Abstract: A method of designing an acoustic waveguide in which acoustic waves travelling along the waveguide are treated as exhibiting single parameter behaviour, and in which the waveguide provides a boundary confining the acoustic waves as they travel along the wave propagation path and has two substantially parallel, primary surfaces spaced apart a distance less than a wavelength of a high frequency acoustic wave. The primary surfaces may be planar, curved, or a combination of planar portions and curved portions.

Abstract: A method of designing an acoustic waveguide in which acoustic waves travelling along the waveguide are treated as exhibiting single parameter behaviour, and in which the waveguide provides a boundary confining the acoustic waves as they travel along the wave propagation path and has two substantially parallel, primary surfaces spaced apart a distance less than a wavelength of a high frequency acoustic wave. The primary surfaces may be planar, curved, or a combination of planar portions and curved portions.

Abstract: Sound emanating from the high-frequency diaphragm of a coaxial speaker will diffract into the annular gap between the tweeter unit and the midrange cone. This results in response irregularities. We therefore disclose a loudspeaker, comprising first and second drivers located substantially coaxially with the first driver located centrally and the second driver located concentrically around the first driver, the loudspeaker being bounded at its radially outer side for at least part of its extent by the voice coil former of the second driver and including a spacing between the outermost extent of the first driver and the innermost extent of the second driver thus defining an annular space, the annular space containing a sound-absorbent material. By placing the sound-absorbing material in the annular space, the resonances within this space are damped, thus alleviating their effect. The annular space can have a lower resonant frequency that is below the passband of the first driver.

Abstract: Sound emanating from the high-frequency diaphragm of a coaxial speaker will diffract into the annular gap between the tweeter unit and the midrange cone. This results in response irregularities. We therefore disclose a loudspeaker, comprising first and second drivers located substantially coaxially with the first driver located centrally and the second driver located concentrically around the first driver, the loudspeaker being bounded at its radially outer side for at least part of its extent by the voice coil former of the second driver and including a spacing between the outermost extent of the first driver and the innermost extent of the second driver thus defining an annular space, the annular space containing a sound-absorbent material. By placing the sound-absorbing material in the annular space, the resonances within this space are damped, thus alleviating their effect. The annular space can have a lower resonant frequency that is below the passband of the first driver.

Abstract: A phase plug for a loudspeaker having a driven diaphragm, wherein at least a portion of the surface of the phase plug disposed in use adjacent the diaphragm is generally annular in two orthogonal directions and has an axis in a third orthogonal direction, and wherein at least a portion of the said annular surface is shaped such that as successive radial cross-sections through the annular surface are generated by rotating a plane about the axis, the cross-sectional shape of the surface of the phase plug varies periodically as the angle of rotation increases.

Abstract: A diaphragm for a loudspeaker, wherein the diaphragm is formed generally in a closed loop around a central void, the loop lying in a plane, the diaphragm having an axis in a direction orthogonal to the plane along which axis the diaphragm is arranged to be driven in use, the diaphragm having inner and outer circumferential edges which are adapted, in use, to be fixed in position, wherein a substantial portion of the diaphragm between the inner and outer edges is shaped in the direction of the said axis so as to protrude from the general plane of the diaphragm in either or both directions along the axis, and wherein said shaped portion when viewed along the direction of the axis comprises at least one series of curves extending radially across substantially all of the driven area of the diaphragm.

Abstract: A phase plug for a loudspeaker having a driven diaphragm, wherein at least a portion of the surface of the phase plug disposed in use adjacent the diaphragm is generally annular in two orthogonal directions and has an axis in a third orthogonal direction, and wherein at least a portion of the said annular surface is shaped such that as successive radial cross-sections through the annular surface are generated by rotating a plane about the axis, the cross-sectional shape of the surface of the phase plug varies periodically as the angle of rotation increases.

Abstract: A diaphragm for a loudspeaker, wherein the diaphragm is formed generally in a closed loop around a central void, the loop lying in a plane, the diaphragm having an axis in a direction orthogonal to the plane along which axis the diaphragm is arranged to be driven in use, the diaphragm having inner and outer circumferential edges which are adapted, in use, to be fixed in position, wherein a substantial portion of the diaphragm between the inner and outer edges is shaped in the direction of the said axis so as to protrude from the general plane of the diaphragm in either or both directions along the axis, and wherein said shaped portion when viewed along the direction of the axis comprises at least one series of curves extending radially across substantially all of the driven area of the diaphragm.

Abstract: The present invention provides a loudspeaker with at least two diaphragm assemblies, in which the reactive forces acting on the magnets in each assembly cancel. By linking the two magnets together via a non-rigid material, resonance in the drive assemblies is highly damped and corresponding distortion of the loudspeaker output is reduced.

Abstract: The present invention provides a loudspeaker with a port tube having an acoustic leakage path through a motile part thereof. In this way, excess energy caused by longitudinal resonance at higher frequencies is radiated transversely through the port tube walls rather than contributing to the output of the loudspeaker itself.

Abstract: A loudspeaker radiating diaphragm can be stiffened to help increase the breakup frequency to above the working frequency range of the driver concerned, by forming it of a molded part and an attached formed part. The molded part is a radiating surface with stiffening ribs. The formed part is a thin surface of high modulus material, attached to the rear of the ribs. The overall structure can have significantly higher stiffness than either of the two parts. This helps in designing a loudspeaker driver that does not breakup within its working frequency range.

Abstract: A loudspeaker comprises a reflex port located within the enclosure at a point substantially co-incident with a nodal surface of at least one resonant mode within the enclosure. The amplitude of that resonance at the input to the duct is minimized, hence assisting in filtering out the effect of that resonance without needing absorptive material. Ideally, it is placed at the intersection of two or more nodal surfaces.

Abstract: The present invention provides a loudspeaker with at least two diaphragm assemblies, in which the reactive forces acting on the magnets in each assembly cancel. By linking the two magnets together via a non-rigid material, resonance in the drive assemblies is highly damped and corresponding distortion of the loudspeaker output is reduced.

Abstract: The present invention provides a loudspeaker with a port tube having an acoustic leakage path through a motile part thereof. In this way, excess energy caused by longitudinal resonance at higher frequencies is radiated transversely through the port tube walls rather than contributing to the output of the loudspeaker itself.

Abstract: A loudspeaker comprises a reflex port located within the enclosure at a point substantially co-incident with a nodal surface of at least one resonant mode within the enclosure. The amplitude of that resonance at the input to the duct is minimised, hence assisting in filtering out the effect of that resonance without needing absorptive material. Ideally, it is placed at the intersection of two or more nodal surfaces.

Abstract: A loudspeaker radiating diaphragm can be stiffened to help increase the breakup frequency to above the working frequency range of the driver concerned, by forming it of a moulded part and an attached formed part. The moulded part is a radiating surface with stiffening ribs. The formed part is a thin surface of high modulus material, attached to the rear of the ribs. The overall structure can have significantly higher stiffness than either of the two parts. This helps in designing a loudspeaker driver that does not breakup within its working frequency range.