EP1964440A2

EP1964440A2 - Improved linear array transducer and improved methods of manufacture

Info

Publication number: EP1964440A2
Application number: EP06839430A
Authority: EP
Inventors: Mads Fynboe; Kevin C. Corr; Jose F. Garcia; David J Prince; Alireza Jabbari; Birger Jorgensen; Edward T. Norcott Jr.
Original assignee: Tymphany Corp
Current assignee: Tymphany Corp
Priority date: 2005-12-21
Filing date: 2006-12-20
Publication date: 2008-09-03
Also published as: WO2007075674A3; WO2007075674A2; CN101385389A

Abstract

A linear array acoustic transducer with multiple diaphragms arranged in one or more sets uses improved diaphragm designs that increase structural rigidity and acoustic efficiency. In one implementation, a single driving rod is used to drive multiple diaphragms in each set of diaphragms to reduce the number of diaphragm openings and mitigate adverse effects caused by air leakage through the openings. Improved methods of manufacture are also disclosed.

Description

Docket: TYM00401 PCT

- 1 - DESCRIPTION

Improved Linear Array Transducer and

Improved Methods of Manufacture

TECHNICAL FIELD

The present invention is related to the field of audio systems and acoustics, and pertains more specifically to providing an improved acoustic transducer with multiple diaphragms that converts electrical signals into acoustic radiation. BACKGROUND ART

The fundamental design of electrodynamic acoustic transducers used in most sound reproduction systems has remained largely unchanged for the past several decades. One of the main physical principles underlying this design is that the potential of a transducer to generate sound is directly related to the potential volume displacement of the transducer, namely the product of its effective surface area and its excursion capability. This principle is in direct conflict with the increasing consumer demand for ever smaller devices that are still expected to produce impressive sound.

As a result, recent efforts have concentrated on compacting the design of audio transducers without sacrificing their volume displacement. One such effort is our development of the linear array transducer, which distributes the surface area of a single diaphragm into multiple diaphragms driven synchronously through rods by one or more motors. Various implementations of linear array transducers are disclosed in international patent application no. PCT/US 2005/019443 entitled "Acoustic Transducer Comprising a Plurality of Coaxially Arranged Diaphragms" by Unruh et al. This approach leads to transducers with different form factors that occupy less space than traditionally designed single-diaphragm transducers with comparable sound output.

This design approach requires innovative solutions to problems that, if left unsolved, may result in transducers with low sound quality and/or high cost of manufacturing and assembly. Such problems include, but are not limited to, the deformation of diaphragms that may not be rigid enough to withstand the concentrated forces exerted by the rods because they must be light enough to ensure adequate sound generating efficiency and be designed so that they can be manufactured by cost-effective processes; the cost of assembling such a complex electromechanical device; and the adverse effects caused by air leaking through openings in the diaphragms through which the driving rods pass. The adverse effects of air leakage may include intermodulation, harmonic distortion and turbulent noise resulting in poor sound quality; a significant reduction of sound output levels, especially at low frequencies; and a reduction in the power levels at which the transducer exhibits "bottoming", namely hard mechanical contact of moving parts with non-moving parts..

DISCLOSURE OF INVENTION

It is an object of the present invention to provide for a linear array acoustic transducer design that either eliminates or mitigates the adverse effects caused by air leakage and structural rigidity failures and reduces manufacturing costs. One implementation of the linear array acoustic transducer that provides a compact form factor includes two motors, each driving multiple diaphragms. The diaphragms are arranged in two groups; diaphragms in one group are driven by one motor and diaphragms in the other group are driven by the other motor, with the two groups of diaphragms driven in opposition to one another. The diaphragms are driven by the motors using drive rods, which pass through openings in the diaphragms. Unfortunately, air can leak through these openings with adverse effects as explained above.

Current solutions mitigate the air leakage problem through mechanisms that diffuse, reduce or eliminate the air flow through these openings. Such mechanisms include sleeves that surround the openings and reduce airflow through them, seals made of various soft materials with sound absorbing properties, as well as ferromagnetic liquid seals held in place by magnets positioned around the diaphragm openings. Regardless of the seal design used, it is desirable to reduce the overall area of the diaphragm openings because the smaller that area is the less air will attempt to leak through. This reduction can be achieved by making the inner diameter of the diaphragm openings only slightly larger than the outer diameter of the drive rods so that the gaps between the rods and the diaphragms are as small as practically feasible.

Unfortunately, from a production point of view it is not practically feasible to make the diaphragm openings extremely tight around the rods. When the gaps are very small, the alignment between the rods and the multiple diaphragms must be extremely accurate to avoid contact between the rods and the diaphragms during transducer operation. Any such contact results in spurious noises that adversely impact sound quality and it also reduces the long-term reliability of the transducer. Near-perfect alignment in a transducer with multiple diaphragms requires extremely tight tolerances on parts dimensions, particularly diaphragm openings, thereby increasing the cost of such parts considerably. It also requires extreme assembly precision and, therefore, is not well-suited for traditional cost-effective transducer assembly methods. Furthermore, it requires that the motion of all moving parts remain essentially constrained in its intended straight path without any significant lateral movements caused by imbalances or unwanted structural vibrations. In addition to placing further constraints on assembly accuracy and parts uniformity tolerances, this requirement has significant implications on the structural rigidity of the diaphragms, which cannot exhibit vibration modes that deform the diaphragm enough to cause contact with the rods. The overall area of the diaphragm openings can be reduced by minimizing the number of diaphragm openings, which in turn can be achieved by reducing the number of rods used to drive the diaphragms. According to one aspect of the present invention, each set of opposing diaphragms is driven by a single rod. This means that each diaphragm needs only one opening for the rod driving the other set of diaphragms to pass through. This opening may have a sleeve around it to further reduce air leakage through the opening. To balance the forces acting on the diaphragms, the single rod is preferably connected to each diaphragm at a location that is as close as possible to the geometric center of the diaphragm and the surround that suspends the diaphragm from the transducer housing. The two rods driving the two sets of opposing diaphragms may be placed as close as possible to each other at approximately the center of the diaphragms.

