Crate Amplifiers LS3-231, LS1-131, LS2-215 manual An Introduction to Equalizers, Constant Q Response

LS1-131/LS2-215/LS3-231Constant Q Graphic Equalizers

An Introduction to Equalizers:

The Crate Pro Audio Live Sound Graphic Equalizers are available in two mounting configurations: a 1-3/4” single rack space (LS1-131/LS2-215) and a 3-1/2” double rack space (LS3-231). These equalizers are a perfect addition to any professional sound system, particularly the Crate Pro Audio systems.

The Crate Pro Audio LS1-131/LS2-215/LS3-231 equalizers offer precision control of the audio spectrum. Some features of these equalizers include:

•Balanced and unbalanced inputs and outputs

•Constant “Q” bandpass filter sets for precision control

•Two control ranges for greater accuracy

•Hardwire switchable bypass from input jacks to output jacks for total elimination of the equalizer from the system

•Peak LEDs to obtain optimal signal levels

•High signal-to-noise ratio (greater than 94dB) and a wide frequency response (20Hz to 20kHz)

•Flat phase response for accurate reproduction and stereo imaging

•Very low THD (less than 0.01%)

•Maximum input level of +22dBm

•Variable low cut and high cut controls (LS1-131/LS3-231 only)

•Built in power supply

The LS1-131 and LS3-231 provide 31 bands of equalization at standard ISO center frequencies, 1/3 octave apart. They cover the entire audio spectrum from 20Hz to 20kHz. This allows precision control and fine tuning of your audio system. (The LS3-231 offers two channels of 31 band equalizers.) The LS2-215 provides two channels of 15 band equalization at standard ISO center frequencies, 2/3 octave apart from 25Hz to 16kHz.

All of the new Crate Pro Audio Live Sound Equalizers incorporate constant “Q” multiple-feedback bandpass filter sets for high resolution with minimal interaction between bands (see Figure 1 below).

Figure 1: Constant Q Response:

Constant "Q" filters: width of filter does not change with amplitude.

200 500 1k 2k

(dB)
Amplitude	0

200	500	1k	2k
	Frequency (Hz)	ƒ	ƒ
		L	H
		ƒ	ƒ = lower frequency
		C	L

Inferior broad band filters: width of filter changes with amplitude.

5k 200 500 1k 2k 5k

(dB)
Amplitude	0

5k	200	500	1k			2k	5k
	Frequency (Hz)	ƒ	ƒ	ƒ		ƒ
		L	L	H	ƒ	H
			ƒ			= lower frequency
			C		L

ƒ	=	center frequency	ƒ	=	center frequency
C			C
ƒ	=	higher frequency	ƒ	=	higher frequency
H			H

3