On the subject of sweet spot or line in the case of Ambio-
In stereo if you move forward you get a hole in the middle. If you move back you get mono. If you move sideways you hear only one speaker most of the time. Of course these things don't happen abruptly so they are tolerated. Another factor particularly in video is that the sound field is not all that real so if it gets a bit worse it is not so catastrophic.
In Ambiophonics, if you move forward not much happens until you hear normal stereo. If you move backwards nothing happens until you hit a wall. The stage might get a bit wider. If you move sideways you lose the wide stage but you don't localize to a speaker, you just hear mono most everywhere in the room. This because the RACE program actually adds a version of both channels together in each speaker which summation is then undone acoustically along the line/space between them but not elsewhere. Thus in general, offside Ambiophonics has much better fidelity than offside stereo or 5.1. This offside problem in 5.1, where only a left or right signal is heard, is why 5.1 needed a center speaker so offside listeners could at least hear the dialog. In Ambiophonics, offside listeners can always hear the dialog even with no center speaker since left, right, and center are all equal parts of the monophonic soundfield in the room.
