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Use spread for whole dome or plane diffusion?

I’m experimenting with spat5.pan~ knn and vbip on a 26 speaker dome, and would like diffusion to switch from a point source to either the whole dome or the lower ring. What would be the most convenient way to achieve that?

I tried using spread, but am not getting the desired results. I would interpret the /spread/mode omni and azim to be made for that with

  1. whole dome: source position 0 0 0, spread mode omni, spread 100
  2. lower ring: source position 0 0 0, spread mode azim, spread 100

instead, the output is silent, until I wiggle the source position a little bit. Then 2. looks ok but 1. has some silent channels. I must be missing some basic understanding or some parameter like spread “radius”.

Thanks for your hints!

Hello Diemo,

A couple of remarks.

  1. With VBAP (or VBIP), source position 0 0 0 shall be avoided.
    This is an edge case where the panning algorithm cannot work (with or without spread).
    (this explains the “silent output” you noticed)
  2. As you know, KNN and VBAP are fundamentally different: the former is distance-based while the latter is direction-based.
    As the consequence, the “spread” mechanism is also fundamentally different for these 2 algorithms.
  3. For speaker dome, direction-based panning (e.g., VBAP) is usually makes more sense, and is recommended. (but you have the right to use KNN)
  4. Below a download link for Spat 5.3.7 beta-release. This features new spread laws which may fit your needs (?). See also example patch below.
  5. The “/divergence/radius” parameter is only meaningful when “/divergence” is enabled.
    You’ll find some information in spat5.pan.maxhelp (non-tilda spat5.pan).
    (admittedly, this would deserve a comprehensive tutorial !)

Hope this helps,
T.

https://filesender.renater.fr/?s=download&token=fb666475-3d71-4394-91eb-c01921fdbed7


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