Loud Speakers
Speaker Types

Loudspeaker types

Multi driver systems

Home loudspeaker systems are generally multi-driver systems. 'Multi driver' refers to any speaker system that contains two or more separate drive units, including woofers, midranges, tweeters, and sometimes horns or supertweeters. In loudspeaker specifications, one often sees a speaker classified as an "N-way" speaker where N is a positive whole number greater than 1, indicating the number of separate frequency bands into which the system divides the sound (not the number of drivers, as one frequency band may be handled by more than one speaker driver). A 2-way system consists of woofer(s) and tweeter(s) sections; a 3-way system is constructed as a combination of woofer(s), tweeter(s) and mid-range speakers, etc. The frequency bands are separated and routed to the correct driver by an N-way crossover defined in the same manner, most usually a passive crossover within the speaker system, but in audiophile systems, sometimes an active crossover placed before the power amplifier stages.



Main article: Woofer

A woofer is a loudspeaker capable of reproducing the bass frequencies. The frequency range varies widely according to design. Whilst some woofers can cover the audio band from the bass to 3 kHz, others only work up to 1 kHz or less.



Main article: Mid-range speaker

A mid-range loudspeaker, also known as a squawker is designed to cover the middle of the audio spectrum, typically from about 200 Hz to about 4-5 kHz. The distinction between woofers and mid-ranges is blurred however since many woofers can operate up to 3 kHz. These are used when the bass driver (or woofer) is incapable of covering the mid audio range. Mid-ranges typically appear where large (>16 cm or 8") woofers are used for the bass end of the audio spectrum.



Main article: Tweeter

A tweeter is a loudspeaker capable of reproducing the higher end of the audio spectrum, usually from about 1 kHz to 20 or 35 kHz.



Main article: Full-range

A full-range speaker is designed to have as wide a frequency response as possible. These often employ an additional cone called a whizzer to extend the high frequency response and broaden the high frequency directivity. A whizzer is a small, light cone attached to the woofer's apex around the dust cap. The use of a whizzer requires that the main cone decouples from the coil at high frequencies such that most or all of the motion at those frequencies is imparted to the whizzer, which then acts like a second smaller coaxial loudspeaker. This gives many of the benefits of a tweeter without the additional expense or circuitry that is required. A whizzer might not be necessary if the diaphragm is small, stiff and light enough. There exist full-range drivers which are capable of reproducing a frequency range from 50 Hz to 20 kHz and higher without a whizzer cone. These drivers are often quite small, typically 2" to 5" (5 to 13 cm) in diameter.



Main article: Subwoofer

A subwoofer driver is a woofer optimised for the lowest range of the audio spectrum. Modern speaker systems often include a single speaker dedicated to reproducing the very lowest bass frequencies. This speaker (and its enclosure) is referred to as a subwoofer. A typical subwoofer only reproduces sounds below 120 Hz (although some subwoofers allow a choice of the cross-over frequency). Because the range of frequencies that must be reproduced is quite limited, the design of the subwoofer is usually quite simple, often consisting of a single, large, down-firing woofer enclosed in a cubical "bass-reflex" cabinet. Subwoofers often contain integrated power amplifiers that may incorporate sophisticated feedback mechanisms to ensure the least distortion of the reproduced bass acoustic waveform.

The very long wavelength of the very low frequency bass sounds reproduced by the subwoofer usually makes it impossible for the listener to localize the source of these sounds. Localization starts to happen above the 60Hz point. Because of this phenomenon, it is usually satisfactory to provide just a single subwoofer no matter how many individual channels are being used for the full-spectrum sound. For the same reason, the subwoofer does not need a special placement in the sound field (for example, centered between the Left Front and Right Front speakers). It can instead be hidden out of sight. Placing it in the corner of a room may produce louder bass sounds. A subwoofer's powerful bass can often cause items in the room or even the structure of the room itself to vibrate or buzz. Extended periods of high volume bass can cause items throughout a room to "walk" on a flat surface until they fall off.

Amplified subwoofers frequently accept both speaker-level and line-level audio signals. When teamed with a modern surround sound receiver and full range speakers, they are typically driven with the specific LFE (low frequency enhancement) output channel (the ".1" in 5.1, 6.1, or 7.1 specifications) provided by the receiver. This is because most full-range speakers are incapable of delivering the acoustic power required by the LFE in movies or in some cases, music. When used with speakers that do not reproduce low frequencies well, a subwoofer will often be configured to reproduce both the LFE channel and all other bass in the system, the latter being referred to as "bass management".


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