Unless you’re already a master of compression, beware of the Makeup switch.

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What it does is automatically apply “makeup gain” to the signal. As the Threshold and Ratio are adjusted, the compressor determines how much gain reduction it is applying and then raises the output signal up by that amount.

This may seem totally counter-intuitive, but in fact there are many compressors that work this way. Let’s say you’ve got a signal that’s peaking at 0dB. If you reduce the peaks of a signal by 6dB,it’s now peaking at -6. If you then raise it back up by 6dB, it’s once again peaking at 0, but the average loudness has been increased. By making the dynamic range of a signal smaller, you can raise the overall volume without driving it into clipping.

There are two problems, however, with keeping the Makeup switch on. First off, there’s the problem I brought up yesterday – it’s harder to get your ears to zero in on exactly what the compressor is doing when it starts adding gain the moment you pull the Threshold down. There are some cases where you’ll end up thinking that the compressor is making your signal sound better, but what you’re really responding to is the fact that it’s getting louder.

Sometimes the signal doesn’t really need the amount of compression you’re applying – instead it just needs to be made louder or clearer in some other way. It’s not that adding gain with compression is bad, it’s that it’s bad when what’s really needed is a simple change in volume, EQ or even panning to make it pop out a little more.  The right amount of compression helps a track sound awesome; too much will make it sound flat and squished.

The moral of the story is to get good at using Compressor with Makeup turned off. This way, all it will do is reduce peaks. Then, you can manually use the Output control to add gain if you want it.

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Use the process described in this EQ tip to roughly match the volumes between the processed and unprocessed signals, and you’ll get a much clearer understanding of how it’s affecting your sound.