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What Is a Parametric EQ?

parametric EQ screengrab in Logic Pro

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The term “EQ” is something that pretty much everyone who has ever performed or recorded music knows about and recognizes as a critically important feature related to how their music sounds.

Even many people who’ve only ever listened to recorded music, and never set foot in a recording studio, are aware of “EQ” and know that it helps their music sound its best when set correctly. But, surprisingly few of us are actually aware of what this term “EQ” really means, much less how to fully utilize it in music production.

Here’s a short explainer from Soundfly’s Faders Up: Modern Mix Techniques course.

The term “EQ” is a shortened version of “Equalization.”

This name stems from the fact that the sound we hear has many different frequencies, or tones, in it. When we have a sound that contains much more of the lower frequencies (i.e. bass tones) it can sound overly dark and muddy. When a sound contains much more of the higher frequencies (i.e. treble tones) it can sound overly bright and harsh. When we “equalize” these frequencies, such that there is a similar amount of both the lower and higher tones, then it should sound more balanced and correct to our ears.

Hence, equalization is related to creating a balanced presentation of tones in the sound.

Of course, over the years we’ve come to realize that a perfectly equalized sound (sometimes called “flat equalization”) doesn’t always sound the best. Most people have their favorite EQ settings, or use suggested EQ settings, which favor certain frequency ranges in order to get a more exciting or authentic sound. Even though the tones are not presented equally, we still refer to this process as equalization.

Most of the EQ setting options we see on audio players today utilize what is known as “graphic equalization,” which is where there are a series of knobs or sliders that allow the listener to adjust the amount of increase or decrease to predetermined tonal ranges. Often, this is as simple as three frequency ranges: bass, midrange, treble.

But some more advanced graphic equalizers might have 10 or even 25 or more individual present frequency ranges for which you can adjust how much of it to add or take away from the overall sound.

Now that we have a better understanding of EQ, what is different about a “Parametric EQ”? 

It basically comes down to the word “parametric,” which means “containing parameters.” A parametric EQ is simply an equalization device with which you can adjust every aspect of the equalization ranges. In other words, you can choose an exact range of frequencies that you want to have some amount added or taken away from  your sound. You can even say how broadly or tightly you want that range of frequencies selected — a very specific narrow range or a more general wide range.

parametric EQ screengrab in Logic Pro
The built-in Parametric EQ Effect in Logic Pro.

+ Read more on Flypaper: “Shelf EQ vs. Bell EQ: When and How to Use Them Both.”

In a typical parametric EQ, you choose where the center of the frequency range of interest should be. Then you say how wide you want your selection of frequencies around that central tone to be. This is done either by choosing a frequency width or by setting what is known as a “Q” factor. The Q factor is simply the ratio of the frequency width to the central frequency.

So, a smaller Q means a narrower range of frequencies and a larger EQ means a wider range of frequencies.

For example, if I want to apply an EQ to increase everything from 440Hz to 880Hz (that would cover all tones from concert A up through the next octave above it) I would start by choosing the frequency at the center of this range, which is 660Hz (the midpoint between 440 and 880) and setting that as my central frequency value in the parametric EQ. I would then see that I’m wanting to EQ a range of 440Hz worth of frequencies (880 – 440 = 440).

If my parametric EQ lets me enter a frequency width, I would simply enter 440Hz. If it uses a Q factor, I can calculate it easily as the frequency width divided by the central frequency:  660Hz/440Hz = 1.5, and so I would enter 1.5 for the Q factor value in my parametric EQ.

Finally, I set the amount I want to raise or lower that range of tones by as my gain value.  In my example I will set a few dB increase since I wanted to raise the amount of sound I hear in this range of tones.

parametric EQ screengrab in Logic Pro
Parametric EQ set to match our example.

It’s easy to see how a parametric EQ allows you the full freedom to dial in exactly what you want to accomplish in your equalization of frequencies when mixing. In other words, whether you need a wide range of tones to be adjusted by a small amount, or an extremely specific frequency to be greatly altered, a parametric EQ allows you to make the necessary adjustments.

This is quite useful in both live sound and recorded music. In live sound, it’s often used to filter out sounds that might cause feedback in the system. The loud ringing from feedback due to open microphones in a live concert is usually at a very particular tone and so you can locate that tone with a very narrow parametric EQ setting applying a strong reduction to only the sounds specifically around that tone, leaving the rest of the sound untouched.

Viola! The feedback is gone!

And in recorded music, it is used on almost every recorded track in order to boost any weak notes or decrease any overly loud notes from each instrument and voice so that you have a smooth, balanced, natural sound for the whole mix.

So why don’t we use Parametric EQ all the time? 

This is like asking why you take photos with your smartphone instead of setting up a hi-res digital camera with a telephoto lens for each and every photograph you want to capture. Sometimes it’s simply easier to use a quick one-size-fits-all solution that covers the majority of your needs, and your basic graphic equalizer will accomplish this quite nicely.

That being said, certainly for the creation of a professional sounding recording you will definitely want (or need) to employ a parametric EQ in order to fully optimize the sound down to the finest detail.

Don’t stop here!

Continue learning with hundreds more lessons on mixing, home recording, electronic production, beat making, and so much more, with Soundfly’s in-depth online courses, like Modern Pop Vocal ProductionAdvanced Synths & Patch Designand Faders Up: Modern Mix Techniques (to name a few).

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Erik Veach

Erik Veach is the owner and lead audio engineer at Crazy Daisy Productions, providing mixing, mastering, and sound editing services since 2001. He is the original pioneer of automated intelligent mastering systems, introducing them for use in professional music production in 2003.