Filter
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8-14
10 July 1998
implementation of Linkwitz-Riley crossovers, for which the ISP-100
has been optimized. The filters marked optional in Figure 8-5 will be
explained in the Linkwitz-Riley Crossover section, below.
The lowpass filters LP
x
(except for the optional LP
2
) and the
highpass filters HP
x
may each be independently configured as:
Bessel 6 dB/octave (1
st
-order)
Bessel 12 dB/octave (2
nd
-order)
Bessel 18 dB/octave (3
rd
-order)
Bessel 24 dB/octave (4
th
-order)
Butterworth 6 dB/octave (1
st
-order)
Butterworth 12 dB/octave (2
nd
-order)
Butterworth 18 dB/octave (3
rd
-order)
Butterworth 24 dB/octave (4
th
-order)
Linkwitz-Riley (Butterworth-Squared) 12 dB/octave (2
nd
-order)
Linkwitz-Riley (Butterworth-Squared) 24 dB/octave (4
th
-order)
In addition, the cutoff frequency, attenuation, and polarity in the low
band, the mid band, and the high band may be independently
adjusted, and all of the filters in any band may be bypassed entirely.
The cutoff frequency in each filter is continuously variable from 20
Hz to 20 kHz.
The attenuation in each band is continuously variable from -96 dB to
0 dB, plus mute.
The polarity in each band is selectable as + or - (in-phase or out-of-
phase).
Each band may be bypassed, in which case all of the crossover
filters in that band will be bypassed while the crossover filters in the
other bands will not be affected.
Three-way Bessel and Butterworth Crossovers
Figure 8-6
Three-way Bessel & butterworth crossover implementation.