HK1151663B - Acoustic passive radiator rocking mode reducing - Google Patents

Abstract

An acoustic passive radiator that reduces "rocking mode" vibration. An acoustic passive radiator includes a diaphragm for radiating acoustic energy. The diaphragm has a perimeter portion and a central portion. The perimeter portion is thicker than the central portion. The passive radiator further includes a passive radiator suspension. The suspension includes a skin element encasing the diaphragm. The skin element comprises a surround for physically coupling the passive radiator to an acoustic enclosure, pneumatically sealing the diaphragm and the enclosure. The surround has a non-uniform width. The passive radiator has a non-pneumatically sealing, non-surround, non-spider suspension element. The non-surround suspension element and the surround coact to control the motion of the diaphragm and to support the weight of the diaphragm.

Description

Passive acoustic radiator with reduced wobble mode

The present application is a divisional application of the invention patent application entitled "passive acoustic radiator for reducing swing mode", having application number 200510004432.0, filed on.2005, month 1 and day 17 by bos ltd.

Technical Field

The present invention relates to a passive radiator, and more particularly, to an acoustic passive radiator (passive radiator) for reducing vibration in a rocking mode.

Disclosure of Invention

It is an important object of the present invention to provide a passive radiator with reduced oscillatory mode vibrations.

According to the invention, the passive radiator comprises a diaphragm (diaphragm) for radiating acoustic energy. The diaphragm has a peripheral portion and a central portion. The peripheral portion is thicker than the central portion. The passive radiator further comprises a passive radiator suspension (suspension). The suspension comprises a skin element surrounding the diaphragm. The skin element includes a surround for physically engaging the passive radiator with an acoustic enclosure and pneumatically sealing the diaphragm and acoustic enclosure. The surround has a non-uniform width. The passive radiator has non-pneumatically sealed, non-surround (non-surround) and non-spider suspension elements. The non-encircling suspension element and the encircling member together serve to control the motion of the diaphragm and to support the weight of the diaphragm.

In another aspect of the invention, the diaphragm of the passive radiator is constructed and arranged to have a moment of inertia greater than that of a diaphragm of equal mass made of a homogeneous material and having a uniform thickness.

In another aspect of the invention, a passive acoustic radiator includes a diaphragm for radiating acoustic energy; a surround for hermetically sealing the diaphragm and the speaker; and a plurality of discrete non-encircling, non-spider suspension elements for physically joining the diaphragm and the acoustic enclosure. The non-surround suspension element and the surround together serve to control the motion of the diaphragm and to support the weight of the diaphragm.

In another aspect of the invention, a passive acoustic radiator includes a diaphragm for radiating acoustic energy and a surround for hermetically sealing the diaphragm and the acoustic enclosure. The surround is constructed of solid polyurethane.

In another aspect of the invention, a passive acoustic radiator includes a diaphragm for radiating acoustic energy and a surround for hermetically sealing the diaphragm and the acoustic enclosure. The surround has a non-uniform width.

In another aspect of the invention, a passive radiator includes a mass element and a skin element surrounding a portion of the mass element such that the skin element is bonded to the mass element without the need for an adhesive. The skin element includes a surround for mechanically supporting the mass element and providing a surface for engaging the passive acoustic radiator and the acoustic enclosure.

In yet another aspect of the invention, a method for forming a passive radiator includes placing a mass element in a cavity in a mold. The cavity defines the shape of the passive radiator suspension. The method further includes inserting a flowable material in the cavity such that the flowable material fills the cavity and hardens the material into a hard, elastic state.

Other features, objects, and advantages will become apparent from the following detailed description when read in conjunction with the accompanying drawings.

Drawings

Fig. 1A and 1B are generalized perspective views of a passive radiator diaphragm used to illustrate some of the terms used in the specification;

fig. 2A and 2B are diagrams of an acoustic enclosure, a surround-type suspension, and a passive radiator diaphragm, which are used to illustrate terms used in the specification;

FIGS. 3A-3E are diagrams of an acoustic enclosure element, a passive radiator diaphragm, and a passive radiator suspension assembly according to one aspect of the present invention;

fig. 4A-4C are diagrams of a passive radiator diaphragm according to another aspect of the present invention;

fig. 5 is a passive radiator according to another aspect of the present invention;

fig. 6 is a passive radiator according to another aspect of the present invention;

FIG. 7 is a diagram of a passive radiator diaphragm and surround assembly according to yet another aspect of the present invention;

fig. 8 is a diagram of another embodiment of the passive radiator diaphragm and surround assembly of fig. 7.

