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How to design an irregular speaker arrangement in Spat5?

“Hello, I would like to inquire about setting up a performance in a 25-channel spatial venue. Currently, I have learned that the actual speaker positions are somewhat irregular. I am currently using hoad3d and adding phantom speakers, but I’m still encountering a warning from spat5.hoa.decoder~: [16:15:55.792] warning occurred: the reference position (x=0, y=0, z=0) is ‘outside of’ the speaker setup, which is utterly inappropriate for 3D HOA decoding. I’d like to know if there are any algorithms suitable for this speaker layout, or how I can correct this issue?”

This is my setup:
HOA-3D.maxpat (65.1 KB)


The issue here is that all the loudspeakers are declared above the listener (x=y=z=0). Adding phantom speaker(s) is a good idea, but only a partial workaround.

I would suggest that you shift the speaker positions down by a few meters (2m to 3m should work).
This can be easily accomplished with spat5.translate.
If you do so, the speaker setup should behave nicely with the available 3D algorithms : VBAP3D and HOA3D (3rd or 4th order).

Hope this helps,