Right, but for any point source this is effect is going to vary spatially. That's why you can't make one speaker totally cancel out another speaker over a whole room.

Sure, but my point is that there is only one speaker involved so the cancellation happens in the electronics, before any sound is made.

It's interesting to think of 'cancellation' in different mediums. Waves in physical space. Radio in electromagnetism. And now 'computed' waves cancel each other too.