Freeverb

A more recently developed Schroeder reverberator is ``Freeverb'' -- a public domain C++ program by ``Jezar at Dreampoint'' used extensively in the free-software world. It uses four Schroeder allpasses in series and eight parallel Schroeder-Moorer comb-filters for each audio channel, and is said to be especially well tuned.

Figure 2.6 shows the default signal-processing settings for the Freeverb left stereo channel. Processing for the right channel is obtained by adding an integer to each of the twelve delay-line lengths. This integer is called stereospread, and its default value is 23. (See the file tuning.h for all constants and default values used by Freeverb.) Different software distributions may include slightly different default values in tuning.h. The values given in Fig.2.6 were found in the ladspa-cmt-plugins package (``Computer Music Toolkit'') which is included in the Planet CCRMA distribution, and which is based on the June 2000 version of Freeverb, as of this writing. There are at least six more instances of Freeverb in the Planet CCRMA distribution alone.^3.10

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Subsections

• Freeverb Main Loop
• Moorer Lowpass Feedback Comb Filter
• Freeverb Allpass Approximation
• Conclusions

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written by Julius Orion Smith III
Julius Smith's background is in electrical engineering (BS Rice 1975, PhD Stanford 1983). He is presently Professor of Music and Associate Professor (by courtesy) of Electrical Engineering at Stanford's Center for Computer Research in Music and Acoustics (CCRMA), teaching courses and pursuing research related to signal processing applied to music and audio systems. See http://ccrma.stanford.edu/~jos/ for details.