Problem with SPAT
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I have a problem with SPAT. We’ve setup a 27 loudspeaker system but experience some strange movements when panning sources around. By ‘strange’ i mean, standing in the sweetspot, and panning to one end in the room, the sounds seem to be originating from different loudspeakers than those close to where i’m panning. sorry for my bad english – it’s difficult to explain.
The loudspeakers consist of 1 main ring, 8 loudspeakers. A second ring; 4 loudspeakers. A center-top loudspeakers, loudspeakers in the corners + a few other loudspeakers.
I have checked all the physical and software routing – that is correct.
We are not sure if we use the right panning method and / or the right interfacing for SPAT.
I’ve added at .zip file with the max-patch as it looks right now.
We have tried different panning methods; angular panning, vbap2d and 3d but all of them seem to give the result.
We are interfacing with spat.oper using xyz coordinates for the sources. Does this have any influence to how the perception of position is perceived in comparison to using ade placement of sources, given the end position of the source is the same place ? It’s only a message format difference, right?
I’m thinking we are setting up spat in a wrong way somehow but i’m unsure where to look for errors.
|June 18, 2015 at 10:21 #13890|
Several issues to consider:
1) Your speaker setup is 3D. So you need a 3D panning algorithm. ‘angular’ is made for 2D only so it cannot work.
2) Basically we can consider that you have 2 rings of speakers + 1 loudspeaker at the zenith. Am I right ?
3) The lower ring of your setup is problematic (for Spat) : it seems to be made of two (almost) co-located rings
4) Another problematic aspect (for Spat):
5) You will need to align your speakers signals in terms of delays/gains.
Let us know how it goes…
|June 18, 2015 at 10:51 #13895|
Thank you for the quick reply.
We just now tried out the SPCAP method. This seem to work better.
I will look at the 3d methods and spat.pan- and spat.decoder-
3) ah yes ok. The reason for the two co-located rings is, that the audience are ment to be walking around during the concerts, and we wanted to make sure there were ‘presence’ in the signal when audience is listening from outside the ‘dome of speakers’. This meaning the co-located rings are pointed exactly not-the-same-way (<< insert right word here), but are fed two different signals. In this situation, it would be better to feed the same signal to each pair of co-located loudspeakers?
4) Aha !! Just to be sure: It’s only the lower ring that should be moved virtually towards the floor (0 degrees), right? The other loudspeakers should not be moved virtually?
Would it be better to measure at a fixed position in the center of the system, and adjust the loudness to be equal for all loudspeakers?
This could possibly create some issues when you walk around inside the loudspeaker installation – meaning if you are closer to one speaker, then that one would be much dominant – right?
Delays: Are there a quick way of measuring delays using a microphone and some-object-in-spat, or should I just calculate them approximately by the speed of sound (roughly 3 ms pr. meter) ?
|June 18, 2015 at 11:24 #13897|
‘spcap’ is also for 2D not 3D.
3) well, ok. It’s difficult to tell if it’s gonna be good with people walking around.
4) No, you should shift down the whole system
5) as vbap and hoa intend to recreate spatial sound field at the sweet-spot, the system shall be calibrated/aligned with respect to the center of the array.
|June 18, 2015 at 11:43 #13898|
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