Gp Acoustics (UK) Limited

Gp Acoustics International Limited

Jack Anthony Oclee-Brown

Mark Alexander Dodd

Sebastien Degraeve

Christopher Spear

Julia Davidson

Allan James Skellett

Electrical circuitry adapted to drive a dual-coil loudspeaker having a primary voice coil and a second voice coil connected in parallel with the primary voice coil, the second voice coil being in series with an LC resonant circuit of impedance Z, further comprising an inductance compensation filter of impedance Zin parallel with the LC resonant circuit.

Loudspeaker circuitry

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.

Loudspeakers

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.

Acoustic waveguides

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.

Loudpseakers

A loudspeaker driver surroundcomprises a flexible, generally annular element having a central axisalong which in use a diaphragm is driven, an outer edgefor fitment to an enclosure and an inner edgefor fitment to the diaphragm, with a roll surface which extends between the edges and which projects in the direction of the axis, wherein the roll surface has a shape formed by a plurality of axial corrugationsextending generally radially with respect to the annular element between the outer and inner edges thereof, the corrugations being shaped and configured such that the roll surface is non-axisymmetric about the axis, and the arrangement being such that cross-sections of the roll surface which extend radially with respect to the annular element between the outer and inner edges thereof have a substantially constant length at all circumferential positions around the annular element and so that the shape of the said cross-section varies continuously between circumferential positions around the annular element, the corrugations giving the projecting roll surface an order of rotational symmetry of at least 30.

Loudspeaker driver surround

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. Essentially, instead of minimising the effect of the annular gap by reducing its size and seeking to seal its outer opening, we propose to enlarge the space so that the fundamental resonant frequency it exhibits drops out of the passband of the high-frequency driver and hence out of the frequency range of interest. This both prevents the fundamental frequency of the cavity from being excited, and also allows sufficient room within the space to accommodate a sound-absorbent material to absorb these undesirable resonances.

Loudspeaker

An acoustic insert for lining a loudspeaker reflex port, the insert comprising an elongate hollow tube formed of a flexible material, having an outer wall sized and configured to seat within the port and an inner wall extending in the elongate direction, the inner wall having a circumference which varies along the length of the insert, When inserted in a port, the insert alters the port resonance so as to vary the acoustic perfoi mance of the loudspeaker.

Loudspeaker bass reflex system

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.

Acoustic phase plug

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.

Electro acoustic diaphragm

A ring-shaped surround for a loudspeaker is disclosed, in the form of a membrane formed in a shape that, when relaxed (i.e. when not being driven), has a cross sectional shape with a first portion extending in a radial direction for a first distance, a second portion extending in an axial direction for a second distance, and a third portion extending in a radial direction for a third distance, the first and second portions being connected by a first flexible join, and the second and third portions being connected by a second flexible join, the first join having a first radius of curvature that is shorter than at least one of said first and second distances, the second join having a second radius of curvature that is shorter than at least one of said second and third distances. Thus, the surround has a Z-shape, with a first radially extending portion, and a relatively sharp bend leading to an axially-extending portion. The radially outwardly extending portion can have a surface which undulates around its circumference, to provide a stiffening effect to the otherwise planar surface and inhibit resonances. One or more tabs can be provided, extending from a surface of the second portion, in a direction transverse to the local orientation of the second portion. These will adjust the dynamic properties of the surround as required. Typically, the surround will be circular, to fit around a circular driver. However, other shapes are possible.

Surrounds for audio drivers

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.

Loudspeaker and diaphragm therefor

A loudspeaker is disclosed, comprising a driven body and a suspension for providing a restoring force to the driven body, the suspension having a cup geometry wherein its attachment point on the fixed portion of the loudspeaker is displaced along the axis of motion relative to its attachment point on the driven body and comprising a first concentric region that is extendible to allow reciprocating axial movement of the driven body, a second concentric region which extends transversely from the first region toward one of the attachment points, and a circumferential member affixed to the suspension at a location between the first and second concentric regions, the circumferential member being relatively stiff compared to the material forming the first and second concentric regions.

A loudspeaker comprising an acoustically radiating diaphragm comprising a generally frustoconical membrane having a narrow neck end and a wide mouth end, stiffening formations for stiffening the radiating membrane and an interface region by which the diaphragm is adapted to be driven; and a transducer comprising a voice coil mounted to drive the diaphragm via its interface region; wherein the interface region is located at the node of the first mode of vibration of the diaphragm.

Cone loudspeaker

A compound loudspeaker comprises an acoustically radiating first diaphragm and an acoustically radiating second diaphragm. The first and second diaphragms are substantially coaxial and at least part of the second diaphragm is situated radially outwards of the first diaphragm. There is a gap situated between the first and second diaphragms, and a seal is provided in the gap, thereby preventing or hindering the passage of air through the gap. By providing the seal, the invention solves the problem of audible turbulent airflow through the gap.

Compound loudspeaker

A phase plug comprises a body having an input side for receiving acoustic waves and an output side for transmitting acoustic waves, the body including a plurality of channels extending from the input side to the output side for propagating acoustic waves through the body. The input side comprises an input surface which includes a plurality of openings constituting entrances for the channels, the input surface being substantially part of a sphere or an ellipsoid in shape. The areas of the openings vary with radial position on the input surface, the radial position being measured in a direction extending perpendicularly from a central axis extending through the input surface. The variation in the areas is a function of the cosine of an angle subtended at the centre of the sphere or a focus of the ellipsoid between the central axis and the radial position.

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Tonbridge, United Kingdom

Jack Anthony Oclee-Brown