How to EQ

Published: 08-17-2012

EQ is one of the most essential tools in any producer’s arsenal. From the most basic 4-track recorders to high-end mastering studios, engineers will almost always reach for it first, before going in with compressors and other more complex solutions. But for such an important piece of kit, it remains frequently overlooked by many novice producers. So let’s consider the humble EQ in a bit more detail – are you using it properly? Or are you making problems further down the line by not using it at all? Read on…

The main function of an EQ is to help you tweak the frequency balance of an audio signal, to help it sit in the mix better, or show off the important details of the sound to best effect. This means cutting out frequencies that you don’t want, and perhaps boosting frequencies that you do. So far, so simple.

So how should you approach it? Well, if possible, broad brushstrokes should be the order of the day. Cutting or boosting with a sharp ‘Q’ curve can introduce unwanted resonant frequencies around the frequency of the curve, muddying up the sound. You sometimes need a fairly sharp Q if you’re looking to notch out a particular frequency – a ringing sound on a drum kit perhaps, or other odd resonances that shouldn’t be there. In general, however, it’s much better to use wide curves and gentle boosts or cuts; it sounds more natural.

Then, it’s usually good practice to cut out any frequency ranges you don’t want in your signal. Hi-hats frequently don’t need anything below 1kHz, for instance, while many bass sounds don’t need much over 500Hz. Hi-pass and Low-pass filters will serve you well here.

Next, whether you’re looking to boost or cut, start by going extreme. A sharp Q to begin with, a large dB boost (you may want to turn your speakers down a bit here) and sweep the frequency control up and down. Any resonances will scream out at you, any hum or noise will become much more apparent, and the areas where the sound is strongest will also be more obvious. Once you’ve found the frequency you want to work on, turn the Q down a lot, and adjust the boost or cut to taste.

There’s a myth that trundles around the forums suggesting that it’s best never to boost frequencies, rather you should only cut. There’s a degree of sense to this; it’s certainly easier to cut with an EQ. If you’re trying to boost 10kHz on a signal that has hardly any 10kHz in it to begin with, you’ll clearly struggle, and may end up with all sorts of unwanted artifacts or background noise as you try to force the issue. But there’s nothing wrong with a few nudges here and there to accent important parts of a sound if needs be. In general, however, consider that if you’re boosting a frequency on one instrument to help it cut through the mix, you may be just as well turning that frequency down on a different instrument. It stops you getting into the cycle of turning everything up to eleven!

Boosting with EQ really comes into its own when you start getting creative with it, too. If you’re using it for interesting effects, there’s a lot of fun to be had with the humble EQ plug. For instance, a huge frequency spike at 500Hz on a synth patch will give you a ridiculous mid-range honk. Run this into a distortion unit and you’ll get a load of bizarre clipping – then take a cut at 500Hz and you’ll be left with a load of distorted harmonics but without the original honk. Or add a frequency spike, but automate the frequency up and down, to give an effect similar to a resonant filter (but without the filtering). Automating the frequency of an EQ cut, on the other hand, will give a strange flangey effect.

Although this article is about using EQ well, if you can get away without it, you should try to do so. EQ’s will, confusingly, boost the peak level of your signal even if you’re only cutting. Try it with a simple hi-hat – take a sound with no bass in it, then do a low frequency roll-off around 50Hz. You won’t hear any difference, but you’ll notice the level meter on the channel going up by several dB! The science of why that happens is complicated, but this eats up your headroom, so you shouldn’t get into the habit of using EQ just for the sake of it. If you find yourself needing a lot of EQ then it’s usually best to go back to the source; try changing the sound by re-recording with a different mic placement, or swap the sample, or change the synth patch. It’s easier in the long run!

So, to sum things up – if your sound isn’t quite right, see if you can fix it without any effects first. If you can’t, then start with an EQ – cut out any frequency bands that you don’t need, tone down unwanted harshness, and take it from there. Gentle boosts or cuts will usually sound best, and small tweaks to many channels will sound much more natural than large changes to one or two. And one last tip; make sure you constantly use the ‘bypass’ or ‘compare’ button on your EQ plugin to make sure that you are actually improving the sound! Now, with these tips, you should be well on your way to using EQ like the pro’s. So load up that mixdown and see if you can’t give things that extra sparkle…

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