Let’s set the record straight! When it comes to mixing, few audio processors are surrounded by as many myths as compressors. We picked 11 popular myths to separate the facts from fiction.
By Craig Anderton
The audio world has enough mythology to make stories about the ancient Greek gods seem like documentaries. Although compressors have been around since the 1930s, there have always been misconceptions about how they work and what they do. Now that the web is filled with unvetted opinions, misinformation can spread faster than ever.
Of course, if you obtain the desired sound from a compressor, it doesn’t matter how you arrived at that sound or what you believe. Still, it helps not to fall for some of the misinformation that can mislead those who are learning how to use compression.
1. The Pros Use Special, Super-Secret “Pro” Compressor Settings
Consider the 4,295,567 YouTube videos that claim to reveal the best, most “pro” settings for compressing various audio sources. If there actually were universally applicable “best” settings, then all these sites would recommend the same settings—but they don’t. What they’re really saying is, “these settings work for me, and they might work for you.” Pros know enough about compressors to edit the settings themselves to create the effect they want.
2. Trust Presets to Do What They Say
A preset called “Female Vocal” might sound good on female vocals. Or it might not. In any event, unless the input signal level is the same as when the preset was designed, you don’t know whether you’re hearing the intended result. A higher-level input signal will cross over the threshold more often and be more compressed than a lower-level signal. (It would help if presets specified the target amount of gain reduction because then you’d have a clue on how to adjust the input level or threshold.)
3. Bringing up the Compression Ratio Turns it into a Limiter
I’ve seen endless debates about this in forums, but with few exceptions, the audio industry doesn’t have “language police” to provide exact definitions of a limiter or compressor. Purists will say that a limiter must have an infinite ratio, while others will say that a 20:1 ratio is, for all practical purposes, limiting the audio. So really, the myth is that there are official, universally accepted definitions—there aren’t. If you need a limiter, use a limiter. If you don’t have a limiter, turn the compression ratio up as high as you can. Simple!
4. If Your Dynamic Range Is Bad, Compression Is King
Not necessarily, because compressors are only one option. Proper mic technique, like moving a singer closer to the mic or further away to compensate for level changes, helps fix dynamic range variations at the source. A plugin like Waves Vocal Rider evens out dynamic range solely by altering levels, so no “pumping” or “breathing” artifacts occur as they would with compressors. Similarly, you can alter a clip’s amplitude envelope (or track automation) to compensate for level changes. And to control only peaks, a limiter might be best, followed by light compression.
Personal bias alert: I often create amplitude changes manually, using gain envelopes, to even out dynamics before even thinking about compression. Then, only a little bit of compression is needed, if at all.
5. Vocals Are in Love with Fast Attacks
That’s often true, but not always. For example, the consonants at the beginning of words won’t sound as defined with a fast attack. For rap music, the compressor’s attack time can make the difference between an effective, intelligible vocal or one that lacks punch.
6. Very Fast Attack Time on Drums = Dead Sound
Lengthening the attack time is one way to preserve drum transients, but often, parallel compression gives a more natural sound—the compressor does what it does best, while the parallel path preserves transients with the highest possible fidelity. Using a transient shaper like Smack Attack on the dry path’s transients can take this even further—either by emphasizing the transients or tightening the drum sound by attenuating what comes after the transients.
7. Above the Threshold, You’re Knee-Deep in Compression
Soft-knee response doesn’t mean that compression starts with a lower compression ratio when a signal exceeds the threshold. Compression starts before audio reaches the threshold, and the compression ratio continues to increase above the threshold until the signal is subject to the maximum ratio.
8. Compression Is Evil Because It Removes a Vocal’s Human Qualities
Yes—improperly applied compression can make a voice sound unnatural. But also, no—because moderate compression can bring up mouth noises, breaths, and other sounds that make a vocal sound more intimate. The goal is finding the sweet spot between intimacy and unnaturalness. Sometimes limiting is a better choice because you can raise the level of the audio below the threshold to increase intimacy, without processing that audio. The limiter simply reduces peaks.
9. Only Ignorant Newbies Place EQ After Compression
Understandably, there is a logical reason for placing EQ before compression. Suppose a kick drum has too much low-frequency energy. If it feeds the compressor first, the compressor will react to the excessive amount of kick and probably add pumping or breathing artifacts. EQ the drums first, and the compressor will react to a properly equalized kick. However, if you’re using EQ to boost a frequency range, the compressor will tend to “undo” the extra level by trying to compress it. To brighten a compressed sound, add EQ after compression.
10. Do Not Disobey the Laws About Which Compressor Technology You Must Use
Some people believe an Opto-based compressor like the CLA-2A will always sound better on vocals. Although some compressor technologies have become popular choices for certain types of audio, don’t ignore other options. An aggressive vocal might benefit from a FET-based compressor like the CLA-76, while an Opto compressor might help soften up a drum’s release for quieter material…or not. Listen, and decide for yourself. As a bonus, if you don’t use the “default” compressor technology, your music may sound more distinctive than the music made by those who follow the trends.
11. Lots of Compression Makes Your Music Sound Spectacular when it’s Streamed
This is no longer true. Streaming services adjust levels to specific LUFS (Loudness Unit Full Scale) values. Songs with the same LUFS values have an equivalent perceived loudness. Overly compressed music will not sound any louder than music with decent dynamics, and may even sound “lifeless” by comparison. Adding some compression to your master to “glue” the tracks together makes sense, but this will usually be a subtle amount applied for artistic reasons. The loudness wars are essentially over…and I can’t think of a more positive note on which to end this post!
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