Lexicon MPX G2 manual EQ Effects, High Cut Low Cut Bandpass/Notch High Shelf Low Shelf

MPX G2 User Guide Lexicon

EQ Effects

High Cut

Low Cut

Bandpass/Notch

High Shelf

Low Shelf

At its simplest, equalization is the process of cutting and boosting certain frequencies to make portions of program material more or less audible. This is generally accomplished by combining filters which affect a specific “band” of frequencies together with gain controls.The three types of filters commonly used to perform basic EQ functions are: High Cut, Low Cut and Bandpass/Notch.

High cut filters remove frequencies above a fixed level. As this allows frequen- cies below the threshold to pass through unchanged, high cut filters are also commonly referred to as “lowpass” filters.

Low cut filters, which remove frequencies below a fixed level and allow higher frequencies to pass through are also known as “highpass” filters.

Bandpass/Notch filters allow only a certain range of frequencies to pass through without attenuation. They are plotted as curves, with a peak (or dip in the case of notch filters) at the center frequency.

Shelf filters

When a specific frequency value is selected for cutting or boosting, and compensating gain controls are provided, a shelving filter is created, with gradual build up of the boost or cut to the selected frequency, followed by a leveling off beyond the selected frequency. When the effect of the filter is plotted, it resembles a shelf, with constant levels of boost or cut preceding and following the “knee” or “corner point” at the selected frequency.

A typical application of these filters uses 2-band equalization with two shelf filters, one low and one high, to provide bass and treble tone control. These two filters affect only the high and low frequency signals, leaving the center frequencies unaltered. Adding a third or fourth band of equalization in the form of midrange bandpass filters provides more control over those frequencies where hearing is most sensitive, and where most of the energy in music exists. (500Hz-4kHz). These midrange bands peak, or dip, at a center frequency which can be varied to provide much greater control over different aspects of the sound, allowing for bass or treble rolloff to decrease boominess, thicken sounds, reduce noise, or increase brightness.

Parametric EQ

Parametric equalizers provide boost and cut controls, sweepable center fre- quencies, and adjustment of “Q”, or the broadness or sharpness of the EQ curve

—all of the parameters of equalization. This ability to broaden or narrow the peak at certain frequencies allows specific sounds to be accented or diminished with minimal effect on adjacent frequencies. As all equalization has potentially adverse side effects on program material, this ability to precisely adjust only specific frequencies has the advantage of minimizing the amount of EQ applied to program material. It also allows the creation of specific effects such as sharply narrowed EQ curves (notches) which are useful for feedback control or removal of specific noise artifacts.

7-38