Acoustics: Sound Fields, Transducers and Vibration, 2nd Edition

6.9. Efficiency

Medium frequencies

The efficiency of a loudspeaker is defined as 100 times the ratio of the acoustic power radiated to the power supplied by the electrical generator. In the medium frequency range between the suspension resonance and the point where the coil inductance starts to contribute to the electrical impedance, the power supplied by the generator is approximately

W E ≈ e g ( rms ) 2 R E

(6.46)

where we are assuming that R _g   ≪   R _E . Using W from Eq. (6.23), the reference efficiency E _ff is then given by

E f f = 100 W W E ≈ 100 B 2 l 2 S D 2 ρ 0