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In the world of sound engineering, compression stands as an essential but often misunderstood technique. Compression however, isn't just a tool; it's the key to sculpting your sound. In this article we tried to give you a comprehensive guide to demystifying compressors, equipping you with the knowledge and confidence to use it effectively. We'll explore its intricacies, reveal its creative possibilities, and provide practical tips to make your music production shine. Whether you're a novice eager to explore its potential or a seasoned producer seeking deeper insights, this article takes you on a journey to unravel the enigma of downward compression.

What is Dynamic Range and what do compressors do?

Dynamic range is understood as the distance or gap between the loudest and the quietest part in your music. We can measure this distance in levels using decibels (dB).

Dynamic Range of a Waveform

So, what's the deal with compressors, and what do they really do? Well, they work their magic by reducing the overall dynamic range of your audio. In simpler terms, they narrow the gap between the super loud and super quiet parts of your track, making everything sound more consistent. You've probably drawn automation curves for your track's volume before – if so, you’ve likely unknowingly acted as a "human compressor". You tamed the loud bits and boosted the quiet parts. But why use a compressor? Here are three good reasons:

  • It's a huge time-saver (no need for manual curves).
  • It's way more precise than your manual fiddling.
  • it introduces some interesting sonic characteristics that are unique to specific compressors

Before we dive deeper into compression, let's explore the world of dynamics.

Understanding Dynamics and the Need for Compressors

Now, let's get to the basics. When we talk about audio, "dynamics" is all about how the sound's volume changes. We can look at dynamics in two big ways:

Macro Dynamics:

These are the large changes in volume, like the difference between a verse and a chorus. You can control these easily by drawing automations since you're affecting entire song sections.

Macro Dynamics of a (whole) Song

Micro Dynamics:

These are the tiny, quick changes, like how the volume of a single snare hit evolves from the initial impact to its fading tail. Micro-dynamics are tricky to handle manually because they happen so fast. And here's where the compressor steps in to save the day!

Transients are the very first point of a sound's lifecycle.

Now, let's not get too sidetracked, but there are different ways to play with dynamics:

Downward Expansion

It turns down the quiet stuff (making it even quieter). For example, it's great for reducing bleed and noise. A Gate for example is an extreme version of Expansion. 

Downward Compression

This one does the opposite – it tames the loud things and makes them quieter.

Upward Expansion

It cranks up the loud stuff even more.

Upward Compression

And this one brings up the quieter parts.

The first two are the most common, and today, we're going to dive into Downward Compression. Before we explore how these processors work, it's essential to understand a sound's "journey". Different sounds have different "lifecycles". For example, a snare hit (short) has a different lifecycle than an ambient synth pad (long). How a sound's volume changes over time is called its "envelope" or, in fancier terms, "ADSR".

How to use compressors in your music - The Key Parameters

Although there are always exceptions, most compressors share a common set of parameters. Understanding what each one does will allow us to use compression in our music more easily and exactly how we want. 

The Attack and Release Times

So, now that we know what compressors are and why they matter, let's dive into the nitty-gritty. Most compressors, with some exceptions, come with a bunch of knobs and buttons that might look confusing at first. But don't worry, understanding these parameters will make your life easier when using compression in your music.

The "attack" of a compressor, measured in milliseconds (ms), tells you how fast the compressor jumps into action when it hears a loud sound surpassing a certain level. It's like the reflex of your compressor.

Attack Time of an Ableton Compressor

The "release" is just the opposite; it's how long it takes the compressor to relax again and for the sound to return to its natural state after it's been compressed.

Release Time of an Ableton Compressor

Now, here's a pro tip: For your release time, go as short as you can without causing the dreaded "pumping" effect. This is a typical mistake, especially when dealing with low-frequency sounds like kick and bass. On the other hand, if your release time is too short, you'll hear the compressor doing a weird back-and-forth dance, creating a "breathing" effect. Not ideal.

Here's another one: When you're just starting out, set your attack and release times first. They determine which part of the sound you want to shape. The other settings that come after, tell you how much you can affect and fine-tune the sound. This order makes it easier to get the result you want.

A visual image of sound level when passing through a compressor.

The Threshold

The "threshold" on a compressor, expressed in decibels (dB), is like a height limit that we set. It determines the sound level at which the compressor kicks into action. The compressor will start working, the moment a sound exceeds the limit you've set. You can set the threshold to target specific moments in your music. If the snare in your drum groove is just too darn loud for example, you can adjust the threshold so that it's set low enough to catch the snare hit but high enough to leave the rest of the drums untouched. The trick here to raise or lower the threshold slowly until the meter only reacts to the snare. 

A visual image of what happens to a sound wave when passing through a compressor. Depending on how the threshold is set.

The Ratio

Once the compressor detects that the sound has crossed the threshold, it starts to work its magic by turning down the volume. How much it reduces the level is determined by this thing called the "ratio."

Example: Let's say the input signal is hitting -16 dB and you've set the threshold at -20 dB with a 2:1 ratio. Here's what happens: The output signal gets lowered down to -18 dB. Why? Because the input crossed the threshold by 4 dB and the 2:1 ratio sliced that value in half - down to 2 dB. That's how you ended up with an output of -18 dB.

Different Compressor Ratios

A quick side note: A "limiter" is basically a supercharged compressor because it has an 'infinite' ratio - think 10:1 or even more. While a regular compressor, especially one with a lower ratio, gently controls peaks, a limiter slams the brakes on any sound that tries to go above the threshold, also known as its "ceiling." That's why it's called a Brickwall Limiter. 

