A planar-type loudspeaker is provided which includes at least two separate, substantially flat, substantially coplanar diaphragms driven by a common drive mechanism. The diaphragms are each of a material and are dimensioned so that each has only a limited number of natural modes of vibration in the frequency band in which it is to operate and that corresponding natural modes for the diaphragms are close enough to achieve beneficial mechanical coupling and acoustics interference so as to provide a generally uniform acoustic pressure response over the selected frequency band. The diaphragms are preferably coupled only through the drive mechanism and it is preferable that each diaphragm have only two natural modes of vibration in the selected frequency band.