Using compression is a fundamental part of most mixes. You may hear people talk about using compression to balance signals, add punch, create energy or create excitement in a mix. In this article, we’ll learn how you can achieve each of these characteristics using compression.
What is compression?
Compressors reduce the dynamic range of an audio signal. This means that they reduce the difference between loud and quiet. In most common applications, compressors achieve this by turning the loud parts of a signal down.
Using compression for balance and consistency
One of the most common uses of a compressor is simply to balance out the level of a signal and make its dynamic range more consistent. This is useful because, if a signal’s dynamic range is too great, it can be difficult to set the fader to one position for the whole song. Take for example a vocalist who performs a take with varying dynamics. If you set the fader to the correct spot for the quiet parts of the performance, then the vocals will be too loud during the louder parts. If you set the fader for the louder parts, then the vocals will be too quiet during the quieter parts. This is true of any instrument that exhibits significant dynamic range.
You can approach the balancing of levels using compression in different ways. You could set the threshold to the quieter parts of the signal. That way, the compressor will process the majority of the signal. This is a great approach for reducing the overall dynamic range of a track and achieving more balanced levels over the course of the song.
Alternatively, you could set the compressor’s threshold so that compression is only applied to the signal’s loudest parts. Doing this ensures that the compressor clamps down on the loud peaks and contains them. This approach allows you to pin-point specific parts of a signal. So, you can use this method to attenuate a particularly loud snare drum in the overhead recording of a drum kit or a particularly loud note being plucked on a guitar, for example.
When balancing signals, fast attack and release times are generally preferred. This ensures that the compressor reacts quickly to level changes to keep the signal balanced. However, some signals may lose their impact if the attack is too fast. If you are balancing a signal which has a naturally fast attack, like drums for instance, then the attack may need to be slower to retain the instrument’s natural attack whilst still balancing the signal.
Using compression to add punch, energy and excitement
In addition to balancing levels with a compressor, you can also use a compressor to add punch, energy and excitement to your tracks. To achieve this, the process is a little different. Rather than turning down entire notes in the way that you do when balancing signals, you instead use the compressor to alter the dynamics within individual notes. This is achieved by altering the relationship between a note’s attack and decay. This is known as ‘reshaping’ the note’s ‘envelope’.
In order to give a track more punch, energy or excitement, you need to emphasize the note’s attack. This is done by using the compressor to retain the note’s natural attack, but attenuate its decay. To do this, you need to set the compressor’s attack slow enough to allow the note’s natural attack through largely uncompressed, but to apply gain reduction to its decay. You should then set the release slow enough to compress the note’s decay, but fast enough to ensure that the compressor resets before the next note comes along. That’s because you will want to let the next note’s natural attack through largely uncompressed as well. This process enables you to make drums more punchy or to give acoustic guitars more energy and excitement. This helps instruments to cut through and gives them more presence. It also tends to bring instruments forward in the mix.
Using compression to fatten sounds
Using compression can also be a way of making signals in your mix sound fatter and fuller. Just like the previous example, you achieve this by reshaping the notes. This time, you alter the note by emphasizing its decay. To do this, you need to use a fast attack to attenuate the natural attack of an instrument’s notes. You also use a fast release. That way, the attenuation ceases quickly enough to allow the note’s decay to be unaffected.
You can then use make up gain to turn the level of the signal back up to match the input level. So now, the instrument’s notes return to the same level that they entered the compressor at, but with an accentuated decay. This is a great way to fatten up kick drums, snare drums and toms. You can also use this method to make guitars and basses sound fatter and fuller by accentuating their sustain.
As you can see, a compressor is a versatile tool. A compressor can balance out a signal to make its dynamic range more consistent. Alternatively, you can use a compressor to make a track punchier and fatter, or to give it more energy and excitement… How do you like to use compressors in your mixes?