You’ve been told to put a compressor on your track during mastering, but you don’t know how to set it up?
Don’t worry, you’ve come to the right place! 🙂
Indeed, while it is true that compressing the mix is one of the usual steps in mastering, incorrect settings can really harm the track in unexpected ways.
Thus, by incorrectly setting your plugins, you can for example:
- add distortion to the audio signal;
- create a pumping effect that, depending on the music genre, can be particularly unsuitable;
- completely crush the dynamics of the track, which would make it flat and dull;
- make the master messy by over-compressing the highs;
- etc.
Through this article, here are some tips to help you avoid the main pitfalls of compression for audio mastering.
Note: if you are not yet comfortable with compression, know that I offer a course on Projet Home Studio that will explain everything you need to know on the subject and thus greatly improve your mixes.
👉 If you’re interested, click here to discover the course.
Why Compress During Mastering?
The first question to ask when you want to use a compressor during mastering is:
“Why?”
Why do you need compression?
If it’s simply because you read it on a forum or a Facebook group, it’s probably a bad idea: how will you set your plugin?
It is quite common for a master to simply not need compression: perhaps the mix has already been heavily compressed and its dynamic range is therefore reduced, or the musical style does not lend itself to it.
That said, often, using a compressor during mastering is something inevitable — but it must be completely dissociated from the use of a limiter, which has nothing to do with it (I’m talking about mastering here, not mixing).
This brings us back to the initial question: why compress?
I think one of the things we need to focus on when learning to use compression effectively is “Does it make the music more enjoyable?”
Jonathan Wyner (David Bowie, Bruce Springsteen…) on compression during mastering
In mastering, there are potentially several possible answers, which will vary depending on the style of music and the attitude you want to give to the mix. So, perhaps you want to:
- add punch to enhance the rhythm of the track;
- reduce the dynamic range for a denser, more “in your face” sound;
- add sonic glue by enhancing the cohesion of the instruments;
- or control the peaks of the signal at a first level to be able to hit a bit harder on your limiter.
In short, quite a few different possibilities.
Before adding a compressor to your master track, it is therefore essential that you define a goal, a sonic direction that your compressor will help you achieve.
Which Plugin Should You Use for Compression During Mastering?
Again, the question is much more important than it may seem.
(Note: I’m talking about plugins, but it’s the same if you want to compress with a hardware compressor.)
If You’re Just Starting…
If you’re new to mastering, I recommend using the basic plugins included in your DAW first.
Some software even includes mastering-oriented compressors, like Ableton Live with the Glue Compressor:
Also, make sure to master the settings of compression. If you are not well acquainted with the concepts of attack or release, it is pointless to risk destroying a mix with compression.
Compressors all sound different
Now that we’ve said that, we must still take into account the fact that the choice of compression plugin will influence the sound. Especially for mastering, since you will be compressing the entire mix and thus affecting the piece as a whole.
Some plugins will be very transparent, while others will be more colored, punchy…
Here is a marked example of the use of different compressors on a piece by Magma Opus titled “11 After Hours” (Facebook – Bandcamp) :
Impressive, right?
If you are having trouble hearing the differences (perhaps because you are not yet 100% comfortable with compression), pay attention to:
- the attitude of the drum hits (kick, snare…);
- how the mix breathes between these main drum hits;
- the impact on the frequency distribution of each compressor;
- or the influence of each type of compressor on the stereo image, which is more or less wide.
The settings here are intentionally extreme, but which version do you prefer?
From one listener to another, the answer will not necessarily be the same… 🙂
In any case, the difference between all these compressors is audible, so choosing the right plugin is crucial — but this choice should always be made based on your compression goal and the style of the music.
If you want to control only the peaks of the signal, you are likely using a fairly fast compressor like FET or VCA.
On the other hand, if the goal (and this is indeed the most common in mastering) is to level the track a bit by adding sonic glue and bringing cohesion to the instruments, then a slightly slower compressor like opto or vari-mu will probably be more appropriate.
