Bi-amping and tri-amping

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Bi-amping - An active crossover with two amplifiers. Active Crossover.svg
Bi-amping - An active crossover with two amplifiers.

Bi-amping and tri-amping is the practice of using two or three audio amplifiers respectively to amplify different audio frequency ranges, with the amplified signals being routed to different speaker drivers, such as woofers, subwoofers and tweeters. With bi-amping and tri-amping, an audio crossover is used to divide a sound signal into different frequency ranges, each of which is then separately amplified and routed to separate speaker drivers. In powered speakers using bi-amping, multiple speaker drivers are in the same speaker enclosure. In some bi-amp set-ups, the drivers are in separate speaker enclosures, such as with home stereos that contain two speakers and a separate subwoofer.

Contents

Description

Illustration of tri-amping, using three amplifiers to amplify different parts of a sound. Tri-amping.svg
Illustration of tri-amping, using three amplifiers to amplify different parts of a sound.

Bi-amping is the use of two channels of amplification to power each loudspeaker within an audio system. Tri-amping is the practice of connecting three channels of amplification to a loudspeaker unit: one to power the bass driver (woofer), one to power the mid-range and the third to power the treble driver (tweeter). The terms derive from the prefix bi- meaning 'two', tri- meaning 'three', and amp the abbreviation for amplifier.

Crossover

It differs from the conventional arrangement in which each channel of amplification powers a single speaker. Bi-amping typically consists of a crossover network and two or more drivers. With ordinary loudspeakers, a single amplifier can power the woofer, mid-range and tweeter through an audio crossover, which filters the signal into high- medium- and low-frequencies (or high- and low-frequencies in 2-way speakers) a mechanism that protects each driver from signals outside its frequency range. However, the passive crossover itself is inefficient, so splitting the frequencies electronically before these are amplified is a way to avoid this problem. In such a case, each amplifier powers a frequency range determined by an active crossover to each of the drive units. The technique is primarily used in large-scale audio applications such as sound amplification for concerts, in portable powered speakers and by hi-fi enthusiasts.

Wiring

A speaker system has to be wired to accommodate either configuration, typically with two sets of binding posts, one set for the bass and one set for the mid-highs. A single amplifier can usually power a woofer and a tweeter only through a post-amplifier crossover filter, which protects each driver from signals outside its frequency range.

Bi-amping of speakers requires double the channels of amplification and can be accomplished using two ordinary amplifiers in either a vertical or horizontal arrangement.

Benefits

Most audible differences are subtle. If at all noticeable, many benefits of bi-amping cannot be realized if passive crossover networks of a speaker system are not removed. [1] Benefits include transients are less likely to cause amplifier overload (clipping) or speaker damage, and reduced intermodulation distortion, elimination of errors introduced by low-frequency passive crossover, reduction of load presented to the power amplifier, better matching of power amplifier and speaker driver and others. [2] In large professional sound systems, Bi-amping is pretty much the norm with the greater benefits easily outweighing the costs. All speakers are two-way transducers and can introduce current back into the driving circuit from ambient sound. The driving amplifier tries to control the effect of this with its damping factor (having a high resistance to such current), but with a passive crossover, this current can still leak across to the other driver units in the circuit. A Bi-amped system is therefore able to better resist ambient sound feeding back into the circuit. With high volumes and larger venues, such ambient feedback can have a significant damaging effect to the overall sound.

See also

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A subwoofer is a loudspeaker designed to reproduce low-pitched audio frequencies, known as bass and sub-bass, that are lower in frequency than those which can be (optimally) generated by a woofer. The typical frequency range that is covered by a subwoofer is about 20–200 Hz for consumer products, below 100 Hz for professional live sound, and below 80 Hz in THX-certified systems. Thus, one or more subwoofers are important for high-quality sound reproduction as they are responsible for the lowest two to three octaves of the ten octaves that are audible. This very low-frequency (VLF) range reproduces the natural fundamental tones of the bass drum, electric bass, double bass, grand piano, contrabassoon, tuba, in addition to thunder, gunshots, explosions, etc.

<span class="mw-page-title-main">Audio crossover</span> Electronic filter circuitry used in loudspeakers

Audio crossovers are a type of electronic filter circuitry that splits an audio signal into two or more frequency ranges, so that the signals can be sent to loudspeaker drivers that are designed to operate within different frequency ranges. The crossover filters can be either active or passive. They are often described as two-way or three-way, which indicate, respectively, that the crossover splits a given signal into two frequency ranges or three frequency ranges. Crossovers are used in loudspeaker cabinets, power amplifiers in consumer electronics and pro audio and musical instrument amplifier products. For the latter two markets, crossovers are used in bass amplifiers, keyboard amplifiers, bass and keyboard speaker enclosures and sound reinforcement system equipment.

<span class="mw-page-title-main">Tweeter</span> Type of loudspeaker

A tweeter or treble speaker is a special type of loudspeaker that is designed to produce high audio frequencies, typically up to 100 kHz. The name is derived from the high pitched sounds made by some birds (tweets), especially in contrast to the low woofs made by many dogs, after which low-frequency drivers are named (woofers).

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A mid-range speaker is a loudspeaker driver that reproduces sound in the frequency range from 250 to 2000 Hz.

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A bass amplifier is a musical instrument electronic device that uses electrical power to make lower-pitched instruments such as the bass guitar or double bass loud enough to be heard by the performers and audience. Bass amps typically consist of a preamplifier, tone controls, a power amplifier and one or more loudspeakers ("drivers") in a cabinet.

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<span class="mw-page-title-main">Guitar speaker</span>

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<span class="mw-page-title-main">Bi-wiring</span> Method of running wires to speakers

Bi-wiring is a means of connecting a loudspeaker to an audio amplifier, primarily used in hi-fi systems. Normally, there is one pair of connectors on a loudspeaker and a single cable runs from the amplifier output to the terminals at the loudspeaker housing. From this point, connections are made to the loudspeaker drivers – usually through audio crossover networks.

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A keyboard amplifier is a powered electronic amplifier and loudspeaker in a speaker cabinet used for the amplification of electronic keyboard instruments. Keyboard amplifiers are distinct from other types of amplification systems such as guitar amplifiers due to the particular challenges associated with making keyboards sound louder on stage; namely, to provide solid low-frequency sound reproduction for the deep basslines that keyboards can play and crisp high-frequency sound for the high-register notes. Another difference between keyboard amplifiers and guitar/bass amplifiers is that keyboard amps are usually designed with a relatively flat frequency response and low distortion. In contrast, many guitar and bass amp designers purposely make their amplifiers modify the frequency response, typically to "roll-off" very high frequencies, and most rock and blues guitar amps, and since the 1980s and 1990s, even many bass amps are designed to add distortion or overdrive to the instrument tone.

<span class="mw-page-title-main">Linn Isobarik</span> Loudspeaker designed and manufactured by Linn Products

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References

  1. An article from Audioholics online A/V magazine, 30 August 2004, The Difference Between Biamping vs. Biwiring
  2. Elliott, Rod (7 July 2017) [Originally published 1998]. "Benefits of Bi-Amping (Not Quite Magic, But Close) – Parts 1 & 2". Not Quite Magic, But Close). Elliott Sound Products. Archived from the original on 17 July 2019.