ABSTRACT
The professional rack-mounting graphic equaliser will have at least ten frequency bands, spaced at octave or one-third-octave intervals. The ISO (International Standards Organisation) centre frequencies for octave bands are 31 Hz, 63 Hz,
125 Hz, 250 Hz, 500 Hz, 1 kHz, 2 kHz, 4 kHz, 8 kHz, and 16 kHz. Each fader can cut or boost its band by typically 12 dB or more. Figure 13.2 shows two possible types of filter action. The 1 kHz fader is chosen, and three levels of cut and boost are illustrated. Maximum cut and boost of both types produces very similar Q (see Fact File 5.6). A high Q result is obtained by both types when maximum cut or boost is applied. The action of the first type is rather gentler when less cut or boost is applied, and the Q varies according to the degree of deviation from the fader’s central position.
