If you're a music producer, then you've probably been bitten by the compression bug. Slamming that audio is a surefire way to give your sounds the heft and punch they deserve, right?
Turns out, maybe not: On the road to dynamic glory, there are many compression pitfalls you can easily stumble over. Here you will learn how to identify common compression mistakes in your mix and discover how you can use compression appropriately to enhance your sound..
In this piece you’ll learn:
How to identify common audio compression mistakes in mixing
Compression techniques that will enhance your tracks rather than hurt them
Alternative methods to using compression in your mix to create a polished sound
1. Only using one audio compressor
While audio compression can help tame loud transients or boost the quiet parts of a signal, using only one compressor to make huge cuts can result in an unpleasant sound. Say you want to achieve more consistent drums so you compress them with -8dB of gain reduction. While you may get the dynamics and level you want from them, overworking your compressors can result in over-processed sounding mixes.
To achieve transparent compression, try serial compression—a technique that uses multiple compressors in succession to get the same amount of gain reduction with a much more natural sounding result.
The way you want to approach serial compression is to focus on making small cuts, with each compressor reducing only about 1-3 dB. So if you want -8 dB of gain reduction, try spreading it across three compressors rather than having one compressor do all the heavy lifting.
Have each compressor serve a function. For instance, the first compressor can have a fast attack time to attenuate the transients. You can then follow it up with one that has a slow attack time to focus on controlling the dynamics of the overall sound.
2. Using audio compression without intention
There’s really only two reasons for using compression:
To even out the dynamics of a performance
To shape the envelope (attack, decay, sustain, release) of a waveform
Unless you’re trying to achieve one of these two things, you most likely don’t need compression.
Unnecessary compression can ruin the dynamics of your mix and potentially compromise the width of processed stereo elements.
As an example, take this mix, off the record America’s Got Talons by the band Adjective Animal. It’s already got a fair amount of luscious compression, both of the dynamics-restriction kind and the character variety. Observe:
"Washing Machine" Mix
Now, here it is after applying some truly terrible bus compression across the whole mix, with the following abusive settings in Ozone:
"Washing Machine" Bad Compression Audio Example
It may sound fine at first, but consider that it’s about 7 dB louder than the original—and anything louder is usually perceived as better. Let’s reduce the settings and give it another listen with the original mix in mind:
"Washing Machine" Bad Compression, Level Matched
Any groove in that high hat has been destroyed. The mix also “feels” narrower, which we can notice by focusing our attention on the guitars. Lastly, there is a fair amount of audible and bad distortion; this just won’t do.
All of this is because we’re adding compression without intention. The mix is already plenty flavorful. If we want to bring the level up 7-8 dB, a much better approach is to raise the fader or add a trim/gain plug-in.
"Washing Machine" Gain Added
Listen to how much better that sounds—yet we as mixers or producers often reach for audio compressors out of habit.
3. Unrhythmic attack and release times
This common problem affects even experienced engineers: audio compressor attack and release times that fight against the groove of the mix.
Your attack time is too fast
In an attempt to keep up with loudness wars, many producers approach audio compression with the intention of squashing transients to create more headroom in the mix. Because of this, some engineers tend to set fast attack times by default so the compressor can apply gain reduction at the onset of a sound. The problem with setting too fast of an attack time, however, is that it completely destroys your transients.
A transient is the high amplitude bursts of energy that occurs during the attack phase of a sound. They are what gives your sound a sense of impact, and if you remove them, you risk losing the punch and energy that brings life to your mix.
To avoid this mistake, slow your attack time down a bit to preserve your transients. You’ll end up with the benefits of audio compression without the downfall of a flat sounding mix that lacks energy.
Your release time is too slow
Release times that are too slow will make compression last longer than it should which can create undesired effects like unrhythmic pumping. Make sure your audio compressor stops compressing before the next transient. Your release time should follow your song’s rhythm and natural envelope.
Your release time is too fast
Conversely, if you set too fast of a release time, your audio compressor will immediately let go as soon as it begins the process of gain reduction. This can also lead to unrhythmic pumping because you’re not allowing notes to ring out naturally.
