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Chapter 3 - Overview
32 Q20 Reference Manual
Equalization
Equalization, or EQ, provides the ability to control the timbre, or coloration, of an
audio signal by changing the frequency response of a Q20 audio path. Filters and EQ
can be used to compensate for frequency deficiencies in microphones and other sound
equipment. The EQ family of functions in the Q20 contains filters, equalizers, and
several other highly useful studio effects.
Filters
Lowpass, Bandpass, and Highpass
A filter allows the passing of frequencies within a certain range (called a filterÕs
passband), and removes frequencies outside that range. The Q20 features a Lowpass
Filter, which removes frequencies above its cutoff frequency (i.e., it allows low
frequencies to pass through), and a Highpass Filter, which removes frequencies
below its cutoff frequency. At the cutoff frequency, each filter attenuates the signal
level by -3dB, and attenuates by 6dB per octave outside the passband. The
Bandpass Filter passes frequencies near its center frequency, and removes all others.
The Bandpass Filter has a bandwidth parameter to control how wide (in octaves)
the passband is. Bandwidth is inversely related to the conventional ÒQÓ value;
that is, the higher the Q value, the lower the bandwidth. Bandwidth is used in
the Q20 because it is a more familiar term to many musicians, and is more intuitive.
0dB
-3dB
Level Frequency
Cutoff Frequency
Lowpass Filter
0dB
-3dB
Level Frequency
Cutoff Frequency
Highpass Filter
0dB
-3dB
Level Frequency
Center Frequency
Bandpass Filter
(low bandwidth)
Bandpass Filter
(high bandwidth)
0dB
-3dB
Level Frequency
Center Frequency
Bandwidth
Bandwidth