Audio Compression and Compressors
Basics And Performance
Limiters and compressors are two types of amplifiers that are unique because they are used to lower dynamic range. This range is the distance or span between the loudest sounds and the lowest (softest) sounds. When compressors are used during live mixes and recordings, they can help make the sound seem more polished when the maximum levels are controlled and the average loud sounds are maintained.
In addition, physical audio compressors and compressor software is able to have a distinct sound that can be used at random to inject the music with a range of tone and coloration that will brighten up and otherwise empty track. Also, audio compression can be used to slightly add an intelligible and natural sound to a track without further distorting it. As a result, the music will be more pleasant sounding to the ear.
However, it is also important to know that music can become ‘over-compressed’ as well. When music has too much compression, it can sound as though the ‘life’ is being sucked out of it. This means that for those who are not experienced with compressors and the way they work, understanding the basics can be used to benefit your audio productions.
Parameters And Controls
There are some general parameters and controls that you will frequently use to determine the way the effect of the compression behaves. This will be dependent on whether you are using compression hardware, or if you are using software and/or a plug-in. Although the compressor you are using may not include all of the parameters, or dynamic range, and controls, it is still important to have a basic understanding of the functions of each one.
The threshold control determines where the compression effect will be. It is only when the effect is at a level that is higher than the threshold will the effect be compressed. For example, if the threshold level is at -9 dB, signals that go higher than this will be compressed.
The release time is the amount of time that it takes for a signal to be compressed back to uncompressed. A release time is generally much longer than the attack time, and can be as short as 40 ms up to 5 seconds.
The attack time is the exact opposite of attack time. This is the amount of time it takes for a signal to go from uncompressed, or its original state, to compressed.
The Several Types Of Compression Types
Your choice of compressor will also play a role in the sound of the effect. There are some types of compressors that will have ‘release’ and ‘attack’ times that are faster or slower than others. Then, there are some compressors that will have a vibe or sound that is more vintage or has more coloration based on the internal parts.
Also known as the Voltage Controlled Amplifier, the VCA compressor uses integrated circuits or solid state. These are typically cheaper than optical or tube compressors.
The tube compression is considered the oldest type of compression. Tube compressors normally slower responses than other types of compressors. However, it is because of this slower response that allow tube compressors to have a distinct vintage sound that other compressors cannot achieve.
Field Effect Transistor, FET, compressors create a sound that is similar to the sound that is created from transistor circuits. These compressors produce a sound that is clean, reliable and fast. A good example of this compressor is the 1176LN Classic Limiting Amplifier.
Keep in mind that you should use caution when you are compressing a whole mix. If the compression you use that counters a ‘horn’ sound, the mix will drop at that point and the base line will begin to pump. However, let your ear be your guide.