How to use compression for live vocalsMark Ellis
Compression in the studio is an incredibly useful – if often overused – tool. But it has significant benefits on the road, too.
Despite this, a compressor is often the one thing missing from a band’s toolbox; they’re all too easily dismissed as an unnecessary expense and one that requires far too much time and attention in order to fully benefit from.
In reality, compression is the glue that holds any mix together, be it live or recorded within the confines of a studio. It hunts down inconsistencies, mellows the stuff that’s trying to should too loudly and offers the audience a far more balanced and pleasing sound.
Look no further than radio for the benefits of compression
If you’re new to compression, think about radio. Broadcasts in that medium are remarkably consistent. The DJ’s voice is powerful yet not overbearing; the dialogue fluctuates little in volume but still somehow manages to sound natural. Whispers can be heard and, if someone shouts, it doesn’t force you to jump out of your chair.
That’s a compressor at work. It reduces (compresses) the loudest sounds by reducing their dynamic range, (which is simply the variation in loudness they are capable of emitting). Without a compressor, the sound engineer would have to constantly increase and decrease levels in order to account for natural changes in volume.
And we all know how annoying that can be.
Over-use and creative compression
Unfortunately, compression can be used far too flamboyantly, too. Cranking it up simply drains any sound of its character and creates nothing more than a very artificial-sounding mix.
It should also be noted, however, that modern music producers sometimes use compression creatively. The method of ‘side-chaining’ is a great example of this, as it enables producers to give certain sounds the effect of ducking in and out of the mix, in time with the music (i.e. as though their level is being reduced and increased rhythmically). You’ll hear it most commonly in dance music (have a listen to the strings on the intro of Call on Me by Eric Prydz), but side-chaining is also used to stop low-end elements from clashing by automatically reducing the level of a bass part as a kick drum hits.
Step-by-step mic compression guide
As much as we’d love to show you how to be creative with compression and treat it as a toy (it’s fun, after all), in this post, we’re going to get all sensible and look at how to compress a vocal properly in a live situation.
Good news: it’s really straightforward. This mini guide assumes you already have a compressor either connected to your mixer or directly built-in.
The first knob you’ll encounter is the threshold dial. This is the control that defines exactly when the compressor will come into effect and does so by enabling you to choose the volume at which it kicks in.
The threshold can usually be set anywhere between -40db to +20db. Treat this knob with kid gloves; the amount you’ll need will depend on the vocalist and the input sensitivity on the mixer channel. Go slowly until the needle on your compressor starts to show the minutest of reactions.
Once the threshold is reached, the compressor needs to know how much gain reduction to apply. This is where the ratio comes in.
A 1:1 setting will do nothing to the vocal, but the more you turn the dial, the more drastically the volume will be reduced when the threshold is hit. You want the audio to exceed the threshold occasionally in order to ensure a natural mix, so be careful with this one, too.
3. Soft knee
Compressors shouldn’t be noticeable, and some offer a ‘soft knee’ dial, that smooths out the threshold transition. Only use this if the vocal starts to sound unnaturally-compressed and – again – be careful.
4. Attack and release
Some compressors will give you individual control over attack and release while others will handle this element automatically. If it’s the latter, you’ve got one less job to perform, but if you have two knobs on your compressor labelled ‘attack’ and ‘release’, you’ve got a bit more tweaking to do.
These two vital aspects of compression dictate how fast the vocal is compressed when the threshold is passed in either direction; attack specifies how quickly to react when reducing gain, while release specifies how fast the gain reduction should be reset.
Getting this stage right is tricky, but the meter is your friend. If it seems to be labouring the point whenever compression kicks in, try adjusting both the attack and release until it reacts more smoothly. And use your ears! Does it still sound unnatural? Then make a further adjustment!
Have fun with compression. It should be the final stage of any vocal mix and will ensure a natural sound that draws in the crowd.
Just be careful with those knobs!