According to one teaching of the present invention, the two sets of opposing diaphragms are exactly aligned with each other and the two driving rods are positioned only a very small distance away from the geometric center of the diaphragms.

According to another teaching of the present invention, the two sets of opposing diaphragms are slightly offset with respect to each other so that each driving rod is attached to the geometric center of the driven diaphragms. If the subassembly of the diaphragm and surround is circular or has some other regular shape, the geometric center coincides with the center of rotation of the diaphragm/surround subassembly. The two sets of diaphragms may be offset with respect to each in any direction along the plane that is perpendicular to the long axis of the transducer. The direction of the offset affects the final shape of the linear array transducer and can be chosen to satisfy various form factor constraints and/or acoustic performance criteria. In any implementation of a linear array transducer having one or more sets of diaphragms driven by rods, the force driving each diaphragm is concentrated in the small area where the driving rod is attached to the diaphragm, This is very different from conventional transducers, in which the corresponding force is distributed across a continuous circular joint where the top of a voice coil bobbin is attached to the driven diaphragm. In a linear array transducer according to one implementation of the present invention, this force distribution occurs only on the first diaphragm in each set of moving diaphragms, namely on the diaphragm that is connected directly to the voice coil of the driving motor. The first diaphragm is connected to the driving rod that transmits the driving force to the remaining diaphragms in the same set of diaphragms. Conventional diaphragms typically are not designed to operate under such locally concentrated forces and may be inappropriate for this application because the localization of forces may excite undesirable vibrational modes and induce significant undesirable stress forces on the diaphragm. These vibrational modes may lead to lateral motions or deformations, which in turn may cause the rods to come in contact with the edges of the diaphragm openings. This problem is especially likely if the clearances between the openings and the rods are small to reduce the air leakage effects. Moreover, even if they do not result in contact between the diaphragms and the rods, such vibrational modes may result in sonic artifacts that reduce the sound quality of the linear array transducer. In addition, localized stress forces have a negative impact on the longevity of the corresponding components, and may also result in undesirable sonic artifacts.

According to one aspect of the present invention, the diaphragms used in the linear array transducer are designed in a way that reduces undesirable vibrations and localized stress forces in the presence of highly localized forces transmitted by the driving rods. This may be achieved by adding features that increase the structural rigidity of the diaphragm and designing these features to have smooth surfaces without any sharp edges that would result in highly localized stress forces.

Without benefit of the teachings of the present invention, however, the addition of such features may have the undesirable effects of increasing the mass of the diaphragm, thereby reducing the acoustic efficiency of the transducer and making the thickness of the diaphragm non-uniform across its surface, which has adverse implications on manufacturability and cost of the diaphragm. In particular, existing molding processes can be used to produce parts with tight dimensional tolerances only when the thickness of the part is fairly uniform across its surface. Areas of increased thickness contain more material, which implies that they cool more slowly than other thinner areas after the parts are removed from the mold. The different cooling rates in different areas of the molded part result in deformations that alter the critical dimensions of the part, which can require the use of cost-prohibitive materials or secondary machining operations to ensure that the resulting parts adhere to tight dimensional tolerances. Various teachings of the present invention may be used to obtain transducer designs that avoid these problems.

According to one teaching of the present invention, the structural rigidity of the diaphragm is increased by shaping the surface of the diaphragm to create the features necessary to suppress unwanted vibrational modes and reduce localized stress forces. In particular, the thickness of the diaphragm is kept essentially uniform across its surface but the surface itself is raised or lowered to create ridges that increase structural rigidity. These ridges may be oriented symmetrically or asymmetrically with respect to the center of the diaphragm. Their specific shape and orientation may be altered to accommodate the number and location of openings for driving rods either to be attached to or pass through. The increased structural rigidity resulting from these ridges reduces vibrations, thereby allowing the clearances between a rod and the sleeve of a corresponding pass-through opening to be made smaller. That reduces the effective surface of the opening through which air can flow through the diaphragm. According to another teaching of the present invention, the structural rigidity of the diaphragm is increased by using a composite structure that includes a small rigid component attached to a diaphragm preferably at its center. The diaphragm may be flat, cone-shaped or essentially any other shape that may be desired. The rigid component of a corresponding diaphragm may be circular, elliptical or essentially any other shape that may be desired. This rigid component is preferably made of a stiff and well-damped plastic material such as a glass-filled or mica- filled polypropelene-polyphenylene-oxide- styrene material. The rigid component may have a first set of one or more openings for attaching rods that drive the corresponding diaphragm. The rigid component may also have a second set of one or more openings to allow rods to pass through that drive other diaphragms. The second set of openings may be slightly larger than those of the first set so that the driving rods that drive other diaphragms can pass through without coming into contact with the diaphragm. The outer part of the diaphragm is preferably made of a conventional acoustic diaphragm material such as paper or thin plastic that is light yet reasonably stiff. This second part is preferably much larger than the rigid component and contributes most of the sound-generating surface of each diaphragm subassembly. Using a lightweight material in this comparatively large part ensures that the overall moving mass of the transducer remains low. At the same time, using a very stiff and well-damped material in the rigid component ensures that the force from the driving rod is distributed along the circumference of this rigid component and is transmitted to the surrounding diaphragm in a manner that is much closer to conventional transducers, especially if the rigid component is shaped as a circular disk. The resulting two-part diaphragm is both rigid and light. Moreover, the rigid component preferably has uniform thickness across its surface except for the two sets of openings and can be manufactured using existing cost- efficient molding processes while still maintaining very tight dimensional tolerances. In addition, the rigid component may be designed to be thick around the opening for the rod to pass through so that the opening is long enough to function as a sleeve that further mitigates the effects of air leakage. The assembly process of a linear array transducer is more elaborate than that of a conventional acoustic transducer. It involves the assembly of several component modules including two motor modules and multiple body modules composed of a housing section with a surround and a diaphragm attached to it. These modules are attached to each other and the driving rods. According to another aspect of the present invention, the assembly of a linear array transducer includes two or more rods or bars preferably made of a hard material such as steel or Qarolite. These rods or bars pass through appropriately shaped openings in the housing sections and are secured tightly at both ends to the corresponding housing sections, thereby providing the tension necessary for the housing sections to remain tightly connected to each other. In a preferred embodiment, four such rods are used, distributed symmetrically about the transducer. These rods or bars may be concealed inside the housing sections or may protrude from the housing sections. Two of these rods or bars are preferably located on the sides where the transducer is connected to the enclosure to which it is mounted. These two rods or bars may protrude from the housing sections and be shaped appropriately with a flat external section that has mounting holes so that they can function as mounting flanges. By providing tension to connect the housing sections together, these rods or bars obviate the need for adhesives between the housing sections, thereby simplifying the assembly process. They also increase the bending and torsional rigidity of the overall transducer structure. This benefit is particularly important when the housing sections are made of a material like plastic for reduced overall weight and cost. Plastic housing sections themselves may not provide the structural rigidity necessary to avoid unwanted vibrations of the transducer assembly but the reinforcement provided by these rigid rods or bars can eliminate or at least reduce these vibrations.

