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Compression Settings for Mastering

Master your understanding of compression settings:

Quick guides to compression settings for instruments:

So, you’ve been trying to master your own tracks and looked up some tutorials on YouTube but when you were done, things didn’t really sound as good. But why is that? It took me a long time before realizing that I was using compression wrong. This might be happening to you too, so in this article, I’ll show you how to properly use compression in mastering to get better results next time you sit down to work.

Do You Need Compression When Mastering? Things To Check Before Compression

Yes and no. You only need compression when there’s a need to reduce the dynamic range of a mix, bring the different elements closer together or improve their relationship with each other, add more punch, or control the balance in different parts of the frequency spectrum.

To make it easier to distinguish which mixes need or don’t need compression, here’s an example:

EDM Mix

EDM Mix

We can both observe and hear in the EDM mix that compression isn’t necessary because everything sounds even and the correlation between instruments is pretty tight.

Acoustic Mix

Acoustic Mix
In the acoustic mix, it’s clear that we need compression because it is a live performance sounds a lot more dynamic and the percussionist accentuates each beat in a different way.

In the EDM mix, compression would destroy the integrity of the mix, the instruments wouldn’t be distinguishable from each other and it’d suck all of the energy from it.

It’s also worth mentioning that the majority of the instruments are synthesized or sampled which makes the whole mix less dynamic because there’s a lot less variation in the intensity of each hit.

On the other hand, in the acoustic mix compression would be necessary to reduce the peak level in a way that transients aren’t audibly affected. In such cases, I like to use serial compression before the rest of the chain.

Things To Check Before Compression

Before going around loading up any sort of processing, there are a few things we need to check to ensure that our track is prepared for mastering.

First, let’s talk about headroom.

There’s a common misconception that mixes need to be peaking at a certain level, and many people say different values, like -6dB, others say -12dB, and the reality is that it doesn’t matter.

In modern DAWs it’s possible to work with a 32-bit float system, sometimes even 64-bit.

In simple words, this feature allows the mix engine to accurately represent values above 0dBFS because it provides extra headroom to preserve all the information without clipping.

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We can see the difference in how a 24-bit (to the left) system interprets the same signal as a 32-bit (to the right).

That being said, it’s a fact that mixes are getting louder by the day, so as you load your mix for mastering it’s convenient to take the clip gain down to -6dB, to prevent overcharging the plugins in our processing chain.

Check the phase

Phase cancellation, no matter how low it might be, will always show up, so you need to prevent it from getting in your way later on in your mastering session.

It’s always good advice to check the phase correlation, especially if you hear the mix being thumpy, muddy, or even hear like it’s lacking frequencies. Chances are that you should probably check the phase.

Check the tonal balance

Sometimes you will find a mix that sounds like it needs compression but it’s just lacking energy in the low mids, has too much low-end, or frequencies are masking each other.

check tonal balance

It’s always good to have your meters close, particularly the spectrum analyser, because if you ever want to sound as loud as everyone else, you need to balance the frequency spectrum properly.

Once each one of these things is in check, now it’s time to set up our mastering compressor.

How To Set Up Your Compressor For Best Results When Mastering

1. Gain Staging

Gain Staging is balancing the inputs and outputs of a signal as it passes from its source through a processor. The idea is to balance the input and output so that the level remains consistent across the board.

This step is particularly important to avoid any unwanted clipping distortion, may it be digital or analog.

Personally, I like to take the input gain down to -6dBFS because it gives me a lot of headroom to work with transparency.

Another reason why I do this is that most analog emulation plugins (which I use a lot) react in a non-linear way depending on the level of the input and -6dBFS usually give me the best point of reference for consistency and best results.

2. Choosing The Right Compressor type

Let’s begin with reality, there’s no such thing as the right compressor for mastering as long as you use it with moderation.

However, depending on what you’re trying to accomplish, there are different tools that will help you get there easier, for example:

Optical compressors

With a soft or emotional track, you’d want things to feel fuller, some times you’d want a smooth compressor with a soft knee that’s program dependent.

If we listen to this track:

It’s almost there but still needs a little push to get to where it needs to be.

Since this is a chill song, it’s slow, and contained, and it doesn’t have any crazy spikes or dynamic jumps, I load an LA2A and set it to compress less than 1dB.

OVERLOUD GEM COMP LA

Here’s the result:

Before
After
Notice how an optical compressor can make things sound fuller because their soft knee and slow release operate in a way that shapes the sustain of a signal and brings it up to be more perceivable.

VCA compressors

For more aggressive music, like rock and metal VCA compressors have been a rule since the analog days. This is because VCA compressors are a lot faster and have a linear-phase reaction and because they make things sound punchier.

For instance, if we listen to this example:

waves api 2500 compressor

The mix needs more energy, the guitars, the lead synth, and the vocals are suffocating the snare drum and make it very hard for us to follow the rhythm. So we want to add punch and create more movement.

In this case, I used an API2500, because it’s my go-to VCA compressor for this type of situation, although any would do just as fine.