Detailed Description

Reference is made to the drawings, and in particular to figures 1A and 1B, which are pictorial illustrations of passive radiator diaphragms for use in some of the terms used in the specification. A passive radiator (sometimes referred to as a "drop") typically includes a diaphragm 10 disposed within an acoustic enclosure (not shown) by a suspension system (not shown). An acoustic driver radiates acoustic energy into an enclosure causing a pressure change within the enclosure. The diaphragm vibrates in response to pressure changes inside the enclosure. In one conventional form of passive radiator, the diaphragm and suspension are arranged so that the diaphragm can undergo pistonic (piston) motion. In piston motion, all points on the diaphragm move in unison along a predetermined axis of motion, as shown by velocity vector 42, and the points on the diaphragm do not move relative to each other. However, in some cases (e.g., in the presence of lateral forces, uneven pressure or acoustic loading across the radiating surface, or suspension non-linearity), points on the radiating surface may move non-uniformly along a predetermined axis of motion, such that the points on the diaphragm move relative to each other and produce an oscillating rotational motion about axis 46, as indicated by velocity vector 43, as indicated by arrow 44. Non-piston type movements of the type shown in fig. 1B are sometimes referred to as "rocking mode" vibrations, and the shaft 46 is referred to as a rocking shaft. The oscillatory mode vibrations have undesirable acoustic effects such as reduced acoustic efficiency or acoustic distortion radiated by passive radiators. Oscillatory mode vibrations tend to occur at specific frequencies related to diaphragm, suspension and tank characteristics, configuration, mechanical and acoustic characteristics of the sound driver, and other factors. Some arrangements or devices (e.g., multiple surrounds, "spider" and other suspension elements, and acoustic drivers symmetrically disposed with respect to the passive radiator) may reduce roll mode vibration, but are difficult to implement in some types of speaker assemblies, such as compact low frequency bass or subwoofer (subwoofer) speaker assemblies.

The above-described types of oscillatory mode vibrations are the most commonly observed forms of oscillatory modes. The devices and techniques described herein are generally used to prevent or control other more complex forms of wobble patterns. For simplicity of illustration, some devices and techniques are described with respect to the type of swing pattern described above.

The above discussion also relates to the movement of a rigid diaphragm. In the case of diaphragms that are not rigid (rigid), other ways of having an undesired acoustic effect may occur in most cases. The "buckling" and "potato chip" modes are examples of non-rigid diaphragm modes that have undesirable acoustic effects. The devices and techniques described herein may be used to prevent or control undesirable non-rigid modes. For simplicity of explanation, apparatus and techniques are described with respect to oscillatory mode vibration of a rigid diaphragm.

Referring to fig. 2A, there is shown a cross-sectional view of portions of an acoustic enclosure, surround type suspension, and passive radiator diaphragm 10 as that term is used in the description. The passive radiator diaphragm is shown as a planar element for convenience, but may take a variety of shapes, such as a conical structure or a structure having one or more non-planar surfaces. The suspension system includes a surround 12 that mechanically couples the passive radiator diaphragm 10 to an enclosure element 14 or other structure. The diaphragm is typically disposed in an opening in the enclosure element 14. The surround is arranged to enable the passive radiator diaphragm to vibrate in the direction indicated by arrow 16 and to dampen movement in the direction indicated by arrow 18 (a direction transverse to direction 16). In addition to controlling the motion of the passive radiator diaphragm 10, the suspension also supports the weight of the passive radiator diaphragm 10 and seals the passive radiator diaphragm and the enclosure element so that air does not leak from one side of the enclosure element and diaphragm to other parts through openings in the enclosure element 14. To facilitate the engagement of the surround with the enclosure element 14, the surround may have an outer engagement region 20 and the enclosure element may have a frame structure (not shown). The surround can have a passive radiator engagement region 22 to facilitate engagement of the surround and passive radiator diaphragm 10. The surround has roller areas (roller areas) 24 formed with a geometry that facilitates movement in direction 16. The configuration shown is referred to as a "twin roll" configuration, but several other configurations may be used, such as a single roll, corrugated (corrugation), double roll, etc. configuration.

