Using an equalizer for mixing music is an essential step toward achieving a high quality and clear sound. There are multiple types of equalizers (EQs), but the three main types are shelving, graphic and parametric. Each type differs in its own way, but offers clarity and enhancement to your audio.
Shelving
This type of EQ is the basic type that includes bass knobs and treble knobs for adjusting tone control. It gives you an adjustment for lows and highs and is found in nearly all sound mixers and amplifiers. The mid-range knob is sometimes included and usually features an adjustable midpoint frequency. The shelving equalizer got its name simply because the high-frequency lines and the low-frequency lines on a graph reveal a shelf-like figure. The high frequencies are measured around 10,000 hertz (Hz) and above; the low frequencies are measured around 100 Hz and below.
Graphic
The graphic equalizer got its name from how it appears on a graph. This EQ is broken up into different filters, and each filter appears differently on the scale of the graph. There are three parts that come along with the graphic EQ; they are distinct from each other with how their filters are spread apart. The smallest filter is called the octave band, which is generally 10 filters with their center frequencies set one octave apart. The next part is the 2/3 octave band, which has more than 10 filters and are spaced 2/3 of an octave apart. Finally, the 1/3 octave band equalizer offers the highest degree of control and reveals that the center frequencies are 1/3 of an octave apart.
Parametric
The Parametric EQ provides a separate adjustment of boost/cut, center frequency and "Q" (the sharpness of peak/dip). This is a more complicated but useful EQ to obtain while mixing audio. With it, you can not only adjust the amount of cut or boost, but you can also control what frequency is most affected. In addition, you can adjust the bandwidth, which is the amount of frequencies affected by the EQ. This equalizer has numerous features.
Features of the Parametric EQ
Parametric is taken from the word "parameter" because this EQ has several parameters. Although the parametric EQ only has four bands, the parameters in the bands gives more flexibility than other types of EQs. The boost and cut, bandwidth and sweep are the parameters. The boost and cut controls appear on most EQs and give parametric equalizers anywhere between 12 and 18 decibels (db; unit used to measure loudness). The bandwidth allows you to decide how wide or narrow you want your frequency to be and can also be used to control feedback. The frequency sweep is a dial (or other knob) that allows you to select the center frequency. You will see four basic frequency ranges (the four bands), but the sweep allows you to select one of them.
Other Features
The notch filter is found in most EQs, especially in the parametric. It is specifically designed to control feedback and displays narrow bandwidths that can pull out a certain frequency that is feeding back without affecting the sound of the music. Notch filters are not able to control boost capabilities, but can affect the cut. Some of the most recent notch filters contain a feedback detection unit that locates the feedback frequency and then automatically cuts it.
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