How to dial in rhythmic compression settings
Improper use of attack and release can take a glorious sound and smother it to death, while proper settings can pleasantly emphasize the rhythm as they tame the peaks.
If you’re learning how to hear compression, one of the first things you want to do when dialing in your audio compression settings is to temporarily set an exaggerated threshold and ratio so you can better hear how the compressor is pumping. With a better sense of how the compressor is reacting to your audio signal, you can fine tune the attack until you like how it’s clamping down and then work on getting the release to a place where you like how the signal returns to its original state.
Let’s use “Washing Machine” again, from the previous example. First, we drop the threshold significantly to -40 dB or so. Given that this is a stereo bus application, we chose a low ratio of 2:1 (if it were an individual instrument like drums or bass and we wanted more gain reduction, then we’d choose a ratio of around 4:1). Now, we can play with the attack and release until we get the bounce we want. This is what we wound up with:
"Washing Machine" Tuning Compressor
The trick here is not to care about pumping at this stage. In fact, we want pumping. We want to love how it's pumping.
Listen for the musical feel the compressor imparts at this exaggerated state, and once you hear something you like, bring the ratio lower and lower—past where you would want it, just to be sure. Finally,swing back to the sweet spot, which in this case, sounds like -20.8 dB:
"Washing Machine" Compressed with Good Threshold Settings
Threshold comes next, with the following tip:
4. Improper thresholds
The compressor’s threshold determines the dB level at which gain reduction starts to take place. Set it too high and you won’t achieve the desirable “glued” sound because not enough gain reduction will happen. Set it too low, however, and you risk boosting unwanted noise and squashing your signal to the point of audible pumping—a characteristic of low quality mixes.
The level at which you set your threshold depends on the part of your audio you want to compress (anything that crosses the threshold gets compressed). There are a couple different ways to find the optimal threshold for your audio source.
You can set the threshold just below your signal’s peaks so you only apply gain reduction to the loudest parts of a signal. This can be useful in a situation where the transients are too harsh and the difference between the loudest and quietest part of an audio signal are too significant. By applying compression to only the loudest parts of a signal, you can tame these sudden spikes to achieve a more consistent overall level.
You can set the threshold lower to apply gain reduction to more of the signal. The lower the threshold, the more of the audio signal will experience gain reduction. This approach is useful for evening out a performance or gluing together a group of instruments.
The first step is to know which one you’re going for. Here’s a drum bus, for example:
Drum Bus Audio Example
On a drum bus, the best approach is option 2: setting your threshold at : the action point, around which the audio begins to bounce or dance in a pleasant manner.
But with this bass part, some of the notes are louder than others:
Bass Audio Example
The solution here would be approach 1: setting the threshold just below the peaks to attenuate the loudest notes, which will result in a more even bass part in the mix.
In either case, you can use the same technique in the previous tip to dial in the right threshold setting.
5. Compressing audio that doesn’t need compression
Remember, the sound in your session might’ve been compressed already—and not just by the engineer. A distorted electric guitar is compressed by virtue of its overdrive. Likewise, most synth patches have already been treated by the producer. They might come to you with compression, but they definitely arrive at your digital doorstep with their envelopes and LFOs finely-tuned for maximum impact. Your compression could negatively impact these parameters. If you're working with a sample, well, it’s probably been processed too.
You might be noticing a theme here—yes, the “don't overdo it on the compression” mantra might be wearing thin—but it’s simply the biggest trap when learning how to tame dynamics.
Training yourself to hear compression
So here’s an exercise to get you speedily over the hump: Take a track (any track will do) and squash it to the point where you can easily hear that it's too squashed. Now study the aspects of its timbre, so that you drill down on what too much compression sounds like. Home in, specifically, on resulting tonal changes that might be unfavorable, or unmusical changes in the feel/groove. Now dial all the settings back halfway or so, and listen again. This time, switch between bypassed signal and instantiated sound when listening. Upon hearing the compressed signal, do you recognize any tell-tales of over-compression? Keep playing around with the ratio of these settings until you start to notice when things sound just right. Then, when you do make the call to compress any instrument, you’ll know exactly why.
