Reverbs and Diffusion

Deepfield can build reverberation from complete Reverb/DelayNet modules or from lower-level delays, allpasses, diffusors and feedback networks. The second approach is where the modular graph becomes especially useful.

What diffusion does

A delay gives distinct repeats. A diffusion stage smears energy in time so individual impulses become a denser cloud. Allpass/diffusor stages are useful because they can increase echo density without behaving like a simple low-pass decay.

Use Diffusor for a series allpass structure, ModDiffuser when randomized/modulated sections are useful, and ModDisperser when you want dense phase dispersion from generated one-sample allpass sections.

A simple reverb architecture

A useful learning design is:

  1. input diffusion;
  2. several delay lines of different lengths;
  3. a mixing/feedback matrix;
  4. damping inside the feedback paths;
  5. output diffusion/modulation;
  6. wet/dry and output level control.

The delay times should not all share the same obvious period. Small structural differences help prevent the tail from collapsing into a recognizable repeating pattern.

Feedback matrices

A feedback matrix redistributes energy between delay lines rather than sending each delay only back to itself. Even a small matrix can make the tail denser and more spatial.

Deepfield's Mixers, Scale and control mapping utilities are useful here. Keep the overall feedback energy bounded; a matrix can become unstable even when no individual-looking gain control seems extreme.

Modulation

Very small modulation of delay/allpass times can reduce metallic static resonances. Too much modulation turns the reverb into an obvious chorus. The interesting region is often where motion is audible in the tail but not perceived as a separate pitch wobble.

Spring-like structures

A spring impression benefits from dispersion: different frequencies arrive with different phase/time relationships. Cascaded disperser/allpass structures can approximate this character, but dense dispersion can be CPU-heavy. Use the smallest number of sections that gives the desired character before stacking more stages.

CPU strategy

A reverb can contain many control paths that do not need audio-rate evaluation. Keep slow random/LFO/control systems in the modulation or parameter domains where possible and reserve full audio rate for the signal paths that actually require it.

Front-panel design

A complex reverb graph can still have a simple panel. Good user-facing controls might be:

  • Decay
  • Size / Delay scale
  • Diffusion
  • Modulation
  • Tone / Damping
  • Width
  • Mix or wet level

Use Variants for complete room characters such as Chamber, Hall, and Cathedral when those states share one graph architecture.