What I’m getting from reading about recording techniques, is that godd recording techniques will fool the ear-brain location finding function to create an approximate aural image, but does not actually duplicate the exact sonic signature (amplitude, phase) that would impinge on the ears during a live performance.
Right. It doesn’t have to be the exact same information. It just has to be enough of the essential information.
The (highly recommended) XLO Test CD has a wonderful track where Roger Skoff simply describes the room dimensions and microphone placement and where is in the room. As he’s talking you realize what you are hearing is exactly as if you are there in the room. Not your room, his. He walks and talks and occasionally hits a clavis (wood block) letting you hear the acoustic signature of the room. At one point he walks to the extreme back of the room and hits the clavis. It sounds as if he is behind you.
How technically is it possible for two speakers in front of you to create the illusion not only of depth front to back but even behind?
The answer is the sound from further away, its not just that there’s a time difference between the direct and reflected sounds, its that there is also a frequency and volume difference as well. Everything about the sound changes depending on where in the recording space the sound originates. That is the lesson of the XLO track. You’d never hear him behind you if speakers were needed back there. Instead all that’s needed is to faithfully reproduce in detail the full acoustic signature of the event. Especially including the faint room echoes.
The speakers must of course be symmetrical and equidistant. Matters more L to R than front to back. I’m simplifying, obviously. But really, its the spacial information captured in the acoustic signature that does the trick more than anything else.