A Little Crush
Shaping A Drum Mix With Compression
Few things are more satisfying than well-recorded drums dialed up fat and punchy in a good mix. Naturally, that all starts with a nicely tuned kit, great playing, and good miking practices, but other factors are involved in achieving a good mix for your recorded drum tracks. The compressor is a powerful tool, which can even out levels (such as an inconsistent kick drum performance) or help certain tracks have more presence. However, if it’s overdone it can totally kill the dynamic life of your mix, removing the sense of depth and dimension and making it sound flat.
But there is more to compression than just reducing dynamic range. If you become familiar with the tool and use some imagination, you’ll discover creative approaches that can actually fatten a drum sound or make cymbal hits blossom. And there’s also a time and a place to get heavy-handed (in a tasteful way) to really jack up a drum sound and give a recorded track something different.
Before we begin goosing sounds, let’s take a quick look at a compressor’s basic functions and standard controls (be it a piece of gear or a software plug-in). A compressor is essentially an automatic volume controller that uses the input signal to control the level of the output. It can make loud sounds softer and bring up the quieter stuff, which is why it’s referred to as a dynamics processor.
A compressor usually gets “inserted” on a mixer channel via the insert send/return jack (or on a DAW by selecting the insert option on the desired channel or subgroup). Typical adjustable parameters include threshold, ratio, attack, release, and make-up gain. Some models have fewer user-adjustable options, such as the dbx163, an older unit that has a lone slider on the front that simply goes from “less” to “more.”
The threshold determines at what level the compressor will kick in while the ratio controls the input-to-output level for signals that go over the threshold. If you were to select 6:1 as your ratio, an input signal that goes 6dB above the threshold would result in an output that is 1dB above the threshold. These two controls work in close association with each other, as adjusting one will affect what is happening with the other.
Attack determines how fast the compressor will react to input levels that go over the threshold. Slower attack times will let a transient through to sound more natural, while a faster attack may squash that initial peak. Release sets the rate at which the compressor will stop compressing once the signal drops below the threshold. This parameter determines the effect the compressor has on the decay of the sound. Make-up gain is used to bring the level back up after the compressor has applied gain reduction to the initial signal. This has the effect of making the quiet stuff louder.
There are several approaches to applying compression to drums. One way is to compress individual tracks on a multi-miked kit. For instance, a snare drum track that was played inconsistently could become more solid with compression. Another way would be to sum the tracks to stereo and compress the entire drum set, which would bring the kit forward in the overall mix. Or you could go for a hybrid approach and compress individual tracks as well as compressing the entire mix. While this is over-compressing to a degree, it is pretty much the basis of the modern rock sound.
And then there’s the angle of using compression as a creative tool to shape and affect the overall sound of the recorded drums – individual tracks, the mix, or both – which is where it becomes exciting. To get a broad range of techniques, we spoke with several recording engineers who agreed to share their drum compression tricks: Steve Orlando, John Scanlon, and George Borden (who are also drummers and percussionists), Timo Preece and Drew Webster (who both delve into electronic music in different ways), and Scott Theakston (a bassist who is a veritable encyclopedia of recording and mixing know-how).
The Conservative Route
Some folks prefer to use only a slight amount of compression to give the drums a bit more presence in the mix while preserving the better part of the original dynamic range of the tracks. Borden subscribes to this camp, opting to compress only the kick drum track. Although, in order to bring the sound of the whole kit together, he’ll then assign the entire drum mix to a subgroup and send that through a compressor with conservative settings. A ratio between 2:1 and 4:1 with a carefully set threshold will push down the peaks a bit, reducing the crest factor so that he can turn the overall level back up with make-up gain. This helps the drums sound fuller and more forward in the mix without being obviously compressed.
Compression will make the transient lower in value in relation to the body of the sound, so it can be used to highlight body and tone. The other side of getting a thicker sound is that the attack may be lacking. To keep the defining transient, you could lengthen the attack time to let the leading edge of the hit through before the compressor kicks in.
Here’s another way to enhance the body and punch of a recorded drum track path while maintaining the dynamics. Rather than using the compressor to make loud sounds quieter for more headroom, so that you can bring level back up, this approach allows you essentially to make the quiet sounds louder with some creative routing, processing, and mixing.
This technique involves taking a copy of the track, sending it through a compressor, and returning the processed version back into an open channel to mix in with the unprocessed track. In order to send a version of the track(s) to a compressor while preserving the original, you could use a splitter, make a track copy in a DAW, or use a subgroup or aux send.