Bobby Bloomfield Producer, DJ, drummer, member of Does It Offend You, Yeah?
Monday, 13 May 2013
Dynamic Processing - How Dynamic Are You?
Dynamics are hardware units or software plugins that control the volume (or dynamic range) of a sound signal. For example a compressor will compress the dynamic range of a signal so that the peaks (loudest parts) of the signal are controlled (made quieter) and a gate will allow a signal through only when it reaches a certain volume.
Not only do dynamic processors control the way in which the dynamic range is controlled, different dynamic processors can pleasingly “colour” the sound in unique ways. Some of the older studio hardware units are so loved by engineers for their ability to colour the sound and adding some esoteric magical sparkle, that they have been emulated by software plugin companies. For example the LA2A compressor is a classic from the 1960s that has such a favourable character that almost all plugin companies have sought to emulate what it does. Equally some processors are highly prized for their ability to do their job without colouring the sound noticeably and these are referred to as “transparent”.
I could ramble on about the various coloration traits of various plugins and hardware but instead for now I will explain what these dynamic processors fundamentally do to a signal. Later I will give some examples of how these processors are used creatively in music production.
The compressor – as the name suggests – compresses or narrows a signal’s dynamic range. For example if you have a singer that sings one word very quietly and another loudly it would be hard to hear certain words in the mix of the song. A compressor will quieten the louder words and can effectively make all the words roughly the same volume.
The compressor is used to smooth out the difference between loud and quiet sounds, to make drums pump and can be used creatively to create all sorts of musical results. Heavy rock and dance music producers use compression to make some sounds appear loud and make a mix “pump”.
Most compressors will give you multiple options to control the way in which it works. A standard compressor will usually have these basic options:
With the threshold setting you can control the volume level at which the compressor will work. Sounds that remain under the threshold volume limit will pass through the compressor unaffected and those over the threshold will kick the compressor into action squashing the signal by reducing the gain (volume).
You can control the ratio of the compressor’s gain reduction. A ratio of 4:1 will mean that if the input level goes 4db over the threshold, the compressor will limit it to just 1db over the threshold. At ∞:1 (infinity to one) even if the input signal is way above the threshold limit, the output signal will not be allowed to go above the threshold limit.
3. Attack / Release
This is the speed at which the compressor will begin and end working. A fast attack will compress the very instance that the sound rises above the threshold. A slow attack will allow some time to pass through before going into action. The speed of the release is how long it will take for the compressor to stop working once the sound has gone below the threshold.
4. Make up gain
As the compressor will make the output signal lower by design, this allows you to turn the output gain up.
A limiter is effectively a compressor with a fixed fast attack and its ratio fixed to infinite. Usually a limiter will give you only a threshold and release option.
A gate is a processor that will only let the signal through once it reaches the threshold. You can think of it as a door that opens and lets sound through only when the sound is loud enough to blow the door open. You can set the strength of the door and how quickly it opens and closes. These are very useful for removing bleed or unwanted low level noise on recorded tracks. A basic gate will give you these options:
The threshold in this case is the point at which the gate will open. Sound above the volume of the threshold will be let through and sound below the threshold will not.
3. Attack / Release
As with the compressor you can set the speed at which this processor will work. The attack is the speed at which the gate will open and the release is the speed at which the gate will close.
Sidechaining is when a dynamic processor is used on a signal but a separate signal triggers its action. You may have noticed that when a radio DJ talks over a song, the song will drop in volume when he speaks. This isn’t the DJ pushing the fader up and down on every word, this is an automatic effect made with side chaining. A compressor will be placed on the music track and the DJ’s microphone will be inputted into the side chain of that compressor. The result is that when the DJ’s voice hits the threshold of that compressor, the volume of the music will drop.
One very noticeable (and often horribly overused) sidechaining effect is used in dance music. The compressor will duck the volume of the whole track when the bass drum signal hits the compressor to give that cliche’d sucking feel. If used well it can make a track seem loud and pumping. If used too much it can be extremely tiring to listen to.
Sidechaining is also used more subtly in other genres of music. Sometimes a similar effect to the DJ ducking to make a vocal more prominent or to make a bass guitar and bass drum pump.
I hope that this basic intro into dynamic processing is helpful. I will go into more detail how these are used later on.