# [PD] 8 channel circle panner, how?

Dudley Brooks dbrooks at runforyourlife.org
Thu Sep 12 19:39:57 CEST 2019

```On 9/12/19 6:35 AM, Winfried Ritsch wrote:

> Am Mittwoch, 11. September 2019, 01:01:01 CEST schrieb Dudley Brooks:
>> A quick question, of purely academic interest:
>>
>> In theory, wouldn't it be possible to get 3D spatialization with just
>> four speakers arranged in, say, the corners of a tetrahedron, such as
>> one directly above and three in an equilateral triangle below the
>> listener's "horizon" (i.e. the plane of the listener's ears)?  I'm sure
>> that six speakers would be preferable -- maybe fewer "dead spots"?
>> But, strictly speaking, four could do it, right?
> yes,
>
> ... done 1951 with pupitre d'espace, even with 3D-Soundcontroller, the
> function of controlling a weigthed Amplification matrix like done in
> Ambisonics, so you can use it as Ambisonics 1st order,.. ;-).
>
> id=psKyCwAAQBAJ&pg=PA205&lpg=PA205&dq=pupitre+de+espace#v=onepage&q&f=false
>
> mfg
>   winfried

Thank you, Winfried!  I was sure it was possible.  Mathematically, four
non-coplanar points allow you to define three axes which span 3D space.
The tetrahedral placement I described gives you one speaker above your
ears and three below, so that up and down are defined; one in front (and
below) and two behind (and below), so that front and back are defined;
and one left (and behind and below) and one right (and behind and
below), so that right and left are defined.  Thus any (x,y,z) can be
specified, and Ambisonics can translate any (x,y,z) into this speaker
placement.

Perhaps there are "dead spots" because of the shape of the coverage of
the individual speakers.  I don't know anything about that aspect of the
problem.

-- Dudley

>> On 9/10/19 12:39 PM, Roman Haefeli wrote:
>>> On Tue, 2019-09-10 at 14:43 -0300, Alexandre Torres Porres wrote:
>>>> Em ter, 10 de set de 2019 às 06:15, Roman Haefeli <reduzent at gmail.com
>>>>
>>>>> escreveu:
>>>>> For true spatialization
>>>> what is "true spatialization"?
>>> I mean true spatialization as opposed to simple panning. You asked for
>>> a panner and you were given a panner. Then you said you were thinking
>>> of a more sophisticated panner. And I said what you want might be
>>> spatialization that not only emulates a sound source traveling along a
>>> virtual circle, but that is able to emulate also every position in
>>> between. Sounds to me like true spatialization. But I'm only guessing.
>>> I can't read your mind, don't know what you really want. I can only
>>> read you mails. Only apt has super-cow powers.
>>>
>>>> And why would else/pan4~ not be "truthful"?
>>> Did I say it is not "truthful"? I'm sure it's a very true panner. It's
>>> even 2D (it positions the sound source anywhere between the speakers,
>>> not only on the outlines). Now, isn't that exactly what you want, but
>>> only with four channels? I'm confused now.
>>>
>>>>> - it sounds to me that is what you're aiming at
>>>>> - use Ambisonics[1].
>>>> hmm, I don't really know, and here's a silly question. It seems to me
>>>> ambisonics tries to locate a sound source in a 3D sphere, but the
>>>> idea would actually be to pan the sound source in a 2D circle space.
>>> It's a totally fine question. I'm not an expert either. Ambisonics is
>>> able to render in 3D, but you can also do 2D (for instance, if you
>>> place all speakers on the same plane). What I understand is special
>>> about Ambisonics, is that you do not need to know beforehand for which
>>> speaker setup you're making a recording or a rendering for. Only the
>>> decoder needs to know the exact configuration of the speakers. This
>>> allows for setups that are not a perfect circle or sphere.
>>>
>>>> So, can ambisonics help there or is it overcomplicated for that
>>>> matter? And how is it possible with 8 speakers to simulate a 3D
>>>> sphere?
>>> Again, not an expert speaking here, but depending on your goals you
>>> need that complexity. If your speaker setup is for some reason not a
>>> perfect circle, or the positions are not evenly spaced, the image of
>>> your virtual sound source(s) is distorted. If  you want to account for
>>> that, it's probably easier to use Ambisonics than figuring out all the
>>> calculations on your own. Do you care for a good reproduction of
>>> spatial image? Do you need the flexibility that Ambisoncis gives you?
>>> Do you want re-invent things each time the setup is different? Would
>>> like to be able to switch between 2D and 3D with the same system? Do
>>> you want your piece to be played "correctly" at some other venue that
>>> is not the studio where you worked on your piece?
>>>
>>> I'm not saying you want all that. I'm just thinking that the more you
>>> deal with the stuff, the more those aspect are going to matter.
>>>
>>>>> There seem to be Pd externals for this.
>>>> yeah, I know, just not sure if all the complicated encoding and
>>>> everything is indispensable and stuff
>>> I don't know. I'm not sure if what you want is different from
>>> [else/pan4~], but with 8 channels...
>>>
>>> Roman
>>>
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```