Telex Integrated Signal Processor ISP-100 - Manual (Page 87)

8-17
Processing Components - Crossover
Four-Way Crossovers
Figure 8-8 Four-way crossover implementation.
In the ISP-100, 4-way crossovers are implemented as shown in
Figure 8-8.
This parallel structure was selected over the more common binary-
tree structure for its suitability to the distribution of filters among
multiple DSPs. The parallel structure is also capable of perfect
implementation of Linkwitz-Riley crossovers, for which the ISP-100
has been optimized. The filters marked optional in Figure 8-8 will be
explained in the Linkwitz-Riley Crossover section.
The lowpass filters LP
x
(except for the optional LP
2
) and the
highpass filters HP
x
(except for the optional HP
2
) 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 low-mid band, the mid-high 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.