Audio

Amplifier power & headroom

Target SPL at the listener → amplifier watts per channel, with headroom.

Start from the SPL you need at the furthest listener, the speaker's sensitivity, and the distance. Get back the continuous power required, the peak power with your chosen crest-factor headroom, and how the speaker's power rating and impedance line up against it.

inputs

Distance unit

Target SPL at listenerdB

Listener distancem

Speaker sensitivitydB @ 1 W / 1 m

From the datasheet. If quoted as 2.83 V / 1 m on a 4 Ω box, subtract 3 dB to get the 1 W figure.

Headroom (crest factor)

How far the peaks sit above the average level. The amp must pass the peaks cleanly.

Nominal impedance

Speaker ratingW cont.

Optional — continuous / RMS rating.

Recommended amplifier (per channel @ 8 Ω)

500W

next stock size above 316 W peak

32 W continuous + 10 dB headroom = 316 W peak

Required SPL at 1 m

105.0dB

85 dB at 10 m + 20.0 dB inverse-square loss

▸ Rule of thumb: amp rated at 1–2× the speaker's continuous rating, at the speaker's impedance. Under-powering plus clipping kills more drivers than over-powering does.
▸ Assumes one point source in free field — 6 dB lost per doubling of distance. Indoors, room gain and reflections help you; line arrays and column speakers lose closer to 3 dB per doubling in the near field.
▸ Two identical speakers driven together add up to +6 dB at the listener (coherent, on-axis); in practice budget +3 dB.
▸ Sensitivity is a 1 W figure; a 4 Ω speaker quoted at 2.83 V is actually drawing 2 W.

power ladder

Log scale. Grey = continuous, lime = peak and chosen amp, coral = speaker rating. The lime band is the headroom the crest factor demands.

Need this math wired into a real system? We do that for a living.

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