One of a handful of types of EQ, parametric EQ is what we typically think of when we think of an EQ. It has all of the typical features we associate with EQs and is arguably the most versatile for sculpting the frequencies of our audio for the better. Let’s define what is parametric EQ, including what that term means and what makes it parametric, how it differs from other EQs, and why it’s (arguably) the best for getting the results we want in our mix.
What is Parametric EQ
Parametric is simply an EQ which features multiple parameters, or settings. The term parametric quite literally means “relating to or expressed in terms of a parameter or parameters”.
I recently did an overview on the most common EQ settings or parameters you’ll find on a parametric EQ.
These parameters include:
Filter Type
There are roughly six types of EQ filters. Each filter type or shape allows you to target the frequencies you want to affect in different ways.
The filter types include:
Bell
A bell filter creates a cut or boost (depending on the gain which we’ll talk about in a moment) at a specific frequency.
As that frequency goes up or down, the surrounding frequencies move with it to a lesser degree (depending on the Q setting which we’ll get to in a moment, as well). This results in the shape of a bell or an upside down bell, depending if it’s a boost or a cut, respectively.
Notch
A notch is similar to a bell in that it affects an internal range, albeit much more surgically. For instance, a notch cut filter at 500 creates a very tight cut down to infinite negative gain, meaning 500Hz is completely removed from the audio. This is compared to a bell filter which would just attenuate it by the amount of gain you dial in.
At the same time, the surrounding frequencies are much less affected as the width and steepness of the grade are narrow and extreme that the gain line returns to flat just a few Hz around 500Hz.
High and Low Pass Filters
High and low pass filters allow you to roll off the bottom and top end of your audio while allowing the high and low frequencies pass through unaffected, respectively.
High pass filters in particular are useful for removing unwanted low end noise on every track in your mix, creating space for the kick, bass, or any other low end instruments which need these frequencies. Check out my low end mixing tutorial for more information.
High and Low Shelves
High shelves and low shelves affect the frequencies above or below your frequency point, respectively, so that you can cut or boost.
In the case of cutting, when you don’t want to remove say the low end entirely with a high pass filter, a low shelf cut can attenuate the presence of the low end while simultaneously boosting the high end via subtractive EQ.
Frequency
Frequency is just that – the frequency point you want to be at the center of whatever filter type you use.
In the case of a bell or notch filter, that frequency becomes ground zero for whatever adjustment you want to make, positive or negative.
With a high pass filter, the frequency you set becomes the point at which you begin to roll off Hz. The same idea is true for a low pass filter or high or low shelves, as well.
Gain
The gain is measured in decibels and determines if you’re adding to the frequency point (positive dB) or taking away from the frequency point (negative dB).
While you can make a significant change, positive or negative, to a frequency point, smaller adjustments result in a more natural and transparent sound.
When making greater cuts or boosts, that’s when you run the risk of introducing phase issues which can make your audio sound thin.
Generally you want to keep the gain change within a few decibels when possible.
Q Setting
The Q setting is a big part of what makes a parametric EQ what it is and separates it from other types.
As I alluded to earlier, with a bell filter the Q setting affects the width of the adjustment you’re making.
If you make a 3dB cut at 500Hz, adjusting the Q setting will determine how much of the surrounding frequencies are affected by that cut.
A higher Q results in a narrower band, meaning less of the surrounding frequencies will be affected. Setting the Q as high as it can go means that the 3dB cut will exclusively target 500Hz whereas 400Hz and 600Hz will be flat.
Conversely, a low Q results in a wider band (like the one shown above), meaning more of the surrounding frequencies will be affected. Setting the Q as low as it can go means the 3dB cut will likely extend out by hundreds of Hz on either side before the curve fully flattens out.
While we may prefer to target a more surgical or precise area with a high Q, a lower Q sounds more natural and helps to avoid phase issues, just like using less gain in your adjustments.
Slope
The slope EQ setting often gets confused with the Q setting because they both affect how quickly the curves of your adjustments flatten out.
The difference is the slope setting, measured in dB/oct, affects the steepness or grade of the curves themselves rather than the width. Setting a high slope, like say 96dB/oct, results in a much sharper transition between the peak of the curve and flatness:
The above image shows a gentle slope versus an aggressive slope, each applied to same default Q setting.
Just like with the Q or gain, a more conservative or gentler/smaller slope results in a more natural and transparent sound which is less likely to cause phase issues.
Dynamic
Dynamic EQ is a special feature which some parametric EQs like my favorite FabFilter Pro-Q 3 offer (see my FabFilter Pro-Q 3 review).
Dynamic EQ introduces an extra setting of a threshold to a filter band. Adjusting the threshold allows you to attenuate or boost the frequency range you’re targeting more or less relative to the level of that particular range.
If you notice some harshness around 5k which is only a problem during a few select instances during the entire track, using a dynamic EQ band makes more sense than just doing a conventional, uniform/static cut.
You simply set the threshold so that it only catches those surges, thereby pulling 5k down in those instances but otherwise leaving it untouched.
This keeps the track sounding natural and keeps 5k untouched save for the few instances when it needs that attenuation when that frequency surges.
Parametric vs Semi Parametric
So we’ve talked at length about the features which generally make a parametric EQ a parametric EQ.
But to better exemplify this, let’s compare a parametric vs semi parametric, a different type of EQ.
Here’s a shot of Ableton Live‘s stock EQ Three which is a semi parametric EQ:
As you can see, we don’t have anywhere near the degree of control we have with our parametric.
First and as the name “EQ Three” suggests, we’re limited to 3 bands. To set the frequency points, you specify the frequency range for the “FreqLow” and “FreqHi” bands, and basically everything else makes up that mid band.
In the above example, our lowest band is 0-250Hz and the highest band is 2.5k and up (to probably roughly 20k, the practical top end frequency limit to which humans can perceive).
This means that 250Hz to 2500Hz is the mid band.
We then have gain knobs for each band to boost or attenuate their influence over the sound, accordingly.
That’s it, though, no bells and whistles. It’s also not ideal for those who prefer a more visual approach like the display you get from an EQ like the Pro-Q 3.
There is a certain appeal or even advantage to a minimalist and simplistic EQ like this, though, as it’s difficult to overthink it. With less controls and bands available, every move you make is more of a broad stroke which again sounds more natural and allows you to get results more quickly.
Speaking of less controls and quicker results…
Parametric vs Graphic EQ
There’s also a pretty sizable difference between parametric vs graphic EQ.
A graphic EQ also doesn’t offer any bells or whistles. In fact you can even specify a custom frequency to target on most graphic EQs.
Instead, they have a set number of band presets which are represented by simple sliders. Turning a slider up adds gain to boost that frequency, turning it down subtracts gain to cut that frequency.
As I mentioned in my overview of graphic EQ, the name comes from the fact that the interface resembles a grid with the X-axis representing the frequencies left to right and the Y-axis representing the gain.
Part of the appeal of graphic EQs is that it’s easy to adjust a band and hear the impact immediately. With all of the preset sliders, you simply boost or cut a frequency to determine whether or not it added to the sound.
Graphic EQs are primarily still used by live sound engineers to quickly mitigate problems like feedback. It’s as simple as dropping a slider by a few dB.
Still, nothing compares to the control you get via a parametric EQ which is why they’re far and away the most useful and practical when it comes to EQing the tracks in your mix.
Speaking of which, grab my free EQ cheat sheet for in depth tutorials for quickly dialing in the best EQ settings for every instrument in your mix using a parametric EQ.