In todays lessons we explore the use of compression and expansion. the aim of compression is to control dynamic range. We look at how compression is used in radio by listening to different stations to determine how dynamic range affects the sounds. -18 DP was determine as the average volume in which a sound is set.
we also saw examples of this in Pro tools. with the Use of Channel Strip, side channel and reverb. All this are used as an insert to enable a smooth sound.
Compression is the process of lessening the dynamic range between the loudest and quietest parts of an audio signal. This is done by boosting the quieter signals and attenuating the louder signals. The controls you are given to set up a compressor are usually:
Threshold – how loud the signal has to be 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 soon after the signal dips 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 attenuates the signal significantly.
Output – allows you to boost or attenuate the level of the signal output from the compressor.
Compressors come in various different flavors. These are used by engineers for different tasks and some sound far better in certain situations than others.
Voltage Controlled Amplifier compressors use an integrated circuit to give very precise control. They are less colored and suffer from very few side effects like distortion, which make them ideal for lots of different tasks. The dBx 160 is a VCA compressor.
Opto, meaning optical, describes the light sensitive circuits that control the compression amount in opto compressors. They often react more slowly than other compressor types, but this can be desirable. The famed Teletronix LA2A is an optical compressor that many producers swear by for vocals and mix bus compression. The LA2A is also a ‘leveling amplifier’ — which means it is working nearly all the time, not just when a threshold is reached.
Field Effect Compressors use transistors to emulate a valve sound with more reliability, but with a higher signal to noise ratio. They are popular for vocals and great for drum compression. The Urei 1176 is a FET compressor.
Valve compressors work in one of the three ways described above, but use valves in the amplifier circuit to get that ‘creamy’ sound. The LA2A, which is an opto compressor, uses valves.
This is examples different Waves compressors