FEM simulations of horn loudspeakers and their experimental verification

Abstract

Horn loudspeakers are in common use for sound reinforcement of large rooms because of their high efficiency. In the design of horn loudspeakers, special care has to be taken on the horn’s geometry and its interaction with the properties of the driver. In the present work, the finite-element analysis of these coupled acoustical–mechanical systems is compared with classical analytical and finite-difference methods. All simulations are compared with experimental data, obtained from two different horn loudspeakers: First, a folded bass cabinet transducer and, second, a midrange horn loudspeaker. The bass cabinet is 50×54×104 cm in size; the midrange horn measures 40×44×44 cm. Both cabinets are made from wood; therefore, the horn’s geometry can only be approximated to the ideal exponential characteristics. In general, the effect of finite horn length, resulting in reflections at the mouth due to mismatch in acoustical impedance, has to be considered. The bass horn, especially, has to be simulated very precisely, since this loudspeaker shows higher impedance mismatch. The finite-element simulations carried out with ANSYS show excellent agreement with the measurements. The sound-pressure level generated was investigated as a function of frequency and angle of radiation.