We covered a general guide to compression in my last post. There are many different types of compressor though, and getting to know them and how they work, will help yo ass out, so here we go…
Regular ole’ Compressor
In McDSP’s 4030c compressor above, you can see all of the controls I mentioned in my last post. These are the most familiar and commonly found controls for a compressor, with one notable exception – the Mix control. This control is becoming more popular and is a way to mix the uncompressed signal with the compressed signal – something often referred to as Parallel Compression or New York Compression. Why would you want to do this? Well sometimes you want to compress the heck-a-dee-heck out of your track but in doing so, you realise that you’ve sucked all the life and musicality out of it at the same time. Sad times. Mixing in some of the original uncompressed track will add back in some of the transients and life. Parallel compression is often applied using a compressor on an aux send, but this little mix knob accomplishes much the same thing without having to set up another track.
The Simpleton’s Compressor
If all those knobs are a bit too bewildering, don’t worry! Compression is a very confusing subject, and sometimes you just want to deal with one or two knobs instead of 5 or 6, so enter the 2 knob compressor… the famous Teletronix LA2A pictured was introduced in the 1960s and enjoys a place in most big studios the world over, as well as in numerous plugins.
There’s no pesky attack and release times here – they’re fixed, or at least done behind the scenes. You basically just tweak up the Peak Reduction knob – this is like a threshold and ratio control in one, then use the gain control to compensate for any gain reduction. Simples!
Compressors like this would be chosen for their inherent qualities. The LA2A pictured was quite a smooth compressor with relatively slow attack and release times and was good for general levelling. It also had a lovely vintage vibe to it which imparted character to material: compressors are chosen for their sonic character as well as their features.
It’s entirely feasible to have a single-control compressor which as you crank it adjusts relative levels of threshold, ratio AND gain at the same time.
The excellent (and free) Klanghelm DC1A uses another combination of 2 controls: input and output. Here, there’s a fixed threshold, and the more you crank the input knob, the more compression is applied to the signal as it rises above that fixed threshold, whilst the output control limits or boosts the output, essentially working as the Make-up Gain control. The various controls at the bottom are specific to the plugin and aren’t really commonly used terms for compression control.
Stillwell’s excellent ‘The Rocket’ compressor features in it’s gorgeous interface some other terms for common compressor controls. Here, Compensation is another term for Make-up Gain.
Ratio is applied in fixed steps, 4:1, 8:1, 12:1 or 20:1. There’s also an ALL button to emulate the famous 1176 compressor’s mode where all buttons could be pressed at the same time resulting in MONSTER compression!
This compressor features an Impetus control which essentially allows you to dial in more vintage character or saturation. The side chain button allows you to set the compressor to react to audio input from a channel other than the one the plugin is enabled on. A Detector HPF (High Pass Filter) allows you to filter out frequencies from the sidechain that could trigger unwanted compression. Finally, the Parallel Compression knob functions like the mix control mentioned earlier. The decadence control just oversamples the processing for added sound quality at the expense of your CPU.
Interpreting Foreign Terms
There are more terms used in compressors by different manufacturers / plugin developers. The trick is to understand the core set of controls and interpret the way other controls have been labeled – they often do similar things to threshold, ratio, and gain, it’s just understanding which controls relate to these. If in doubt, there’s usually a manual somewhere!