Small loudspeakers radiate omnidirectionally because they are small relative to wavelength

Evidence

Although a standard loudspeaker looks like it should radiate sound in the direction that its drivers are pointing, in practice it doesn’t. This is because at many frequencies, it is small with respect to the wavelength; for example, a 200 mm (8”) loudspeaker will only start becoming directive at about 1 kHz! Note that the size of the box has very little influence; it is the size of the part that radiates the sound that matters. So we can consider any small loudspeaker to be similar to a torch or flashlight bulb without a reflector, irrespective of what it looks like! — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2501

Categorization

• DEFINE: Clarifies why speaker size, not box size, determines directivity onset — the radiating element’s size in wavelengths governs diffraction behavior.
• SEED: The flashlight-bulb analogy is a crisp way to explain why small speakers sound omnidirectional — usable in any audio explainer.