AU595703B2 - Shallow loudspeaker - Google Patents

Description

i AU-AI-14819/ 8 8 PCT WORLD INTELLECTUAL PROPERTY ORGANIZATION PCT Internatinal Buru is INTERNATIONAL APPLICATION PUBLISH U9E E P7TEU OZ RATION TREATY (PCT) (51) International Patent Classification 4 International Publication Number: WO 88/ 08239 H04R 9/04, 9/00, 9/06 Al (43) International Publication Date: 20 October 1988 (20.10.88) (21) International Application Number: PCT/US88/00685 (72) Inventor; and Inventor/Applicant (for US only) HOUSE, William, S (22) International Filing Date: 9 March 1988 (09.03.88) Neal [US/US]; 1401 East Prairie Drive, Bloomington, IN 47401 (US).

(31) Priority Application Number: 036,566 (74) Agent: CONARD, Richard, Barnes Thornburg, 11 South Meridian Street, Suite 1313, Indianapolis, (32) Priority Date: 8 April 1987 (08.04.87) IN 46204 (US).

(33) Priority Country: US (81) Designated States: AT (European patent), AU, BE (European patent), CH (European patent), DE (Euro- Parent Application or Grant pean patent), DK, FR (European patent), GB (Euro- (63) Related by Continuation pean patent), IT (European patent), JP, LU (Euro- US 036,566 (CON) pean patent), NL (European patent), SE (European Filed on 8 April 1987 (08.04.87) patent), US.

(71) Applicant (for all designated States except US): HAR- Published MAN INTERNATIONAL INDUSTRIES, INCOR- With international search report.

PORATED [US/US]; 8500 Balho Blvd., P.O. Box A. 0. J. P. DEC 1988 2200, Northridge, CA 91329 (U )r T fet's dso c j AUSTRAULIAN /ecmoh WecA 3 4 NOV 1988 Rad PATENT OFFICE (54)Title: SHALLOW LOUDSPEAKER (57) Abstract A loudspeaker comprises a basket-like frame (12) for supporting and housing the remaining loudspeaker components. The Frame includes a back wall and a perimetral wall, and a magnet assembly (10) for providing an air gap. The magnet assembly includes a center pole piece and a yoke. The center pole piece and the yoke are mounted to the back wall to define the air gap. One of the center pole piece and yoke includes a permanent magnet to provide a magnetic field in the air gap. The loudspeaker further includes a voice coil, a voice coil form (40) for supporting the voice coil in the air gap, a spider (64) for positioning the voice coil form in the air gap, and a diaphragm (22) having an apex and a perimeter. The diaphragm is coupled to the frame at the perimetrally outer extent of the diaphragm. The diaphragm is coupled to the voice coil form inward from the perimeter of the diaphragm. The spider is mounted between the diaphragm and the magnet assembly. The spider is generally concave on the side of the spider facing the magnet assembly to enclose and house the magnet assembly without limitiig or interfering with the movement of the spider. The spider is generally convex on the side of the spider facing away fron, the magnet assembly and toward the diaphragm. The apex of the diaphragm extends away from the back wall farther than the perimeter of the diaphragm to enclose and house the spider without limiting or interfering with the movement o"ithe spider or diaphgram.

-i i WO 88/08239 PCT/US88/00685 -1- SHALLOW LOUDSPEAKER Background and Summary of the Invention This invention relates to moving coil piston-type acoustical transducers. It is disclosed in the context of a loudspeaker which is of shallow depth.

This shallow loudspeaker is useful where optimization of both performance and dimensional aspects is important.

For instance, in high performance automotive sound systems, severe design constraints may be placed on the loudspeaker mounti.g depth, power capability, efficiency, and frequency response bandwidth.

Unfortunately, the constraints placed on performance generally work against the dimensional constraints.

This is particularly true of low frequency performance and loudspeaker depth and diameter. As automobiles become smaller and more compact, the available space for loudspeaker installations becomes smaller. In order to accommodate the smaller installation space, the loudspeaker size must be reduced. The performance requirements must still be achieved, even with the reduction in size.

The ability of a piston-type loudspeaker to produce low frequencies is basically dependent upon two factors, the radiating surface area and the diaphragm excursion. Diaphragm excursion is proportional to the power input and inversely proportional to frequency.

For a given loudspeaker diameter and power output level at a particular low frequency, there is a specific distance which the diaphragm must travel. If the diaphragm is restricted from moving the required

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WO 88/08239 PCT/US88/00685' -2distance, the low frequency performance objective will not be met.

