Abstract: The present invention relates to a loudspeaker array comprising: a high frequency driver and a midrange driver forming a unitary assembly and configured to direct acoustic waves towards a listener in front of the loudspeaker array along an axis in a forward direction; at least one low frequency driver located generally rearwardly of the unitary assembly, and a woofer volume extending along and perpendicular to the axis between the at least one low frequency driver and the unitary assembly, in which the rear of the unitary assembly is configured and acoustically open so as to allow sound from the rear of the midrange driver to radiate rearwardly into the woofer volume.

Abstract: A loudspeaker comprising: an acoustic diaphragm having front and rear surfaces, the acoustic diaphragm in use being driven so as to vibrate and radiate acoustic waves from its front surface in a forward direction away from the loudspeaker and from its rear surface in a rearward direction, and a drive unit located rearwardly or to the front/outside of the diaphragm, there being at least one open duct leading in a rearward direction away from the diaphragm, in which the at least one open duct has a cross-sectional area which decreases in the rearward direction, and in which acoustic waves radiated from the rear surface of the diaphragm pass through the open duct before contacting a front surface of an acoustic metamaterial absorber located generally behind the drive unit and immediately to the rear of the duct.

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 loudspeaker comprising two acoustic diaphragms mounted to face in axially-opposed directions, two voice coils each having an axis and an axial length and being configured to reciprocate along its axis to drive one of the diaphragms, the axes being substantially parallel and both axes passing through both diaphragms, and at least one magnet forming part of a chassis assembly configured to provide two axially-extending gaps, one for each of the voice coils to reciprocate within, wherein the at least one magnet and the chassis assembly are adapted so that magnetic flux flows across the gaps in opposite directions, and wherein when in use the diaphragms are at their predetermined maximum negative excursions the voice coils overlap in the axial direction by between 10% and 90% of their average axial length, and wherein when in use the diaphragms are in a relaxed position, between their maximum negative and positive excursions, the voice coils do not overlap in the axial direction.

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 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.