A sound with a position plays on a 3D channel, but those are mono: a stereo one (a Custom Edition map's gunfire, a bullet's impact) fell back to a stereo channel, which the Xbox never panned, so it was only faded with distance and came from nowhere. update_channels now gives a stereo channel's sound in the world a pan towards it, as the mixer pans a 3D voice; the mixer pans the channels' middle and keeps their difference as wide as the far ear's gain. Unpositioned stereo plays as before, and no channel pools change.