You see, nothing complicated 
Finally is working with this set up and the Direction facing -Z.
Listener
.Direction = new Vector3f
(0,
0,
-1)Thank you, I think I'm getting the audio's fell I want now.
This works for a platform game where -x/+x avatar's displacement fits with the 'logical' position of left/right speakers.
But what if I decide to make a topdown 2D game, where the avatar's receive rotations, I think this setup will not work anymore, right?
The avatar is rotated so the sound is on his left side, like the second section of this figure.
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How should I configure the Listener.Direction and Listener.VectorUp to this setup? Direction = Vector3(cos(90), 0, sin(90)) and VectorUp(0, 1, 0) ?