2:1, 4:1, 20:1… what IS the best compression ratio? Let’s identify how substantially these all vary from one another and identify what is arguably the best compression ratio.
What is Compression Ratio
Before we identify what is the best compression ratio, let’s quickly answer what is the compression ratio.
The compression ratio is arguably the most impactful parameter on an audio compressor. Ultimately this is the setting which determines the DEGREE to which audio is compressed.
We set the threshold on a compressor to identify how much of the peaks of our audio track will be compressed, but how much those peaks get dialed down is determined by the ratio.
As you can see above, with a 4:1 ratio, we’re turning every 4 decibels which EXCEED our threshold into 1 decibel.
With a 2:1 ratio, we’re turning every 2dB which exceed our threshold into 1dB (the 1 never changes, hence the X:1 ratio formula).
So with that groundwork laid, let’s get back to the initial question: what is the best compression ratio?
What is the Best Compression Ratio
No cop outs here… are you ready for it?
The BEST compression ratio is 4:1. Why? Because this is arguably the most average ratio for taming peaks without over-compressing and completely draining and compressing the dynamic range from your audio.
If you’re ever in a situation where you’re not sure which ratio to use, 4:1 is a great place to start.
As I just mentioned, a 4:1 ratio means that every 4 decibels which exceed your threshold, they get turned into 1dB.
So if our threshold is set at -10dB and our audio peaks at -6dB, with a 4:1 ratio, the 4dB which exceed the threshold (10-6=4) will get converted to 1dB. This means that we have 3dB in gain reduction as that new peak is -9dB.
In most of the guides in my complete Compression Cheat Sheet which covers the complete ideal compressor settings for virtually every track in your mix, I recommend a 4:1 ratio.
Exceptions to 4:1 Being the Best Compressor Ratio
There are a few exceptions to the rule of 4:1 being the best compressor ratio.
Light Bus Compression
When you want truly light bus compression, you might want to knock your ratio down to 2:1.
I’ve talked about the wonder that is glue compression for tightening up an instrument bus, vocal bus, or entire mix bus. While I recommend and oftentimes use a 4:1 ratio, occasionally I’ll favor a 2:1 ratio when I want a truly transparent and subtle touch of cohesion.
This is occasionally the case when I’m compressing my entire mix bus chain.
Up Front Vocals or Bass
Conversely, I’ll favor a slightly more aggressive ratio, doubling the normally best compression ratio of 4:1 in going up to an 8:1, particularly when I want to keep a dynamically complicated track present in the mix.
This is the case both on up front vocal compression:
… as well as compression on bass:
8:1 is where you’re really starting to get into the more aggressive ratios for seriously taming peaks and leaving relatively little dynamic range with any peaks which exceed the threshold.
This makes it ideal for keeping a track up front in the mix when there’s not a lot of movement between the quietest and loudest bits in the audio but without flattening it altogether.
Parallel Compression
Speaking of flattening your audio, a 4:1 ratio isn’t what we want when we want to apply parallel compression to a track.
Parallel compression takes a copy of a track and applies extreme compression to it. Between a very generous threshold and an infinite/maxed out ratio, the track essentially remains the same volume throughout its entirety.
While it sounds anything but natural, the flattened audio sausage has a lot of energy to it. The idea is to then blend it in alongside the original “dry” audio at a low volume with subtlety which helps to thicken out that track.
Once again, if you’re not sure what the best compression ratio is, you generally can’t go wrong with 4:1 as has a more noticeable and oftentimes desirable effect than a 2:1 which itself is better for the subtlest of peak smoothing.
Unless you want a lighter setting for compressing a bus or conversely you’re going for a specific instance where you need a much more aggressive ratio like the scenarios I detailed, 4:1 is the best place to start (and oftentimes finish).
Remember once again to grab my free complete Compression Cheat Sheet to see the absolute best compression ratios on a case by case basis along with the rest of the settings necessary to dial in the best compression on every track in your mix.
