eli5 – How do spacial audio technologies like Dolby Atmos work in headphones, with only two drivers?
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Your ears can’t really tell where sound is coming from, so you only need one driver per ear. The trick is knowing what sound each ear should hear, so your brain thinks the sound is coming from a specific place. So you take the “raw” unmodified sound in the recording, then modify it to simulate position.
If the sound source is to your left, then it will appear louder to your left ear than it does to your right ear. It will also arrive a little bit earlier to your left ear than it does to your right ear. Your head is maybe 20cm across, so it takes sound 0.6ms to go from one side to the other. A tiny difference, but enough for your brain to pick up on.
You know how things sound muffled when you hear them throw a hat or something like that? Your head and your ears do the same thing. Sound coming from behind you has to go through the back of your ears, and that muffles it. Sound from one side has to go through your whole skull to reach the other.
Then you have reverberation: all the sound bouncing off the walls and other surfaces. That gives you a ton of cues as to the size and shape of the room.
Spatial audio technologies basically try to simulate these effects (and more) to build a nice realistic model of what it sounds like for a noise to come from a certain place.
You might want to look at [head-related transfer functions](https://en.m.wikipedia.org/wiki/Head-related_transfer_function) for more details.
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