Parametric EQ: What it is, How to Use it and Why.

By now we’ve gone over the importance of mixing with EQ several times. In our discussion of the different types of EQ, we briefly mentioned parametric EQ. But there are things about parametric EQ we have yet to go over. So let’s dive deeper into the nuances of this type of EQ, and what makes it a cut above.

A refresher on EQ

Remember that EQ stands for equalization, which refers to the manipulation and balancing of audio frequencies within and between electronic signals. Sound waves vibrate at different speeds, or, frequencies. High-pitched notes, for instance, vibrate more quickly than lower notes. When we discuss a particular note, however, we’re actually referring to the fundamental frequency of that note. Still, other frequencies will rear their heads in any given recording. This is due to resonance, or the resultant frequencies reflected by other objects due to the initial vibration. The old trope involving the finger circling the wine glass demonstrates resonance. This all gets into complex physics jargon, so we won’t go much further than that.

To keep things simple, any track in your mix will contain multiple frequencies, some more present than others. The core of the bass guitar, for instance, a low-end instrument, can be found mostly between 60 Hz and 250 Hz. This isn’t to say, however, that the bass won’t resonate at other frequencies. In fact, some powerful bass overtones can be found as high as 1k Hz. Likewise, different aspects of a crash cymbal, snare, or tom can be emphasized depending on which frequencies are boosted or cut. This holds true for every instrument you track.

All this means is that any instrument you record can be placed all over the frequency spectrum. But only certain frequencies will allow that instrument to really shine and reach its full potential, so to speak. Additionally, every mix must juggle several tracks and instruments at once. Frequencies will naturally collide, cancel, and overwhelm the ear if left alone. The best-sounding vocal track might sound dull given the rest of the mix. This is why proper EQ practices matter.

What is parametric EQ?

Of the several types of EQ, parametric EQ sounds like the most complicated. The word parametric boils down to the prefix para, meaning multiple or distinct, and metric, or measurement. Not much can be derived from this definition. After all, every type of EQ deals with distinct measurements of frequencies. However, parametric EQ has distinct advantages, namely four variables: frequency, type of filter, Q factor, and gain.

Frequency refers to the specific frequency you wish to focus on. Filter types include high-pass, low-pass, peak, notch, high-shelf, and low-shelf. Q factor essentially means how wide or narrow the frequency band is (more on that later). And gain simply refers to the increase or decrease in dB. Now, let’s dig a bit deeper into these variables and why they matter.

If you recall, graphic EQ splits up the frequency spectrum into bands. These bands can number from 8 to 31, with more bands meaning more precision and control. Each band can be adjusted for gain, or, prominence. So if you want to really boost your bass guitar, you can jack up the gain on the 60 Hz band of your graphic EQ. If too much high-end is leaking in, cut the gain on that 8k Hz band.

Parametric EQ takes a different, more nuanced approach. While parametric EQs typically feature fewer bands than graphic EQs, they actually yield more control. Now, you might wonder how fewer bands could result in more precision. The answer is this: bandwidth.

A brief aside on bandwidth and the Q factor

Bandwidth refers to the difference between a lower frequency and a higher one. A center frequency lies equidistant to the lower and higher frequencies that bookend the bandwidth. The bandwidth can be adjusted around this center frequency to yield a wider or narrower gap. The narrower the gap, the higher the Q factor. Visually, a high Q factor means a narrower, steeper, and sharper EQ. A low Q factor means a wider, more shallow, soft EQ.

It’s definitely more important to understand bandwidth and Q in practice than in technical terms. Still, the two words get conflated often. To be clear, bandwidth and Q are not one in the same! They’re related, yes, but they’re in fact inversely related. This simply means that as one goes up the other goes down. So, as bandwidth increases, Q decreases. As bandwidth decreases, Q increases.

Another way to drive this home is to think of Q as «pointiness,» or «sharpness.» The higher the Q factor, the more cone-shaped and angular the visual appears. The lower the Q factor, the more hill-shaped and round. It should be noted that «semi-parametric» EQs typically refer to EQs that have all the features of parametric EQs, except for a fully adjustable Q factor.

How to use parametric EQ and Why

Sometimes a certain frequency or frequency cluster contributes to a muddy mix. The bandwidth option adds a lot more control to your EQing process. It essentially allows you to hone in on a specific frequency or group of frequencies. This group might be very intimate, say, between 500 and 550 Hz (high Q factor), or quite vast, like 100 to 1k Hz (low Q factor). Depending on how a specific instrument resonates, parametric EQ can easily cut out unwanted frequencies and boost others with a gentle or harsh touch. Graphic EQ can achieve much of the same thing, but it takes more finagling considering each frequency band is already set in stone and can only be adjusted one at a time.

In Logic Pro X, changing frequency, filter, Q, and gain is as simple as sliding the mouse or trackpad left, right, up, or down. The visual display shows you in real-time what you’re changing and how it affects the audio via the analyzer. You can manipulate each frequency band individually, or adjust the gain for all bands simultaneously with the slider on the right.

In terms of fluidity, parametric EQ provides the best option for both additive and subtractive EQ. You can easily manipulate the parameters in your DAW in real-time, making frequency shaping more intuitive. If your ear comes across unwanted frequencies, the bandwidth control offers unparalleled precision. You can remove some of the noise, or all of it, depending on the Q factor and gain reduction amount.

Conclusion

Both graphic EQ and parametric EQ present viable options for shaping the frequencies of a given mix. However, most engineers and producers primarily incorporate the latter into their mixes. Plus, just about every DAW now features built-in parametric EQ controls. Parametric EQ makes the EQing process easier and more effective, particularly when you get free plugins for Windows and Mac. The amount of control might be overwhelming at first, but it becomes intuitive before long.