Setting The Threshold on Compressors

Setting the Threshold on Compressors

The following question came to Mixcoach:

“I have a concern that’s been bugging me for months. It’s about setting the Threshold on compressors. I understand the concept of what a compressor does, but I notice that a lot of people (specifically in tutorials) set the Threshold down way lower than just below the peaks that they’re trying to compress, so in effect, the compressor is always compressing & not just when those unwanted peaks pop up. What’s up with that? I’m also having trouble hearing the effects of the compressor, maybe it’s my ears, maybe it’s the Threshold thing…?”

I am honored to have the possibility to share my way of thinking about “setting the threshold” and “always compressing,” but “…hearing the effect…” is rather an attack-release thing, so I’ll answer it in another post.

Since all the parameters of compressors (number can exceed 30!) are in correlation and different types can give similar results with quite different settings and different results with the same settings, I thought to give a bit wider explanation.

This deeper understanding is needed because if I say, for example, “Set the threshold to -30 dB to treat vocals” I have told nothing, but rather something foolish! Why? Because a threshold is a relative value that depends on the incoming signal level, that is the input gain of the compressor.

Without setting and knowing the proper input gain of the track, it is senseless to talk about any threshold value.

This old Nomad Factory compressor knew that and I am using it in the following video to show you the basics of understanding thresholds and how thresholds depend on the input gain to get the compressor to work at all.

2 knobs Nomad

Many years back, I thought I invented the Spanish Wax when I realized the interdependence and function of gain-fader-threshold-sweet spot and cried out “Eureka! I understand compressors!” I had made a little summary of that “invention” at that time and you can Check It Out Here

Vid 1. deals with Setting Threshold in compressors: 


Types of Parameters Found On Compressors:

For practicing what the general parameters of a compressor can do, you must find one that has these parameters. I call them Easy to Know What It Does compressors.

They generally have 5 knobs: Threshold and Ratio, Attack and Release, and the Makeup gain.

If there is a switch between RMS and Peak  or the type is known, it is an extra joy. In this compressor, the input signal level has to be set properly by the channel input gain.

compressor 4 knobs

– There are also “Hard To Know What It Does” compressors with strange names on their 2 or 30 knobs, and takes some experimenting to learn what they really refer to and exactly do. This extra learning process does not take anything away from their being great sounding, and easy to use, it just takes a little extra time to learn how to operate these compressors.

copressor 2 knobs 2     compressor lot knobs 2

You can see I have avoided mentioning VCA, FET, Optical, OTA, Tube, Feed-forward, Feed-back, Vocal, Bus, Slow, Fast… and so on types of compressors because if you start learning all these at this stage of knowledge, you are lost for ever!

Regardless, all of these hundreds of types have only three things in common:

  1. Gain Reduction (GR, tweaked by Threshold and Ratio) for your       eyes
  1. Wave shaping, sound forming (tweaked by Attack and Release) for your ears
  2. Adding Harmonic Distortion (the character of the compressor) for your   ears


The second question was “Compressor is always compressing

Without knowing or having the tracks in question, or what the intention or use of the compressor, I cannot tell if it was right or wrong.

I can imagine, for example, to get a bass, claps or snare to sound totally consistent, the compressor or limiter can be set a hair lower than the lowest signal level, thus the compressor will be working all the time.

Limiters on individual tracks are sometimes used and can seem like they are doing nothing, and gain reduction only rarely shown. Nevertheless, the limiter is already working, but the inner algorithm has not triggered its led or needle because this visible signal needs maybe 3 dB (like in SSL channel), but it reduces the 0-2.9 dB signals. The sound gets more consistent.

The other case can be when the compressor/limiter is used to perform sound shaping (snare is a good example that I will show in another video post.) In this case, the plugin needs harder settings to get the shaped sound even at its lower signal levels to be consistent.

There can be many other reasons, so please provide us some more details of the material in question.

Your third question  Hearing the effects of the compressorexceeds the Threshold topic, so I will deal with it in another post soon.

Good-bye for now,


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