Hearing Compression
The idea of compression is most often taken as a somewhat magical way of turning up amplitude or somehow just magically makes the mix sound better and bigger/louder.
Well in a way, that’s somewhat true, except.. for the magic part.
Most beginners testify to difficulties in hearing compression. From a personal perspective, I’d say this is because most don’t understand how or why it works.
The ideal definition of Compression in the POV of a normie would be Squashing the sound hard enough to hear a noticeable difference…. And That..’s… not quite…what it does.
What do Compressors really do?
Compressors do exactly what their name says; It compresses. But not the way you’re thinking it, Lol.
A compressor typically makes music/sounds louder without increasing its amplitude (Volume)
Now, how it does this is what’s most important in understanding how to properly use Compressors.
Yes, it makes the sound louder without increasing its amplitude, but that’s not quite all it does.
In detail, the sole purpose of compression is to even out signal levels in the sound/track, making it sound more even, or consistent.
It does this by taking the loudest parts of a signal and bringing them down to a point where they sound more even with the lower parts of the signal. Also Similarly doing the same for the much lower parts.
(illustration below)
The compressor achieves this process using a Knob called a “THRESHOLD”
THRESHOLD:
The Threshold is a set level that must be exceeded for the compressor to be triggered. Meaning that if the signal doesn’t peak or reach the set threshold level, nothing would be done, and no compression would take place.
Measured in decibels, the threshold knob is undoubtedly one important thing to understand as a beginner.
I.e the more you turn the threshold knob down, the more the signal is affected and compression is applied.
Extensively, some compressors provide the capabilities to affect a threshold’s behavior as to how fast or slow it responds.
This feature is characterized by 2 other knobs known as ATTACK AND RELEASE.
ATTACK & RELEASE:
Attack simply is how fast the compressor grabs the sound.
Slower attack times allow the transients through and adds more punch to the sound.
For example, if you have a snare drum that doesn't hit or punch that hard, you would want to have a slow attack time on your compressor. Similarly, if you have a snare drum that feels like too much punch, you would want to set the attack time to go a little faster and control the punch. The faster the attack time, the lesser transients are let through.
This feature can as well be used on a drum group/bus to control the overall punch.
Attack basically has to deal with keywords like impact & punch.
THINGS YOU MIGHT WANT TO HAVE A FAST ATTACK TIME ON
- Bass, Acoustic Guitar,
- Synths/ Sounds with quick transients.
- Vocals (sometimes)
- Pretty much anything that sounds like it needs it.
Release time is simply how fast/quickly the compressor lets go of the sound. In other words, this means how long the compressor holds before attacking again.
For Example
Load up a bass guitar, Play a single note. Now load up another instance of the same bass and play the same note. Throw a compressor on the second instance and turn the release really up.
What you would find is, if the first instance (uncompressed bass note) dies off really fast, the second instance (compressed bass note) takes a little longer before it dies off. This is because the release time is set to take a little longer.
RATIO
Ratio simply put, is the knob that controls how much compression is actually applied to a signal. I.e it sets the amount of applied compression.
1:1 is basically no compression.
2:1 Mild Compression
4:1 Moderate Compression
6:1 Medium Compression
10: 1 Strong Compression
20:1 Stronger Compression
∞:1 Limiting
How ratio works
Using the 2:1 model as an example for illustration
If the ratio on a compressor is set to 2:1, any signal exceeding the threshold by 2dB will be attenuated by 1dB.
If any signal exceeds the threshold by 4dB will be attenuated by 2dB.
If it exceeds by 8dB, it will be attenuated by 4dB, and so on.
∞:1 However is basically called limiting because the sound cannot exceed the threshold level.
TYPES OF COMPRESSION
There are 2 basic types of compression
·Downward Compression
·Upward Compression
Downward compression: reduces loud signals over a certain threshold while quiet signals remain unaffected.
Upward compression: increases the loudness of sounds below a certain threshold while leaving louder sounds unaffected.
Both downward and upward compression reduce the dynamic range of an audio signal.
To hear compression, one has to first understand. Even as you advance, most times when you load compression up on a track, you might not hear it but feel it subtly because you know what it’s doing there, and why it’s there.
However, on the contrary, there are some modules that do the exact opposite of compression, known as Expansion.
Using the same technique,
What this does is to make the quieter parts of the signal less audible than they already are and the louder parts much louder. Such devices are often called noise gates: Fabfilter Pro G
