Abstract: An inertial vibration exciter having a magnet assembly defining an annular gap, a coil assembly disposed in the annular gap, suspension means mounting the coil assembly for reciprocating movement in the gap, means coupling the coil assembly to a member to be vibrated, and a hermetically sealed housing in which the magnet assembly, the coil assembly, the suspension means and the coupling means are disposed. The housing may comprise a heat sink thermally coupled to the magnet assembly and the heat sink may be resiliently coupled to the housing. The coupling means may comprise a plate-like member to which the coil is rigidly attached and of a size substantially greater than the diameter of the coil. The plate-like member may be resiliently coupled to the housing.

Abstract: An inertial vibration exciter having a magnet assembly defining an annular gap, a coil assembly disposed in the annular gap, suspension means mounting the coil assembly for reciprocating movement in the gap, means coupling the coil assembly to a member to be vibrated, and a hermetically sealed housing in which the magnet assembly, the coil assembly, the suspension means and the coupling means are disposed. The housing may comprise a heat sink thermally coupled to the magnet assembly and the heat sink may be resiliently coupled to the housing. The coupling means may comprise a plate-like member to which the coil is rigidly attached and of a size substantially greater than the diameter of the coil. The plate-like member may be resiliently coupled to the housing.

Abstract: A bending wave panel-form acoustic radiator formed from sheet material to define an acoustically active area and having at least one integral stiffening member in the form of a corrugation extending out of the plane of the sheet and at least partially across the acoustically active area of the radiator, which stiffening member is of substantially U-shaped cross section. Also disclosed is a method of making a bending wave panel-form acoustic radiator, comprising forming a sheet into a panel having at least one integral corrugation member extending out of the plane of the sheet and at least partly across the sheet and of substantially U-shape cross-section, to stiffen the sheet to have a desired ability to support and propagate bending waves.

Abstract: A method of making an acoustic member for a loudspeaker having an operative frequency range and acoustic output which depends on the values of parameters of geometry, bending stiffness, areal mass distribution, damping, tension modulus, compression modulus and shear modulus of the member, the method comprising providing an acoustic member having at least one frequency dependent parameter with a variation which depends on frequency, selecting the variation which depends on frequency, selecting the variation of the frequency dependent parameter to effect a desired acoustic output from the loudspeaker and making the member having said selected variation. The method may comprise selecting an acoustic member having a component made from a frequency dependent material which has a glass to rubber transition Tg in the operative frequency range of the speaker.

Abstract: A resonant bending wave loudspeaker comprising a panel-form acoustic radiator in the form of a beam and a vibration transducer mounted to the beam at a position to apply bending wave energy thereto to enable low frequency modes to be excited in the radiator both lengthwise of the radiator and crosswise of the radiator, and means mounting the radiator to permit the excitation of low frequency lengthwise and crosswise modes therein.

Abstract: A method of making an acoustic device in the form of a loudspeaker drive unit having a resonant panel-form member adapted to provide an acoustic output when excited with bending wave energy, comprising forming a resilient suspension for the panel-form member by molding and simultaneously fixing the resilient suspension to the panel-form member.

Abstract: A bending wave panel-form acoustic radiator formed from sheet material to define an acoustically active area and having at least one integral stiffening member in the form of a corrugation extending out of the plane of the sheet and at least partially across the acoustically active area of the radiator, which stiffening member is of substantially U-shaped cross section. Also disclosed is a method of making a bending wave panel-form acoustic radiator, comprising forming a sheet into a panel having at least one integral corrugation member extending out of the plane of the sheet and at least partly across the sheet and of substantially U-shape cross-section, to stiffen the sheet to have a desired ability to support and propagate bending waves.

Abstract: A loudspeaker comprising a bending wave panel, an enclosure in which the bending wave panel is mounted to enclose one face of the panel, a compliant suspension between the panel and the enclosure by which the panel is supported in the enclosure, a vibration exciter attached to the panel to apply bending wave energy thereto, and an acoustic absorber in the enclosure to reduce standing waves in the enclosure, wherein the compliant suspension and the acoustic absorber are integral. A method of making such a loudspeaker is also disclosed.

Abstract: A loudspeaker comprising a bending wave panel, an enclosure in which the bending wave panel is mounted to enclose one face of the panel, a compliant suspension between the panel and the enclosure by which the panel is supported in the enclosure, a vibration exciter attached to the panel to apply bending wave energy thereto, and an acoustic absorber in the enclosure to reduce standing waves in the enclosure, wherein the compliant suspension and the acoustic absorber are integral. A method of making such a loudspeaker is also disclosed.

Abstract: A method of making an acoustic device in the form of a loudspeaker drive unit having a resonant panel-form member adapted to provide an acoustic output when excited with bending wave energy, comprising forming a resilient suspension for the panel-form member by moulding and simultaneously fixing the resilient suspension to the panel-form member.