According to yet another aspect of the invention, the assembly of a linear array transducer that uses the aforementioned two-part diaphragm with the rigid component may be altered to provide improved alignment. The motor modules consisting of a yoke, magnet and top plate are assembled separately without their corresponding housing sections. The motor modules are typically the most expensive parts of a linear array transducer, yet they are easy to assemble accurately using traditional transducer assembly methods. If desired, they may be assembled to the transducer after the body sections have been assembled correctly. The two-part diaphragms may be assembled separately by attaching the rigid components to the corresponding outer part of the^" diaphragm. The two-part diaphragms are attached to their corresponding surrounds. The housing sections need not be used in this part of the assembly process. The diaphragm-surround subassemblies are attached to the driving rods to form the interior moving subassembly. Specifically, the driving rods are secured in place using an appropriate fixture and the diaphragm-surround subassemblies are slid over the rods and attached to them at appropriate locations, which may be indicated on the rods with small notches. Each of the diaphragm-surround subassemblies is attached to its corresponding driving rod with the correct orientation so that the non-driving rod is centered through the corresponding diaphragm opening. For this purpose, removable sleeves may be inserted into the diaphragm openings. These sleeves can be used to ensure the non-driving rod is centered in the opening and removed later. The housing sections are slid over the interior moving subassembly and attached to the corresponding surrounds. When all of the housing sections have been attached to the surrounds, the rods or bars mentioned above may be slid into place through the housing sections and tightened or attached in place. Preferably, the attachment of the two motor modules is the final part of the assembly. For each motor module, the voice coil is attached to the corresponding end diaphragm using an appropriate fixture and the motor module consisting of the yoke, magnet and top plate is attached to the last housing section using another appropriate fixture. According to another aspect of the invention, the assembly of a linear array transducer may be simplified by molding together the yoke of the motor with the end cap that covers the end of the motor. These two parts are typically separate; their integration into a single part may require an additional molding step during manufacture but it can improve alignment accuracy between the motor yoke and end cap and can simplify the process used to assemble component parts into a finished transducer.

According to yet another aspect of the invention, the assembly of a linear array transducer may be made more efficient by using two or more different housing sections, whose design is slightly altered to provide a unified mechanical interface, in order to allow the entire transducer housing to be assembled using the same automated assembly process.

The various features of the present invention may be better understood by referring to the following discussion and the accompanying drawings in which like reference numerals refer to like elements in the several figures. The contents of the following discussion and the drawings are set forth as examples only and should not be understood to represent limitations upon the scope of the present invention.

BRIEF DESCRIPTION OF DRAWINGS

Figs. 1A-1B are schematic illustrations of an implementation of a linear array transducer that uses one rod to drive each set of opposing diaphragms, where both sets of diaphragms are aligned with each other.

Figs. 2A-2B are schematic illustrations of an implementation of a linear array transducer that uses one rod to drive each set of opposing diaphragms, where the two sets of diaphragms are offset with respect to each other.

Figs. 3 A-3B are schematic illustrations of a housing section for the linear array transducer shown in Figs. 2A-2B.

Figs. 4A-4B are schematic illustrations of a diaphragm with a rigid component shaped like a disk at its center that may be used in the linear array transducer shown in Figs. IA-I B.

Figs. 5A-5B are schematic illustrations of the rigid component shown in Figs. 4A- 4B.

Figs. 6A-6B are schematic illustrations of a diaphragm with a rigid component shaped like a disk at its center that may be used in the linear array transducer shown in Figs. 2A-2B. Figs. 7A-7B are schematic illustrations of the rigid component shown in Figs. 6A- 6B.

Figs. 8A-8B and 9A-9B are schematic illustrations of diaphragms made of a material with uniform thickness and ridges to increase structural rigidity and reduce localized stress forces.

Fig. 10 is a schematic illustration of a continuous connection between the end diaphragm and the voice coil.

