Advertised constant-directivity specs are often meaningless across most speech frequencies.

Evidence

One of the authors has seen a loudspeaker advertised as having a constant directivity of 90° × 60° using a horn whose mouth dimensions were 130 × 130 mm. This gives an Fθmin of 2.4 kHz and 3.4 kHz, respectively. As most human speech energy is between 100 Hz and 5 kHz, this speaker’s directivity is going to have very little influence on the intelligibility of the speech! — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2508

Categorization

• SEED: Angle: ‘Specmanship’ — how loudspeaker (and headphone) datasheets exploit the frequency range where listeners can’t verify the claim.
• CANDY: A ‘constant directivity 90x60’ speaker that only achieves it above 2.4 kHz is a great one-liner for anyone who’s bought PA gear.