Dynamic range compression: Difference between revisions

Revision as of 21:17, 8 October 2021

Revision as of 20:50, 8 November 2021

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There are a number of technologies used for variable-gain amplification, each having different advantages and disadvantages. [[Vacuum tube]]s are used in a configuration called ''variable-mu'' where the grid-to-cathode voltage changes to alter the gain.<ref>{{Cite web |url=http://www.tangible-technology.com/dynamics/comp_lim_ec_dh_pw2.html |title=An Overview of Compressor/Limiters and Their Guts |last1=Ciletti |first1=Eddie |last2=Hill |first2=David |date=2008-04-19 |website=www.tangible-technology.com |access-date=2019-11-03 |last3=Wolff |first3=Paul}}</ref> Optical compressors use a [[photoresistor]] and a small lamp ([[Incandescent light bulb|incandescent]], [[Light-emitting diode|LED]], or [[Electroluminescence|electroluminescent panel]])<ref>{{Cite web |url=http://media.uaudio.com/assetlibrary/l/a/la-2a_manual.pdf |title=Model LA-2A Leveling Amplifier |website=Universal Audio |type=Manual }}</ref> to create changes in signal gain. Other technologies used include [[field effect transistor]]s and a [[diode bridge]].<ref>{{Cite magazine |last=Berners |first=Dave |date=April 2006 |title=Compression Technology and Topology |url=https://www.uaudio.com/webzine/2006/april/text/content4.html |department=Analog Obsession |magazine=Universal Audio WebZine |publisher=Universal Audio |volume=4 |issue=3 |access-date=2016-08-29}}</ref>

When working with digital audio, [[digital signal processing]] (DSP) techniques are commonly used to implement compression as [[audio plug-in]]s, in [[mixing console]]s, and in [[digital audio workstation]]s. Often the algorithms are used to emulate the above analog technologies.{{citation needed|date=May 2019}}

== Controls and features ==

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==Parallel compression==

Insert the compressor in a parallel signal path is known as [[parallel compression]]. It is a form of upward compression that facilitates dynamic control without significant audible side effects so long as the ratio is relatively low and the compressor's sound is relatively neutral. On the other hand, a high compression ratio with significant audible artifacts can be chosen in one of the two parallel signal paths. This is used by some concert mixers and recording engineers as an artistic effect called ''New York compression'' or ''Motown compression''. Combining a linear signal with a compressor and then reducing the output gain of the compression chain results in low-level detail enhancement without any peak reduction; The compressor significantly adds to the combined gain at low levels only.<!--[[User:Kvng/RTH]]-->

== {{visible anchor|Multiband compression}} == <!-- [[Multiband compression]] redirects here -->

Multiband compressors can act differently on different frequency bands. The advantage of multiband compression over full-bandwidth compression is that problems related to a specific frequency range can be fixed without unnecessary compression in the other, unrelated frequencies. The downside is that frequency-specific compression introducesis somemore phasingcomplex and requires more processing capacity than full-bandwidth compression and can introduce phase issues.<ref>{{citation |url=https://www.waves.com/1lib/pdf/plugins/linear-phase-multiband-compressor.pdf |title=Waves – Linear-Phase MultiBand Software Audio Processor Users Guide |page=3 |access-date=2021-11-08}}</ref>

Multiband compressors work by first splitting the signal through some number of [[band-pass filters]], [[audio crossover|crossover filters]] or [[filter bank]]s. Each split signal then passes through its own compressor and is independently adjustable for threshold, ratio, attack, and release. The signals are then recombined and an additional limiting circuit may be employed to ensure that the combined effectssignals do not create unwanted peak levels.

In music production, multiband compressors are primarily an [[audio mastering]] tool, but their inclusion in [[digital audio workstation]] plug-in sets is increasing their use among mix engineers.

Software plug-ins or [[digital signal processing|DSP]] emulations of multiband compressors can be complex, with many bands, and require corresponding computing power.

Multiband compressors are primarily an [[audio mastering]] tool, but their inclusion in [[digital audio workstation]] plug-in sets is increasing their use among mix engineers. On-air signal chains of [[radio station]]s commonly use hardware multiband compressors to increase apparent [[loudness]] withoutwhile fear ofavoiding [[overmodulation]]. Having a louder sound is often considered an advantage in commercial competitionbroadcasting. However, adjusting a radio station's multiband output compressor requires some artistic sense of style, plenty of time, and good ears. This is because the constantly changing <!--[[spectral balanceUser:Kvng/RTH]] between audio bands may have an equalizing effect on the output, by dynamically modifying the on-air frequency response. A further development of this approach is programmable radio output processing, where the parameters of the multiband compressor automatically change between different settings according to the current program block style or the time of day.->

==Serial compression==