"Lobing" between two spherical wavefronts (something like loudspeaker) occurs when they are greater than 1/4 wavelength apart.
Below this, they "sum" acoustically, as if they were a single source with double the output.
Above this, destructive interference gets gradually worse as you rise in frequency,
or lower (size of) wavelength. There is some summation and some destruction.
Most listeners say they don't notice any loss of uppermost octave info when listening to the 1/2 wavelength method.