Abstract: A panel form loudspeaker comprises a resonant multi-mode radiator (11) which in turn comprises a plurality of substantially concentric sub-panels (20, 21, 22, 23). A plurality of analogue drivers (10) drive the radiator (11), one or more of the drivers being operational at any time. A signal level measured at the input to the loudspeaker determines the operational state of each of the drivers (10). The concentric sub-panels may take various shapes and have different areas.

Abstract: A panel form loudspeaker comprises a resonant multi-mode radiator (11) which in turn comprises a plurality of substantially concentric sub-panels (20, 21, 22, 23). A plurality of analogue drivers (10) drive the radiator (11), one or more of the drivers being operational at any time. A signal level measured at the input to the loudspeaker determines the operational state of each of the drivers (10). The concentric sub-panels may take various shapes and have different areas.

Abstract: A panel-form loudspeaker has a resonant multi-mode radiator panel which is excited at frequencies above the fundamental frequency and the coincidence frequency of the panel to provide high radiation efficiency through multi-modal motions within the panel, in contrast to the pistonic motions required of conventional loudspeakers. The radiator panel is a skinned composite with a honeycomb or similar core and must be such that it has a ratio of bending stiffness to the third power of panel mass per unit area (in mks units) of at least 10 and preferably at least 100. An aluminum skinned, aluminum honeycomb cored composite can meet this more severe criterion easily.