Figs. 1 IA-I IB and 12 are schematic illustrations of linear array transducers that use the diaphragms shown in Figs. 8A-8B and 9A-9B and the diaphragm-coil connection shown in Fig. 10.

Figs. 13A-13B are schematic illustrations of an alternate implementation of a linear array transducer that uses one rod to drive each set of opposing diaphragms, where both sets of diaphragms are aligned with each other.

Figs. 14A-14E are schematic illustrations of diaphragms designed with uniform thickness and ridges that increase structural rigidity and reduce localized stress forces.

Figs. 15A-15B, 16A-16B, and 17A-17B are schematic illustrations of three different housing sections used in the linear array transducer shown in Figs. 13A-13B.

Figs. 18A-18B are schematic illustrations of the integrated motor yoke and motor end cap used in the linear array transducer shown in Figs. 13A-13B.

DETAILED DESCRIPTION OF THE INVENTION Two implementations of a linear array transducer that uses a single rod to drive each of two sets of diaphragms are illustrated in Figs. IA- IB and Figs. 2A-2B.

Fig. IA shows a perspective view and Fig. IB shows a cross-sectional view of a linear array transducer 1000 with two motors 1320 and 1340 each driving one of two sets of diaphragms 1100. The diaphragms 1100 in each of the two sets of diaphragms are connected to each other via a single rod 1200, so there is a total of two rods 1200 in the transducer 1000. In this implementation, each diaphragm 1100 has a rigid component 1 120 at its center and the two sets of diaphragms 1 100 are aligned with each other so that the two motors 1320 and 1340 are aligned with each other as well. Each rod 1200 is attached to the rigid component 1120 of a diaphragm 1100 at a point 1140 that is slightly away from the geometric center of the disk 1120 and the corresponding diaphragm 1100. The tension bars 1700 slide through notches in the housing sections 1500 and increase the rigidity of the transducer 1000 while also functioning as mounting flanges.

Fig. 2 A shows a perspective view and Fig. 2B shows a cross-sectional view of a linear array transducer 2000 with two motors 2320 and 2340 each driving one of two sets of diaphragms 2100. The diaphragms 2100 in each of the two sets of diaphragms are connected to each other via a single rod 2200, so there is a total of two rods 2200 in the transducer 2000. In this implementation, each diaphragm 2100 has a rigid component 2120 at its center and each rod 2200 is attached to the rigid component 2120 of a diaphragm 2100 at a point 2140 that is located at the geometric center of the disk 2120 and the corresponding diaphragm 2100. The two sets of diaphragms 2100 are slightly offset with respect to each other, as are the two motors 2320 and 2340. The diaphragms 2100 are more steeply coned than the diaphragms 1100; the cone angle of the diaphragm in a linear array transducer may be chosen to satisfy acoustic requirements and form factor requirements. In particular, a steeper diaphragm cone may extend the frequency response of the transducer to higher frequencies but may reduce the maximum excursion compared to a shallower diaphragm cone for the same transducer length. The tension bars 2700 slide through notches in the housing sections 2500 and increase the rigidity of the transducer 2000 while also functioning as mounting flanges.

The resulting transducer 2000 has a slightly more elliptical shape as compared to the transducer 1000. In the implementation illustrated here, the direction of the offset is parallel to the mounting plane of the transducer; therefore, the offset increases the width of the transducer but not its height. Other implementations may have the offset in a different direction. For example, if it is desirable for the transducer to fit in as narrow an opening as possible, the offset may be perpendicular to the mounting plane of the transducer, thereby increasing the transducer height but not its width. The housing section 2500 used in the assembly of the transducer 2000 is illustrated in Figs. 3A-3B. The semicircular extensions 2520 and 2540 on opposite faces of the housing section 2500 are added to accommodate the offset between the two sets of diaphragms. The extensions 2520 and 2540 allow adjacent surrounds to be attached to the housing section 2500 at the appropriate offset positions with respect to each other. In the final assembly 2000, adjacent housing sections 2500 are rotated 180 degrees with respect to each other so that the extension 2520 of a section mates with the extension 2540 of the next section, and the outermost section of a respective surround 2600 as shown in Figs. 6A-6B is compressed between these two extensions.

The two-part diaphragm 1100 used in the assembly of the transducer 1000 is illustrated in Figs. 4A-4B, where it is shown attached to the surround 1600, forming the diaphragm-surround subassembly 4000. Fig. 4A shows a top view and Fig. 4B shows a cross-sectional view of the diaphragm-surround subassembly 4000. The two-part diaphragm 1 100 is composed of a rigid component 1 120 at its center and a lightweight cone 1 180 that provides most of the sound-generating surface of the diaphragm. The surround 1600 is attached to the cone 1180. The cone 1180 and the disk 1120 are attached at the joint 1190. The disk 1120 is attached to the driving rod 1200 at the opening 1140. The opening 1140 is located slightly away from the geometric center of the disk 1120 and the diaphragm 1100. The second opening 1150 allows the rod that drives the other set of diaphragms to pass through the diaphragm i 100. The interior surface of the opening 1150 is smooth and its diameter is only slightly larger than the outer diameter of the rods 1200. Owing to the thickness of the disk 112ϋ, the opening 1150 functions as a sleeve that reduces adverse effects caused by air leaking through the opening.

