In this post, you’ll learn the difference between the two most common types of equalizers in pro audio: graphic EQ and parametric EQ.
What’s the difference between a graphic EQ and a parametric EQ?
A graphic equalizer offers gain control of a fixed set of frequencies, usually the ISO third-octave frequencies. A parametric equalizer offers gain control over any frequency within a range and also allows users to control the bandwidth or Q of each filter.
What Is an Equalizer?
An equalizer is a tool used in audio to adjust the frequency balance of a signal.
There are four basic concepts to understand when learning about EQs: Frequency Band, Center Frequency, Gain, and Bandwidth.
A frequency band is simply a range of frequencies.
This graph shows lowest frequencies on the left and highest frequencies on the right. To illustrate the concept of a frequency band, I’ll highlight the frequency band between 500Hz and 2khz.
When selecting an equalizer, you’ll notice that each one offers a certain number of bands.
A 3-band EQ, for example, offers control of three ranges of frequencies. In many cases, these bands are labeled low, mid, and high.
In many cases, the frequency bands will be indicated by the center frequency.
The center frequency is the frequency which falls in the center of the frequency band.
An equalizer allows you to adjust the gain, or level, of the selected frequency band.
The center frequency will be affected the most, but the frequencies above and below that point are also affected.
Some equalizers allow you to change the width of the gain adjustment. This setting is called bandwidth, or sometimes “Q”.
It allows for very narrow adjustments, very wide adjustments, or anywhere in between.
What Is a Graphic EQ?
Graphic equalizers come in a variety of sizes, each offering a fixed quantity of frequency bands.
The most common in professional audio is a 31-band graphic EQ, where the frequency bands are centered on the ISO 1/3rd octave frequencies.
A graphic equalizer allows the user to adjust the gain of each frequency band, but the bandwidth is fixed.
What Is a Parametric EQ?
Parametric equalizers provide users with significantly more control.
With a parametric EQ, you can select the center frequency for each band, the gain, and the bandwidth.
Choosing a Graphic EQ or a Parametric EQ
There are no rules that determine when to use a graphic EQ and when to use a parametric EQ.
I tend to use a parametric EQ in most situations, because they allow for more precise control.
Parametric equalizers also allow you to sweep through frequency ranges when you’re having trouble locating that specific problem frequency.
I choose to use graphic EQs in some live sound situations, such as mixing stage monitors.
It’s nice to have easy access to many frequencies to quickly eliminate microphone feedback on stage.