Original subtitles

Hello and welcome back to Compression Explained. In this video, we're going to

attempt to understand the most basic fundamentals of compression.

As the title of this video may suggest, we're here to learn what is compression.

And in the most basic sense, a compressor is something that turns down

volume of an input source when that volume exceeds a certain level. You

imagine this as your hand on the fader of an analog channel strip, the volume

fader. Every time the volume gets too loud, your hand moves the fader down and

lowers the volume to control the peaks.

The problem with this is that our hands are very slow, and we can only react to

the compressor in a given time, the time that it takes us to hear the sound,

recognize that it's too high in volume, and turn down the fader. When it comes

to music, that's probably a little bit too slow. We want to deal more in

milliseconds rather than seconds, and that's where compressors come in.

In its most simple sense, a compressor simply listens to the volume of your

incoming audio and reduces that volume when it gets above a certain level. That

level is called the threshold.

And on many compressors, we'll see different thresholds available to us.

Sometimes we'll see a slider. Sometimes we'll see a fader or a knob. Sometimes

it will just be a simple numerical value.

Once the audio volume crosses that threshold, it has to be reduced.

and the amount that it is reduced by is determined by the ratio.

Generally, the ratio will be displayed as blank to 1, meaning that for every 3

.5 decibels that crosses the threshold in this case, it will actually put out 1

decibel above the threshold. If we change that ratio, for every 11 decibels

comes in, 1 decibel comes out. And remember, it's very important that this

above the threshold.

So if we have our threshold set, at, let's say, negative 10 dB, then a peak

coming in of, say, negative 5 dB, 5 decibels over the threshold, with a

5 to 1, will only come out as negative 9 dB.

Since 5 decibels go over the threshold, 1 decibel comes out over the threshold.

That's because our ratio is 5 to 1. We'll be delving deeper into the concept

relationship between threshold and ratio in later videos.

But for the purposes of understanding the basics of compression now, it's

something that we need to know.

Every compressor has two basic elements.

The first is called the detection circuit. The detection circuit is the

of the compressor behind the scenes that is actually listening to your audio and

telling the compressor how much volume the audio has.

The second part of the compressor is the gain reduction circuit.

This is the part that applies the threshold and ratio and our various

and tells the compressor how much volume to cut out of our signal. Now, some

compressors have more sections than this. For example, if we look at this

included logic compressor, after all of our controls that have to do with

detection and gain reduction, we have an output gain stage and even a limiter,

which is a type of compressor that we'll discuss later. The most important thing

to take away from understanding these two parts is that almost every control

that we see on a compressor either has to do with the detection circuit or the

gain reduction circuit, with very few exceptions. If we look at this logic

compressor one more time, we have attack, release, ratio, and knee. Among

four main controls, two of them have to do with the gain reduction circuit, and

two of them have to do with the detection circuit. We'll discuss the

relationship between all of these controls later.

But those are the essential parts that make up any compressor that we're

at. In any plugin, we can simplify this down to the detection and gain reduction

circuit. No matter what types of controls or what type of interface they

that's the main purpose of a compressor. To listen to the incoming audio and

reduce its volume based on our settings.

Let's use our kick drum track to show an example of this effect.

I've soldered out the kick drum.

And I'm going to bring in a compression plugin that we have here on our kick

drum channel.

At the moment, I have some pretty aggressive settings so that we'll be

hear the effect very clearly. Now this kick drum track was recorded in a drum

room. So there's not just kick drum on the track. There's actually some cymbals

and snare as well.

Specifically, what we want to pay attention to is the volume relationship

between the kick drum hits in this track and the hits of the other drums that we

hear. particularly the snare. As we reduce the compression threshold, the

drum, the main instrument that's mic'd in this track, is going to exceed the

threshold and be reduced by our ratio, whereas everything below the threshold

going to stay at the same volume. So our kick drum is going to get quieter, and

our snare is going to appear to get louder in relation to the kick drum.

listen to this in effect.

If I take the compressor threshold any lower than it is right now, we're also

going to have the volume of the snare triggering the compressor.

So at this setting here, this is about as much as we could compress the kick

drum without affecting the snare in the track.

Notice the difference when I raise the threshold.

If you were watching the gain reduction meter during that time, you could see

that as we lowered the threshold, more gain reduction was introduced. Our ratio

was 10 to 1. So the further we lower the threshold, the more volume in this

track is going over the threshold, and therefore more gain reduction is

That's the basic concept of compression.

No matter how much you put into it, the compressor controls what comes out, but

only above a certain level.

As I've said before, in theory, this is quite simple. But in practice, it gets

complicated because when we're reducing the peaks of any given audio track or

mix, we're actually lowering the dynamic range or the range between the lowest

and highest volume points in our particular track or mix. So sometimes

have to do when we reduce the peak too far is add some gain to make up the

additional lost volume. This is often called makeup gain.

So we know that all of the controls in a compressor are designed to accomplish a

broad yet somewhat specific function. We want to reduce the dynamic range.

We want to lower the distance between the loudest and quietest points in our

track. We can either use this to tame certain peaks or to bring up things that

are normally low in volume. And how we use the compressor depends on our

understanding of its various concepts and controls.

Compression has been around since almost the beginning of audio recording, so

the compressors that people used in the past are quite different than the

software compressors that we have available to us in DAWs these days. What

want to do next in the next video is attempt to explain the history of

compression. How did it get started? Why do people use it? What were the early

compressors like?

And how did those things affect the way that we see and we use compressors

nowadays in our software audio hosts?

All of these things are very important to consider when we use a compressor.

I've seen people make disasters with compression by just lowering the

raising the gain, and saying things like, yeah, it's compressed, it's louder

now. But without understanding the fundamental concepts, they're going to

literally suck the volume out of their tracks. They're going to suck the life

right out of it.

by using the very plugin that they thought would help them. We want to

that, and by understanding the history of compression, we get a little better

idea of how to use it. Thanks for watching!