Live Sound Consulting & Speaker Design
Speaker Sensitivity represents one of the most useful specifications published for any transducer.
Loudspeaker manufacturers follow different rules to obtaining this value with most expressing this value as the average output across the usable frequency when applying 1W/1M into a nominal impedance.
This represents the efficiency and volume that can be expected from a speaker when applying 1 watt into the nominal impedance and measuring the dBSPL at a distance of 1 meter with a reference voltage for this measurement is 2.83V into 8 ohms.
Why is this so important? When selecting a speaker or speaker cabinet, if I can increase the sensitivity by 3 dB, you will reduce my power requirement by half and this can be a considerable cost savings when purchasing a power amplifier.
This value can be used to determine the required amplifier wattage required to provide a certain given dB level at a given distance for an application.
This equations can be used to calculate the required wattage by first using:
dBW = Lreq – Lsens + 20 * Log (D2/Dref) + HR
Then using the dBW result to get the required wattage with:
Watts = 10 to the power of (dBW / 10)
Lreq = required SPL at listener
Lsens = loudspeaker sensitivity (1W/1M)
D2 = loudspeaker-to-listener distance
Dref = reference distance
HR = desired amplifier headroom
dBW = ratio of power referenced to 1 watt
W = power required
I do this in a spreadsheet for comparison calculations.
Doing this calculation yourself is not required, an app is provided the Crown site at: www.crownaudio.com/en/tools/calculators
and select the Amplifier Power Required.