true, batted balls that first contact the field between home plate and first or third base are considered fair if they subsequently bounce over or directly contact either base, or otherwise pass either base while in fair territory. that's what the mlb glossary says, at least.
Answer:because each speaker has a large angle of of coverage (horizontal and vertical)
They place them apart to prevent their signals (sounds produced) from getting into each other's way as this may cause interference (which may be destructive.