Arturia MICROFREAK, Руководство пользователя

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7.1.4. Cutoff frequency
The cutoff frequency is the point where the actual filtering takes place. Early users of filters
discovered that they could alter the sonic properties of a filter by feeding the output of the
filter back into itself. Creating such a feedback loop results in a resonance peak around the
cutoff frequency. In the MicroFreak filter, you control this effect with the resonance knob.
The amount of resonance can be controlled manually, or by the LFO or the Envelopes. To
achieve this, you have to assign it to your favorite control in the Matrix.
Filters differ in how they remove frequencies above the cutoff point. It is possible to design
a filter that will reduce the frequencies above the cutoff frequency in a very drastic way; if
the cutoff point is at 500 Hz, it will make a frequency of 501 Hz inaudible. The result of such
filtering is very unmusical. Instead, filters are designed to dampen frequencies gradually.
In the above example, it would mean that the 501 Hz frequency is still audible but somewhat
reduced in amplitude. A frequency of 550 Hz will probably also be audible but will be
even more reduced in amplitude. This is referred to as the roll-off of a filter. Some filters
have a steep roll-off, others a more gradual roll-off. The number of its poles determines the
steepness of filter's roll-off; four-pole filters have a roll-off that is much steeper than two-
pole filters. The MicroFreak filter has a roll-off of 12dB per octave.
The Cutoff knob enables you to control the filter cutoff point manually. In its fully counter-
clockwise position, the frequency cutoff point is approximately 30Hz. As you rotate the
knob clockwise the frequency cutoff point will increase until, in its fully clockwise position, it
exceeds 15kHz.
7.1.5. Resonance or Q
A second setting to complement the cutoff frequency: Resonance. It is sometimes called
“Emphasis” or “Q” – for Quality of filtering.
Resonance
The Resonance knob increases the amount of resonance; it amplifies frequencies close to
the cutoff frequency. When you add resonance by turning the resonance knob clockwise
the filter becomes increasingly selective, the sound begins to “ring” and will severely color
any signal passing through it. As stated above, in its extreme position the Filter will go into
self-oscillation.
7.2. Animating sound
As seen above a lowpass filter modifies sound by removing frequencies above the cutoff
point. Doing this manually is not very effective, although it helps in getting a grasp of what
is happening. What turns the filter into a compelling musical tool is changing the cutoff
point and its resonance dynamically. In the MicroFreak you do this by using an LFO, an
Arpeggiator, or an Envelope to control the cutoff frequency and resonance of the filter.
Please refer to the LFO [p.49] , Arpeggiator [p.67] and Envelope [p.52] chapters for more
details.
47 Arturia - User Manual MicroFreak - The filter: sound in close-up