Prior art shallow loudspeakers meet the objective of reduced depth, but generally fail from a performance standpoint. The low frequency performance and power capability are reduced in proportion to the reduction in size. Also, in some instances, the manufacturability and cost increase with the use of exotic diaphragm, suspension, or magnet assembly materials..

This invention utilizes a novel structure to overcome many of the problems associated with prior art shallow loudspeakers. The basis of this invention is the utilization of similar geometry among components, and sharing common space, in terms of depth, between components. This permits the assembly of components to be dimensionally compressed in depth. Assembly compression occurs to the point at which optimization of the excursion requirements is met. This permits performance and dimensional objectives to be achieved.

Another benefit of this structure is that the loudspeaker materials and construction methods do not depart from those currently used. This helps keep the loudspeaker cost to a minimum.

Various types of loudspeaker constructions employing reverse cone- or reverse horn-shaped diaphragms are known. There are, for example, the proposals illustrated in U.S. Patents 2,512,323 and 4,029,910. Flat or substantially flat diaphragm 30 loudspeaker constructions are also known. There are, i,:U :~~ir~~ii WO 88/08239 PCT/US88/00685 -3for example, the proposals illustrated in U.S. Patents: 4,379,951; 4,327,257; and 4,317,965. Space saving proposals for loudspeakers are also known. There are, for example, the proposals of U.S. Patents 2,423,037 and 3,024,323. There are also the systems illustrated in U.S. Patents 3,201,529 and 4,206,832.

An object of the present invention is to provide a loudspeaker design in which the overall depth of the loudspeaker is reduced from the depth of conventional loudspeakers currently available.

A loudspeaker comprises a basket-like frame for supporting and housing the remaining loudspeaker components. The frame includes a back wall and a perimetral wall, a magnet assembly for providing an air gap, the magnet assembly includes a center pole piece and a yoke, and means for mounting the center pole piece and the yoke to the back wall to define the air gap. At least one of the center pole piece and yoke includes a permanent magnet to provide a magnetic field in the air gap. The loudspeaker further includes a voice coil, a voice coil form for supporting the voice coil in the air gap, a spider for positioning the voice coil form in the air gap, a diaphragm having an apex and a perimeter, means for coupling the diaphragm to the frame at the perimetrally outer extent of the diaphragm, means for coupling the diaphragm to the voice coil form inward from the perimeter of the diaphragm, and means for mounting the spider between the diaphragm and the magnet assembly. The spider is generally concave on the side of the spider facing the magnet assembly to enclose and I ca rr r r i ii.

4 house the magnet assembly without limiting or interfering with the movement of the spider. The spider is generally convex on the side of the spider facing away from the magnet assembly and toward the diaphragm. The apex of the diaphragm extends away from the back wall farther than the perimeter of the diaphragm to enclose and house the spider without limiting or interfering with the movement of the spider or diaphragm.

In a preferred embodiment of the invention, the perimetral wall includes means defining a mounting surface extending around the inner perimeter of the perimetral wall, the loudspeaker further including means for coupling the perimeter of the diaphragm to the mounting surface.

A further preferred feature is that the yoke includes an outer somewhat convex surface on the side of the yoke facing the spider.

A preferred embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawing which is a traverse sectional side elevational view of a loudspeaker constructed according to :the present invention.

o A loudspeaker 10 according to the present invention .includes a shallow cylindrical basket-like frame 12. The cross-sectional shape, or plan view, of frame 12 .:Dose 9 transverse to the plane of the section of the drawing can be round, elliptical or other suitable shape. The frame 12 includes a rear wall 14 and an upstanding perimetral, or side, wall 16. Wall 14 0 S. J I_ z i 11-1 L-ZYS -~h WO 88/08239 PCT/US88/00685 illustratively is not solid, but includes several openings 18 to vent the rearward surface 20 of the diaphragm 22 of loudspeaker 10, as well as to reduce the weight of the frame 12. Wall 16 includes an interior surface 24 provided with a perimetral, inwardly extending mounting ring 26. The perimeter 28 of diaphragm 22 is coupled by means of a compliance ring to the mounting ring 26. The frame 12 is open at end 33 of wall 16 opposite wall 14 to expose the front surface 32 of diaphragm 22. Front surface 32 is the primary radiating surface of diaphragm 22.

