Source Audio Spectrum Intelligent Filter User Manual page 26

Please note that unlike the Distortion Processor, both of the Filter Processors run independently,
meaning that it is possible to run two filters simultaneously. The Filter types and parameter controls
for Processors 1 and 2 will run independently of one another.
On Button: Engages or disengages the Filter module.
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Voice Mix Monitors: The four meters labeled Voice 1 through 4 monitor the Processor 1 & 2
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ratio of each Voice routed to the Filter.
Filter Type Dropdown Menu: Choose from any of the Spectrum's 28 different filter types
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(see below for a detailed description of the filters and the response plots).
Invert Button: Inverts the direction of the filter modulation. For example if a single low-pass
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filter is set to modulate its cut-off point from the lower frequencies to the higher frequencies,
the Invert button will change the direction of the filter modulation and move it from the
higher frequencies to the lower frequencies.
Depth Knob: Adjusts the breadth of the filter modulation. As the Depth knob is increased, so
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does the frequency range over which the filter moves.
Frequency Knob: Adjusts the starting point of the filter modulation. Turning the knob to the
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left causes the filter to modulate over lower frequencies and turning the knob to the right
causes the filter to modulate over higher frequencies.
Q Knob: Adjusts the intensity (also referred to as "resonance") of the filter. Increasing the Q
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knob essentially boosts the height (or "level") of the frequency peaks and deepens the
notches in the frequency cuts.
Envelope/LFO Selector Dropdown Menu: Selects whether Envelope/LFO 1 or Envelope/LFO
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2 controls the filter modulation.
Pitch Tracking Drop Down: Engaging the Pitch Tracking initiates a function where the Filter
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modulation and Pitch Tracking work in tandem, meaning that the filter will move its starting
point in the frequency spectrum based on the note that is being played. There are three
different pitch-to-filter frequency ratios: 1/3 Octave, 2/3 Octave, and 1 Octave. So for
example, if you set your Pitch Tracking to 1/3 Octave and play a low E then an E up one
octave, the filter's frequency starting point will move up 1/3
from where it was for the lower E. If you set the your Pitch Tracking to 1 Octave, the
frequency starting point will move up a full octave when moving from a low E to E at the next
octave.
More details on the Filter Processors
Theory of operation: Internally, the Spectrum contains two independent processing blocks that
perform the filtering operations. Each block has three sections, each capable of a variety of two-
pole filters. These are then connected in series or parallel, with small mixers to sum as the case
may be. This gives us a large variety of frequency response shapes. While the sound is, of course,
determined from its frequency response, that doesn't mean it's easy to tell what something will
sound like just from looking at the frequency response. Not even for us. The Frequency control
for the filter moves the entire frequency response up and down in frequency, with all three filter
sections moving together. When Modulation is applied, the three sections may move together
or independently, with some moving up while others move down, or they may move in the same
SA248 Spectrum Intelligent Filter User Guide
of an octave with the higher E
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