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Loudspeakers positions in large hall

Spat
#1

Hi all,

I’m working on a pre-producion for an opera in a large opera house and I’m using Spat to realize all the spatialization.

I’ve a (probably stupid) question about loudspeaker’s positions and distances in such a large hall.
I know the dimensions and shape of the hall, let’s say a big rectangle, and the goal is to create a realistic source localization. Do I have to set the speakers position exactly in meters and angles or I can set them in the right shape letting the Spat to simulate the correct sources’ positions?

Thanks
L

#2

Hi Lorenzo,

it depends on the rendering method: if you use a pairwise method like “angular”, “vbap” or “panr”, and if a realistic doppler effect is not mandatory, then only the angles are important for the panner, but… in any case, you have also to care about the time synchronization between all loudspeakers, namely that they should be synchronized (by delaying the closest ones) on the chosen sweet spot. Then you have to decide if you want to make the time synchronization inside the spat, or with the mixing board.

If you use a more complex rendering method like ambisonics, as far as I know (I’m not a specialist of ambisonics), the angles and the distances are important for the rendering itself.

Remember that a good time synchronization between all loudspeakers can only be achieved on the sweet spot. All the other positions are out of sync.

Best

Alexis

#3

Hi Lorenzo,

Two different aspects shall be considered :

  1. for the panning itself, spat only needs to know the « directions » (i.e. azimuth and elevation angles) of the loudpseakers; their distances are not relevant.
    In other words, the panning algorithms actually assume that all loudspeakers are at the same distance.

  2. for the actual sound reproduction in the room, all the loudspeakers shall be « aligned » (in delay and gain) with respect to a given position (usually in the middle of the room). The alignment compensates for the different distances of the speakers.
    This alignment can be either done with spat.align~ or at the mixing desk by the sound engineer. (make sure that you dont do both !)

Dont know if this is clear ?

T.

#4

Thank you all for the replies.

Yes, the sound engineer will set up the delays at the mixing desk.
This time it’s only a pre-production, so by now we can just experiment with the hall.

So, T., if I understood well your point n°1 where you say that “the panning algorithms actually assume that all loudspeakers are at the same distance”:
In the case of a rectangular hall: I have to set the right angles without modifying the loudspeakers’ distances (and I will align the loudspeakers at the mixing desk or with spat.align~).
This would work even if in this case the loudspeakers aren’t at an equal distance.

Am I right?
thanks

#5

Yes, you are right !

NB : in your spat.spat~ (or spat.pan~ or whatever object you use), you could also give the actual loudspeakers positions; the panning module will just ignore the speakers’ distances, and only consider their angles.

T.

#6

Cool, thank you! I’ve just do that in one of the large rehearsing halls of Royal Opera House and it works fine.
Thank you