Signal Processing: Frequency Based - EQ - Posted on 2013-06-27 by Heath Drum

After talking to my mentor and having a remote study session, i've learned several new things about equalization. Equalizers allow the engineer to change the tonal balance of whatever they're controlling. Another way to look at it, EQ allows us to increase (boost) or decrease (cut) the desired frequencies of a recorded signal. Linear filters allow the adjustment from the low end to the high end of the audio spectrum to be changed through the use of Q. Starting with the low, low mid, mid, high mid, and high filters. There are different types of filters that can be applied, such as, a shelving filter, which allows the signal to be boosted or cut at a constant amount and stops where the frequency filter is set. The signal levels off and continues to the end of the spectrum. Another type of filter is the pass filter. Pass filters cut only and have a slope, usually a certain amount per octave. Pass filters differ from shelving filters because the reduction (cut) continues at a steep slope and never levels off. Another type is the parametric or peaking filter. This type of filter is commonly referred to as a selectable frequency filter, in which it allows the engineer to freely adjust and move the center of a fixed width of frequency and boost or cut them. The notch filter is a version of the parametric having a very small bandwidth fixed to one cut only. It is used to remove unwanted frequencies that are narrow in bandwidth. Another type is the graphic equalizer, which is mainly used for live performances and not so much inside the studio.