LinPlug Spectral - Manual (Page 23)

Filter
In Spectral each Oscillator is followed by its own Filter. These filters are
structural identical but can take an specific individual shape out of many
thousand shapes.
To turn a filter module on or off, select the On/Off button to the right of the
Filter label. Note: when a filter is turned off no filtering is applied so that the
audio signal from the Oscillator passes straight through it without being
altered.
On the far right you find the Tool Menu as described in the Tool Menu info
box on page 15.
Freq (Frequency) is used to set the operation frequency of the filter. When
using the filter as a simple Low Pass, higher settings produce brighter
sounds while lower settings result in darker sounds. However, as the
Spectral's filters can be of arbitrary any shape you better think of it as a
possibility to shift the whole filter towards higher or lower operation
frequencies.
This parameter can be modulated using the Mod Matrix (Fil / Frequency).
The Reso (Resonance) dial is used to set the amount of emphasis around
the operation frequency. Higher settings create a more pronounced peak in
the signal while lower settings produce a flatter response.
This parameter can be modulated using the Mod Matrix (Fil / Resonance).
Next is the Subsequent Filter, labeled LP+ (because its an additional 18dB
Lowpass). Due to the internal structure of Spectral harmonics created when