Loudspeaker efficiency

Loudspeakers convert only about 0.25 to 2.5 per cent of the electrical energy supplied to them into acoustic energy. The re- maining 97.5 odd per cent is converted into heat. The energy efficiency, or simply efficiency, )70, of a loudspeaker is the ratio of the useful acoustic energy to the signal energy input. /70=10/ogio(P1/PE) [dB] [1] where Pi is the total radiated acoustic power in watts, and PE is the elec- tric power delivered to the speech coil. The efficiency may, of course, also be expressed as a percentage, when it is /7a=100(PLIPE) [%] [2] Nowadays, it is customary for producers to state the sensitivity of a drive unit in the relevant data sheet. The sensitivity is the inten- sity level in decibels at a distance of 1 metre from the unit (dB m-1), when the electrical signal input is 1 watt, referred to the inter- national standard refer- ence intensity. The intensity, I, of a plane or spherical "free" sound wave (no reflections) in the direction of propagation is 1=p211...