Modal crossover networks for flat-panel loudspeakers

Loudspeakers that produce sound from the bending vibrations of flat plates offer an attractive design alternative for applications in which a low-profile speaker form factor is desirable, such as displays, windows, and other architectural elements. However, vibrating panel speakers may exhibit irregular low-frequency response and phase distortions due to the presence of isolated low-frequency panel modes. In this paper a method is presented for tuning the frequency response of flat-panel loudspeakers by employing force-driver arrays. The method enables independent actuation of specific panel bending modes, which can be combined with a frequency crossover network to enable extensive tuning of the loudspeaker. Experiments demonstrate that independent control of plate modes is achievable with a small array of inertial drivers affixed to the plate and that a wide variety of acoustic responses are possible, including cancellation of the adverse effects of isolated low-frequency plate modes.