Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
  • H04R7/00—Diaphragms for electromechanical transducers; Cones
  • H04R7/02—Diaphragms for electromechanical transducers; Cones characterised by the construction
  • H04R7/04—Plane diaphragms
  • H04R7/06—Plane diaphragms comprising a plurality of sections or layers
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
  • H04R7/00—Diaphragms for electromechanical transducers; Cones
  • H04R7/02—Diaphragms for electromechanical transducers; Cones characterised by the construction
  • H04R7/04—Plane diaphragms
  • H04R7/045—Plane diaphragms using the distributed mode principle, i.e. whereby the acoustic radiation is emanated from uniformly distributed free bending wave vibration induced in a stiff panel and not from pistonic motion

Definitions

• the invention relates to loudspeakers and more particularly to panel-form loudspeakers of the kind adapted to be excited by launching bending waves into a resonant panel to cause it to resonate to produce an acoustic output.
• loudspeakers are described in our International patent application WO97/09842, and are known as distributed mode loudspeakers.
• a moving diaphragm In conventional pistonic loudspeakers, a moving diaphragm, usually a cone, is held in position on a frame or chassis by at least one flexible member which forms a resilient suspension.
• This suspension performs at least the following functions, namely:- 1. location in the frame of an assembly comprising the diaphragm and a vibrator usually including a moving coil motor;
• a resonant panel-form loudspeaker comprising suspension means located wholly in one or more panel regions of low average velocity.
• suspension means may be used to suspend the panel in a support and/or to support a vibration exciter on the panel.
• the support may comprise a surrounding area of the panel, which surrounding region may be acoustically inactive.
• the resonant panel-form loudspeaker may comprise a panel having an acoustically active area and panel regions of low average velocity surrounding the acoustically active area, with slots or grooves in the panel structure defining the acoustically active area.
• the slots or grooves may be such that they extend only partly through the panel structure.
• the idea of using low energy regions of the panel for the mechanical support of the panel itself or of an exciter on the panel may be extended to include the use of slots or through incisions in the panel for the purpose of areal definition of a desired acoustically active panel area for distributed mode operation or at least desired acoustic vibration behaviour set within, or as a part of a larger panel component.
• Such slotting will, for example, permit a wide range of distributed mode type vibrating panels to be produced as an integrated design with arbitrarily formed and contoured vehicle trim panels.
• the slots may be of any suitable form or shape consistent with the desired vibration behaviour in the required frequency range.
• FEA finite element analysis
• the low vibration energy in the suspension regions has the benefit of allowing the use of stronger suspension elements than would otherwise be possible, so increasing the durability of the resulting assembly.
• a compliant suspension may be created by incising the panel to form integral finger-like cantilever members.
• the incisions may comprise a parallel pair of slots through the panel structure.
• the cantilever members may be straight or otherwise, e.g. curved.
• straight cantilevers might be preferred in order better to span the distance between areas of low average velocity and a region of high activity where the exciter is coupled to the panel.
• the suspension may consist of an array of such cantilever members.
• the panel may be incised to form cantilever members which retain stiffness in the plane of the panel and which are compliant in the plane of a frame or the like supporting the panel.
• a separate compliant suspension e.g.
• the rubber-like suspension may be mounted on the cantilevers.
• the resonant panel -form loudspeaker may comprise a distributed mode acoustic radiator, e.g. of the kind defined in International patent application WO97/09842.
• the invention is a decorative trim panel, e.g. for a vehicle or the like and incorporating a loudspeaker as defined above.
• the invention is a vehicle, e.g. an automobile, comprising a loudspeaker as defined above or a decorative trim panel as defined above.
• the invention is a method of making a resonant panel acoustic device characterised by identifying the location of at least one panel region of low average velocity and positioning suspension means within the said region (s) .
• the method may comprise defining an acoustically active area of the panel by locating panel regions of low average velocity surrounding the acoustically active area and disrupting the panel structure in the said regions to form panel suspension means.
• the method may comprise defining the acoustically active area by slotting the panel structure. The slots may be such that they extend only partly through the panel structure.
• the method may further comprise identifying the desired panel location, e.g. an anti-node, for coupling the vibration exciter to drive the panel, and identifying one or more nodal regions adjacent to the drive location in which to position the exciter suspension.
• desired panel location e.g. an anti-node
• the method may comprise incising the panel material to define cantilevers forming the suspension means.
• the suspension means may be such as to have at least three cantilevers .
• Figure 1 is a cross-sectional side view through part of a resonant panel-form loudspeaker and showing a suspension for a vibration exciter;
