Driver spacing exceeding half a wavelength causes spatial aliasing.

Evidence

Array loudspeakers can also exhibit unwanted side lobes at higher fre­ quencies, due to aliasing, which reduce their utility; that is, above some frequencies the spacing between the drivers is greater than half the wave­ length of the sound being produced. This results in spatial aliasing and in a loss of control of the beam pattern. — David Howard, Jamie Angus, coustics and Psychoacoustics, 2890

Categorization

• DEFINE: Defines spatial aliasing concretely as the driver-spacing-to-wavelength ratio, not just ‘unwanted lobes’.