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

9.3. Reference efficiency

In the middle-frequency range many approximations usually can be made to simplify the analogous circuit of Fig. 9.3. Because the drive unit is very small, the mass of the diaphragm and the voice coil M _MD is very small. This in turn usually means that the compliance of the suspension C _MS is large to keep the resonance frequency low. Also, the conductance of the suspension G _MS usually is large, and the reactance ωC _M1 is small. Hence, in this frequency range, the circuit reduces essentially to that of Fig. 9.4a, where the conductance behind the diaphragm is

G M B ≡ 1 ρ 0 c S D m · N/s .

(9.2)

With the area-changing and electromechanical transformers removed, we get Fig. 9.4b, where ...