6.2.7. Creating Reverb Algorithms in VSig¶
This short guide is meant to demystify VSig’s reverb modules and show how they may be used with one another, or with other modules from other categories.
Download the sigfile here: Creating Reverb Algorithms in VSig.
6.2.7.1. “Plug and Play” Modules¶
6 of the available reverb modules can be considered “plug and play” in the sense that they do not require any additional modules to function as reverbs. The highest quality reverb algorithms, however, will make use of other modules to better simulate acoustic space.
Plug and play modules include:
Reverb_2016
Reverb_a
Reverb_b
Reverb_c
Reverb_d
Stereo_room
6.2.7.1.1. Reverb_a,b,c,d¶
Reverb_a,b,c, and d function identically and use the same parameters, the difference between them being delay density. The modules are of high, medium, low, and adjustable densities respectively.
Parameters
Decay (s) - controls the decay time (overall RT60)
Roomsize – adjusts the relative room size of the reverb
Predelay (ms) - the amount of delay between the onset of sound and the onset of reverberant sound
Low_freq (Hz) - controls the frequency at which LF attenuation works
High_freq (Hz) - controls the frequency at which HF attenuation works
Low_decay (dB) - controls the attenuation of frequencies below low_freq
High_decay (dB) - controls the attenuation of frequencies above high_freq
*Moddepth – controls the amount of delay randomization
*Modrate – controls the rate of delay randomization
*Modratespan – adjusts the degree to which different internal delays will be swept at different rates
*Gliderate – adjusts the rate at which changes to delay values are “glided”
**Delay(n) - controls the internal delays of the reverb; amount (n) of delays depends on which module is used (12, 8, 6, or selectable in multiples of 4)
*The reverb_n family includes built-in delay randomization which is controlled by the modulation/glide controls. This randomization helps reduce flutter/resonances and is often best utilized by setting a constant value inaccessible to the user. Overly high moddepth or modrate values may introduce undesirable sounds of their own.
**Adjusting internal delay times is the primary means by which a distinct room “character” can be created. Used in combination with roomsize, adjustment of delay times allows for the creation of distinct, varied reverb sounds within a single module.
Things to know about the reverb_a,b,c,d family:
Smaller roomsize values tend to introduce more fluttering, with the smallest room sizes sounding very harsh and metallic. This can be partially remedied using the modulation settings, but not completely
Larger roomsizes may also have audible flutters, but can be much more easily fixed using the modulation settings without introducing further artifacts
In practice, the perceived room size depends both on the roomsize parameter and the individual delay values
6.2.7.2. Diffusors¶
Diffusor – creates a dense field of delay repeats that is typically used to create reverberator structures; essentially a chain of series-connected all pass filters
On its own, the diffusor module almost acts like a regular delay module with a feedback loop. The way in which delay builds up overtime, however, is a better approximation of how echo density builds up in a real space (during early reflections) than some of the plug and play reverbs can achieve. For plug and play modules without a built-in diffusion control (reverb_a-d), diffusor modules may be necessary to create a more realistic buildup of echo density.
Fig. 6.33 Reverb algorithm utilizing diffusors and the reverb_c module¶
The above algorithm demonstrates how diffusor modules may be used in combination with reverb_a-d (reverb_c in this case). The presence of diffusors before the reverb module causes the reverb to swell more extremely and quickly than if signal was routed directly into the reverb module. To hear the difference for yourself, download the algorithm and toggle the diffusors between on and off using the knob labeled “Diff on.” A value of 0 means the diffusors are on, and a value of 1 means they are off.