Fig. 2B is a top plan view of the assembly of fig. 2A, with the edge 26 of the enclosure element 14 and the edge 28 of the passive radiator diaphragm 10 shown in phantom. In addition, the reference line shows the correspondence of the respective points of the surround 12 in the two diagrams. The surround is joined to the enclosure element 14 along an outer joint region 20 and to the passive radiator diaphragm 10 along a passive radiator joint region 22. The engagement is typically achieved by adhesive or some other securing element or method. Desirably, the acoustic enclosure element and passive radiator diaphragm are joined in an airtight manner along the joint regions 20 and 22 so that air does not escape from one side of the surround to the other. As used herein, the "width" of the surround is the length w of the unbonded surround between the enclosure element 14 and the passive radiator diaphragm.

Referring to fig. 3A and 3B, a top plan view and a cross-sectional view of an acoustic enclosure element 14, a passive radiator diaphragm 10, and a passive radiator suspension assembly are shown, according to one aspect of the present invention. The suspension assembly includes a surround 12 similar to the surround in the previous figures. In addition to the surround 12, the suspension assembly includes two or more discrete non-surrounding suspension elements 32, such as flexures. The discrete suspension element is bonded at any convenient point on the diaphragm (which may be in the bonding region 22 as shown in the drawings). The suspension assembly performs the same functions (controlling the direction of motion, supporting the weight of the diaphragm, and pneumatically sealing the enclosure element and passive radiator diaphragm) as the suspension in the previous figures. The surround provides an air seal, while the combination of the surround and non-surrounding suspension elements enables weight support and motion control.

The use of a material that has good stiffness, good internal damping, and is thermally stable helps to reduce or control the rocking mode. In addition to good stiffness, good internal damping and thermal stability, the material should have other properties required of the surround material, such as linearity and easy adhesion. Thermal stability is particularly important for use in small enclosures. Solid polyurethanes having an elastic modulus in the range of 1.4X 107N/m 2, tan. delta. of 0.1, good thermal stability, good linearity and good adhesion are suitable.

In one embodiment of the construction shown in fig. 3A and 3B, the passive radiator diaphragm 10 is a planar aluminum disk about 12.5 inches (31.75 cm) in diameter and about 0.5 inches (1.27 cm) thick. The wrap was a single roll wrap of polyurethane foam 0.05 inches (1.27 mm) thick and 0.8 inches (2.03 cm) wide. The non-encircling suspension elements comprise four spring steel bands that are 0.006 inches (0.15 mm) thick, 1.2 inches (3.05 cm) wide, and 1.2 inches (3.05 cm) long.

Fig. 3C shows an alternative configuration of the device of fig. 3A and 3B. In the configuration of fig. 3C, the diaphragm 10 has a so-called "racetrack" shape. In other constructions, the diaphragm may have other shapes, such as circular or elliptical, and may take other shapes, such as a conical configuration. Fig. 3C illustrates another feature of the present invention, namely the reduction or control of oscillatory mode vibrations. The surround is relatively wide (and also relatively thick) at locations prone to oscillatory mode vibrations. For example, width w1 is greater than width w 2.

Fig. 3D and 3E show an alternative configuration of the surround 12 and discrete non-surrounding suspension elements 32. The discrete non-surround suspension element 32 and surround may be disposed on the same side of the diaphragm 10 as shown in fig. 3A, or on opposite sides as shown in fig. 3D and 3E.

The passive radiating suspension device according to fig. 3A-3E is advantageous over conventional passive radiating suspension devices because the non-surrounding suspension elements allow sharing of the weight support function between the surrounding and non-surrounding suspension elements. This greatly increases the flexibility of the setup and allows the use of a heavy diaphragm without the need for spider or complex bulky surrounds that restrict the motion of the diaphragm or take up more space required or both. The non-encircling suspension element may be arranged at a location more inclined to withstand oscillation causing a rocking mode than at other locations, such as at a location on the diaphragm that, depending on the geometry, is subjected to a greater pressure, or at a location on the diaphragm where a pressure differential exists. The suspension system can be more easily arranged so that the loudspeaker incorporating the invention is oriented so that the intended direction of movement of the passive radiator is horizontal (so that gravity is a force perpendicular to the direction of diaphragm movement) or vertical (so that gravity is a force parallel to the direction of diaphragm movement). In addition, the passive radiating suspension can be formed to be more difficult to deflect or creep so that it maintains its characteristics at all times. Still further, the suspension can be formed to be less affected by deformation of the surround due to air pressure.

