Figure 14:
A feedback delay network structure proposed for artificial reverberation by Jot (1992).
Figure 14 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. 14).
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 which serves to equalize modal energy amongst the three bands.
The delay-line lengths are generally chosen to be mutually prime. System “tuning” remains a manual, trial and error process.