Figs. 5A-5B show a more detailed view of the rigid component 1120. Fig. 5 A shows a top view and Fig. 5B shows a cross-sectional view of the disk 1120 with the opening 1140 for attaching the driving rod and the opening 1150 for the non-driving rod to pass through. The opening 1140 may be flared at its top and bottom to provide a glue well 1160 for any adhesive that may be used. In addition, the opening 1140 may contain additional indentations 1170 that allow the adhesive to run parallel to the driving rod 1200 and form a stronger adhesive bond between the disk 1120 and the rod 1200. The two-part diaphragm 2100 used in the assembly of the transducer 2000 is illustrated in Figs. 6A-6B, where it is shown attached to the surround 2600, forming the diaphragm-surround subassembly 6000. Fig. 6A shows a top view and Fig. 6B a cross- sectional view of the diaphragm-surround subassembly 6000. The two-part diaphragm 2100 is composed of a rigid component 2120 at its center and a lightweight cone 2180 that provides most of the sound-generating surface of the diaphragm. The surround 2600 is attached to the cone 2180. The cone 2180 and the disk 2120 are attached at the joint

2190. The disk 2120 is attached to the driving rod 2200 at the opening 2140. The opening 2140 is located at the geometric center of the disk 2120 and the diaphragm 2100. The second opening 2150 is located slightly away from the geometric center of the disk 2120. The opening 2150 allows the rod that drives the other set of diaphragms to pass through the diaphragm 2100. The interior surface of the opening 2150 is smooth and its diameter is only .slightly larger than the outer diameter of the rods 2200. Owing to the thickness of the rigid component 2120, the opening 2150 functions as a sleeve that reduces adverse effects caused by air leaking through the opening.

Figs. 7A- 7B show a more detailed view of the rigid component 2120. Fig. 7A shows a top view and Fig. 7B shows a cross-sectional view of the disk 2120 with the opening 2140 for attaching the driving rod at its geometric center and the opening 2150 for the non-driving rod to pass through. The opening 2140 may be flared at its top and bottom to provide a glue well 2160 for any adhesive that may be used. In addition, the opening 2140 may contain additional indentations 2170 that allow the adhesive to run parallel to the driving rod 2200 and form a stronger adhesive bond between the disk 2120 and the driving rod 2200.

The assembly of a linear array transducer 1000 may be accomplished in several steps. The motor modules 1320 and 1340 consisting of a yoke, magnet and top plate are assembled separately without their corresponding housing sections. The two-part diaphragms 1100 are also assembled separately by attaching the rigid components 1120 to the cones 1180. The two-part diaphragms 1100 are attached to their corresponding surrounds 1600 to produce the diaphragm-surround subassemblies 4000 illustrated in Figs. 4A-4B. The diaphragm-surround subassemblies 4000 are then attached to the driving rods 1200 to form the interior moving subassembly. Specifically, the driving rods 1200 are secured in place using an appropriate fixture and then the diaphragm-surround subassemblies 4000 are slid over the rods and attached to them at appropriate locations, which may be indicated on the rods with small notches. Each of the diaphragm-surround subassemblies 4000 is attached to its corresponding driving rod with the correct orientation so that the non-driving rod is centered through the corresponding diaphragm opening. For this purpose, removable sleeves may be inserted into the diaphragm openings 1150. These sleeves are used to facilitate centering the non-driving rod in the opening and are removed later. The attachment of the diaphragm-surround subassemblies 4000 to the driving rods may be accomplished by adding adhesive that fills the glue wells 1160 and the indentations 1 170 to provide a strong bond. The housing sections 1500 are slid over the interior moving subassembly and attached to the corresponding surrounds 1600. When all of the housing sections 1500 are attached to the corresponding surrounds 1600, the tension bars 1700 are slid through notches in the housing sections 1500 and attached in place. For each of the two motor modules 1320 and 1340, the voice coil is attached to the corresponding end diaphragm using an appropriate fixture and the motor module consisting of the yoke, magnet and top plate is attached to the last housing section using another appropriate fixture.

The assembly of a linear array transducer 2000 may also be accomplished with a similar process consisting of several steps. The motor modules 2320 and 2340 consisting of a yoke, magnet and top plate are assembled separately without their corresponding housing sections. The two-part diaphragms 2100 are also assembled separately by attaching the rigid components 2120 to the cones 2180. The two-part diaphragms 2100 are attached to their corresponding surrounds 2600 to produce the diaphragm-surround subassemblies 6000 illustrated in Figs. 6A-6B. The diaphragm-surround subassemblies 6000 are attached to the driving rods 2200 to form the interior moving subassembly. Specifically, the driving rods 2200 are secured in place using an appropriate fixture and the diaphragm-surround subassemblies 6000 are slid over the rods and attached to them at appropriate locations, which may be indicated on the rods with small notches. Each of the diaphragm-surround subassemblies 6000 is attached to its corresponding driving rod with the correct orientation so that the non-driving rod is centered through the corresponding diaphragm opening. Removable sleeves may be inserted into the diaphragm openings 2150 to facilitate centering the non-driving rod in the opening. The attachment of the diaphragm-surround subassemblies 6000 to the driving rods may be accomplished by adding adhesive that fills the glue wells 2160 and the indentations 2170 to provide a strong bond. The housing sections 2500 are slid over the interior moving subassembly and attached to the corresponding surrounds 2600. When all of the housing sections 2500 have been attached to the corresponding surrounds 2600, the tension bars 2700 are slid through notches in the housing sections 2500 and attached in place. For each of the two motor modules 2320 and 2340, the voice coil is attached to the corresponding end diaphragm using an appropriate fixture and the motor module consisting of the yoke, magnet and top plate is attached to the last housing section using another appropriate fixture.

