What Are Audio Equalizers?

Equalization is a term used to signify a method that adjusts, corrects or modifies the balance of different frequencies within electronic signals.  It is a process used with sound recordings and audio reproduction for effective tone control, as well as for frequency response in telecommunications.  Equalization is commonly referred to today as EQ, which is a popular and preferred shorter alternative to the longer word.  The process of equalization is accomplished by the usage of equipment or circuits known as equalizers, often with the use of frequency filters.


The Use of Equalizers

The most well known use of equalizers is for audio equalization, where they are utilized to adjust frequency response of audio systems for proper tone control.  They are most commonly used in simple stereo systems to adjust settings such as bass and treble.  Equalizers can also be found in recording studios, broadcast centers, and other relevant locations–basically anywhere that requires the equalization of sounds coming from microphones, loudspeakers, or other electronic devices.  Equalizers are generally used for emphasizing or reducing audio sounds, instruments, and/or voices to create the required frequency mix.  A good example of this might be where two instruments in a musical recording are producing a jumbled sound, but EQ can be used to harmonize the mix by adjusting the frequencies.

There are various types of equalizers for diverse objectives, including shelving, graphic, and parametric equalizers.  These different types of equalizers often vary in complexity with some requiring greater skill for proper usage.


Shelving Equalizers

A shelving equalizer is the most common type used for audio equalization, often found on sound mixers, amplifiers, and other consumer audio electronics.  They basically are quite simple with two knobs for bass and treble.  It may sound like the name “shelving” has something to do with equipment you might fit onto a shelf, but this is not the case.  Its name was chosen based on its frequency graph that displays a shelf-like image (this happens because all of the frequencies that are below or above a specified position are cut or boosted by an equal amount).

Digital Shelving Equalizer
Digital Shelving Equalizer

A shelving equalizer allows for the tone control of bass and treble by starting from a midpoint frequency, but affects only the frequencies either over or beneath the stop point offered by the specific equalizer depending on the type of filter.  A high-pass filter will only affect those frequencies beneath its stop point while a low-pass filter will affect those over it.


Graphic Equalizers

Like shelving equalizers, graphic equalizers also get their name from the appearance of frequencies on a graph (they have more of a graph-type look).  This equalizer consists of a row of faders on the front of the audio device and each one of those faders controls a small section of the audio range.  They each represent a band with a midpoint fixed frequency that can be adjusted by moving the fader up for boost and down for cut (except for the lowest and highest faders since they control shelving filters).  The bands are fixed at approximately 1/3 of an octave apart from each other.  The more bands, the more control you will have over your EQ.

Digital Graphic Equalizer
Digital Graphic Equalizer
Rack Mount Graphic Equalizer
Rack Mount Graphic Equalizer

Though graphic equalizers are easy to adjust and allow some degree of control for equalization, they are not always as precise as we might like.  Graphic equalizers are quite commonly found in live sound systems.


Parametric Equalizers

This type of equalizer gets its name based on the fact that it has several parameters within its available bands.  Though it commonly only offers four frequency range bands, each of those bands has the parameters of cut, boost, bandwidth and sweep.  The cut and boost parameters allow from 12 to 18 decibels, the bandwidth control lets you determine the width or “Q” value of your frequency, and the frequency sweep allows you to choose one of the four bands as the center frequency.  Because of this, it offers more control than other types of equalization.

Parametric Equalizer
Parametric Equalizer

Parametric Equalization has more features, has greater flexibility and is more complex, allowing you to effectively fine tune your tone control to the specific frequencies you desire.  This type of equalizer is usually on mixing systems and some guitars or public announcement amplifiers.  Rather than using faders like the graphic equalizer, the parametric equalizer usually has basic knobs.

Paragraphic Equalizers

Paragraphic Equalizers are just what they sound like, a hybrid of parametric and graphic equalizers.  The concept is simple, the the science behind them is not, but we will get to that later on.

Equalizing Audio Today

When equalizing audio or sound, it is best to select audio equalizers that conform to your specific needs and your capacity to handle any complexities that may be involved.  You must consider how much control you really want over the ability to equalize the frequency of the audio output you hear.

With the technology available today, EQ can be used to attune most audio frequencies so that you can get close to producing the sound you want or need.  Yet, it is always important to maximize the quality of sound from the original source first since even the best equalization equipment has its limitations.


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