How to Set Up Bus Compression

In this tutorial you will find out about three different techniques for mix bus compression and learn how to do them safely. These are all techniques I like to use.

Many people I’ve talked to recently have expressed they’re uncomfortable doing bus compression because they’re afraid they might be doing it wrong.

These concerns are valid because the mix bus is a very sensitive place to do processing. It is very easy to ruin the entire mix if you don’t know what you’re doing. But you also won’t learn new skills or unlock new potential if you always stick to your old ways.

I would encourage you to at least give mix bus compression a try, because it has certainly helped take my work to a new level.

And if you discover it’s not for you… That’s good also! Then you know. It’s not something you have to do.

Personally I would find it difficult to work without bus compression. It’s such an integral part of how I like to work these days. I love the sound I get from it and it also helps me keep my gain staging in check. That in turn makes the entire production/mixing process easier.

So, if you’re interested in getting your feet wet with bus compression, this tutorial is for you. If not… You might still learn a thing of two!

How to Set Up Bus Compression Video

Below you’ll find a video version of this tutorial. There’s a lot of information you will only find in this blog post though – they’re designed to go together!

This is the short form version of the video which contains the essential basics. The more in depth, uncut versions of my videos are available through Patreon.

What Is Bus Compression?

Bus compression is the method of applying compression to your master output channel while you are working on the mix. Most commonly, the compressor is set up early on in the project. It sits on the master bus and you mix into it.

Bus compression is also sometimes called “mix bus compression”, “master bus compression” or “2-bus compression”. They all mean the same thing.

Why do it? Bus compression contributes to creating a uniform sound and feel in the mix and across different pieces of music. It can also increase loudness, enhance the groove and add some punch to your mix.

Working with a compressor on the mix bus also teaches you to keep an eye on your levels while you work. If you are coming in too hot, your mix will begin to sound cramped. Mix bus compression will teach you good gain staging practice, which in turn makes the entire mixing and production process easier.

It also has the potential to screw up the mix if not done correctly. Are you completely new when it comes to compression? I would advice to start learning by using compression on the individual tracks first. Become comfortable with the controls. Learn how you can shape sounds with compression. Once you understand those things properly, you’re ready to start experimenting with using compression on the mix bus.

Before We Begin

Before we jump to the actual techniques, an important note:

All compressors are different. To match a 30ms attack time of one compressor, you may have to dial 70ms on another. Especially old analog gear or any plugin versions of them can be really quirky. The numbers don’t necessarily correspond with reality.

With analog compressors, there is often also variation between different units of the same model (this is one of the reasons why different plugin modelings of the same compressor often don’t sound the same).

The ideal settings for a situation also depend on the type of music you are working with. There is no one size fits all solution.

This is why I am not giving you exact numbers for setting up bus compression. Instead, I am giving you something much more useful: Good, safe, general principles to guide you when making adjustments.

Technique #1: “SSL Style” Bus Compression

This is the bus compression technique I go for most of the time in my own music. The idea here is to add a little bit of movement, glue and punch. It can make a static mix sound more organic. And if you do a little bit more gain reduction it can enhance the groove of your track in a very nice way.

How to Set Up “SSL Style” Bus Compression

• Slow attack. This allows the transients to pass through, thus retaining and enhancing the punch.
• Release is entirely dependent on the material. Explore the entire range and set it where you think it sounds the nicest. I usually look for a little bit of bouncy pumping movement. But you may prefer a more natural sound.
• Light to moderate ratio.
• Set the threshold so that the gain reduction returns to zero (or close to zero) between the compression actions. You’re usually looking for maximum of 2-3 dB of gain reduction. In many cases, as little as 0.5 dB is enough.
• If your compressor has a knee setting, it’s worth experimenting with it to find where it sounds the best. The knee determines how quickly the compression kicks into full gear (set by the ratio control) after it has been triggered.
• 100% Wet.

Recommended Plugins for This Technique

The typical plugins to use for this technique are any classic SSL Bus Compressor emulations, such as the Waves SSL G-Master Bus Compressor. In general, this technique will work with most other VCA based compressors and many others. Experiment with different ones to see what works best for you. It will generally not work well with slow reacting compressors, such as most optical units.

Technique #2: Parallel Style (or “New York Style”) Bus Compression

This is a great compression style to use when you want to add some loudness or a sense of weight, thickness and glue. It allows you to raise the RMS level of your mix without squashing the transients.

If you feel like low level details are getting lost in the mix, parallel compression can really help to bring those out more.

Depending on the settings you could also use this style of compression to add punch and movement, but it has the potential to change the sound of your mix a lot when used for that purpose.

In parallel style compression the signal is slammed hard. The Wet/Dry control is then used to mix only a little bit of the processed (Wet) signal into the original (Dry) signal.

