Filter
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8-35
Processing Components - Filter
Cutoff Frequency
The cutoff frequency is the design frequency of the highpass
filter, and is only approximately representative of the location of
the magnitude peak. In the ISP-100 the cutoff frequency is
continuously variable from 20 Hz to 20 kHz.
AllPass Filters
AllPass Filters shift phase without altering magnitude. The allpass
filters supplied with the ISP-100 are designed to provide phase
compensation for multiway Linkwitz-Riley crossover networks. The
1st-order allpass filters compensate for 2nd-order (12 dB/octave)
Linkwitz-Riley crossovers; the 2nd-order allpass filters compensate
for 4th-order (24 dB/octave) Linkwitz-Riley crossovers.
A detailed explanation of the use of allpass compensation may be
found in “Active Realization of Multiway All-Pass Crossover
Systems” by Joseph A. D’Appolito;
Journal of the Audio Engineering
Society
, Volume 35, Number 4, April 1987.
In the ISP-100 allpass filters the filter order is selectable from 1st-
order and 2nd-order.
In the ISP-100 allpass filters the center frequency is continuously
variable from 20 Hz to 20 kHz.
Filter Type
To change settings, click on the arrow next to the entry in the text
box. A selection list will appear. The list may or may not be
scrollable. To make a selection click on the desired entry.
Active Band
To change settings, click on the arrow next to the number in the text
box. A selection list will appear. The list may or may not be
scrollable. To make a selection click on the desired entry.
Bypass
The Bypass control bypasses an individual filter band. If the LED on
the button is gray, then the filter band is active. If the LED on the
button is red, then the filter band is bypassed.
Bypass Control (master)
This button determines if the component is in the processing chain. If
the LED on the button is gray, then the component is inserted into
the signal processing chain. If the LED is red, then the component is
bypassed in the signal processing chain. A bypassed component will
be colored red in the QuickMAP.
Frequency in Hz
The center frequency of a filter can be adjusted three ways:
Using the Text Box
Click in the box. Using the Back Space and/or Delete keys
erases the current entry and enters the new level. Be sure to
press the Enter key after the entry is made. Clicking outside the