ALLEGRO_AUDIO_PAN_NONE - Allegro 5 API

       A  special  value  for the pan property of sample instances and audio streams.  Use this value to disable
       panning on sample instances and audio streams, and play them  without  attentuation  implied  by  panning
       support.

       ALLEGRO_AUDIO_PAN_NONE  is different from a pan value of 0.0 (centered) because, when panning is enabled,
       we try to maintain a constant sound power level as a sample is panned from left to right.  A sound coming
       out of one speaker should sound as loud as it does when split over two speakers.   As  a  consequence,  a
       sample with pan value 0.0 will be 3 dB softer than the original level.

       (Please correct us if this is wrong.)

Allegro reference manual                                                         ALLEGRO_AUDIO_PAN_NONE(3alleg5)

       ALLEGRO_AUDIO_PAN_NONE - Allegro 5 API

              #include <allegro5/allegro_audio.h>

              #define ALLEGRO_AUDIO_PAN_NONE      (-1000.0f)