costing many thousands of dollars. Loudspeakers are the most variable elements in any audio system, regardless of cost, and are responsible for marked audible differences between otherwise identical sound systems. Loudspeakers commonly have distortion a hundred to a thousand times greater than that of preamps, amplifiers or wire.

Full-range speaker systems are typically multi-driver systems, particularly when high SPL output or high accuracy are required. "Multi driver" means a speaker system containing two or more drive units, possibly including subwoofers, woofers, midranges, tweeters, or supertweeters. In loudspeaker specifications, systems are often classified as "N-way speakers", where N indicates the number of separate frequency bands, usually separated by an electrical filter called a crossover. A 2-way system will have woofer and tweeter sections; a 3-way system a combination of woofer, tweeter, and mid-range speakers, and so on.

History

Alexander Graham Bell patented the first loudspeaker as part of his telephone in 1876. This was soon followed by an improved version from Ernst Siemens in Germany and England (1878). Nikola Tesla is believed to have created a similar device in 1881. The modern design of moving-coil drivers was established by Oliver Lodge in (1898). The moving coil principle was patented in 1924 by Chester W. Rice and Edward W. Kellogg.

These first loudspeakers used electromagnets because large, powerful permanent magnets were not available at reasonable cost. The coil of an electromagnet, called a field coil, was energized by current through a second pair of connections to the driver. This winding usually served a dual role, acting also as a choke coil filtering the power supply of the amplifier to which the loudspeaker was connected. AC ripple in the current was attenuated by the action of passing through the choke coil; however, AC line frequencies tended to modulate the audio signal being sent to the voice coil and added to the audible hum of a powered-up sound reproduction device.

The quality of loudspeaker systems until the 1950s was, to modern ears, poor. Continuous developments in enclosure design and materials have led to significant audible improvements. The most notable improvements in modern speakers are improvements in cone materials, the introduction of higher temperature adhesives, improved permanent magnet materials, improved measurement techniques, computer aided design and finite element analysis.

Read more at Wikipedia.org