As can be appreciated by referring to the drawing, diaphragm 22 is cone-shaped. However, the apex 36 of diaphragm 22 projects forward toward open end 33 of frame 12 from the base of the cone which is at perimeter 28 of diaphragm 22. A right circular cylindrical cross-section voice coil form 40 is affixed to the apex 36 of diaphragm 22 and extends rearwardly toward the back wall 14 of frame 12.

The magnet structure 10 includes a somewhat cup- or dome-shaped annular pole piece, or yoke, 46 of soft iron or other ferromagnetic material. The yoke 46 is attached at its larger open end 48 to rear wall 16 and projects forward therefrom. The magnet structure of loudspeaker 10 also includes a right circular cylindrical cross-section center pole piece 42, illustratively formed from a stack including a right circular cylindrical magnet 43 and generally right circular cylindrical ferromagnetic slugs 45, 47. Slug 45 has a radially projecting flange 49 at its rear end WO 88/08239 PCT/US88/00685 -6which engages a relief 51 formed in the larger open end 48 of yoke 46. Pole piece 42 extends forward from wall 16 toward diaphragm 22. The center pole piece 42 projects through an opening 50 in the front of annular pole piece 46 and a radial air gap 54 is thus formed between the adjacent radially outer surface 56 provided by opening 50 and the adjacent radially inner surface 58, the sidewall of center pole piece 42. The flux provided by magnet 43 is uniformly distributed in the air gap 54, which is of uniform radial dimension. The flux is conducted through the yoke 46 and returned to center pole piece 42 and thus to magnet 43.

The voice coil form 40 is centered in the air gap 54 by its attachment at 62 at its forward end to the apex 36 of diaphragm 22 to a centering spider 64.

Centering spider 64 includes a lip 66 surrounding a central opening 68 in the centering spider 64. Voice coil form 40 extends through opening 68 and lip 66 is attached to form 40, illustratively by a suitable adhesive. Spider 64 is somewhat cup- or dome-shaped, ignoring the pleats 70 which provide sufficient compliance to accommodate the excursions of voice coil form 40 as current is passed through a voice coil 72 wound on form 40 to drive the diaphragm 22 and generate acoustical energy. Spider 64 is attached at its perimeter 74 to back wall 14 of basket 12 between the perimeter of pole piece 46 and sidewall 16.

Claims (9)

1. A shallow loudspeaker comprising a basket-like frame for supporting and housing the remaining shallow loudspeaker components, the frame including a back wall and a perimetral wall, a magnet assembly for providing an air gap, the magnet assembly including a center pole piece and a yoke, means for mounting the center pole piece and the yoke to the back wall to define the air gap, either the center pole piece or the yoke including a permanent magnet to provide a magnetic field in the air gap, a voice coil, a voice coil form for supporting the voice coil in the air gap, a spider for positioning the voice coil form in the air gap, a diaphragm having an apex and a perimeter, means for coupling the diaphragm to the frame at the perimetrally outer extent of the diaphragm, means for coupling the diaphragm to the voice coil form inward from the perimeter of the diaphragm, means for mounting the spider between the diaphragm and the magnet assembly, the spider having an inner perimeter attached either to the voice coil form or to the diaphragm and an outer perimeter attached either to the perimetral wall or to the back wall, the spider being generally concave on the side of the spider facing the magnet assembly so that the magnet assembly is enclosed and housed within the space defined beneath or behind the spider without limiting or interfering with the movement of the spider, the spider being generally convex on the side of the spider facing away from the magnet assembly and toward the diaphragm, the apex of the diaphragm extending away a 0 0 -8- from the back wall farther than the perimeter of the diaphragm so that the spider is enclosed and housed within the space defined beneath or behind the diaphragm without limiting or interfering with the movement of the spider or diaphragm.

2. The shallow loudspeaker of claim 1 wherein the perimetral wall includes means defining a mounting surface extending around the inner perimeter of the perimetral wall, the shallow loudspeaker further including means for coupling the perimeter of the diaphragm to the mounting surface.

3. The shallow loudspeaker of claim 1 wherein the yoke includes an outer generally convex surface on the side of the yoke facing the spider.

