How do I calculate how much PA power I need?

Start with the desired sound pressure level (SPL) at the farthest listener. For live music, target 100–105 dB continuous with peaks up to 120 dB. Measure the distance from the speaker to that listener and note your speaker’s sensitivity (e.g., 98 dB @ 1W/1m). Each doubling of distance reduces SPL by 6 dB in free field; indoors, the reduction is less due to reflections, but use 6 dB as a conservative estimate.

Calculate the SPL at distance using: SPL at distance = sensitivity – 20 log(distance in meters). Then find the power needed to reach your target: power (watts) = 10^((target SPL – SPL at distance)/10). Add 6–10 dB of headroom to handle transients without distortion. For example, to get 105 dB at 30m from a 98 dB/1W/1m speaker: SPL at 30m = 98 – 20 log(30) ≈ 98 – 29.5 = 68.5 dB. Power for 105 dB = 10^((105 – 68.5)/10) = 10^3.65 ≈ 4467 W. With 6 dB headroom, target 111 dB → 10^((111 – 68.5)/10) = 10^4.25 ≈ 17,783 W. This shows why professional systems use multiple cabinets and line arrays.

For real-world systems, use manufacturer coverage prediction software. SSOUNDS provides AI-assisted acoustic modeling that accounts for array configuration, venue geometry, and audience coverage. This ensures you specify the right number of cabinets and amplifiers for consistent SPL across the venue without over- or under-powering. Always consider amplifier power rating vs. speaker continuous and peak handling to avoid damage.