Power, sensitivity and sound pressure
Watt ratings alone do not tell you how loud a loudspeaker will play. Sensitivity, distance, power compression and excursion are equally important.
Sensitivity comes first
A sensitivity figure describes the acoustic level produced for a defined electrical input and distance. A few decibels of sensitivity difference can require a large change in amplifier power to compensate.
Power adds logarithmically
Doubling amplifier power ideally adds about 3 dB. Ten times the power adds about 10 dB. In real drivers, thermal compression and excursion limits reduce the gain before the theoretical number is reached.
Distance matters
In free field, doubling distance reduces sound pressure by roughly 6 dB. Rooms alter this through reflections and modal behaviour, especially at low frequencies.
Maximum output is therefore a system property: driver displacement, thermal capacity, enclosure alignment, filtering, amplifier voltage and listening distance all interact.