October 10, 2011  

How to Use Compression, Logic Mixing Tips: Threshold, Ratio & Gain

In this classic tutorial from our youtube vault Danny J Lewis defines the terms, threshold, ratio and gain reduction to help explain the basic techniques of compression.

We explore the other parameters in detail on the Mixing Dance Music courses in Logic and Ableton. Take a free sample of those courses here

Danny J Lewis is otherwise known as Enzyme Black, with releases on labels such as Defected, Ministry of Sound and his own imprint Enzyme Black Recordings. He is the head of course development at Point Blank’s online music production school.

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Video Transcription:

The two most common controls on the compresses are ratio and threshold. Both are very important to understand, so we’re going to focus on that in this video. I’ve got the transport here. I’m going to use that as a ruler, and in the waveform itself, I want you to have a look, you see the middle point here, which is silence? Sound radiates downwards and upwards, so basically, volume is radiating out from the center. The top and very bottom is our 0 dB point, so if I do this at the top here, the threshold is a control that is reduced and we bring it down. And then what happens is if anything is above that line, it’s turned down. If I flip this around, this would show you what would be turned down. The threshold comes down from zero and minus dB figures, and then once the signal goes above that threshold, it’s turned down, and that’s what the ratio is.

What we’re going to do is we’re going to come to the compressor. This is placed as an insert, and I’m going to give you some settings to use to start off with so that you can learn this. Once you’ve understood this, you might want to make tweaks to these. The ratio we’re going to take to 5 to 1, and also, the [knee] we’re going to take to hard knee, going to take the compressor threshold to 0. We’re going to stick with the RMS, but what we’re going to do is take the gain down. I’m going to explain what these are and you’ll understand why I’m doing what I’m doing.

At the moment, our threshold is 0, so let’s take our fake threshold to the top, and as I reduce this, imagine this line is coming down. We’re going to get to a point where if anything’s above that line, it will start flashing down, gain reduction, on the meter here, and it will show us how much it’s turning the volume down. Let’s take the threshold up, let’s try and mirror this as we go, so let’s get this looping. Bring it down, the note compression tool, you don’t see any gain reduction at the moment. Let’s bring it down. There you go. You can see at certain points, the volume is turned down. Let’s try and replicate what’s happening here.

Anything above that line is being turned down at a ratio of 5 to 1. What we need to do is to make a note of the amount it’s being turned down, so if you have a look here, the maximum value so far is about -2, -3, there we go. In order to make up for the fact that we’re turning the signal down, we use the gain here, we add 3 dBs. Now what’s happening now is that the signal is being evened out. I’ll bypass it, and have a listen. Let’s come back, let’s put the compression on. Did you hear there was more energy on the ‘let’ of the actual performance? Let’s come back again to bypass. Once again, with the compression on.

We’ve got more energy in the performance. It’s balancing it out so that means it’s easier to compete with the actual backing music. That’s the introduction of the threshold and ratio. I would suggest you guys all do that, but I’m going to show you how things could be if it was actually done wrong, all right? The kind of arguments about what’s right or wrong could probably go on until the end of time, but the aim of the vocal is to try to keep things reasonably natural. Let me show you how things would sound if they were not natural. If we increase the ratio really high, for example, let’s take it to about 10 to 1. Let’s bring the threshold down. Have a listen to this. What I do is I’ll compensate for the reduction, going about 15.

So even further down. I’m going to take this so that the breaths are being reduced as well. Can you hear how all the background noise has really come to the foreground now, as well? And just to emphasize this, I’m going to make the release really fast. This is very unnatural. If you go through that exercise with a variety of different sound, get used to the way that the compressor is working. The problem with Logic’s compressor is that the default settings are not there to help you learn.

I recommend when you’re learning compression, take your threshold to 0, gradually bring it down until you see the compressor start working. Then, increase the gain to compensate the amount it’s actually being reduced.

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