My settings were a 2:1 ratio, 1s attack, 100ms release, hard knee, in feedback mode, the tone was set on loud and the stereo image totally unlinked, and these were my results:

Before
After
Although the after sample has prior EQ, notice how the hits of the kick and snare sound more aggressive and snappy than the original version and pops out a little bit more.

Multiband compressors

Multiband compressors are a controverted topic because many mastering engineers recommend using them on every master as a part of the typical processing, which isn’t much of good advice.

For once, multiband compression isn’t something to be taken lightly because the crossovers use high-pass and low-pass filters to split the signals into different bands and this causes phase cancellation around the crossover points.

Multiband compressors should only be brought up on a mastering session if you need to fix the relationship of two instruments that belong to the same frequency range.

01 fig 1 multiband

It’s important for you to know that if you want to use this type of compression on low frequencies, you should use oversampling to prevent aliasing and unwanted cancellation since the lower range is very susceptible to phase shifting.

To give you an example of a situation where a multiband compressor might be helpful here’s an example:

Before
Notice how the lower frequencies aren’t working with each other and the midrange is also lacking energy.
After
Notice how the balance in the lower and mid frequencies is much better and how much rounder it sounds. FYI, I’m only applying 1-1.5dB of gain reduction to each band.

Saturation

Lastly, saturation combines soft knee compression with harmonics, which basically means it simultaneously reduces peaks and brings up quieter details.

The soft knee compression controls dynamics and the saturation makes the fundamental frequencies easier to hear, resulting in a louder and fuller sound.

Try different types of saturation to see which are best for your master. A good rule of thumb is using 3rd order harmonics when you want a brighter sound and 2nd order harmonics for darker.

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For example, in this case, I’m using a warm tube saturation (3rd order harmonics) on the fundamental, and hearing how it changes:

Before
After
See how adding these harmonics creates a wider and louder sound, which also feels more energic than before. FYI, although it sounds perceivably loud, both peak at the same levels.

3. Setting your Attack & Release Times

The release time is one of the most important settings of a compressor because it can completely change the timbre of your signal by attenuating transients or letting part of them pass.

The release time in mastering shouldn’t be any less than 50ms because anything below this time will distort low frequencies because it’ll be faster than the waveform.

Slower release times are great for gluing things together, 50ms is good for transparency.

On the other hand, the attack time is just as important because it determines the amount of compression, for instance, a slower attack causes less compression and is good for a louder signal, a faster attack causes more compression and is good to achieve a smoother sound.

4. Setting Your Ratio Controls

When setting up the ratio of an audio compressor in mastering, the following steps can be used as a general guideline:

  1. Start with a moderate ratio: A ratio of around 4:1 is a good starting point for mastering. This ratio will provide enough compression to make a noticeable difference in the dynamic range of the audio, without being too aggressive.
  2. Adjust the threshold: The threshold is the level at which the compression will start to take effect. To set the threshold, listen to the audio and adjust the threshold level so that the loudest parts of the audio are hitting the threshold, but not exceeding it.
  3. Monitor the gain reduction: The gain reduction meter on the compressor will show you how much the audio is being compressed. As you adjust the ratio, threshold, and other settings, monitor the gain reduction meter to ensure that the audio is being compressed in a way that is suitable for your desired result.
  4. Experiment with different ratios: Once you have set the threshold, you can experiment with different ratios to find the one that sounds best for your audio. Ratios of 2:1, 4:1, and 8:1 are common choices for mastering, but you may want to try higher or lower ratios depending on the audio.
  5. Check the sound: Make sure to listen to the audio to check the sound after you have set the ratio and other settings.

It’s important to note that the settings that work best for one audio may not be the best for another audio and it’s also good to use your ears to make the final decision rather than relying solely on the numbers.

5. Managing Gain Reduction With Makeup Gain

In audio mastering, gain reduction is typically achieved by using a compressor, while the make-up gain is used to restore the overall level of the audio after the compression has been applied.

The process usually involves setting the threshold and ratio of the compressor and then adjusting the make-up gain to bring the overall level of the audio back to where it was before the compression was applied.

It is important to pay attention to the level of the audio throughout the process to avoid clipping or distortion. Aliasing and digital glitches are other possible consequences of not compensating for the difference in gain after the signal goes out of the compressor.

Using Advanced Mastering Compression Techniques

Parallel compression

what is parallel compression

Using parallel compression in mastering is good to add energy to a mix that feels dull or needs more energy. It can be incredibly convenient for the chorus section of the song if you automate it.

One of my top ways to go with this is parallel M/S compression because it gives an awesome sense of movement and stereo expansion and makes things sound huge with just a little compression.

pultec parallel compression settings

My favourite way to do this is by first adding a Pultec EQP1A and boosting the low and high bands at around 5 or 7 and attenuating around 3 or 5 with a broad bandwidth

The Pultec will be followed by a Vari-Mu compressor with a M/S function, I like to use Slate Digital’s FG-MU and compress the middle (upper channel) more aggressively than the sides (lower channel) because it makes the audio sound fuller, thicker, and with a lot more dimension.

