This is another good question I get from time to time that should be asked more often. As a follow-up to my previous article on how to set a graphic equalizer, I will go into the differences between parametric and graphic equalizers, why there are two types in the first place, and when & why to use one over the other.
By definition, graphic equalizers are called this because they lay out the sound spectrum in order from lowest frequency to highest from left to right, in a graphical or “graph-like” fashion. This is also known as a “matrix”, where left to right is the frequencies, and up and down are the levels of each one. These are perfect for shaping the entire spectrum of a sound system or recording from the deepest bass, to the highest treble. You have the entire sonic landscape in front of you at your disposal.
Please see my previous article on “What Is The Proper Way To Set An Equalizer” for the best method for setting a graphic equalizer.
These are quite different than graphic equalizers in that the sound spectrum is NOT set out in order from left to right by lowest to highest frequency. Also, there aren’t as many “bands” as a graphic, which may have 7, 9, 15, or 31 bands to play with. Most parametric EQs have only 2, 3, 4, 5, or 7 bands. Unlike the graphic equalizer, each band is NOT “preset” at a certain frequency, but rather variable.
A parametric EQ has 3 basic controls, Level, Frequency, and “Q”, or width of the section of the spectrum you are adjusting. Not all parametrics have the “Q” control, like most parametric midranges on mixers and multitrack recorders. We’ll look at the controls one at a time.
The level control determines whether you are cutting, or boosting a frequency. Place it at 12 O’clock and it’s not doing either, in other words, not changing the sound at all. The more left or counter-clockwise you go, the more you are cutting a frequency. The more right or clockwise, the more you are boosting a frequency.
This is the control that sets what frequency you are cutting or boosting with the level control. Some parametrics have different ranges of frequencies you can control for each band. Others let any one of the bands affect anywhere in the entire audio frequency spectrum. This means that the band on right of the EQ could be affecting bass, and the one on the left could be affecting treble! Very different than the graphic EQ.
“Q” or width
This control is the most mis-understood one, and not all parametric EQ controls have it. Let’s say you are cutting -6dB with the level control. You set the frequency to 250Hz. Now the “Q” control determines how wide a swath centered on 250Hz you are affecting. If you make it very narrow, you are affecting only like 245-255Hz. If you make it the widest, you might be affecting all the way from 100-400Hz, with 250 as the center. The wider settings with take a bigger “bite” out of the frequency spectrum, and the narrow settings let you focus in on a very specific frequency.
In conclusion, parametric equalizers are used to target specific or specific sets of adjacent frequencies, anywhere you want to. This is perfect for finding and cutting bad sounding frequencies, or enhancing weak ones in order to balance out your frequency spectrum. This is unlike the graphic EQ which lets you adjust the entire spectrum from low to high. The decision on which one to use is just that: Is it just one, or a small set of frequencies that are not sounding right, or do you just want to control the entire spectrum from bass to treble?
About the Author
Patrick Smolinksi is a recording industry veteran with over 15 years of pro audio retail sales experience, over 11 years of running his own recording studio in central Wisconsin, and is a multi-instrumentalist playing all of the instruments on songwriter demos. Pat is a musician at heart and has also found himself playing gigs with several bands over the past 30 years. He loves his twins, the Packers, music, and pro audio gear.