If desired, more than one rod may be used to drive a set of diaphragms. One implementation is shown in Figs. 8A-8B and 9A-9B, which illustrate a diaphragm 8100 designed to accommodate three driving rods and three non-driving rods. The thickness of the diaphragm 8100 is essentially uniform across its surface and its surface is shaped with ridges 8130 that increase structural rigidity. Fig. 8A shows a top view and Fig. SB shows a cross-sectional view of the diaphragm 8100, The ridges 8130 are shaped to increase structural rigidity between the three main stress points on the diaphragm 8100, namely the three openings 8140 where the driving rods are attached. This configuration of ridges reduces unwanted vibrational modes without increasing the mass of the diaphragm 8100. The diaphragm openings 8150 where the non-driving rods pass through are shaped as sleeves to mitigate any adverse effects caused by air leakage. Fig. 9A shows a top perspective view and Fig. 9B shows a bottom perspective view of the diaphragm 8100. The ridges 8130 are more clearly visible in these views. In particular, in the top view of Fig. 9 A the ridges 8130 appear as elevations on the top surface of the diaphragm 8100, while in the bottom view of Fig. 9B the same ridges 8130 appear as depressions on the bottom surface of the diaphragm 8100.

Fig. 10 provides a cross-sectional perspective view of one implementation of an end-diaphragm assembly 10000 that may be used to attach to a motor at the end of a set of diaphragms. The assembly 10000 consists of a diaphragm coupler 10800, a surround 10600 and a voice coil 10350. The diaphragm coupler 10800 is attached to a voice coil bobbin 10355 via a continuous adhesive joint 10890 that provides glue wells at both its top and bottom edges. With this continuous joint 10890, the step of attaching the diaphragm coupler 10800 to the voice coil 10350 can be performed with cost-efficient traditional speaker assembly methods. The legs 10810 provide structural rigidity for the diaphragm coupler 10800 while reducing its mass. The end-diaphragm assembly 10000 has a coupler cover over the middle section of the diaphragm coupler 10800; the driving rods are attached to this coupler cover, which is not shown in Fig. 10. Figs. 11 A-1 1 B and 12 illustrate two linear array transducers that use the diaphragm 8100 along with tension rods and an end-diaphragm assembly connection 10000. Fig. 1 IA shows a perspective view and Fig. 1 IB shows a cross-sectional view of a linear array transducer 11000 with tension rods 11700 that slide through the housing sections and are tightened at the ends. The tension rods 11700 are not visible in the perspective view of Fig. 1 1 A because their ends, which are the only externally visible parts, are covered by the end caps 11900. Fig. 1 IB shows that the end caps 11900 may be constructed to cover only the front part of the motors that may be visible to the listener. Fig. 13A shows a perspective view and Fig. 13B shows a cross-sectional view of a linear array transducer 13000 with two motors 13320 and 13340 each driving one of two sets of diaphragms 13100, with a single rod connecting each set of diaphragms. This configuration is similar to that of the transducer 1000 shown in Figs. IA and IB; however, the transducer 13000 comprises motors 13320 and 13340 that include spiders- 13352 to reduce unwanted lateral vibrations of the voice coil 13350. In addition, the motors 13320 and 13340 comprise motor yokes that are molded together with the corresponding motor end caps into integrated assembly components 13360. The transducer 13000 also comprises a regular housing section 13500, a special end housing section 13530, a special middle housing section 13560 and a motor mating section 13590 that is used to secure the outer section of the spider 13352. These four types of housing sections as well as the integrated motor end 13360 have integrated extensions that constitute the mounting flanges 13700 after assembly so that the transducer 13000 does not require tension rods. Moreover, the transducer 13000 comprises one-part diaphragms 13100 that are shaped to increase structural rigidity and reduce localized stress forces.

Figs. 14A-14E illustrate the diaphragm 13100 designed to accommodate one driving rod and one non-driving rod. The thickness of the diaphragm 13100 is essentially uniform across its surface and its surface is shaped with ridges 14130 that increase structural rigidity and reduce localized stress forces. Fig. 14A shows a top view and Figs. 14B and 14C show cross-sectional views of the diaphragm 13100. The ridges 14130 are shaped to increase structural rigidity and minimize stress on the diaphragm 13100, particularly the stress generated by the force at the opening 14140 where the driving rod is attached. This configuration of ridges reduces unwanted vibrational modes and distributes stress across the surface of the diaphragm 13100 without increasing the mass of the diaphragm. Moreover, as illustrated in Fig. 14C, the ridges 14130 are shaped with smooth surfaces that reduce localized stress forces within the ridges 14130. The diaphragm opening 14150 where the non-driving rod passes through is shaped as a sleeve to mitigate any adverse effects caused by air leakage. Fig. 14D shows a top perspective view and Fig. 14E shows a bottom perspective view of the diaphragm 13100. The ridges 14130 are more clearly visible in these views. In particular, in the top view of Fig. 14D the ridges 14130 appear as elevations on the top surface of the diaphragm 13100, while in the bottom view of Fig. 14E the same ridges 14130 appear as depressions on the bottom surface of the diaphragm 13100. Figs. 15A-15B illustrate the housing section 13500, seven copies of which are used in the assembly of the transducer 13000. The housing section 13500 has on its front side a circular depression 13502 and on its back side a circular protrusion 13504. In addition, the housing section 13500 has pins 13506 on the right-hand side as illustrated in Fig. 15B and has holes 13508 on the left-hand side as illustrated. During assembly, neighboring sections 13500 are rotated 180 degrees with respect to each other so that each circular depression 13502 mates with an adjacent circular protrusion 13504 of a neighboring housing section while each of the pins 13506 mates with an adjacent hole 13508 of a neighboring housing section. Moreover, the outermost section of a respective surround such as the surround 2600 is seated in the circular depression 13502 and is compressed and held in place by the circular protrusion 13504 of the neighboring housing section.

