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How it Works: LPF/HPF Filter
When the LPF/HPF Style is active, Filter Mod controls
the cutoff frequency of either the LowPass or HighPass
filter (LPF and HPF).
The overlap of these two filters’ frequency response
creates a sweeping BandPass filter (BPF) effect.
Each filter has a passband, or band of frequencies it will pass at full gain. The LowPass filter (LPF, shown in red)
only lets low frequencies pass, while the HighPass filter (HPF, shown in cyan) only lets high frequencies pass.
Both filters each have a cutoff frequency that defines where their respective passband ends or begins (LPF &
HPF respectively). On the left side of the ring, Filter Mod sweeps the cutoff frequency of the LPF from 20 Hz all
the way up to 20,000 Hz. While this is happening, the cutoff frequency of the HPF stays fixed at 20 Hz.
Where the two filter passbands overlap (shown in white) is the passband of the LPF/HPF combination - all
frequencies in this band make it through, while the rest are filtered out by either the LowPass filter or the
HighPass filter. You can see how the white band gets progressively wider, allowing increasingly high frequency
content to pass as you rotate the knob up to the middle LED position.
At center LED Filter Mod position, you have the widest passband
possible: 20 to 20,000 Hz. You won’t hear any filtering at this setting,
since all your audio frequency content will make it through unchanged.
On the right side of the ring, Filter Mod sweeps the cutoff frequency of the HighPass filter (cyan) from 20 Hz all
the way up to 20,000 Hz. On this side of the ring, the cutoff frequency of the LowPass filter (red) remains fixed at
20,000 Hz.
Now you can see the combined passband (white) gets progressively narrower as your rotate the knob to
maximum, preventing increasingly higher frequencies from passing through.
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