A Schroeder Reverberator called JCRev

JCRev was developed by John Chowning and others at CCRMA based on the ideas of Schroeder.

• Three Schroeder allpass sections:
  $$\hbox{AP}_{N}^{\,g} \mathrel{\stackrel{\mathrm{\Delta}}{=}}\frac{g + z^{-N}}{1 + g z^{-N}}$$

• Four feedforward comb-filters (STK uses FBCFs):
  $$\hbox{FFCF}_{N}^{\,g} \mathrel{\stackrel{\mathrm{\Delta}}{=}}g + z^{-N}$$

• Schroeder suggests a progression of delays close to
  $$M_iT \approx \frac{100\hbox{ ms}}{3^i}, \quad i=0,1,2,3,4.$$

• Comb filters impart distinctive coloration:
  • Early reflections
  • Room size
  • Could be one tapped delay line
• Usage: Instrument adds scaled output to RevIn
• Reverberator output RevOut goes to four delay lines
  • Four channels decorrelated
  • Imaging of reverberation between speakers avoided
• For stereo listening, Schroeder suggests a mixing matrix at the reverberator output, replacing the decorrelating delay lines
• A mixing matrix should produce maximally rich yet uncorrelated output signals
• JCRev is in the Synthesis Tool Kit (STK)
  • JCRev.cpp
  • JCRev.h.