- From the efficiency, we may calculate sensitivity, which is the sound pressure level a speaker produces for a given input:
A speaker with an efficiency of 100% (1.0) would output a watt of energy for every watt input. Considering the driver as a point source in an infinite baffle, at one meter this would be distributed over a hemisphere with area 2π mē for an intensity of (1/(2π))=0.159154 W/mē, which gives an SPL of 112.02 dB.
SPL at 1 meter for an input of 1 watt is then:
dB(1 watt) = 112.02 + 10*log(η0)
SPL at 1 meter for an input of 2.83 volts is then:
dB(2.83 V) = dB(1 watt) + 10*log(8/Re) = 112.02 + 10*log(η0) + 10*log(8/Re)