Flat-panel loudspeakers, often called Distributed-Mode Loudspeakers (DMLs), are created by using one or more force exciters to induced vibrations in an elastic flat surface. This report describes a lumped element equivalent model of a flat-panel loudspeaker including multiple bending modes of an elastic plate, the dynamical influence of affixed inertial exciters, and the contribution of the enclosure. Unlike a classical loudspeaker driver, flat panels have many more degrees of freedom. The panel’s natural resonant frequencies are shifted by the dynamical coupling to the exciters and the enclosure. Three important design aspects are illustrated through simulations: (1) the effective low-frequency cutoff of the flat-panel speaker is determined by the higher of either the exciter resonant frequencies or the lowest panel resonant mode; (2) rigidly backed exciters can be employed to avoid mode-splitting at low frequencies, and (3) achieving resonances below 100 Hz with a panel mounted near a wall requires the use of panels with considerable mass. Experimentally, the models were shown to accurately predict the vibrational behavior of a panel with resonant exciters and a rear enclosure.
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