Acoustic lobing refers to the radiation pattern of a combination of two or more loudspeaker drivers at a certain frequency, as seen looking at the speaker from its side.
Since a true spherical wavefront cannot be achieved in practice, designers try to make the lobe as wide as possible at the crossover frequency, such that at typical listening positions, the speaker appears omnidirectional.
[citation needed] For the sake of simplicity, the following assumes two point sources separated by a distance d vertically‡, both radiating into half-space at a certain frequency f. Thus we can express lobing as a function of d and its relation to the wavelength λ.
The large black dot is the vertical listening position relative to the centre, at a certain fixed horizontal distance from the speaker.
For wavelengths much greater than d, the wavefront is almost spherical (circular, when seen from the side) and the sound level is constant for a variety of such listening positions - the off-axis response of the speaker is almost omnidirectional.