4. A shallow loudspeaker comprising a basket-like frame for supporting and housing the remaining shallow loudspeaker components, a magnet assembly for providing an air gap, the magnet assembly including a center pole piece and a yoke, means for mounting the center pole piece and the yoke in the frame •to define the air gap, either the center pole piece or the yoke including a permanent magnet to provide a magnetic field in the air gap, a voice coil, a voice 10 coil form for supporting the voice coil in the air gap, a spider for positioning the voice coil form in the air gap, a diaphragm, means for coupling the diaphragm to the frame at the perimetrally outer extent of the i diaphragm, means for coupling the diaphragm to the voice S- coil form inward from the perimeter of the diaphragm, means for mounting the spider between the diaphragm and *i 0 N USoo i)FFIG -9- the magnet assembly, the spider having an inner perimeter attached either to the voice coil form or to the diaphragm and an outer perimeter attached to the frame, the spider being generally concave on the side of the spider facing the magnet assembly so that the magnet assembly is enclosed and housed within the space defined beneath or behind the spider without limiting or interfering with the movement of the spider, the spider being generally convex on the side of the spider facing away from the magnet assembly and toward the diaphragm, the diaphragm being generally concave on the side of the diaphragm facing the spider so that the spider is enclosed and housed within the space defined beneath or behind the diaphragm without limiting or interfering with the movement of the spider or diaphragm, the diaphragm being generally convex on the side of the diaphragm facing away from the spider. The shallow loudspeaker of claim 4 wherein the basket-like frame includes a frame bottom, a frame sidewall and means for attaching the frame sidewall to %goes: •the frame bottom at the perimeter of the frame bottom O ss• and at one end of the frame sidewall, and the means for mounting the center pole piece and the yoke in the frame eoo includes means for mounting the center pole piece and the yoke to the bottom of the frame to project away from the bottom of the frame.

6. The shallow loudspeaker of claim 5 wherein the sidewall includes means defining a mounting surface se ,o extending around the inner perimeter of the sidewall, the shallow loudspeaker further including means for 0 se oloo• S .O 00 L ••O66 S coupling the perimeter of the diaphragm to the mounting surface.

7. The shallow loudspeaker of claim 4 wherein the yoke includes an outer somewhat convex surface on the side of the yoke facing the spider.

8. A shallow loudspeaker comprising a basket-like frame for supporting and housing the remaining shallow loudspeaker components, a magnet assembly for providing an air gap, the magnet assembly including a center pole piece and a yoke, means for mounting the center pole piece and the yoke in the frame, either the center pole piece or the yoke including a permanent magnet to provide a magnetic field in the air gap, a voice coil, a tubular voice coil form for supporting the voice coil in the air gap, a spider for supporting the voice coil form in the air gap, a diaphragm, means for coupling the diaphragm to the basket-like frame at the perimetrally outer extent of the diaphragm and at the perimetrally outer extent of 6* the frame, means for coupling the diaphragm to the voice 000000 S" coil form inward from the perimeter of the diaphragm, S. the spider having a central aperture surrounding and attached to the voice coil form and a perimeter attached to the frame, the region of the spider between its central aperture and perimeter being generally concave on the side of the spider facing the magnet assembly so that the magnet assembly is enclosed and housed within the space defined beneath or behind the spider without limiting or interfering with the movement of the spider, o• the region of the spider between the central aperture o••oe I oSoSoS -11- and perimeter being generally convex on the side of the spider facing away from the magnet assembly and toward the diaphragm, the diaphragm being generally concave on tie side of the diaphragm facing the spider so that the spider is enclosed and housed within the space defined beneath or behind the diaphragm without limiting or interfering with the movement of the spider or diaphragm, the diaphragm being generally convex on the side of the diaphragm facing away from the spider.

9. The shallow loudspeaker of claim 8 wherein the basket-like frame includes a frame bottom, a frame sidewall and means for attaching the frime sidewall to the frame bottom at the perimeter of the frame bottom and at one end of the frame sidewall, and the means for mounting the center pole piece and the yoke in the frame includes means for mounting the center pole piece and the yoke to the bottom of the frame to project away from the bottom of the frame. The shallow loudspeaker of claim 9 wherein t the sidewall includes means defining a mounting surface extending around the inner perimeter of the sidewall, the shallow loudspeaker further including means for s e* coupling the perimeter of the diaphragm to the mounting Ssurface. S11. The shallow loudspeaker of claim 8 wherein the yoke includes an outer generally convex surface on the side of the yoke facing the spider.

12. A shallow loudspeaker substantially as hereinbefore described with reference to the accompanying drawing. DATED this 15th Day of January, 1990. HARMAN INTERNAIONAL INDL3TRIES, INCORPORATED. Attorney: WILLIAM S. LLOYD Fellow Institute of Patent Attorneys of Australia of SHELSTON WATERS 04 a 0 1 i'