How to Set Up Parallel Style Bus Compression

• First set Wet/Dry to 100% Wet.
• Set a fast attack time. Don’t worry about killing the transients. You will dial them back with the Wet/Dry control later.
• I like to keep the release time fairly fast. This way the compression moves a little bit more with the music, contributing to the groove. If you don’t want that to happen, increase the release time.
• Many compressors start distorting with really fast release times and lots of gain reduction. Look out for this. Increase release time until the distortion dissappears.
• High ratio! Don’t be afraid to go all in if you want. Whatever sounds good to you.
• We are looking for a good amount of gain reduction. Over 10 dB is normal. Set the threshold accordingly. The more gain reduction you have, the more low level details you are pulling up in the mix.
• If the compressor you’re using has a knee adjustment, set a hard knee to clamp down on the material properly. For a more natural sound, softer knee will work.
• Finally set Wet/Dry to 100% Dry and dial in a little bit of the Wet signal. Generally 20-30% Wet often works, but adjust to your liking.

Recommended Plugins for This Technique

For this technique you will need to use a compressor that has a Wet/Dry control. Because we are compressing hard, it’s also great to have the ability to dial some bass out from the detection circuit. Otherwise the compression will react to the low end information too much and start pumping.

Eventide Omnipressor is a favourite of mine for this type of compression. It can grab the signal hard and make it nice and fat. I have written a separate review of it, which you can read here. FET-type compressors (especially the 1176) are also a classic for this technique, but you can do it with any compressor that can react to transients super quick.

Technique #3: Shaping Transients with Bus Compression

This is a good technique for dynamic mixes where you just want to control the transients. It can make your mix sound more even and polished.

It can be especially useful to tame the transients a little bit if you are doing more compression or limiting later on in the chain. The processing that comes later will have an easier time dealing with the material after the rogue transients have been tamed. It helps to make your mix louder while maintaining integrity, if that’s what you want.

If your transients are really all over the place though, it’s a better idea to fix it at the source though. Look at your individual tracks and use compression, clipping or limiting to get them under control if needed. You can then apply this technique on the mix bus as final polish.

How to Set Up Bus Compression for Shaping Transients

• Super fast attack to grab the transients.
• Fast to medium release. Enough to hold down the transients, but not more.
• Set threshold so that the compression is only hitting the tops of the transients and nothing else. In most cases you should be seeing only a modest amount of gain reduction.
• Use a very high ratio if you want maximum control over the transients. Smaller ratios will work if you only want to reduce transients a little bit.
• If the compressor you’re using has a knee adjustment, set a hard knee to clamp down on the transients hard or a softer knee to allow a little bit of them to push through.
• 100% Wet

Recommended Plugins for This Technique

FabFilter Pro-C2 is a great one for this technique. It gives you a microscopic visual view into the sound and what the compressor is doing. This allows you to hone in on the transients super precisely. And then it gives you a lot of options for actually controlling the transients.

I like setting the release to zero and using the hold control instead. This allows you to hold the transient down where as using the release will begin to relax gain reduction immediately.

Pro-C2 has adjustable oversampling. Using it taxes your CPU and creates some latency. In a bus compression scenario I would advice to use oversampling if you can, as it will reduce the amount of aliasing that is created as a side product of the the processing.

Combining Different Techniques

You don’t have to stick with just one compressor on your mix bus. I typically have at least two, each fulfilling their own purpose.

I don’t recommend doing that when you’re first starting out. But once you’re comfortable with bus compression, you might find it interesting to combine different compressors and techniques and play off the strengths of each.

You could, for example, use technique #3 to tame some transients first. You could then set up parallel compression (technique #2) to gain a little bit more loudness and weight. And finally, you could use SSL style compression (technique #1) to create some subtle movement and groove.

Just keep it subtle because if you have several compressors in a chain, you might find the sum equals more than its parts.

How to Set Up Bus Compression – General Tips

• All compressors are different. Some also offer lots of eye candy and visual metering options. It can be helpful but it can also distract you from listening. Always focus on the sound.
• Can any compressor be used on the mix bus? I don’t recommend it. You want to make sure the compressor is of good quality and isn’t creating problems you might be unaware of. There are many bad plugins out there that will cause severe aliasing for instance. The integrity of your entire mix is at risk here. I’ve listed a bunch of my favourite bus compressors here: The Best Bus Compressor Plugins.
• Many compressors also EQ the signal subtly. Make sure to listen for this. Is it adding bass or removing it perhaps? Is it affecting the top end? High or low mids? This is one of the reasons why it’s a good idea to mix into bus compression instead of just slapping it on at the end of the project.
• Crank up ratio and/or threshold when adjusting the attack and release times. It’s easier to hear what the compressor is doing when you have more gain reduction happening.
• The bus compressor is often initially reacting too much to low frequencies. This is especially true in bass-heavy styles of music. The low frequency components contain the most energy in your mix, so the compressor reacts to it the most. It can make the compressor unresponsive or sounding uneven or jumpy. This can be fixed by removing some low end from the detection circuit (if your compressor has that feature).
• Always use the makeup gain or output gain in your compressor to match the processed gain to the pre-processing gain. This way you won’t be fooled by the gain differences when using Bypass to do before/after comparisons.
• If the compressor you are using has a quality setting (usually this would be oversampling), I encourage you to make use of it. Do everything you can to maintain the integrity of your mix.
• Read the manuals and get to properly know the tools you are using. Create testing sessions and put them against other similar tools. It will improve your understanding as well as your ears.

Mix Bus Compression – Questions?

Any questions or comments? Leave them below and I’ll get back to them.

You may also want to check out my article about The Best Bus Compressor Plugins.

Now go have some fun and see what you can do with bus compression!