Electro-Voice EQ-231 specifications Description, Features, Architects’ Engineers’ Specifications

EQ-231

Stereo One-Third Octave Graphic Equalizer

•31 1/3-octave filters on each channel for effective sound system equalization

•Switchable infrasonic filter and ground-lift

•Selectable (6 or 12 dB) range of boost/cut

•Active-balanced 3-pin XLR-type and TRS 1/4-inch inputs

•Two rack space chassis with internal power supply with IEC connector

Description

The Electro-Voice EQ-231 is a boost-and- cut stereo 1/3-octave graphic equalizer whose primary use is for tuning the overall fre- quency response of a sound reinforcement system, both to increase gain-before-feed- back and to compensate for the deficiencies in the acoustic environment and the sound system.

Features

The variable-Q active filter sets used in the EQ-231 allow effective equalization with few problematic side effects. As Figure 1 il- lustrates, the filter characteristics vary with the amount of boost or cut used. At low con- trol settings, the filter Q is very wide. As the control is boosted or cut, the filter Q nar- rows so that there is minimum interaction between adjacent frequency bands.

Each of the 31 1/3-octave filters per channel provides 12 dB of boost or cut at ISO fre- quencies 20 through 20,000 Hz (see Figure 2). The faders have a positive detent in the center, flat-response position.

The gain control also has a center detent at unity gain. It should be adjusted so that the

adjacent peak LED rarely or never lights. This will help achieve maximum possible signal- to-noise ratio.

The infrasonic low-cut filter, with a 43-Hz corner frequency and a slope of 18 dB per octave, is engaged by the front-panel Lo-Cut switch (see Figure 3). For most applications, the filter should be engaged. Most profes- sional speaker systems have little output be- low 45 Hz. At best, driving them in this range wastes amplifier power, and can result in excessive, ultra-low-frequency cone motion which distorts the output in the reproduced frequency range and, most seriously, could damage the speaker from excessive cone motion or “bottoming.”

The range select switch allows selection of either 6 or 12 dB of boost and cut on either channel. The 6-dB range will allow more control selectivity while the 12-dB range al- lows for greater range of adjustment.

The EQ-231 has an IEC connector to allow compatibility with ac connections anywhere. The integral fuseholder also doubles as the voltage selector to allow for operation any- where in the world.

Figure 5 shows front and rear panel details.

Architects’ and

Engineers’ Specifications

The equalizer shall have 31 filters for each channel centered at the ISO standard 1/3-oc- tave frequencies between 20 and 20,000 Hz. The filters shall provide either 6 or 12 dB of boost or cut and be set by 22.5-mm linear controls. The front panel shall have the fol- lowing controls: a gain control that is con- tinuously variable from -12 dB to +12 dB from unity gain; a high-pass filter with a slope of 18 dB per octave and a corner fre- quency of 43 Hz; a range switch to select either 6 or 12 dB of boost or cut from the filters; an EQ-on switch to put the filters in the signal path and an on/off switch.

The rear panel shall have the input and out- put connectors, a ground-lift switch and a IEC connector with an integral fuse holder that allows voltage selection by the way it is inserted.

The inputs and outputs of the equalizer shall be accessible via 3-pin XLR-type and 1/4-inch TRS phone jacks located on the rear of the unit. The input shall be actively balanced. The output shall be balanced on the 3-pin XLR-type plug.