As we start talking about the dynamic processors that we have available, they're going to be our, expanders, gates, compressors and limiters. And all of these have really the same basic fundamental, functional components, in that they're all split up into two segments. we saw with the vocal riding example that you have to kind of listen to the vocal, analyze it and respond to it. And all these devices are doing just that. They have one section that's designed to analyze the input signal, that's called the side chain section, or the key section. And the other section of it, is really just a volume fader, it just brings it up and down. So the first thing I'd like to look at is that kind of, key, or side chain section. Its role is to analyze the signal and calculate the envelope of the audio, and the envelope is kind of a signal that represents the average level at any point in time. And though it seems like a simple thing to do, it actually is kind of complicated, and the, the way it happens is, and you, you've seen this term, I'm sure, is RMS, which stands for root mean squared. And so it's trying to calculate the average level over a little bit of time of that signal. But sound, as we saw, is alternating it's gong up and down and up and down. So if we were just to average out the sound, it would always end up with zero. Because it sends, it spends just as much time as above as below zero. So we need a mathematical process to kind of give us the average level over time. So what we do is first square the signal. We take every sample and multiply it by itself. Any time you multiply something by itself, you get a positive number, right? A negative times a negative is a positive. And a positive times a positive is a positive. So every single sample is multiplied by itself, giving us a compltely positive version of the signal. And then we can take an average. So then we might say that over 30 samples, or 50, or 100 samples, we take an average of it. Which gives us a nice slowly moving envelope, and then we take the square root of that, to get it back into a reasonable range. So we see the RMS all the time, and really all RMS is kind of a average level, of what's going on in the signal. Once we have that information, once we have that envelope we can use it to control the volume fader right? So in our vocal writing example we saw when the signal got loud we brought the level down and that's functioning like a compressor does. So compressor has that volume fader, and whenever the envelope goes up, the volume fader goes down, same thing we were doing with vocal riding. Now when we're kind of programming this, this robot that's going to help us move a volume fader, we have a couple of parameters that we're going to need to configure. The first is at what point does he start bringing down the level? And that's going to be our threshold and all these dynamic devices are going to have a specific threshold. And in a compressor when we're below that threshold the compressor does nothing. It's completely linear below the threshold. Once the emblem gets above that threshold which we can set at any point we like, then the level will start coming down. Now, how much it comes down, is the ratio. The ratio will always be expressed as a number to one, something over one. And that's going to be input to output above the threshold. So, if we have a one to one ratio Above the threshold, nothing happens. Input equals output. If I had a two-to-one ratio, that's saying if the input goes up two decibels, the output only goes up one decibel. So above the threshold, the, the output will be half the level of the input. And we can keep on going up with that ratio. In fact, a limiter is a compressor with a very high ration, usually considered above ten to one to be limiting instead of compression. So they are really the same device a compressor and a limiter, with that one thing changed. So threshold will always need to be adjusted. No matter what signal you're going through. You can't rely on a preset to set your threshold. because threshold has to be related to the underlying musical material. If you have someone playing quite quietly, they'll never hit that threshold. So the compressor won't do anything. If you have someone that's always playing loud, you might always be a thre, above the threshold. Maybe not what you want. So you'll always have to adjust that. Ratio. You're going to adjust for how much reduction you really want the compressor to give you. The other parameters we're going to have to address are how fast that volume fader moves. And that's going to be your attack and your release parameters. They're going to control how fast that robot moves that volume fader for you. The lower and they were expressed in an amount of time, usually in milliseconds. So the lower they are, the faster that volume fader will move. But when I think of attack and release, I like to think of it as they're functioning at the beginning of the sound or at the transcient. Because for a compressor, attack is going to be how fast the volume fader comes down. Once the sound goes above the threshold. Release is going to be how fast the fader comes back up after the sound has gone below the threshold. And they can be set differently. So you can have the robot move the fader really quick down and slowly back up, or move it down slowly and come back up quickly. And all those things have a great impact on the end result of the sound. and the challenge of working with these dynamic processors is all these controls are kind of interrelated. and it really, it really requires a deep understanding of their functionality before you can use them in a musical way. Now, there, those are the main primers you're going to have to deal with of all the dynamic effects. Again, that's threshold, the point at which the dynamic effect starts functioning. Ratio. How much it functions once it crosses the threshold. Attack. How fast the fader moves or the volume will change at the beginning of the sound. When the sound crosses the threshold. And release, how fast the fader moves or the volume changes when the signal crosses back through the threshold. Now there are some other parameters you'll see on most dynamic effects. The first one is knee. And that's going to be, if you can imagine a threshold that is kind of, a, a, a point, right, and we describe this as kind of an on, off procedure. Where as soon as a signal crosses that threshold, the volume starts changing. But, that's really kind of, a not very musical thing. Right. Everything in nature is all curves, and that's what the knee gives us, is as we approach the threshold, we'll start moving a little bit as we get there. So it kind of softens that out and if you have a signal that's crossing a threshold a lot, increasing the knee can be, can kind of soften the effect and make it a little more, comfortable for the listener. We'll also see a look ahead parameter on many dyamic effects. And a look ahead parameter is a delay imposed on the signal but not imposed on the envelope. And what that does is it makes it so that the envelope is seeing a little bit into the future in that the envelope parameter is seeing maybe 10 milliseconds before the volume fader actually gets there. So, if we set that. High, we can actually reduce the level before the transient actually happens. So it can be a really effective limiter or compressor in that it can stop that transient even before it happens. So we've seen the most important parameters of all dynamic effects, and honestly it is difficult. We're going to start now going through individual effects and seeing how we can manipulate the parameters on them. We'll look at. Expanders and gates. And then we will look at compressors and limiters and see how we actually manipulate those perimeters for a musical effect.