From there, it’s up to you to test several options to see which compressor seems most effective to you.
Some plugin examples
To guide you a bit, here are some suggestions for compressors that I personally use (also take a look, by the way, at my selection of plugins for mastering).
Overloud Comp G
Based on a famous SSL bus compressor, Overloud’s Comp G is really easy to adjust.
However, be careful not to push it too hard, as beyond 4 dB of gain reduction (GR), it becomes very audible….
For more info, check out my review of this plugin.
TDR Kotelnikov
If you need a free mastering compressor, this is the one for you.
In addition to offering a great sound, Kotelnikov features a dual compression algorithm that allows you to target both peaks and control the overall perceived level (RMS).
Note that there is also a “Gentleman’s Edition” version, which is paid but includes even more features.
To test this plugin, visit the official site.
Pulsar Audio Mu
Finally, the last suggestion (there are really many others I could make, but I prefer to give a few ideas rather than drown you in tons of plugins), Mu from the French brand Pulsar Audio.
Based on a particularly expensive hardware compressor (Manley Labs Stereo Variable Mu), this plugin will help you give cohesion and punch to your mix, with a true analog feel.
Check out my review of Mu for more info…
How to set a compressor for mastering?
Depending on the goal you want to achieve with your compressor and the track you are mastering, the settings you will apply will vary significantly.
It is therefore impossible to provide a unique, magical setting that would work for all tracks and all genres of music.
Clearly, I would be lying to you if I made you believe that such a thing existed…
The Attack & Release Combo
If your goal is to better control the peaks of the signal, for example in anticipation of the limiter that will come later in your mastering chain, then I recommend aiming for:
- a fast or even very fast attack;
- a fast release (so that the compression stops just after the transients);
- and a threshold high enough to only capture the peaks and avoid altering the rest of the signal too much.
On the other hand, to level the track and gain cohesion, it will be common to have:
- a slow attack (to let the peaks through)
- a fast to medium release (from 200 to 600 ms, let’s say)
- and a threshold slightly lower than before.
The combination of attack and release is crucial for the success of the operation.
For example, if your release is really too fast, you will experience a pumping phenomenon that will make the compression far too audible, far too apparent.
Conversely, if the release is too slow, the mix will lose its dynamics and will be squashed.
Not great.
A good approach is to set the release so that the compressor returns almost (but not completely) to zero before each beat.
No need to pull out the calculator, just set the release of your compressor until the mix sounds the most pleasant — and there you go, you’ve found the sweet spot.
The Ratio
Mastering the temporal parameters of the compressor is essential in mastering, but choosing a good ratio is just as important.
Typically, for mastering, we will use very low ratios, between 1.2:1 and 2:1.
Especially if the goal is to add sonic glue, I indeed recommend starting with these types of values while avoiding too much gain reduction.
If you exceed 2 or 3 decibels of GR, there is probably a problem somewhere…
If this surprises you, remember that normally the instruments and the different busses (groups) of the mix have already been compressed individually.
Thus, compression during mastering usually serves only to add a final layer of polish — and is not meant to replace the mixing stage.
The Before/After Tests
For me, a good mastering should remain subtle.
Also, don’t forget to regularly check that the settings you make on your compressor do not harm the track: do before/after compression tests regularly while keeping an eye on the Gain Reduction (GR) level.
This will help you avoid going too far in the processing you apply to your master.
In Conclusion
To summarize, here are the three things to do when you want to use compression during mastering:
- Ask yourself the question of the goal: “Why do I need to compress this track?”;
- Choose the right plugin depending on whether you need a fast compressor or not, transparent or colored;
- Set the compressor while paying attention to the gain reduction level and taking into account the goal defined in step #1.
And it’s as simple as that.
A large part of the choices you will make are indeed related to your feeling about what you hear: there are no absolute rules, and sometimes you can even do without adding compression during mastering! 🙂
However, there are still situations where compression can help solve specific problems: this is the case, for example, with multiband compression, which can be very useful in a mastering context.