• Figure 2 is an underneath plan view to smaller scale of the resonant loudspeaker panel of Figure 1 ;
• Figure 3 is an underneath plan view of a resonant loudspeaker panel showing three embodiments of vibration exciter suspension;
• Figure 4 is a plan view of a panel incorporating a resonant panel-form loudspeaker
• Figure 5 is a scrap plan view, to an enlarged scale, of detail V A' of Figure 4, and
• Figures 6 and 7 are alternative scrap cross-sectional views on the line A-A of Figure 5.
• a resonant panel-form loudspeaker 14 e.g. of the general kind described in International patent application WO97/09842 and comprising a resonant generally rectangular flat panel 1 usually of a stiff lightweight material forming an acoustic radiator and an inertial vibration exciter 4 mounted on the panel 1 to induce bending wave vibration in the panel to cause it to resonate to produce an acoustic output.
• the panel may be of monolithic construction, but as shown comprises a cellular core 2 sandwiched between opposed face skins 3.
• the inertial vibration exciter 4 comprises a voice coil/tubular coil former assembly 13 mounted, e.g. by bonding in a circular aperture 12 in the panel 1 whereby the assembly 13 extends from one face of the panel (the upper face as shown in Figure 1) and projects into an annular gap 15 in a magnet assembly 5,6,7 and defined between a disc-like pole piece 7 and a pole cap 6 which together sandwich a disc-like magnet 5.
• the assembly comprising the magnet 5 and poles 6 and 7 is mounted on the panel 1 for axial movement relative to the coil/former assembly 13, when the coil is energised with a signal, on a compliant suspension attached to an annular flange 8 projecting from the cup 6 and comprising three equi-spaced rubber-like pads 9, only one of which is visible in Figure 1.
• the pads 9 are mounted on finger-like cantilevers 10 formed by incising U-shaped slots 11 through the panel and equi-spaced round and concentric with the aperture 12 as best can be seen in Figure 2 in panel regions of low average velocity, such that the inner ends 16 of the cantilevers are free for movement normal to the plane of the panel 1.
• the pads 9 are attached near to the free ends 16 of the cantilevers 10. It will be understood that, if desired, the pads 9 might be omitted and the magnet assembly 5,6,7 might instead be mounted directly on the cantilevers 10.
• Figure 3 of the drawings show various alternative embodiments of cantilever for suspending a vibration exciter on the panel 1.
• These include a single straight finger-like cantilever 10 defined by a U-shaped slot or incision 11 of the kind shown in Figures 1 and 2, a curved cantilever 17 defined by a spiral slot 18, and a resilient suspension comprising a cantilever member 19 defined between an opposed pair of arcuate slots 20 and having a central part circular portion 21 and an opposed pair of projections 22 attached at their distal ends to the panel, with the magnet system connected at a central position 23 of the portion 21.
• Figures 4 to 7 disclose an embodiment of resonant panel-form loudspeaker 14 of the general kind described above and having a resonant panel 1 forming part of a larger panel 24, which may, for example, be a decorative trim panel in an automobile or the like vehicle.
• the loudspeaker 14 has a rectangular resonant panel 1 defined within the larger panel 24 by grooves or slots 25, the panel 1 being suspended in the panel 24 by suspension cantilevers 27 defined by opposed parallel slots 26 arranged to bridge the slot 25 in regions round the panel 1 of low average velocity.
• One cantilever is disposed on each side of the panel 1.
• the vibration exciter 4 may be suspended as described above or conveniently as desired.
• the slot 25 may extend only partly through the panel 1.
• the slot 25 extends through the upper skin 3 and through the core 2 of the panel 1 to leave the lower skin intact and covering the slot.
• the slot 25 may extend completely through the panel 1.
• the slotting may be made at an early stage of manufacture, e.g. with laser or water jet cutting and the slots need only be wide enough to achieve a stable clearance for the vibrating component.
• a width of 1mm or 2mm may generally be sufficient.
• the width of the suspension component depends upon the effective cantilever length, the toughness and linear stiffness of the panel in that region and the acceleration forces which the whole assembly might be reasonably required to sustain. Values of about 4 to about 25mm have proved effective for cantilever width.
• a relatively narrow slot width allow for a safe grounding of the panel in contrast to surface configurations using adhesive bonding to compliant suspension components. In this later case the suspension may suffer damage due to de-bonding.
• the larger general panel may act as a baffle, generally augmented by local structures such as vehicle door frame or some overall framing and support. In an architectural application the structural panel will be augmented by the design of the room or building. Acoustic leakage via the narrow slots is likely to be negligible between front and back. Such low leakage is also beneficial in respect of stray noise isolation from the back to the front of the panel which may be important in some applications.
• suspension can use same material as panel , so cost is low;
• suspension may be located within the panel thickness, or with only a small increase of thickness
• a number of such suspension positions can be found either to suspend the panel to the relatively stationary part of a vibration exciter, e.g. a magnet assembly, and/or to suspend the panel to a frame or other support, and,

