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Let’s assume we have a nasty 808 Sub-Bass the music industry has grown to love.
Let’s note first what a compressor actually does.
A compressor essentially creates an average output signal of sound. It takes the lowest, softest point of the waveform, and the highest, loudest point of the waveform to create somewhat of an average. Before we continue, let’s go over some definitions of the different parts, knobs and settings of a compressor.
The following are essential in your compressor tool box of knowledge.
A level at which the signal is treated (when the signal is several decibels, or db, under the threshold, the signal will pass unmodified. Threshold is symbolized on an x-y graph where the x and y meet).
Any signal above the threshold is brought down to the threshold (gain reduction is controlled by ratio. A ratio of 3:1 means any signal that goes 3 db above the threshold will be reduced to 1db above the threshold. The gain and output at this point have been reduced by 2db).
Attack and Release:
The attack is the period when the compressor decreases gain in response to the increasing level of input signal. The release is the period when the compressor is increasing gain in response to the decreasing level of signal.
Soft and Hard Knees:
This controls whether the bend in the response curve is where, below threshold and above threshold is abrupt or gradual. (Abrupt is hard, gradual is soft. This is normally seen on an x-y graph. Where the x and y meet is the threshold). Soft knees bend where the threshold sits; hard knees turn with an angle.
Soft Knee Hard Knee
Applies equal amount of compression to bout the left and right stereo file.
Due to signal reduction, the output gain allows us to set the desired output level.
Some compressors have High and Low Pass Filters where you can set a high and low frequency to eliminate, but we’ll just assume we’re using a compressor without this option. Below is what the option would look like. Adjusting these knobs will then display a frequency number, which you would then eliminate:
Enough of the definitions! Now, let’s get to some actual compression. Let’s say we have a heavy bass kick that last for 2 bars on a project that is 130bpm, lasting almost 4 seconds. If we look at our signal, it clips at nominal right away and slowly decreases over the remaining 4 seconds. Let’s say our compressor is at -18 db threshold with a 1:1 ratio and a heavy output gain. This will blast our signal to the roof, clipping the signal for around 3 seconds, decreasing on that last second. This compression would be too aggressive, in my opinion. Here’s an example of what the signal would look like:
A nice compression on a bass would be more subtle. We could keep the same threshold, at -18 db with a 3:1 ratio and we would create a very nice signal that is not clipping the life of its signal. A 2.5:1 ratio would work as well. Here is an example of that:
Here’s another example of a nice compression applied to the same bass. We could keep our threshold at -18 db, a ratio of 2:1 and an output gain of 5 db, and we would have a signal that looks like this:
I hope the examples were helpful! Overall, it is suggested that engineers and producers start with gentle compression. Compression can negatively affect your instruments in ways you’ve never imagined. Apply different types of compression ratios, thresholds, knees, attacks and releases, and output gains.
Export the files and listen to them notate the differences, and see what works best for you. Oftentimes, less is more. Try compression on something simple; a vocal, a yell, maybe a loud snare or a kick. Listen to the drastic differences and apply these same practices to your mixes.
Now that I’m done here, I think I’m gonna decompress with a nice cocktail. . . . pun fully intended.