[LAD] ambisonics UHJ encoder

Jörn Nettingsmeier nettings at folkwang-hochschule.de
Wed Feb 24 20:04:37 UTC 2010

On 02/24/2010 03:29 PM, fons at kokkinizita.net wrote:
> On Wed, Feb 24, 2010 at 05:01:20PM +0300, alex stone wrote:
>> Jorn, Fons,
>> I'm getting deeper into a setup now, and trialling a few different configs.
>> A further question.
>> Given that an amb sphere is equal on all "sides", and the sweet spot
>> is the centre (roughly speaking), should i be configuring my dry sound
>> orchestral instruments/sections to use the upper-rear/rear quadrant of
>> the sphere, assuming the centre is the listener, in a total space? In
>> a real world setup, my orchestra is on the stage, and the listener may
>> well be (at my choice) sitting in a spot equidistant from the
>> back/front/left/right of the total space. Should i assume this as a
>> point of reference to begin with?

there is no "back/front/left/right of total space" you could be
equidistant from - ambisonics is not concerned with walls at all, just
with directions. sources can be as close or as far away as you want, but
the panner won't do that for you - you have to create the illusion
manually, with delay, eq treble rolloff to simulate air-damping, and
more reverb (unless you're mixing an outside scene). in theory, HOA
could do distance coding, but i don't know how to do that, yet. fons
might be able to point to some information, but i doubt it would be
worth the trouble at this point, as it's mostly about proximity effect
anyways (i.e. bass boost for close sources)...

your "point of reference" is your listening position. it's the origin of
your coordinate system (see farina's page for an illustration of the
axes). 0° azimuth is to the front, positive angles are to the right
(mathematicians have it the other way round, but the AMB panners do it
so that the motion of the slider will correspond to the motion of a
source). 0° elevation is on the horizonal plane, 90° is the zenith
(right above your head), -90° is the nadir (watch for bum diffraction :-D)

>> My "speakers" will be not only on stage, but as ambient
>> sound/reflections in the rest of the space as well. The
>> space isn't exactly spherical.

ah, you want to fake wall reflections. tricky. you would want a room
synthesizer for that... how are you generating those reflections?

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