Coverage Calculator — Speaker Dispersion & Throw Distance

Dispersion (or coverage angle) is the angle at which the speaker output drops by 6 dB from the on-axis level. Typical PA speakers have 60-90 degrees horizontal and 40-60 degrees vertical dispersion. Horn-loaded speakers can have tighter patterns (40-60 degrees).

Width = 2 × distance × tan(angle/2). For a 90-degree horizontal dispersion at 15 metres: width = 2 × 15 × tan(45°) = 30 metres. This is the -6 dB coverage width — sound extends beyond this but at lower levels.

The first speaker covers one full coverage width; each extra speaker adds only the non-overlapping part, (1 − overlap) × coverage width. So speakers needed ≈ 1 + ceil((venue width − one coverage width) ÷ (coverage width × (1 − overlap))). With 50% overlap, speakers that each cover 15 m, and a 30 m wide venue: 1 + ceil((30 − 15) ÷ (15 × 0.5)) = 1 + ceil(15 ÷ 7.5) = 3 speakers spanning 30 m. State your overlap explicitly (typically 25–50%) rather than using a vague multiplier, and stack or array vertically for extra height coverage.

Throw distance is the maximum distance at which a speaker can deliver adequate SPL. It depends on speaker power, sensitivity and acceptable level drop. For PA design, it is the distance from the speaker to the furthest listener.