Designing Sound in SuperCollider/Schroeder reverb

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Fig 14.28: recirculating schroeder reverb[edit]

First start the server, if you haven't already:

s.boot;

Then so we have some source material, we'll load the standard sound file that comes bundled with SC:

b = Buffer.read(s, "sounds/a11wlk01-44_1.aiff");
// Hear it raw:
b.play

Now here's the code which creates the reverb in a single Synth, with four separate delay lines cross-fertilising each other:

(
Ndef(\verb, {	
	var input, output, delrd, sig, deltimes;
 
	// Choose which sort of input you want by (un)commenting these lines:
	input = Pan2.ar(PlayBuf.ar(1, b, loop: 0), -0.5); // buffer playback, panned halfway left
	//input = SoundIn.ar([0,1]); // TAKE CARE of feedback - use headphones
	//input = Dust2.ar([0.1, 0.01]); // Occasional clicks
 
	// Read our 4-channel delayed signals back from the feedback loop
	delrd = LocalIn.ar(4);
 
	// This will be our eventual output, which will also be recirculated
	output = input + delrd[[0,1]];
 
	// Cross-fertilise the four delay lines with each other:
	sig = [output[0]+output[1], output[0]-output[1], delrd[2]+delrd[3], delrd[2]-delrd[3]];
	sig = [sig[0]+sig[2], sig[1]+sig[3], sig[0]-sig[2], sig[1]-sig[3]];
	// Attenutate the delayed signals so they decay:
	sig = sig * [0.4, 0.37, 0.333, 0.3];
 
	// Here we give delay times in milliseconds, convert to seconds,
	// then compensate with ControlDur for the one-block delay 
	// which is always introduced when using the LocalIn/Out fdbk loop
	deltimes = [101, 143, 165, 177] * 0.001 - ControlDur.ir;
 
	// Apply the delays and send the signals into the feedback loop
	LocalOut.ar(DelayC.ar(sig, deltimes, deltimes));
 
	// Now let's hear it:
	Out.ar(0, output);
 
}).play
)

And here's an alternative way of doing exactly the same thing, this time using a matrix to represent the cross-mixing of the delayed streams. The single matrix replaces all those plusses and minusses so it's a neat way to represent the mixing - see which you find most readable.

(
Ndef(\verb, {	
	var input, output, delrd, sig, deltimes;
 
	// Choose which sort of input you want by (un)commenting these lines:
	input = Pan2.ar(PlayBuf.ar(1, b, loop: 0), -0.5); // buffer playback, panned halfway left
	//input = SoundIn.ar([0,1]); // TAKE CARE of feedback - use headphones
	//input = Dust2.ar([0.1, 0.01]); // Occasional clicks
 
	// Read our 4-channel delayed signals back from the feedback loop
	delrd = LocalIn.ar(4);
 
	// This will be our eventual output, which will also be recirculated
	output = input + delrd[[0,1]];
 
	sig = output ++ delrd[[2,3]];
	// Cross-fertilise the four delay lines with each other:
	sig = ([ [1,  1,  1,  1],
	         [1, -1,  1, -1],
	         [1,  1, -1, -1],
	         [1, -1, -1,  1]] * sig).sum;
	// Attenutate the delayed signals so they decay:
	sig = sig * [0.4, 0.37, 0.333, 0.3];
 
	// Here we give delay times in milliseconds, convert to seconds,
	// then compensate with ControlDur for the one-block delay 
	// which is always introduced when using the LocalIn/Out fdbk loop
	deltimes = [101, 143, 165, 177] * 0.001 - ControlDur.ir;
 
	// Apply the delays and send the signals into the feedback loop
	LocalOut.ar(DelayC.ar(sig, deltimes, deltimes));
 
	// Now let's hear it:
	Out.ar(0, output);
 
}).play
)
 
// To stop it:
Ndef(\verb).free;