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"diffuse" attribute and Ambisonics

Spat
#1

Hello T.

I have a question about the “diffuse” attribute of the pan~ object. I am trying spatialise in Ambisonic the cluster and late reverberation section’s of a reverb I am tweaking and I am simply wondering about the necessity of “decoding” the output channels of the panner which uses this subtype.
I’m on a first order ambisonic rig and (concerning those 2 sections) I am declaring 4 outputs to the pan~ object with a “hoa3d” type and a “diffuse” subtype, then the 4 encoded channels are routed to the decoder~ object.

Does the diffuse attribute still generate the WXYZ signals? I can’t find any informations about this subtype in the documentations or in the exemple patches.

Best Regards,
Philippe.

#2

Hi Philippe,

Let’s say that the “diffuse” attribute is here for consistency with the general spat framework.
In this framework, we have to pan 3 types of elements: the direct sound, the early reflections,
and the diffuse sections (a.k.a. cluster and reverb).

In most cases, [spat.pan~ @numinputs N @numoutputs M @subtype diffuse] corresponds to a “diffusion” matrix
that will spread out the N inputs channels (i.e. the signals coming from the cluster and/or reverb; usually N = 8 = numinternals)
towards the M output channels (i.e. loudspeakers).
The role of this matrix is to keep the channels uncorrelated (as much as possible).

Now, to answer your question :
no, in your case (ambisonic), it is not necessary to decode these signals.
These are uncorrelated signals that can be sent to the loudspeakers directly.

Best regards,
T.

#3

Thank you T. for your reply and for the explanations, especially that late in the night.

Philippe.