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4.2 The Edit View 31

4.2.8 The Filter Module

In order to expand the sonic possibilities of String Studio, a multi-mode

ﬁlter has been inserted between the String and Body modules. This multi-

mode ﬁlter includes a resonant low-pass, band-pass, high-pass, notch and a

formant ﬁlter which can be selected using the Type drop-down menu. The

order of the ﬁlter can be adjusted to 2 (-12 dB/oct for low-pass and high-pass

and -6 db/oct for band-pass) or 4 (-24 dB/oct for low-pass and high-pass and

-12 db/oct for band-pass) with the help of the Order drop-down menu. The

resonance frequency of the ﬁlter is adjusted with the Cutoff knob while its Q-

factor or resonance is controlled with the Q knob. When the formant ﬁlter is

used, the Q knob is used to cycle between the vowels (a, e, i, o, u).

The cutoff frequency and resonance of the ﬁlters can be modulated with

different modulation sources. The modulation sources include the keyboard pitch signal and the

output of the envelope generator (Env) and LFO modules. Now let’s have a closer look at the

different ﬁlter types available.

Resonant Low-Pass Filter

Amplitude (dB)

Frequency (Hz)

Q=10

Q=4

Q=2

Q=1

Cutoff

Frequency

0dB

−3dB

Slope (dB/Oct)

Figure 14: Frequency response of the low-pass ﬁlter.

A low-pass ﬁlter is used to remove the higher spectral components of the signal while leaving

the lower components unchanged. The frequency at which attenuation begins to take effect is

called the cutoff frequency. In a resonant ﬁlter, frequencies located around the cutoff frequency

can also be emphasized by an amount called the quality factor or Q-factor of the ﬁlter as illustrated

in Figure 14. The higher the Q-factor, the louder and sharper the response of the ﬁlter around

the cut-off frequency. When the Q-factor is set to 1 (Q knob fully turned to the left), there is no

emphasis around the cutoff frequency and the attenuation is -3dB at the cutoff frequency. The

attenuation for frequencies located above the cut-off frequency depends on the order of the ﬁlter

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APPLIED ACOUSTICS SYSTEMS STRINGSTUDIO Bedienungsanleitung Seite 31