Listen to the difference:

Before

After

Listen how it sounds three-dimensional and has much more energy.

Sidechain compression

In audio mastering, side chain compression is often used to create space and definition in the mix by reducing the range of frequencies that are triggering your compressor.

what is sidechain compression

This can be done with some compressors like FabFilter’s Pro C2, which include an internal crossover with a high-pass and/or low-pass filter to prevent certain frequencies from causing compression.

ProC2 sidechain

Typically, this technique is used to filter out low frequencies and compress the rest of the signal more evenly, since low-frequency information usually has the most energy in a mix.

In this particular case, we’ll use the sidechain filter on the compressor to prevent it from being triggered by frequencies below 300hz.

The idea is to make the guitars bigger by compressing the mid and high ranges.

Listen to the difference in sound when the sidechain filter is on and when it’s off:

Off

Notice how the mix falls appart with these settings when the sidechain filter isn’t on.

On

Notice how it sounds bigger and louder, has more energy, and feels more alive after activating the sidechain.

Multiband compression

Multiband compression is not recommended for every mastering session. The crossovers can introduce phase shifting and they can completely annihilate a good mix if used wrong.

However, it’s a good resource to use in specific cases where you need to improve the relationship between different elements of the mix that share similar frequencies and are fighting with each other.

If I need to adjust the envelope of a frequency range, let’s say the low end, I reach for FabFilter’s Pro MB and set it to 4x oversampling and linear phase to avoid any phase issue in the lower frequencies.

Then, I would create a low shelf band for the low mids setting the crossover slope to 12db/oct to have it react more musically.

MB compression in mastering

The individual compression settings depend on the context, but typically slower attack and release, softer knees, and higher ratios are best for low and low-mid frequencies. Intermediate values are better for mid-range frequencies and fast attack and release, hard knee, and lower ratios tend to work better for high frequencies.

Here’s an example:

Before

After

Notice how it sounds more balanced and it stops being so muddy and congested.

The Best Mastering Compressor Settings

When starting to compress an audio signal in mastering, it’s best, to begin with, a moderate threshold, ratio, and attack and release settings, and then adjust them based on the specific needs of the audio.

A good starting point for the threshold would be around -18dB to -12dB:

Threshold-18dB to -12dByou’ll be able to catch some of the louder peaks of the audio signal.
Ratio2:1 to 3:1you’ll be able to achieve some level of compression without making the audio sound too squashed
Attack10ms to 20ms you’ll be able to catch some of the transients of the audio signal and avoid compressing the initial transient of the audio.
Release50ms to 100msyou’ll be able to release the compression quickly enough to avoid the pumping effect while still allowing the audio to sound natural.

Keep in mind that these are just general starting points and you should adjust them based on the specific needs of the audio. It is important to listen to the audio carefully and make adjustments as needed to achieve the desired sound.

So for instance – when a track sounds like its dynamics are all over the place like it has excessive transient information, I tend to reach for an API 2500 and start with a 3 or 4:1 ratio with a hard knee and very fast attack and release to catch the peaks and prevent bouncing.

If the mix sounds like things are too separate from each other and needs some glue, I often resort to a Vari-MU compressor, like the Puigchild 670 by Waves Audio which has a softer knee, slow attack, and relatively fast release to preserve more transient information and glue things together nicely.

FAQ

How Should A Mastering Processing Chain Look?

An audio mastering processing chain typically includes EQ, compression, stereo enhancement, limiting, and loudness normalization. These tools are used to improve the balance of a mix so that it translates properly on different playback systems.

To achieve this balance, we use:

  1. Equalization: Adjust the balance of frequencies in the mix to create a more cohesive sound.
  2. Compression: Control the dynamic range of the audio by reducing the difference between the loudest and softest parts.
  3. Limiting: Increase the overall loudness of the audio by preventing clipping and distortion.
  4. Stereo enhancement: Widening the stereo image to create a more spacious sound.
  5. Loudness normalization: Adjust the overall loudness of the audio to “industry standards”, A.K.A. as loud as any other similar songs on Spotify.

Note that the order of processing steps can change depending on the audio engineer and the material. And sometimes the order of the steps can be changed depending on the desired result.

How Do I Know How Much Is Too Much Compression?

The easiest way to determine if you are using too much compression is to actually over compressing and listening for audible artifacts, such as pumping or breathing, and dial the settings until the artifacts are less noticeable or dissapear. Then, taking down the compression to a reasonable amount.

Another way to determine if you are using too much compression is to check the amount of gain reduction being applied by the compressor. A good rule of thumb is to keep the gain reduction below -6dB. If the gain reduction is consistently above -6dB, it may be an indication that you are using too much compression.

What’s The Difference Between Compression and Limiting In Mastering?

Compression and limiting are both important processes in mastering, but they serve different purposes. Compression is used to even out the levels and make the audio more consistent, while limiting is used to prevent clipping and ensure that the audio stays within a safe level range.

Compression reduces the level of loud sounds and increases the level of quiet sounds to make the audio more consistent, while limiting prevents audio from exceeding a certain level, known as the threshold, to prevent clipping.

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