Abstract: An acoustic device intended to operate pistonically and in bending comprising a panel-form acoustic radiator, a magnetic drive system including a voice coil on a tubular bobbin, the bobbin being directly coupled to the radiator to drive the radiator directly; and a coupling device connected to the bobbin, and to the radiator at a position at or near to the first nodal line of bending resonance of the radiator. A method of improving the on-axis response of a loudspeaker having a panel-form radiator and intended to operate both pistonically and in bending, comprising driving the radiator by a directly connected tubular bobbin, and substantially suppressing the lowest natural frequency of the radiator by providing a coupler connected from the bobbin to the radiator at or near to its first nodal line.