TL;DW: Ultralight is the most low-CPU matrix reverb I can make.

Ultralight.zip (610k) standalone(AU, VST2)
Ultralight in Airwindows Consolidated under ‘Reverb’ (CLAP, AU, VST3, LV2)

This plugin continues work I’m doing, trying to make working demos of ideas for the Godot game engine.

Much like FastDistance is a filter that (when not pushed to really heavy attenuation of brightness) is way more efficient than using a DF1 biquad filter, Ultralight is a reverb that’s way more efficient than using any of my other reverbs. Why? Because it’s extremely limited. There’s nearly nothing to it, just a 4×4 Householder matrix and some tone shaping. (all my test audio of potential patches for this reverb are even simpler, showing only the raw matrix without even tone shaping.)

Why? Because I want to put dozens, maybe hundreds of them, into a game… and have the game still run and have room for graphics and gameplay.

This would involve placing them as ultrasimple mono instances, each with its own delay times and settings, in a scene. They’d all get fed all of the sounds in the scene, and then your environment would be composed of all the distinct spaces sounding off at once.

This is the plugin version of that, so unless you can compile it with your own reverb patch (generated by IntoTheMatrix) you get the built-in space and can manipulate it with the controls. Warning, if you set the RT60 control (which is ‘damping’) to zero, you get infinite sustain! I wanted that in case some patch and combination of settings worked, when set to ‘infinite’, though I’m not sure that can ever happen.

Furnish goes from zero to four, and specifies how many of the first four comb filters should be replaced with allpass filters.

SolidWl goes from zero to four and works on the feedback paths. It’s a highpass filter that also cuts back regeneration a lot. The idea is that it’ll mimic the walls being less than solid as rock, since normal construction doesn’t contain superlow frequencies very well. Don’t expect much adjustability as it is a very cheap efficient hack for doing it.

ReflcWl goes from zero to four and works on the feedback paths. It’s the same kind of lowpass filter that’s in FastDistance, which leads to some funny behavior at high regeneration (low RT60 damping). Again, it’s a very cheap hack, as efficiency is all that matters.

Predlay is the predelay, in samples, and goes from 0 (1 for the AU) to 4096, which in Ultralight runs inside a simplified version of my undersampling, so it’ll act consistent if you’re running it at high sample rate. It’s enough predelay to account for some pretty huge spaces.

Dry/Wet is the reverb (there are no early reflections) and works as usual, except that in Ultralight…

Distnce is the distance high frequency attentuation, just like in FastDistance, and runs AFTER dry/wet so you can hear what a sound, its predelay, and its reverb, sound like in a game engine with all of them far away from you. That’s because, like my earlier plugin VerbSixes, this plugin is the tool I use to audition possible 4×4 reverbs to add to the game engine. I paste in the new values in the header file, build it, and do a sound example to hear what it did. Especially when dialing in settings, that’s helpful. Again, this is NOT really meant for musician or mix use, though if you must run a reverb on impossibly potato hardware, this might save you :)

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All this is free and open source under the MIT license, brought to you by my Patreon.