Barr II — a dual-band reverb based on Keith Barr’s design

I’ve already released on patch based on Keith Barr’s reverb loop design; this patch actually precedes For Keith Barr, but I’m calling it Barr II because it’s the second patch I’m releasing using the approach. (More info on the design in the For Keith Barr patch notes.)

Although it uses the same algorithm, the results are quite different: Barr II actually employs two, independent reverbs, one for low frequencies and another for high frequencies. The incoming audio is separated by filters and fed into each reverb. Then the outputs are mixed together with the dry level, each having its own level control.

The design allows for a lot of fine-tuning: the high reverb might be set to a long decay but a low volume, while the low reverb might be louder in the mix but decay more quickly, for instance. One reverb might be more lush and expansive while the other is more confined. There are limits to the flexibility of the controls and underlying reverb design, but you can produce a lot of variety from a relatively simple dual-band approach. You could also silence one reverb entirely if you wanted, producing only a high or low band reverb sound.

One quirk: since I decided to use SV filters for the band separation, I also included a resonance control. Pushing this can produce some… uncommon and peculiar results.

The patch is stereo throughout (although left and right get a bit confused in the reverb tank).

Controls:

Stompswitches:

Left — freezes the low reverb

Middle — freezes the high reverb

Front page:

Each reverb shares the same controls:

Decay — sets the overall length of the reverb

Diffuser gain — think of this as a ‘character’ control. Low values will produce a less dense reverb, while higher values will produce more lush, modulated reverb.

Diffusion size — this will control the size of the reverb (but also contribute to its character).

Size — controls the length of the delays used in the reverb loop, it also contributes to the size of the reverb and how modulation affects it

Mod — controls the rate of modulation in a given tank

Level — controls the amplitude of that band’s reverb

There are also global controls:

Pre-delay — extends up to 1 second (1000 milliseconds)

Crossover — determines the frequency at which the bands are separated

Resonance — adds resonance to the crossover frequencies; this can produce some strange, resonant effects

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