Understanding audio compression, how it works and how to use the compressor is an important part of audio mixing. This knowledge can take your mixing skills to the next level.
Audio compression is one of the most confusing techniques for new engineers and producers.
In my opinion, this is because young engineers haven’t yet grasped the concept of compression ratio, and they haven’t yet learned to identify the difference between compressed and uncompressed audio.
In the article, I will explain what audio compression is, how it works, why you would need audio compression, and when to use it.
The article finishes off with a list of different type of audio compression technique used in audio mixing.
What is audio compression?
In music production, audio compression is the process used to reduce the dynamic range of an audio signal.
Dynamic range is the difference between the loudest and softest parts of the audio signal.
The process of audio compression reduces the loudest level by a set ratio so that it closely matches the softest level.
Audio engineers use audio compression in mixing to control the maximum levels and maintain a higher average loudness.
For a deeper understanding, here we explain more in-depth what an audio compression is.
How Does Audio Compression Work?
As I mentioned before, audio compression turns down (compresses) the loudest parts of an audio signal by a certain ratio once the signal passes the threshold.
The ratio is responsible for the amount of compression or gain-reduction is applied to the signal that excesses the threshold.
A ratio of 4:1 means for every 4dB over the threshold, the compressor reduces the signal to 1dB.
Why Do you Need Audio Compression
If you are mixing popular music, compression is a must! To get the big loud sound that is synonymous to commercial music without blowing up your speakers, you need compression.
Your responsibility is the learn how, when and what type of compression to use when you are mixing.
In audio mixing, audio compression is mostly used to control or correct balance issues and maximise loudness. On occasions, audio engineers use a compressor as an effect to give the track the unique tone of that compressor.
Since you are still learning how to use the compressor, you shouldn’t worry about the latter – your focus is balance.
Types of Audio Compression
Now it is time to learn about the different types of audio compression used in audio mixing. Below are three common types that you should get to know.
Parallel compression, also known as the New York compression, uses the send and return setup. Simply bus/send the audio signal to an auxiliary track that has a compressor inserted.
The audio signal sent to the auxiliary track is heavily compressed, then blend to taste with the original audio signal.
What makes the parallel compression technique so great is the depth from the heavily compressed signal and the natural sound from the original recording.
The audio signal will sound bigger and louder in the mix without sounding over compressed.
In popular music, parallel compression is used on vocals, drums and the master bus for a bigger puncher mix.
Side-chain compression works slightly different from the regular compression technique.
Instead of compressing the audio signal once it exceeds the threshold, side-chain compression uses the level of another instrument to control the compressor.
A very popular example is using the kick to control the compression on the bass. Whenever the kick plays, the bass track gets compressed to make space for the kick.
This is why side-chain compression technique is also called ducking because everything the kick plays the bass “ducks” gets compressed so that the kick is heard more clearly.
EDM producers use side-chain compression a lot as an effect, but in audio mixing, side-chain compression is used to create space and prevent clashing of instruments in a similar frequency range
Multiband compression allows you to divide the frequency spectrum into different bands and compress them separately. Almost like using a different compressor on each band.
Most multiband compressors feature either 3 or 4 different frequency bands, low frequency, mid-frequency, low hi and high hi frequency.
Common applications for multiband compression is on the master bus, a drum bus and the lead or vocal bus.