Peterson Sonuus Wahoo - Manual (Page 15)

Wahoo © Copyright 2012 Sonuus Limited 15
Owner’s Manual
FILTER
freq-hi, freq-lo. The cutoff frequency of the filter can be set by entering the value in Hz.
The cutoff can range from 10Hz (which is lower than you can hear) up to 4000Hz. Values above
999Hz are shown in kHz (
i.e., 2500Hz is shown as “2·50”).
FILTER
shape. A musical sound contains many frequencies. A filter is used to remove some of these
frequencies and to enhance other frequencies. The simplest filter to understand is a low-pass filter.
It is named after the part of the frequency spectrum that remains after the filtering has happened. A
low-pass filter filters out (removes) high frequencies and allows low frequencies to remain (to pass).
The frequency above which the high frequencies are removed is called the cutoff frequency, fc.
The Wahoo filters can be configured as low-pass or band-pass filters. A band-pass filter removes
frequencies above and below a specified frequency and only allows those frequencies in the
specified band to pass. The diagram below shows the frequency response of a low-pass and of a
band-pass filter. The centre frequency, rather than the cutoff frequency, is defined for a band-pass
filter, both are shown as fc.
Reverse filter sweeps Reverse filter sweeps Reverse filter sweeps Reverse filter sweeps
It is simple on the Wahoo to create reverse (inverted) filter sweeps: simply set freq-hi to be
smaller than freq-lo.
“hi” and “lo” refer to the modulator position: when the footpedal is in toe-down position (or
the envelope follower is at a maximum), the value freq-hi is used, whether this is greater
than, or smaller than, freq-lo.
-100
-80
-60
-40
-20
0
Frequency
S
ign
al
Le
ve
l [
dB
]
low-pass
band-pass
fc
24dB per octave roll-off