Landscapes

• Engineering & Computer Science (AREA)
• Multimedia (AREA)
• Physics & Mathematics (AREA)
• Acoustics & Sound (AREA)
• Signal Processing (AREA)
• Fittings On The Vehicle Exterior For Carrying Loads, And Devices For Holding Or Mounting Articles (AREA)
• Diaphragms For Electromechanical Transducers (AREA)
• Audible-Bandwidth Dynamoelectric Transducers Other Than Pickups (AREA)

Priority Applications (10)

Applications Claiming Priority (2)

Publications (1)

Family

ID=10820766

Family Applications (1)

Country Status (14)

Cited By (26)

Families Citing this family (4)

Citations (2)

• 1997
  • 1997-10-21 GB GBGB9722079.2A patent/GB9722079D0/en not_active Ceased
• 1998
  • 1998-10-16 JP JP2000517579A patent/JP2001521353A/ja active Pending
  • 1998-10-16 BR BR9812949-0A patent/BR9812949A/pt not_active IP Right Cessation
  • 1998-10-16 AT AT98949102T patent/ATE266301T1/de not_active IP Right Cessation
  • 1998-10-16 DE DE69823695T patent/DE69823695D1/de not_active Expired - Lifetime
  • 1998-10-16 AU AU95484/98A patent/AU9548498A/en not_active Abandoned
  • 1998-10-16 EP EP98949102A patent/EP1036484B1/en not_active Expired - Lifetime
  • 1998-10-16 IL IL13567798A patent/IL135677A0/xx unknown
  • 1998-10-16 KR KR1020007004251A patent/KR20010031264A/ko not_active Application Discontinuation
  • 1998-10-16 CA CA002303789A patent/CA2303789A1/en not_active Abandoned
  • 1998-10-16 WO PCT/GB1998/003131 patent/WO1999021397A1/en active IP Right Grant
  • 1998-10-16 CN CN98809523A patent/CN1271508A/zh active Pending
  • 1998-10-28 TW TW087117887A patent/TW410526B/zh not_active IP Right Cessation
• 2000
  • 2000-09-28 HK HK00106173A patent/HK1027251A1/xx not_active IP Right Cessation

Patent Citations (2)

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