the history of compression
DESCRIPTION
Overview of the use of compressors in music prodution.TRANSCRIPT
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Radio producers often idolize studio engineers who work with racks full of high end gear because so
many radio stations now have nothing more than a cost cutter DAW, an RE20 and some cracked plug ins.
It wasn't always that way. In fact, when it comes to compressors, radio developed the technology and
jealous studio engineers adopted it.
In early radio, excessive audio levels could knock a station off the air. Engineers would manually ride gain
to avoid it but, no one can anticipate a sudden spike and the human hand is only so fast. To protect
equipment, leveling amplifiers were developed. They automated the process by acting like limiters.
Recording engineers had the same desire to control levels and borrowed the idea from radio which was
clearly on the cutting edge. Since limiting is just a severe form of compression, the idea for both was
born at the same time.
Fast forward to the 1960s when boxes like the Urei 1176 and the LA-2A hit the market. Even by today's
standards these units are considered audio rocket sauce. They changed the vibe of music production and
are still in use all over the world.
Compression has been a massive force in defining the sound of modern music. Although it's often
misused, it is routinely thought of as a must have for any mix whether it's a hit record or a radio promo.
Recording studios seek out vintage compressors that can cost up to $25,000. No, that's not a misprint
COMPRESSION TIMELINE
1930s-40s - Compression created to control volume of TV/Radio presenters whispering/talking quietly
as-well as an entire audience clapping.
The first compressors just had In/Out functions and no other controls.
1937 – ‘The Western Electric 110 limiting amplifier created, being considered to be the first
commercially available compressor.
1960s - The Urei/Universal Audio 1176 is one of the most revered and popular compressors used in music
production. Bill Putnam introduced the design in 1966. Still revered today.. Click here for an interesting
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history of the infamous Teletronix LA2 (optical compressor)- first mass produced in the 1960s.
1970s - Widely considered to be one of the finest VCA compressors ever built, the diminutive dbx 160,
first introduced in 1971, is all about the ‘knock’!
1980s – DAWs included Compression as standard in their software, rather than needing Compression
Racks.
2007 – Tracks started using less heavy compression, experimenting with different compression levels
Parameters of Compression:
STANDARD PARAMETERS
Threshold – How loud the signal is before compression is applied.
Ratio – How much compression is applied. For example, if the compression ratio is set for 6:1, the input
signal will have to cross the threshold by 6 dB for the output level to increase by 1dB.
Attack – how quickly the compressor starts to work.
Release – how quickly after the signal drops below the threshold the compressor stops.
Knee – sets how the compressor reacts to signals once the threshold is passed. Hard Knee settings
mean it clamps the signal straight away, and Soft Knee means the compression kicks in more gently as
the signal goes further past the threshold.
Make-Up Gain – allows you to boost the compressed signal, as compression often reduces the signal
significantly.
Output – allows you to boost or decrease the level of the signal output from the compressor.
Other controls and compression functions...
Stereo Linking
A compressor in stereo linking mode applies the same amount of gain reduction to both the left and
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right channels. This is done to prevent image shifting that can occur if both channels are compressed
individually. It becomes noticeable when a loud element that is panned to either edge of the stereo field
raises the level of the program to the compressor's threshold, causing its image to shift toward the
center of the stereo field.
Limiting
Limiting and clipping compared. Note that clipping introduces a large amount of distortion whereas
limiting only introduces a small amount while keeping the signal within the threshold.
Compression and limiting are not different in process but in degree and perceived effect. A limiter is a
compressor with a high ratio and, generally, a fast attack time. Most engineers consider compression
with ratio of 10:1 or more as limiting.
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
to be 'brick wall'. The sonic results of more than momentary and infrequent hard/brick-wall limiting are
harsh and unpleasant, thus it is more common as a safety device in live sound and broadcast applications.
Side-Chaining
hen side-chaining, the compressor uses the volume level of an input signal to determine how strongly
the compressor will reduce the gain on its output signal. This is used by DJs for ducking – lowering the
music volume automatically when speaking. The DJ's microphone signal is routed to the compressor's
sidechain so that whenever the DJ speaks the compressor reduces the volume of the music.
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. It can also be used for creative effect,
very popular in trance and much dance music.
Parallel Compression
Essentially, this is a technique whereby you use the
compressor as a send effect (you'd traditionally use it as
an insert), so that the dry and compressed signals are
running in parallel — just as is shown in the diagram on
this page. You'd normally achieve this by taking the
source track and then using an aux send control to 'send'
some of the signal to another channel with your
compressor on it. You might then bus both the source
and compressed channels to a group channel. In a modern DAW, you could achieve a similar thing by
duplicating (or 'multing') a track, but I prefer using sends, as even after edits you'll know that you're
working from the same source audio. Increasingly, new compressor designs include a wet/dry blend
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control, which avoids all this routing and allows you to perform parallel compression on a single channel.
However, you might or might not process the compressed version differently from the dry version, and a
simple wet/dry control doesn't allow you to do this.
Parallel compression is often used on drums, and the technique is frequently referred to as the 'New
York drum trick'. The effect can help to keep a part solid and 'anchored' in the mix, while retaining some
of the dynamics of the original — and you can easily determine how dynamic the part is in different
sections of the song by balancing the two channel faders. A common extension to this trick is to put a
slight 'smile' EQ on the compressed drums.
Multiband compression
Multiband compressors can act differently on different
frequency bands. The advantage of multiband
compression over full-bandwidth (full-band, or
single-band) compression is that unneeded audible gain
changes or "pumping" in other frequency bands is not
caused by changing signal levels in a single frequency
band.
Multiband compressors work by first splitting the signal
through some number of band-pass filters or crossover
filters. The frequency ranges or crossover frequencies
may be adjustable. 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 effects do not create unwanted peak
levels.
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.
Further reading:
● History of the classic Universal Audio 1176 compressor
http://www.uaudio.com/blog/analog-obsession-1176-history/
● The 20 Best Compressors of All Time!
http://www.attackmagazine.com/features/top-20-best-hardware-compressors-ever-made/