In this paper, the equivalent circuit method is used in analysing the performance of the vibrating system of an electropneumatic loudspeaker, and results are given for the input impedance and displacement amplitude as functions of frequency, and applied to typical designs of this kind of loudspeakers, illustrating the value of equivalent circuit analysis in guiding its practical design. The electrical driving power required for the vibrating system is proportional to the fourth power of the mechanical resonance frequency, which is the upper limit of the frequency range of the electro-pneumatic loudspeaker. Thus the high frequency performance is poor. The optimum condition is found for a flat frequency response below the mechanical resonance frequency. Experiments show that under the optimum condition the high frequency response improves slightly with increase of the magnetic induction in the gap of the magnetic structure. Experimental results agree well with theory, and sound pressure levels up to 181 or 184.8 dB re 2×10-5N/m2 under different conditions were obtained in the horn thoat of the loudspeaker.