The middle housing section 13560 shown in Figs. 13A and 13B is very similar to the housing section 13500 but its overall width is smaller than the overall width of the housing section 13500. This width reduction is possible because adjacent diaphragms within the middle section 13560 face each other. The width of the section 13560 may be reduced to bring these two diaphragms closer together without unnecessarily reducing their maximum excursion limit. A benefit of reducing the width of section 13560 is a reduction in the overall length of the transducer 13000. Figs. 16A-16B illustrate the motor mating section 13590, two copies of which are used in the assembly of the transducer 13000. The motor mating section 13590 has on its front side a circular depression 13592 and on its back side a circular protrusion 13594. In addition, the motor mating section 13590 has pins 13596 and 13597 on the left-hand side as illustrated in Fig. 16B and has holes 13598 and 13599 on the right-hand side side as illustrated. During assembly, the motor mating section 13590 is interposed between an integrated motor end component 13360 and a housing section 13500 on the right-hand end of the transducer 13000 as illustrated in Fig. 13B, or is interposed between an integrated motor end component 13360 and the end housing section 13530 on the left- hand end of the transducer 13000 as illustrated. The end housing section 13530 is described below and illustrated in Figs. 17A-17B. On the right-hand end of the transducer 13000, the circular depression 13592 of the motor mating section 13590 mates with the circular protrusion 13504 of the housing section 13500. In addition, the pin 13596 and the hole 13598 of the motor mating section 13590 mate respectively with a hole 13508 and a pin 13506 of the housing section 13500.

Figs. 17A-17B illustrate the end housing section 13530, only one copy of which is used in the assembly of the transducer 13000. The end housing section 13530 has on both its front and back sides circular protrusions 13534. In addition, the end housing section 13590 has a pin 13536 and a hole 13538 on both its right-hand and left-hand sides as illustrated in Fig. 17B. During assembly of the left-hand end of the transducer 13000 as illustrated in Fig. 13B, the end housing section 13530 is attached on its front side to a housing section 13500 and on its rear side to the motor mating section 13590. On the front side, a circular protrusion 13534 of the end housing section 13530 mates with a circular depression 13502 of the housing section 13500. In addition, a pin 13536 and a hole 13538 of the end housing section 13530 mate respectively with a hole 13508 and a pin 13506 of the housing section 13500. Moreover, the outermost section of a respective surround such as the surround 2600 is seated in the circular depression 13502 of the housing section 13500 and is compressed and held in place by the circular protrusion

13534 of the end housing section 13530. On the rear side, a circular protrusion 13534 of the end housing section 13530 mates with a circular depression 13592 of the motor mating section 13590. In addition, a pin 13536 and a hole 13538 of the end housing section 13530 mate respectively with a hole 13598 and a pin 13596 of the motor mating section 13590.

Fig. 18A shows a top perspective view and Fig. 18B shows a bottom perspective view of the integrated motor end 13360. The motor end cap 13365 and the motor yoke 13325 are molded together in an additional step of the manufacturing process. This molding step can assure very high accuracy in the alignment between the two initially separate components. The resulting integrated motor end 13360 may then be used as a reference basis for the assembly of the remaining motor components, resulting in a simplified motor assembly process. During assembly of each of the ends of the transducer 13000, an integrated motor end 13350 is attached to a motor mating section 13590. The circular depression 13362 of the integrated motor end 13360 mates with the circular protrusion 13594 of the motor mating section 13590. In addition, the pin 13366 and the hole 13368 of the integrated motor end 13360 mate respectively with the hole 13599 and the pin 13597 of the motor mating section 13590. Moreover, the outermost section of a respective spider 13352 is seated in the circular depression 13362 of the integrated motor end 13360 and is compressed by the circular protrusion 13594 of the motor mating section 13590.

The implementations described above and illustrated in the figures are only a few examples of how the present invention may be carried out. For example, diaphragms in a set can be driven by more than one rod and the diaphragms may be grouped into more than two sets. The steps of assembly may be performed in a variety of orders to better meet any requirements that may be imposed on the manufacturing process.

Claims

1. An acoustic transducer that comprises: a housing; a first group of two or more first diaphragms mounted in the housing and coupled to one another by one or more first rods, wherein each respective first diaphragm comprises one or more features that increase structural rigidity of the respective first diaphragm with respect to forces applied to the respective first diaphragm by the one or more first rods; a second group of two or more second diaphragms mounted in the housing and coupled to one another by one or more second rods, wherein the first rods pass through second openings with second sleeves in the second diaphragms and the second rods pass through first openings with first sleeves in the first diaphragms, wherein a first sleeve reduces air flow through its respective first opening and a second sleeve reduces air flow through its respective second opening, and wherein each respective second diaphragm comprises one or more features that increase structural rigidity of the respective second diaphragm with respect to forces applied to the respective second diaphragm by the one or more second rods; a first motor mounted in the housing and coupled to the first diaphragms; and a second motor mounted in the housing and coupled to the second diaphragms, wherein the first and second motors drive the first and second diaphragms in opposition to one another.

2. The acoustic transducer according to claim 1, wherein the two or more first diaphragms are coupled to one another by a single first rod and the two or more second diaphragms are coupled to one another by a single second rod.

3. The acoustic transducer according to claim 1 or 2 that comprises: a plurality of first modules each constituting a section of the housing and a respective first diaphragm; a plurality of second modules each constituting a section of the housing and a respective second diaphragm; and one or more third modules each constituting a section of the housing and a respective first diaphragm, wherein the third modules differ from the first modules.

4. The acoustic transducer of claim 3 that comprises a third module that consititutes a section of the housing having a length that differs from the length of the section of the housing provided by each of the first and second modules.

5. The acoustic transducer according to any one of claims 1 through 4, wherein each respective first diaphragm has a uniform thickness and each respective second diaphragm has a uniform thickness.