The Knee

No, it's not an actual joint but an important setting on your compressor. The "knee" determines how the compressor eases into its job of reducing the volume. Most compressors give you a choice between a "soft" or "hard" knee, and some even let you find a sweet spot in between. The knee affects how the compressor treats your sound when it crosses the threshold. A "hard knee" starts the gain reduction suddenly when the sound goes above the threshold, while a "soft knee" introduces the reduction more gradually as the sound gets closer to the threshold.

Here's the lowdown: If you want more noticeable and punchy compression, lean towards a hard knee with fast attack and release times. But if you're going for a gentle and subtle touch, opt for a soft knee with slower attack and release times. The knee setting can be a useful and nifty tool to give your music the right flavour.

The Makeup Gain

When we think of compression, we often picture making our music louder. But here's the kicker: Compression, by its nature, actually turns the volume down. 

Makeup Gain of an Ableton Compressor

The Makeup gain lets us boost the level back up after the compression has done its work. Because we've tamed those nasty peaks with our favourite, we can now crank up the overall volume - don't exaggerate though - without causing any clipping. Again: Don't overdo it, always try to match the original level. We cannot say it too often: Don't make it louder than it was. 

Popular Compressor Types

Compressors come in various shapes and forms, each with its own unique characteristics:

1. Tube / Vari-Mu

Tube compressors have been rocking the music scene since the 1950s. They're known for adding warmth, color, and harmonics, thanks to their tube gain stage. With slower attack and release times, they give your sound that "vintage" vibe that's hard to replicate with other compressors. The UAD Fairchild Tube Limiter Collection, a favourite of legends like the Beatles and Motown, is a top-notch emulation of these classics.

Example: A Fairchild Compressor

2. Optical

Optical compressors came into play in the mid-1960s. They operate using light and optical cells. As your sound gets louder, the light intensifies, signalling the optical cell to reduce the output. These optical compressors are versatile and suitable for various sound sources. The Teletronix LA-2A for example, is a respected optical compressor equipped with a tube for additional gain. It's a popular choice among audio professionals.

Example: A Teletronix LA-2A Compressor

3. FET (Field Effect Transistor)

In the late 1960s, the world of electronics saw a revolution with the birth of transistors and solid-state technology, replacing vacuum tubes. FET compressors bring that tube-like sound with the speed and reliability of transistors. They're perfect for adding punch to drums, vocals, bass, guitars, and more. The 1176 , the very first FET compressor, has rocked the music world, from Led Zeppelin to Michael Jackson.

Example: An 1176 Compressor

4. VCA (Voltage Controlled Amplifier)

Becoming popular in the mid-1970s VCAs are the cleanest and most transparent of the classic analog compressor types. They deliver a "punchy" and fast tonality. Whether you're looking for the smooth compression of the SSL G Bus or E Series or the gritty attitude of the dbx 160, VCA compressors can add unique character to your drums, guitars, and overall mix. The SSL G Bus and E Series, in particular, are known for their transparency and flexibility.

Example: An SSL G-Bus Compressor

Compression Tips: Making Your Sound the 'Cool Kid' on the Block

So, here are six super-secret compression tips that will turn your sound into the neighbourhood rock star. Master these, and you'll feel like a pro with this magical, sometimes perplexing tool.

1. Don't Go Overboard:

Think of compression like seasoning in your favourite recipe. Instead of dumping the entire spice rack into your sauce at once, sprinkle it modestly at different stages of your music journey – recording, mixing, and mastering. This way, your music will have a nuanced flavour more delightful than an over-spiced stew.

2. Picking the Right Tool:

It's like choosing the right superhero for the job. Use compressors with slower attack and release times on mellow sounds like vocals. For louder, harsher and faster instruments like drums and percussion, unleash the fast and furious FET and VCA compressors. 

3.  Keep it Simple:

Before you go all-in on compression for your entire mix, start with individual tracks and subgroups. It's like learning to ride a bike with training wheels before joining the Tour de France. Save the multiband-compressors and limiters for when you're ready to pedal faster.

4. Get to Know your Compressors:

Hardware compressors (and even some types of VST emulations) can be as pricey as a solid gold bathtub. But here's a secret: Google is your friend. If you find your dream compressor's parameters, you can set them into your DAW's stock compressor - it might not have the exact same characteristic, but it sure gets the job done.

5. Embrace the Madness:

Sometimes, you've gotta let your inner mad scientist out. Try dramatic compression as an effect. Squash that clean guitar track or give that snare drum some hot sauce make it stand out. Who knows, you might discover a new sound!

6. Louder Isn't Always Better:

It's human nature to think louder is better, like turning up the volume on your favourite jam. But here's the real scoop: Always, always, always match the output level with the input level. That way, you'll really hear what the compressor is doing to your sound, instead of just tricking your ears into liking the 'louder' version.

The Bigger Picture: The Importance of Compressors

Understanding compression isn't just a neat trick; it's a cornerstone in the world of digital music creation. It's a versatile tool that impacts everything from sound design to the final mix. But, like a double-edged sword, it can either be your musical ally or your worst enemy if used irresponsibly. 

This guide equips you with the basics of compression, demystifying its key parameters. However, becoming a compression maestro is like mastering an instrument – hands-on practice is key. Reading articles or watching videos can't substitute for getting your hands dirty in your DAW. So, it's time to unleash your inner audio sorcerer and experiment with those knobs and sliders. Not only will it save you time (and life is way too short for tedious tasks), but it's where the real magic happens.

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