Reverberation techniques

References : Posted by Sean Costello
Notes :
* Parallel comb filters, followed by series allpass filters. This was the original design by Schroeder, and was extended by Moorer. Has a VERY metallic sound for sharp transients.

* Several allpass filters in serie (also proposed by Schroeder). Also suffers from metallic sound.

* 2nd-order comb and allpass filters (described by Moorer). Not supposed to give much of an advantage over first order sections.

* Nested allpass filters, where an allpass filter will replace the delay line in another allpass filter. Pioneered by Gardner. Haven't heard the results.

* Strange allpass amp delay line based structure in Jon Dattorro article (JAES). Four allpass filters are used as an input to a cool "figure-8" feedback loop, where four allpass reverberators are used in series with
a few delay lines. Outputs derived from various taps in structure. Supposedly based on a Lexicon reverb design. Modulating delay lines are used in some of the allpass structures to "spread out" the eigentones.

* Feedback Delay Networks. Pioneered by Puckette/Stautner, with Jot conducting extensive recent research. Sound VERY good, based on initial experiments. Modulating delay lines and feedback matrixes used to spread out eigentones.

* Waveguide-based reverbs, where the reverb structure is based upon the junction of many waveguides. Julius Smith developed these. Recently, these have been shown to be essentially equivalent to the feedback delay network reverbs. Also sound very nice. Modulating delay lines and scattering values used to spread out eigentones.

* Convolution-based reverbs, where the sound to be reverbed is convolved with the impulse response of a room, or with exponentially-decaying white noise. Supposedly the best sound, but very computationally expensive, and not very flexible.

* FIR-based reverbs. Essentially the same as convolution. Probably not used, but shorter FIR filters are probably used in combination with many of the above techniques, to provide early reflections.
Comments
from : kristian_bauza[AT]yahoo[DOT]it
comment : Hello I am doing de algorith of moore in Matlab simulink and I compare direntes reverb processor to improve something but i dont find anything to improve i ask if you have some idea to make something better in C++ a library DLL and making a plugin.... thanks

from : krs[AT]ms15[DOT]hinet[DOT]net
comment : matlab reverb ..thanks

from : superhotmuffin[AT]hotmail[DOT]com
comment : Hi, after trying a bunch of Schroeder/Moorer designs which never really sounded great, I stumbled upon a "loop" topology that I whipped up in a coffee-fueled coding frenzy at Starbuck's one night. It sounded great - like a real guitar amp reverb. Still uses delays/comb filters and the usual nonsense, but w/ a different topology. Drop me a line and I can send my source. It's fully commented, including "ASCII art" signal flow diagrams. Michael B.

from : superhotmuffin[AT]hotmail[DOT]com
comment : I've received a lot of requests about my `Gardner' topology so I've placed a copy of the comments from my source files on OneDrive here: https://onedrive.live.com/redir?resid=76918537984b2b01!173&authkey=!AIZax2NmDKPcS8w&ithint=file%2ctxt Note that this is a plain text file containing ASCII art diagrams which probably won't render correctly in every text editor/browser so you might have to do a little editing. Send me an email if you have problems.