In this video Julian Rodgers highlights 5 ways the features and UI of FabFilter’s Pro-C2 compressor can help you learn compression, and use compression better!

Whether you’re a novice or a veteran we never stop learning about compression. How something as complex and variable as audio interacts with a compressor is something which is broadly predictable but when you zoom in on the detail things can get interesting.

While there’s a lot to be said for strapping a hardware compressor across a pair of inserts and just listening and tweaking, the tools available today offer visual feedback which goes far beyond a VU meter or a ladder of LEDs. When it comes to visual feedback the best example we can think of is FabFilter’s excellent Pro-C2 compressor. If you’re learning or teaching compression this is a tool which can help.

Here are 5 ways it can help:

1 - Gain Reduction History

All compressors offer an instantaneous gain reduction meter and being able to watch the action of the compressor while listening to the results is the basis of learning to hear the effect of compression. Gain reduction history - a plot of the action of the compressor over time, presents that information in context with the waveform in a way which makes the response of the compressor clear in a different and very useful way.

The really significant thing about this is that it presents the important parts of the action of the compressor as the most interesting part of the compression. The attack and release phases are the bits where the interest lies in a typical compression setting. If you are watching a row of LEDs on a GR meter it might be understandable to assume that more compression (more lights) means there is more to hear but it is while the gain reduction is changing which is of most interest. A flat line of heavy gain reduction on the history trace isn’t as “interesting” as the curves to and from that gain reduction. Pro-C2 shows the changes in gain reduction in a way which attracts the attention they deserve.

2. Audition Triggering

The cool bits of compression are in the attack and release phases. To really fine tune what those crucial settings are doing, and to understand how they interact with the threshold, the Audition Triggering button allows you to listen just to the audio which is being changed by the compressor: The parts of the signal which occur above the threshold and within the ranges of the attack and release times.

As an experiment set up the compressor with a long-ish attack so the transient of a sound can pass through unattenuated. Set it by ear and then hit the Audition Trigger button and tweak that setting. Were you letting the whole transient through?

3. Auto Gain

The most common mistake made by people setting up compressors is to set up a compressed sound which is louder than the uncompressed sound and, as we are all naturally biased to prefer louder sounds over quieter ones, we convince ourselves that our compressed sound is better because it is louder. Manually adjusting the makeup gain to make sure that we are comparing sounds of equal perceived loudness is really important but takes time.

The Auto Gain button in Pro-C2 handles this level matching automatically, and so well that I almost never have to adjust it manually. The time saving is huge and level matched compression is the only way to make sure you are actually improving your mix with your use of compression.

4. Meter Scale

After the “louder is better” trap mentioned above, that we’ve all fallen into, the next biggest pitfall to avoid when compressing is over-compression. We all tend to mix with our eyes to some extent and if you have a gain reduction meter which is barely moving it’s easy to believe that you are compressing gently. However what a meter is showing does depend entirely on the scale it’s set to.

Pro-C2 allows you to set the vertical range of the level meters and gain reduction anywhere from 90dB to 9dB and the setting you choose changes how dramatic your compression looks. Unless there’s a reason to do otherwise I tend to leave Pro-C2 set to the highest (smallest) setting I can. This makes the compression “look” as dramatic as possible. I should be (and am) using my ears but the visual does influence as well as inform us. if I’m overcooking the compression I’d like my meters to let me know. Scaling the meters helps with this.

5. Display Button

Having spent so long talking about how visual feedback can inform but also influence and even distort our perception of the sound, this last point is to switch it all off. The display button hides the waveform and gain reduction history, not to mention the excellent knee display. By reverting back to something more like a conventional compressor you have to rely on your ears more and, while it’s great that FabFilter have large, resizable GUIs, by switching it all off you save a lot of screen space allowing you to have multiple plugin windows open at the same time.