How are my reverb plugins creating stereo image?

[Brandon203113]

A couple of my reverb plugins have stereo knobs inside them, (for instance the stock ableton reverb) but i'm curious what exactly this is doing.. Is it just delaying one of sides being reverbed a certain amount or... is it doing more than this?

[Benedict]

Both that and more. Algorithmic reverbs are built from many Delay Lines running at once (and into each other). Some are panned left, some right and some not so much. This does a surprisingly good job at emulating the sound of a room/space.

This simple Reverb I made may help you understand:



The main Time knob sets the PreDelay and size of the space. In other words, the smaller the room, the closer the delay taps (shorter time).

Those sets of paired knobs are the Right & Left times so each can be different (nothing in a room or the instrument's position is perfect maths so everything is kinda random). By the time those 8 delay lines are feeding back into themselves/each-other you get a pretty nice soup. This is the essence of any reverb.

I then add another simpler delay line to smooth the endings. This part varies from Dev to Dev as we all try different things to get what we think is a nicer sounding reverb (and of course solve the ringing problems inevitable with a lot of close delays flanging & resonating all over the place). Filtering out highs & lows helps heaps as rooms never return a perfect copy of the sound.

The final element is adding modulation to the delay times to help minimize the ringing and make a fatter sound that can go so far as descending every so nicely into noise as the pitches become more & more varied.