Work out sound system power instantly with clear inputs, formula shown and shareable results.
Sound pressure falls 6 dB per doubling of distance, so required gain is target level plus 20 log of distance minus speaker sensitivity, and power is ten to the power of that gain over ten. Because power scales logarithmically, the last 6 dB of headroom costs four times the wattage of the average level, which is why amplifiers seem so oversized.
Distance loss
loss dB = 20 x log10(distance in metres)
Power required
watts = 10 ^ ((target SPL + distance loss - sensitivity + headroom) / 10)
loss dB = 20 x log10(distance in metres). Sound pressure falls 6 dB per doubling of distance, so required gain is target level plus 20 log of distance minus speaker sensitivity, and power is ten to the power of that gain over ten.
Because power scales logarithmically, the last 6 dB of headroom costs four times the wattage of the average level, which is why amplifiers seem so oversized.
Enter target sound pressure level, speaker sensitivity at 1 w, 1 m, listening distance, headroom for peaks. The defaults shown are a realistic worked example — swap in your own figures to get a result you can use.