Why sweet spots exist
Stereo, surround, and object-based audio systems rely on fixed loudspeaker locations. Correct spatial imaging occurs only when the listener is positioned at equal distances from those loudspeakers. As the listener moves, distance relationships change. Arrival time shifts. Sound pressure level changes. Frequency response is altered. Spatial cues collapse. The result is a narrow region of accuracy surrounded by progressively degraded listening experiences.
All conventional stereo, surround, and immersive audio systems are boundary-limited. Sound can only originate from the boundaries of the listening space. Loudspeakers are placed at the perimeter and radiate inward. No matter how many loudspeakers are added, sound always enters the space from the outside. Each listener experiences a different geometric relationship to those boundaries. The sound field collapses differently for each position.