6. The acoustic transducer according to any of one of claims 1 through 5, wherein: the one or more features of the respective first diaphragm comprise one or more ridges adjacent to one or more locations on the respective first diaphragm that are attached to the one or more first rods; and the one or more features of the respective second diaphragm comprise one or more ridges adjacent to one or more locations on the respective second diaphragm that are attached to the one or more second rods.

7. The acoustic transducer according to any one of claims 1 through 5, wherein: the one or more features of the respective first diaphragm comprise a first rigid component at the center of the respective first diaphragm having a first opening at which the single first rod is attached and a second opening through which the single second rod passes and is not attached, wherein the second opening in the first rigid component provides the first sleeve; and the one or more features of the respective second diaphragm comprise a second rigid component at the center of the respective second diaphragm having a second opening at which the single second rod is attached and a first opening through which the first rod passes and is not attached, wherein the first opening in the second rigid component provides the second sleeve.

8. The acoustic transducer according to claim 7, wherein the first and second openings in the first rigid component are on opposing sides of the center of the respective first diaphragm and the first and second openings in the second rigid component are on opposing sides of the center of the respective second diaphragm.

9. The acoustic transducer according to claim 8, wherein the centers of respective first diaphragms are aligned with the centers of respective second diaphragms.

10. The acoustic transducer according to claim 7, wherein the first opening in the first rigid component is at the center of the respective first diaphragm and the second opening in the second rigid component is at the center of the respective second diaphragm.

1 1. The acoustic transducer according to claim 10, wherein the centers of respective first diaphragms are aligned with one another, the centers of respective second diaphragms are aligned with one another, and the centers of the first diaphragms are offset relative to the centers of the second diaphragms.

12. A method for manufacturing an acoustic transducer according to any one of claims I through 11 , wherein the acoustic transducer comprises a plurality of first diaphragm modules each having a first diaphragm attached to a surround and a plurality of second diaphragm modules each having a second diaphragm attached to a surround, and wherein the method comprises: passing a respective first rod through a respective opening in the first diaphragm of a respective first diaphragm module and through a respective opening in the second diaphragm of a respective second diaphragm module and affixing the respective first rod to the first diaphragm of the respective first diaphragm module; passing a respective second rod through a respective opening in the first diaphragm of a respective first diaphragm module and through a respective opening in the second diaphragm of a respective second diaphragm module and affixing the respective second rod to the second diaphragm of the respective second diaphragm module; assembling the housing by attaching sections of the housing to surrounds of the respective first and second diaphragm modules; attaching the first motor to a first end of the housing such that the first motor is coupled to the one or more first rods; and attaching the second motor to a second end of the housing such that the second motor is coupled to the one or more second rods.

13. The method of manufacture according to claim 12 for manufacturing an acoustic transducer according to any one of claims 7 through 1 1, wherein: the respective first rod is passed through a respective first opening in the first rigid component of the first diaphragm of the respective first diaphragm module and through a respective second opening in the second rigid component of the second diaphragm of the respective second diaphragm module and the respective first rod is affixed to the first rigid component; and the respective second rod is passed through a respective second opening in the second rigid component of the second diaphragm of the respective second diaphragm module and through a respective first opening in the first rigid component of the first diaphragm in the respective first diaphragm module and the respective second rod is affixed to the second rigid component.

14. The method according to claim 12 or 13 that comprises: passing one or more bars through openings in the sections of housing; and applying tension to the one or more bars such that the one or more bars apply a compressing force to the sections of housing in a direction parallel to the first and second rods.

15. The method according to claim 12 or 13 that comprises: orienting the first diaphragm of the respective first diaphragm module prior to affixing the respective first rod to align the openings in the first diaphragm with the openings of other diaphragms in the first group of diaphragms; and orienting the second diaphragm of the respective second diaphragm module prior to affixing the respective second rod to align the openings of the second diaphragm with the openings of other diaphragms in the second group of diaphragms.

16. The method according to any one of claims 12 through 15 that comprises: placing the respective first rod in a secured position; passing the respective first rod through the respective opening of the first diaphragm by sliding the first diaphragm along the length of the respective first rod; removing the respective first rod from its secured position; placing the respective second rod in a secured position; passing the respective second rod through the respective opening of the second diaphragm by sliding the second diaphragm along the length of the respective second rod; and removing the respective second rod from its secured position.

17. The method according to any one of claims 12 through 15 that comprises: using a first removable sleeve on the respective first rod to facilitate alignment of the second diaphragm; removing the first removable sleeve from the respective first rod; using a second removable sleeve on the respective second rod to facilitate alignment of the first diaphragm; and removing the second removable sleeve from the respective second rod.

18. A method for manufacturing an acoustic transducer according to any one of claims 1 through 11, wherein the acoustic transducer comprises a plurality of first diaphragm modules each having a first diaphragm attached to a first surround, the first surround being mounted in a section of the housing, and a plurality of second diaphragm modules each having a second diaphragm attached to a second surround, the second surround being mounted in a section of the housing, and wherein the method comprises: passing one or more bars through openings in the sections of housing; and applying tension to the one or more bars such that the one or more bars apply a compressing force to the sections of housing in a direction parallel to the first and second rods.

19. The method of manufacture according to any one of claims 12 through 18 that comprises: attaching the first motor to the first end of the housing by affixing a first motor module to the first end of the housing, wherein the first motor module comprises the first motor, a first end cap and a first yoke adapted to attach to the first end of the housing; and attaching the second motor to the second end of the housing by affixing a second motor module to the second end of the housing, wherein the second motor module comprises the second motor, a second end cap and a second yoke adapted to attach to the second end of the housing.