The ‘Lo Damp Gain’ & ‘Hi Damp Gain’ sliders attenuate (dampen) the level at the specified frequency ranges between -24 and 0 dB. The frequency region is specified in Hz via the ‘Lo Damp Frequency’ & ‘Hi Damp Frequency’ dials.
Rather than being a surgical EQ, this section aims to help you shape the general contour of the audio going through the feedback delay network in the plugin.
The ‘Hi Damp’ dial affects the frequency spectrum exponentially from 15000 Hz to 1900 Hz. The ‘Lo Damp’ dial affects the frequency spectrum exponentially from 45 Hz to 300 Hz. So with both dials, turning them upwards reduces the width of the frequency band (produces narrower filtering and greater damping if ‘Gain’ is attenuated).
So these are more like general tone control sections you would find on amplifiers. The regions of operation are chosen carefully to match the resonant frequencies of the plugin with a nod to the shaping controls on certain digital hardware devices on which Diffuse is based.
These tone shaping controls actually affect eight high shelf and eight low shelf filters in and around the allpass diffusion network in the FDN at the heart of the plugin algorithm.
For more information of the “Tone Controls” part of the “Reference” section of the Diffuse manual.