Nov 30, 2010
Using compression in your mixes is essential – and you need to use it right.
OK, maybe not if you play classical harp or Polynesian nose-flute – but in most genres, using compression to control the dynamic range of instruments in the mix is fundamental.
The problem is, learning to use compression isn’t easy. And it’s not helped by the fact that most explanations start out saying something like “a compressor reduces the dynamic range of it’s input by attenuating signals that exceed a pre-defined threshold”.
Personally I don’t find this kind of description very intuitive, so this post will try and keep things straightforward. So before we go to much further:
What is compression, and why use it ?
Here is the explanation I was given as a trainee:
Compression is used to make things louder
Meaning, you can use it to lift levels in the mix without overwhelming everything else. Most sounds are very “peaky” to begin with, with lots of contrast between the loudest and the softest notes.
Compressors automatically turn down the loudest parts of a sound, and as a result make the average level more consistent. So, you can turn the overall level up in the mix without distorting or “sticking out”.
There can be all kinds of positive side-effects of this process, like making things sound fuller, richer, more controlled or punchier, but at the end of the day it’s all about loudness. Not excessive loudness, but something musically beneficial.
Using a compressor – an introduction
Here’s a fantastic video introduction to compression by Joe Gilder from the excellent Home Studio Corner blog. Check it out, and then I’ll expand on some of the points he makes, and offer some suggestions for achieving specific effects using compression.
Exploring compressor controls
Joe’s video is great, but there’s no substitute for trying this stuff yourself. Try overdoing everything to begin with, so you get a feeling of what the different parameters do. Toggle bypass on and off to clearly hear the effect, but make sure you adjust the make-up gain so the levels before and after are similar for a fair comparison.
Here are some pointers to get you started.
Ratio & Threshold
- High ratios (4:1) with high thresholds give a “hard hitting” sound for punch and thump. Watch out for pumping and sucking, or even distortion
- Lower ratios (2:1) with lower thresholds give softer “warming” or “thickening” effects
- A low threshold with a high ratio will give lots of hard compression and probably sound very squashed and lifeless
Attack & Release Time
- As a rule, avoid short (low) attack and release times, as Joe says.
- Fast attack times can be useful, for softening very spiky sounds (eg. slapped bass) but can remove life and impact if overdone, especially with a high ratio
- Long attack times with high ratio and threshold give the classic “thump-suck-relax” pumping sound – for example, listen to “One More Time” by Daft Punk
- Automatic or “intelligent” settings reduce “unnatural” effects like this, but increase the risk of using too much compression without realising it.
The Golden Rule (of thumb)
If the gain reduction meter doesn’t return to zero several times a bar, you’re almost certainly using too much compression
- because this means that the signal is being compressed all the time, and will probably sound squashed or flattened as a result. Try a higher threshold, and then higher ratio if it’s not doing enough.
Use your ears
Don’t be tempted to compress everything, or to over-compress. The TT Dynamic Range Meter plugin can be a valuable aid to judging how much compression to use, but always listen to the sound before and after compression, and ask yourself these questions:
- Which do I prefer ?
- Have I achieved what I wanted ? (ie. made it punchier, fuller, with more impact & excitement)
- Does the compressed version still sound lively and exciting, or is it too squashed ?
- Does it sound closer to similar tracks I’m trying to emulate ?
- Can I hear more of the quiet details in the mix, or is it getting “mushy” and confused ?
- Does it still sound natural ?
Advanced compression techniques
This post is to help get people started – it doesn’t cover “creative compression”, meaning breaking these rules-of-thumb to achieve a specific sound.
In particular, “classic” or analogue compressors are often driven hard for a distorted sound, or to exploit unusual settings, like the Urei 1176′s famous “all-button” option. To learn more about this, check out this post:
This post is also talking about “single band” compression. Multiband compression is a whole other subject, and I get so many questions about it that I’ve released an eBook and video about using it in mastering. To watch a free 50-minute webinar about multiband compression, click here.
If you found this post useful, you might also like Joe’s excellent video tutorial package “Understanding Compression” – to find out more, click here.