Sound system designers frequently want to know much amplifier power will be needed to deliver adequate sound pressure levels for the application. This can be determined based on the desired listener distance from the speaker, the desired sound pressure level of the audio at this distance, and the loudspeaker's published sensitivity rating to provide the reference acoustical output at 1 watt at 1 meter. For Extron speakers, use the dropdown box and select the desired Extron speaker to automatically load its sensitivity into the calculator field. Additional headroom should be added for the amplifier, for example, 10 dB, to account for variability in program audio levels.
This audio tool calculates the acoustical attenuation from the reference location of 1 meter (3.28 feet) to the listener, and then applies this, together with the sensitivity rating and amplifier headroom, to determine the necessary output power from the amplifier.
- APR = 10((LP + H - LS + 20 log (D2/ DR))/10)
- APR = amplifier required power
- LP = required SPL at listener
- H = desired amplifier headroom
- LS = loudspeaker sensitivity at 1 watt and 1 meter
- D2 = distance to farthest listener
- DR = 1 meter or 3.28 feet reference distance