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How to Use a Parametric Equalizer

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The equalizer is an important piece of audio technology. As one of my Conservatorium tutors once said, when you’re setting up a session, adding an EQ as the first insert is almost as essential as creating the tracks themselves. Studio audio isn’t about capturing every frequency of every sound: it’s about creating a polished track that highlights the best of each instrument. Let’s take a look at this basic yet widely misunderstood tool, the parametric EQ plug-in.

The Parametric EQ

Let’s take a look at the plug-in itself. I’m using the one that comes with Pro Tools LE, but you can use any parametric EQ in any DAW with these steps:

There are several controls you’ll be using all the time, but three you’ll be using the most. We’ll cover those three in a second - let’s get the others out of the way first:

  • In: the In button turns that particular EQ control on or off. If you equalize a frequency and then decide you don’t want to keep the change, you can just turn off that EQ band until you need it, instead of having to zero out the settings.
  • Shelf/Notch: the two buttons next to the EQ band name determine the shape of your EQ when it is at one end or the other of the frequency spectrum. Those in the middle are notch, meaning they affect a set range of frequencies, but these end bands can be shelved which means they are affected from the bottom of the frequency spectrum (for the LF) up to the set frequency, or the top of the spectrum for the HF.

Gain

Once you’ve pushed a band in, the first control you should tweak is the Gain control. The EQ have no effect without some gain reduction or addition, no matter what you do with the other controls. Gain determines how much of a certain frequency is added or removed. Gain is the vertical axis on the EQ graph, and the taller it is, the more of that frequency is being added:

Q

Q determines how wide or narrow the EQ band is. A setting of 0 will pretty well encompass the entire spectrum (depending on your gain) while a setting of 10 will only affect a very small range of frequencies. Here’s a Q that’s fairly average, though a little on the narrow side:

Frequency

The third control is Frequency. This determines which frequency the band affects, or in most cases where the Q determines that a range of frequencies will be affected, where the center of the frequency range is.

Subtractive EQ is the Best EQ

As we just discussed, you can either boost a frequency or attenuate it. However, just because you can boost doesn’t mean you necessarily should: it’s better to pull frequencies down. When you increase a frequency, the plug-in has to create extra sounds that weren’t there before. When you attenuate, you’re just reducing part of the existing sound, so it stays more natural and realistic.

So what do you do if you want to get a beefier bottom-end? Simple - pull down the high-end!

Here’s a picture of what subtractive EQ looks like:

And this is what additive EQ looks like:

Of course, you can boost if you want to, but it’s a good idea to try the subtractive approach first.

Cut Narrow, Boost Wide!

While we’re on the topic, there are a few best practices for cutting and boosting frequencies. When you’re cutting a frequency, it’s best to make it narrow (a higher Q) and a bit deeper, whereas if you’re boosting, it’s better for it to be wider (a low Q) but shallower (in other words, use gain sparingly).

This is not a hard and fast rule. If you’re recording at home, or have a less-than-perfect take in the studio, you may find yourself cutting wide fairly regularly. And if you just need a sound to poke through in a small range, you might introduce a narrow (though still shallow) EQ.

You can get an idea of how it’s done by looking at this image:

Low and Hi Pass Filters

I find one of the reasons I most frequently use EQ is to slap a low or hi pass filter on.

A low pass filter boosts or attenuates the high frequencies, while the high pass filter does the same for the low frequencies. Usually it’s attenuation that’s happening, though you might find a slight LPF boost on drum overheads, for example, gives things a bit more sparkle.

When I mix a session, I slap a HPF on every track other than the kick drum and bass guitar (unless I have other instruments in the session that are there to be bass instruments). Low frequencies get muddy ridiculously quickly, so it’s important to be ruthless to keep your studio sound sparkle. It’s worst in rock and metal, which is what I usually work with, so do some tests before taking my advice completely in a lighter genre.

Cutting Holes

Even when you’re not controlling low frequency build-up, you’ll need to cut holes in certain instruments. It’s important to let an instrument dominate it’s primary frequency range, so you should cut holes in your instruments that will compliment each other. For instance, the human voice is (generally) strongest in 3.5kHz, so if I found another instrument was competing with our vocalist in that range, I’d pull them down there like so:

This ties into planning your session and arrangement. Find instruments to fill up each major block along the spectrum, and then make sure they are the strongest in their ranges with the help of subtractive EQ.

Finding Problem Frequencies

Before you get to the stage in your session where you’re cutting holes to prevent instruments from fighting each other, you’ll be using EQ to remove “problem” frequencies. If you find the snare is to boxy or the guitars are to jangly, this trick will help you identify the problem and fix it.

Give one of your bands a high Q (10 is not too high in this case) and raise the gain as high as it goes.

Now you need to perform a “sweep” along the spectrum until the problem sound becomes really prominent. When you find the frequency where the problem is at it’s worst, reduce the gain and change the Q until you’ve controlled it. It’s a fairly simple trick, but you’d be surprised that so many people attempt to fix a problem with EQ before they’ve located the frequency range where it’s occurring.

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