Figure 8:
A feedback delay network structure proposed for artificial reverberation by Jot (1992).
Figure 8 illustrates an example FDN reverberator using three delay lines proposed by Jot (1992).
An FDN can be seen as a vector feedback comb filter, with feedback “channels” (=3 in Fig. 8).
The “mixing matrix” provides diffusion by “scattering” energy amongst the channels. Assuming decay control is handled by the coefficients, this matrix should be “lossless”.
To achieve frequency-dependent decay control, the coefficients can be replaced by low-order digital filters.
The “tonal correction” filter is a low-order filter that serves to equalize modal energy across the spectrum.
The delay-line lengths are generally chosen to be mutually prime. System “tuning” remains a manual, trial and error process.