Specifications

7.4 Effects 85
+~ +~
+~
+~
-~ -~
+~
+~
-~ -~
delwrite~ D 1000
delwrite~ C 1000
delwrite~ B 1000
delwrite~ A 1000
*~ 0.4
*~ 0.37
*~ 0.333
*~ 0.3
delread~ A 101
delread~ B 143
delread~ C 165
delread~ D 177
inlet~
outlet~ routlet~ l
fig 7.28: A r ecirculating Schroeder reverb effect
theory. An apparently well des igned reverb ca n mysteriously explode after many
seconds or even minutes so a common design safety measure is to attenuate the
feedback paths as the reverb decays away. What defines the reverb time is the
point at which the reverb is has fallen to −60dB of the first reflection intensity.
A good design sho uld not be too coloured, which means feedback paths mus t
not be too short leading to a pitched effect. The minimum delay time should
be at least a quarter of the reverberation time and the lengths of delays should
be prime, or collectively co-prime
2
. The density of the reverb is important too .
Too little and you will hear individual echos, too much and the effect will become
muddy and noisy. Schroeder suggests 1000 echoes per second for a reasonable
reverb effect. If you look in the extra directory that comes with Pd there are
three nice reverb abs tractions
rev1~
,
rev2~
and
rev3~
by Miller Puckette
Exercises
Exercise 1
Create any one of the following effects.
• Guitar tremolo effect
• Multi-stage phaser
• Multi-tap tempo-sync delay
• A high quality vocal reverb
Exercise 2
Create a sequencer that provides any two of,
2
A set of integers with no common factors are said to be collectively co-prime.