+18/–6dB) covering a wide spectrum between
dark, mellow, boxy, honky, and harsh—and all
that in stereo!
Some example frequency responses offered by
Zagrzeb at the high pass 24 and low pass
24 outputs are shown in fig. 2. Please note that
low frequencies are not attenuated when the
resonance is high. Note also that the high pass
response is particularly steep at 24dB/oct. This
results in quite a radical filtering effect.
Fig. 3 shows the frequency responses at the
band pass pair of outputs, comparing three set-
tings of the bp config switch: h18l6, h12l12,
and h6 l18. Different slopes result in less or
more radical filtering of components below and
above the center cutoff frequency yielding sig-
nificantly diverse timbres. Please note that the
middle symmetric response features two 12dB/
oct slopes that are twice as steep (hence more
selective) as a classic 2-pole SVF.
GAin Vs REsOnAncE
In every resonant circuit, increasing the reso-
nance introduces higher gain for signals close
to the resonant frequency. In filters, this may
yield increased amplitude of the filtered signal
and some distortion at the output.
Designers of synthesizer filters handle this
problem either by compensating for the gain
increase by mixing some inverted input into
the variable feedback that controls the res-
onance (which results in a weaker response
4
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fig. 2a
fig. 3a
fig. 2b
fig. 3b
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