The equalizer unit (usually referred to EQ), is probably the most common signal processing tool used by sound recording engineers. Signal processors are now considered essential in the creation and processing of modern audio and music production.
But just what do we mean by “signal processors”? What are they used for? – And how can they be used effectively to enhance the sound for the listener?
In this series of articles, we’ll cover equalizers and compressors, what problems they help solve, and a practical introductions to how to use them effectively.
Equalization – what’s it all about?
When an instrument is played, it produces sounds containing many frequencies, making up the frequency spectrum of an instrument. This is what gives it its distinctive timbre or tone quality.
But because of speaker deficiencies and room acoustics, each frequency may not be conveyed equally well to the listener.
The challenge become even more complex when different types of instruments are played together, especially if they cover the same general range of pitch, for example piano, guitar, and voice, they can sound muddy – just a jumble of indistinct noises getting in each other’s way.
So one way recording engineers use an EQ unit is to solve problems with the mix or its components:
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To create a better blend of instruments or sound sources within a mix
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To make a specific track (Example: Guitar) stand out in the mix
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To help fix sound problems (frequencies, unwanted noise and leakage)
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To improve the overall timbre (tone quality) of a specific instrument
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To create a certain effect by altering a sound purely for creative reasons (Making an instrument sound like it’s coming out of a transistor radio, as in the beginning of Pink Floyd’s Wish You Were Here)
How does it work?
Equalization alters the overall sound of an instrument or audio source by boosting and/or cutting specific frequencies within it.
Equalization is characterized by 3 parameters:
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Frequency – measured in Hertz (Hz), this is the mid-point in the range of pitches to be altered
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Bandwidth – (Q) referring to the breadth or narrowness of the frequency range that is altered
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Gain – measured in decibels (dB), this is the amount of cut or boost of a particular frequency range.
With that in mind, there are 3 different types of EQ unit:
Parametric EQ – Usually found in the input section of channel strips on recording consoles. Common in music software because of its flexibility and effectiveness. The parametric EQ can adjust gain, frequency and bandwidth which allows for a smooth transition between frequency bands or to allow multiple curves of a high bandwidth (Q) to be placed in a narrow frequency range. In other words, If a guitar and a vocal track appear to be clashing with one another, applying parametric EQ can help give them their own space in a mix.
Shelving EQ – The second most common type. This EQ provides an overall adjustment to the highs and lows of an instrument or audio source – rather like the Bass and Treble controls on your home stereo.
Graphic EQ – This is often found on higher end stereo systems. This type of EQ allows for boosting and cutting of individual frequency bands. Positioned physically side by side as vertical sliders, they provide a graphical representation of the overall frequency curve. The bandwidth and frequency are usually fixed which only allows for gain of each frequency band to be varied. Graphic EQ is widely used to match the acoustics of a room where the main sound source is located.
Most EQ units, whether hardware in a studio rack, or the software equivalent in your Digital Audio Workstation, have the following adjustable controls:
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Input selection
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Frequency
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Gain
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Q (Bandwidth)
Next time, we’ll cover how to use an equalizer unit effectively.
