Getting the right compressor settings is critical to make your music sound more professional, consistent and glued together.
What is the Purpose of Compression
Before we dive deep into how a compressor works and how to find the right settings, it is fundamental to understand the main functions of a compressor. One great habit to keep in mind before adding a compressor to your signal (or any other effect processor) is to ask yourself: “Why should I add a compressor?”
Here are the reasons you might want to add a compressor to your signal:
1- Envelope Shaping
It can be creative, or precise to fit in the mix.
2- Glue a set of tracks together
This works especially well in groups of sounds. Try to group your tracks and apply compression on the group (ex: group all of your drum tracks together). You will notice that your group of tracks is more consistent with the whole mix and the group sounds unified with and musical.
3- Enhance Transients
Sometimes a specific sound (ex: kick) might lack some punch due to not sharp enough transients. Transients are those little peaks at the beginning of a sound that makes it pop. When these peaks are too low in relation to your whole mix, your sound (ex: kick) might sound a bit dull and masked.
You can bring your sound to the forefront and give it the right power by enhancing the transients. This is doable by adding a compressor with slow Attack (ex: 15 - 30ms) and fast release settings (eg: 1-10 ms) with a ratio between 3:1 and 4:1.
4- Tame Transients
Sometimes your Snare, Vocal, or other elements might have aggressive transients that add up and conflict with say your kick resulting in not so pleasant peaks. You might want to tame these transients with a faster attack.
5- Volume Consistency
One thing that makes your whole song well balanced and powerful is track volume’s consistency. Imagine you have an inconsistent vocal that goes up and down by 10 db. This will surely affect your mix badly as the balance of your song will be compromised.
By using the right compressor with a fast attack and a slow release, we get a more consistent volume on the sound. You will notice that your whole song sounds better with more perceived power and consistency.
Now that you are aware of all the reasons involved in using a compressor, let’s dive a bit more into the technicalities.
6- Make space for other elements
Sometimes you might find your bass fighting with your kick for example. As a result, your kick sounds dull and flat. One way of restoring the life back to your kick is by making some room for it by sidechaining your bass. Sidechaining means setting up your compressor in a way where the volume of your bass goes down on every kick hit.
Important Settings of a Compressor
The level at which compression starts taking place. Any level exceeding the threshold will get compressed. How much will it get compressed? This is defined by the Ratio.
The ratio determines how much the volume is reduced by.
Here’s an example:
You place your compressor on your drum group, and it goes 8 db over the threshold. The ratio is set to 4:1 meaning anything over the threshold will get reduced by a factor of 4.
This means our drum bus is now 2db (8db / 4 = 2db) louder instead of 8 db louder.
If we set the ratio now to 2:1 instead of 4:1, our drum bus is 4 db louder instead of 8db.
Let’s say we decide to keep a 4:1 ratio making our drums 2db louder instead of 8db. We’ll need to increase the gain to recover the lost volume.
This is the exact purpose of the Make-up gain.
The attack is how quickly the compressor engages (in milliseconds) after the signal exceeds the threshold.
The release is how long it takes the compressors to disengage after the signal goes below the threshold
This controls how aggressive the volume reduction is done. hard means the reduction is effective instantly after the threshold is exceeded. This works great on rhythmic instruments such as drums and percussions.
A soft knee means the reduction takes place gradually after the threshold is exceeded. The soft knee gives you a more transparent and musical compression. Try it on Synths, Piano, Vocals and melodic instruments.
6. Makeup Gain
Compressing means losing volume. We get back that volume by adjusting the gain knob.
In our previous example where our drums are 2db louder instead of 8db, we would need to add 6db to make up for the lost volume.
How to hear compression and set the right settings
Step 1 - Ratio
Put a ratio of 4:1 in your compressor. Set a fast Attack (and a fast release)
Step 2 - Threshold
Decrease the threshold until you have 10db of gain reduction (Indeed this setting is a bit extreme, but it will help us hear our compression settings with ease before pulling back the threshold).
Step 3 - Attack Starting Point
Set your Attack time very slow (ex: 100 ms)
Step 4 - Release Starting Point
Set your Release time very fast (ex: 5ms)
Step 5 - Decrease Attack Gradually
Lower the attack time gradually until you hear the compression. Decrease the attack time until the transients of your sound become dull and squashed, then back off a little bit.
Step 6 - Increase Release Gradually
Increase the release time until the compressor is breathing in time with the groove of the song.
Step 7 - Adjust Ratio
Now that you hear the compression doing its work in extreme settings, you can back off the ratio to taste.
Step 8 - Adjust Threshold
Same thing here as the previous step. Back off your threshold to taste. If you are using a digital compressor, we strongly advise to back off the threshold until you have between 1db and 3db gain reduction. Why? Digital compressors tend to behave unnaturally in extreme settings unlike their analog counterparts.
Step 9 - Adjust Gain
Set your make up gain until there is no difference in volume between the compressor ON and OFF.
This will help you compare your compressed sound versus the uncompressed one and judge if the sound got better with compression.
Note that our ears have a tendency to judge a sound higher in volume as better. When comparing two sounds, if one is higher in volume, it will be perceived as better even if it is not the case.
5 Tips to make the most out of compression
Tip 1: Keep Perspective in Mind
Most of the time, it is better to adjust compression in your sound while listening to your whole song. Don’t adjust your compression while soloing your track as the result might sound good on its own, but not with the whole song.
Tip 2: Gain Staging
Always make sure to compare the compressed vs uncompressed signal at the same volume. We tend to perceive sounds higher in volume as better. This is definitely the kind of thing that fakes our judgement when comparing a processed version of a sound with its unprocessed one.
Tip 3: Fast Attack on Snare
If your snare is too aggressive, setting a fast attack will help it sit with your kick and the rest of the mix nicely without piercing your ears each time it hits.
In the case where you have a vocal in your song, try to adjust the compression settings of your snare while listening to the vocal at the same time.
Tip 4: Avoid over-compression
It might be tempting to drive your compressor settings to drastic levels, but digital compressors tend to not behave naturally and musically as we push them toward extreme settings.
You will get better results by chaining two or three compressors with minimal gain reduction (1 to 2db gain reduction) than by applying 6 db of gain reduction with only one compressor. The result is in most cases more musical and alive.
Tip 5: Watch your meter
You want to make sure your gain reduction has the time to go back to 0db in most cases. If it’s not the case, this means your threshold is set too low. Bring it up until to make sure your compressor isn’t constantly on.