By all means, compress. But do so smartly: consider all these variables before compressing, because you could end up fighting against the quintessence of the sound.
6. Placing the audio compressor improperly in the signal chain
Pick an engineer’s brain and you might very well hear an absolute statement like, “I always EQ into my compressor," or, "I always compress into an EQ,” or occasionally, “I do all my cuts, then compress, then do all my boosts.”
All of these tactics are fine, but you have to be the judge of which tactic is best because it depends entirely on the circumstances.
EQ before audio compression
Corrective EQ before compression is usually the best approach when the audio signal has unpleasant frequencies that need to be attenuated or removed. If you don’t remove these problems before compression, you risk amplifying them in the process.
Audio compression before EQ
If you’re starting with high quality sounds, then corrective EQ won’t be necessary. Your first task will be to use compression to balance the dynamics of individual tracks and to glue them together in their corresponding bus channels. Once you’ve done that, you’ll then fix frequency masking issues with EQ.
The order of processing should depend on the processors you’re using, the source material, and most importantly, what you wish to achieve in a given operation. Take the drums we showed off earlier. Let’s say we slap some drastic EQ settings across them:
If we place the compressor before these EQs, it sounds like this:
Compression Before EQ
But if we place the compressor after the EQs, we get a different flavor, because the EQ now changes the nature of which sonic information is slamming into the threshold.
Compression After EQ
Pop quiz: which one sounds better?
- Comp before EQ
- Comp after EQ
- This is a trick question; I can’t possibly know the answer unless I heard it in the mix.
The answer is C!
7. Using multiband as a shortcut to “loudness”
One of the biggest mistakes producers make when learning multiband compression is to apply compression to every frequency band at the same time. Splitting a track into too many bands and processing them at the same time, however, can create undesirable artifacts and phasing issues. So, try to use multiband compression sparingly, as a corrective or problem-solving tool.
These are the two main reasons why you’d want to use multiband compression:
As compression: to control dynamics
As EQ: to control unpleasant frequencies
The main difference between the two is that you don’t add makeup gain when you’re using multiband compression as EQ (to control unpleasant frequencies). In this case, you want to attenuate unpleasant frequencies whenever they get too loud without adding back any gain to compensate for gain reduction.
The takeaway: Pay attention to what multiband processing is doing to your signal—particularly at the crossover points—and you’ll get more mileage out of the technique, rather than complete sonic annihilation.
8. Ignoring your meters
The audio compressor in Neutron has a few helpful meters: the gain reduction meter, oscilloscope view, and waveform display. While you should mainly rely on your ears, it can sometimes be difficult to hear how much compression is taking place or how the compressor’s parameters are affecting the envelope of the waveform. So don’t ignore your meters, because they can help you confirm what you’re hearing and inform your decisions.
How to Read Neutron’s Compression Meters
- Oscilloscope view: gives you a visual representation of how your compression settings are affecting your audio signal’s waveform. This can help you determine whether you like the dynamic range of your signal after processing.
- Waveform display: shows your audio signal’s amplitude over time. This display can help you see the amplitude of your waveform’s transients so you can set an optimal threshold level.
- Gain Reduction Trace: Draws a line that represents the gain reduction applied to the selected band over time. Use the Gain Reduction Trace to monitor and to set the response times (attack and release) and gain reduction envelope applied over time.
- Gain reduction meter: shows the amount of gain reduction applied by the compressor. This helps you determine whether you’re applying the amount of compression you want and informs how to set your makeup gain (you should use makeup gain to compensate for the amount of gain reduction).
Lessons learned about compression
This list comprises what we judge to be the biggest errors in audio compression. You’ll notice that the common theme in most of these involves not understanding the basics of dynamics or not understanding when to use compression. Once you’re ready to use audio compression, however, make sure to stay away from these eight mistakes and you’ll be on track to handling dynamics like a pro.