Abstracts Category : Other

Driver-array based flat-panel loudspeakers: theoreticalbackground and design guidelines

by David Allan Anderson

This thesis relates to the simulation and design offlat-panel loudspeakers using moving-coil driver elements. A briefhistory of the industry is given, including a collection ofproducts and patents from 1925 until the present, an overview ofre- search papers, and a discussion of current products available.The mechanics of bending flat panels are developed with respect tolocalized driving forces, both in the frequency domain and thetime domain as an impulse response. These simulations are comparedto measurements on prototype panels. Additional resonant elementsinfluence the behavior of the system: an optional ported rearenclosure and the res- onant characteristics of the drivers. Thegoverning equations for these systems are derived and solutionsare implemented using equivalent mechanical circuits and nu-merical methods. The idea of using driver arrays to independentlyactuate modes of the panel is discussed at length with respect tomodal addressability, modal spillover, and experimentalvalidation. The numerical approach to determining the optimaldriver placement for a given set of modes is derived andexperimentally validated. An investigation of the acousticbehavior of flat panel loudspeakers is presented, using mechanical simulation results to predict the acoustic radiation.The simulations are compared to measurements and found toaccurately predict important mechani- cal and acousticalbehaviors. It is demonstrated that a driver array, with the properbiasing, is capable of creating a flat panel loudspeaker which actsmore like a piston than a "diffuse radiator" flat panelloudspeaker. The techniques of "Modal Crossover Networks" areintroduced, which use multi-band filters to bias the driver arraydiffer- ently for different frequency bands, optimized for audioreproduction. The question of how many drivers are necessary for amodal crossover network is addressed and found to be dependent onthe estimated quality factor (Q) of the panel material and edgeconditions.