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Newfangled Audio Invigorate (A Bus Compressor Like No Other)

Updated: Dec 7, 2022

Ever since we released Elevate we’ve had people asking us to make a master bus compressor. The truth is, we did try using Elevate’s technology to build a compressor, but it didn’t really do what you’d want a bus compressor to do. You see, a mastering limiter like Elevate is meant to make things sound the same, but be louder. While a bus compressor is really meant to make things be the same level, but sound louder. And to do that we had to take a very different approach. The result is our newest plug-in, Invigorate:

Sound Louder? (the physics part)

What do I mean by make things "sound louder" at the same volume level? Well, there are two physical phenomena that happen only with very loud sounds.

The first is based on the air. Sound is just pressure waves in the air, the louder a sound is the more compressed the air gets… to a point. When the sound pressure level gets very high it becomes much harder to squeeze the air together, so higher levels of sound don’t get quite as much more loud as smaller levels of sound do, this nonlinear behavior is very much like audio compression. The louder a sound gets the more compression gets applied and the less loud the output is. In this sense this overcompression of air sound quite like very fast audio compression.

The second is based on our ear. The pressure waves of sound travel into our ear and wiggle our ear drum - which is the first step in how we perceive that sound. However, there’s only so far our eardrum will travel, and after that it will stop. Alongside the physical discomfort this creates a sound quite like clipping or distortion.

These phenomena are both triggers to our brains that this sound is loud, and that the thing that's making this sound is big, and that we should probably pay attention to it. Does that sound like something you want for your music?

But How Can I Use This? (the audio engineering part)

The truth is, audio engineers have known for some time that compression and overdrive can make your audio sound bigger, more energetic, more exciting, livelier, and in a sense, louder - even when it’s not. (They can even “glue” a mix together, or make it gel - which I’ll have to talk about more in another post.) This is why bus compressors exist and why they're a part of most mix or mastering chains.

But now that we know what a bus compressor can do, and why it does it, how can we design a better one? This was the goal we set ourselves with Invigorate - a product that can smoothly morph between compression and overdrive - and use the best aspects of each type of processor - to give you a big sound.

Let me show you an overdrive effect…

Block Diagram of an Overdrive Effect
Block Diagram of an Overdrive Effect

This works by using an INPUT level to drive an audio signal through a nonlinear CURVE. (It’s called nonlinear because it’s not a straight line.) The output (y-axis) from the curve gets louder just as fast as the input (x-axis) does for small input values, but as the input gets louder this tapers off and the output stops getting as loud. Distortion and overdrive effects can have a variety of shapes, and the shape of the curve changes the harmonics they produce - we’ve created SHAPE, SQUASH, and GATE parameters to control the shape in Invigorate. Most distortion or overdrive effects also have some sort of EQ or filtering before and after the nonlinearity, and changing these has a huge effect on the sound.

A compressor, on the other hand, looks like this…

Block Diagram of a Compressor Effect
Block Diagram of a Compressor Effect

Compressors use a similar nonlinear curve at their core. While you may not be used to seeing it drawn two-sided like this, that’s only because you're used to viewing it in the log domain. The curve in a compressor is usually the result of a threshold and ratio control (and sometimes a knee), but the effect is the same: at low input levels the output gets louder just as fast as the input, and at higher levels the output gets louder less fast than the input - this is what causes the compression.

But the real thing that makes a compressor a compressor is the level detector. We don’t just use the instantaneous input level of the audio to find the point on the curve, we use a level detector that has a slower attack and release time to get an average of the signal level, and to slow down the rate at which we change the audio. We’ve also added an “ANTI PUMP” control which is a high pass filter in the level detector and a MIX control, both of which have become common in compressors.

A limiter is similar to a compressor, but the level detector and curve are set up in such a way that the output of the processor is never able to go above the threshold.

Block Diagram of a Limiter Effect
Block Diagram of a Limiter Effect

Now For the Magic Trick

First I will redraw the overdrive with a dummy level detector circuit that just passes the audio through…

Block Diagram of an Overdrive Effect with Sidechain
Block Diagram of an Overdrive Effect with Sidechain

Then count one, two, three, and poof!

Block Diagram of Invigorate
Block Diagram of Invigorate

We have one algorithm that creates all three effects! (Plus a couple you’ve never had before)

You can turn this algorithm into a compressor, limiter, or overdrive simply by selecting the right envelope detector, but we’ve even developed a SECRET ALGORITHM to allow you to MORPH between them, which is so useful.

Additionally, by using the EQs and more interesting CURVE from the overdrive algorithm we’re able to give the compression and limiting an array of sonic characters which were either previously unavailable or very hard to get. Finally, we also added a SENSITIVITY EQ which allows you to shape the tone into the level detector circuit, giving you a ton of control over where you add the energy and where you keep it clean.

The result is a very powerful processor with a very easy to use UI. I know it looks a little different from the bus compressors you might be used to, but the result is the speed and flexibility to get just the sound you’re looking for. We hope you enjoy it as much as we are.

So, go get the demo here and check it out on your own mixes:

Also, it’s currently on sale:

And if you enjoyed this, you’ll probably enjoy the rest of our blog where we talk about our other products:

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Bobby Balow
Bobby Balow
Nov 22, 2022

Always impressed by your ability to communicate complicated DSP concepts in such an approachable way. Will be checking this plug-in out!

Dec 07, 2022
Replying to

Thank you!

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