Dynamic range compression: Difference between revisions

Revision as of 18:37, 23 July 2021

Revision as of 19:16, 24 August 2021

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''Brick wall limiting'' has a very high ratio and a very fast attack time. Ideally, this ensures that an audio signal never exceeds the amplitude of the threshold. Ratios of 20:1 all the way up to ∞:1 are considered ''brick wall''.<ref name="tcelectronic.com" /> The sonic results of more than momentary and infrequent brick-wall limiting are harsh and unpleasant, thus it is more common as a safety device in live sound and broadcast applications.

Some [[bass amp]]s and [[PA system]] amplifiers include limiters to prevent sudden volume peaks from causing distortion or damaging the speakers.<!--[[User:Kvng/RTH]]-->

== Side-chaining ==

[[File:Compressor Sidechain.svg|thumb|300px|The sidechain of a feed-forward compressor]]

{{listen | filename = Uplifting Trance Sidechain.ogg| title = Uplifting Trance Sidechain| description = The first 8 bars are without side-chaining applied, the second 8 are with side-chaining. | format = [[Ogg]]}}

A compressor with a side-chain input controls gain from main input to output based on the level of the signal at the side-chain input.<ref name="Colletti">{{Cite web |url=http://www.sonicscoop.com/2013/06/27/beyond-the-basics-sidechain-compression/ |title=Beyond The Basics: Sidechain Compression |last=Colletti |first=Justin |date=2013-06-27 |website=SonicScoop |access-date=2015-03-16}}</ref> An early innovator of side-chain compression in an effects unit was the [[Eventide, Inc|Eventide]] Omnipressor from 1974.<ref>{{cite web |title=50th Flashback #3: The Omnipressor |url=https://www.eventideaudio.com/blog/aagnello/50th-flashback-3-omnipressor |website=Eventide Audio |access-date=17 May 2021}}</ref> With side-chaining, the compressor behaves in the conventional manner when both main and side-chain inputs are supplied with the same signal. The side-chain input is used by [[disc jockey]]s for [[ducking]] – lowering the music volume automatically when speaking. The DJ's microphone signal is routed to the side-chain input so that whenever the DJ speaks the compressor reduces the volume of the music. A sidechain with [[equalization (audio)|equalization]] controls can be used to reduce the volume of signals that have a strong spectral content within a certain frequency range: it can act as a [[de-esser]], reducing the level of vocal [[sibilance]] in the range of 6–9&nbsp;kHz.<ref>{{Cite magazine |last=Senior |first=Mike |date=May 2009 |title=Techniques For Vocal De-essing |url=http://www.soundonsound.com/sos/may09/articles/deessing.htm |department=Sound Advice |magazine=Sound on Sound |access-date=2015-03-16}}</ref> A de-esser helps reduce high frequencies that tend to overdrive [[preemphasis|preemphasized]] media (such as phonograph records and FM radio). Another use of the side-chain in music production serves to maintain a loud bass track without the [[bass drum]] causing undue peaks that result in loss of overall [[Headroom (audio signal processing)|headroom]].<ref name="Colletti" /><!--[[User:Kvng/RTH]]-->

==Parallel compression==