Referring to fig. 4A-4C, cross-sectional and plan views of certain passive radiator diaphragm arrangements for controlling oscillatory mode vibration are shown. One way to control the oscillatory mode vibration is to control the mass distribution of the diaphragm. Typically, the mass is moved away from the axis of rotation in response to any rotational movement of the diaphragm, thereby increasing the moment of inertia and causing oscillatory mode vibrations that will occur at low frequencies. Moving the mass toward the axis of rotation reduces the moment of inertia and causes oscillatory mode vibrations that occur at high frequencies. By distributing the mass appropriately, it is possible to cause the wobble mode vibration frequency to be lower or higher than the operating frequency of the passive radiator. Lower wobble mode frequencies are generally more beneficial because passive radiators are generally used to increase bass acoustic radiation and the audio signal sent to the speaker using the passive radiator is generally low pass filtered to remove high frequency spectral components. In fig. 4A, the diaphragm has a frustoconical (frustoconical) surface engaging the surround at the outer edge 54 of the diaphragm and the shape of the additional mass 48 engaging the inner edge 56 of the diaphragm to set the mass according to the axis of oscillation 46. The method used to form the embodiment of fig. 4A is to use a conventional acoustic driver cone and dust cover 58 for the diaphragm to engage a tube 60, such as a coil former or similar element, in a conventional manner. Additionally, material may be placed inside the tube such that the additional mass includes the tube and the material may be deposited inside the tube. Other oscillation mode limiting devices, such as spider 50, may provide additional oscillation mode control.

In the embodiment of fig. 4B, the passive radiator diaphragm is thicker at the periphery than at the center. The thickness may increase linearly (as shown by the solid line), exponentially (as shown by the dashed line), or in some regular or irregular manner, either experimentally determined or in computer simulation. Fig. 4C shows another passive radiator diaphragm in which mass distribution has been used to increase the moment of inertia (on a diaphragm of uniform thickness) to change the frequency of the oscillatory mode. The diaphragm of FIG. 4C has a cup-shaped profile with band-type or ring-shaped material at the perimeter locations to increase the mass of the perimeter. In addition, the diaphragm may be joined to the surround at a point other than the lateral outer end portion of the diaphragm, so that the diaphragm is larger than the opening in which the diaphragm is disposed. In one configuration, the diaphragm has a lateral extension 33 such that the passive radiator diaphragm edge 28 is located on the outer edge 26 of the acoustic enclosure element 14. The passive radiator may be arranged so that the loop or strip of material and the lateral extension are located outside the enclosure, if the configuration permits.

Referring now to fig. 5, another passive radiator diaphragm in accordance with the present invention is shown. In the embodiment of fig. 5, the diaphragm 10 includes a skin element 34 and a mass element 36. The skin element 34 may be formed as a unitary member with the surround 12, as shown in the drawings, or may be separate from the surround. The mass element may comprise, for example, a stiffening element, such as a rib 52, if the diaphragm is not sufficiently stiff and exhibits diaphragm properties.

The embodiment according to fig. 5 provides an even more elastic mass distribution. For example, the mass element 36 may be an annular structure as shown in fig. 6, which provides a large concentration of mass at the periphery and a significantly increased moment of inertia over conventional passive radiator diaphragms. The mass element 36 may also take the form of a diaphragm as in fig. 4A-4C, with additional flexibility that the surface of the mass element 36 need not be unbroken or continuous.

Referring to fig. 6, another embodiment of the present invention is shown. In the embodiment of fig. 6, different portions of the diaphragm 10 and the mass element 36 are formed of different materials. For example, the first inner portion 38 may be a low density material and the outer portion 40 may be a higher density material. Examples of low density materials may include light weight paper and plastic, foam, and honeycomb that is unfilled or filled with low density material, while examples of higher density materials may include heavy paper or plastic, metal, wood, compounds, or honeycomb that is filled with higher density material.

Fig. 7 and 8 illustrate various embodiments of fig. 5 and 6. As shown in fig. 7, the skin element 34 surrounds a sufficient portion (e.g., more than half of the surface area) to assemble the passive radiator without the need for adhesive and to hold the elements of the passive radiator in place during operation. In another embodiment (fig. 8), the skin element 36 may completely surround the mass element 36. In the variation shown in fig. 7, the mass element is formed to increase the moment of inertia as described above. In the variant shown in fig. 8, the diaphragm has the form shown in fig. 6. Since the diaphragm can be sealed, materials such as powder, granular materials, liquids, materials that should not be exposed to the surrounding environment, and the like can be used for the mass element portion.

The passive radiator according to fig. 7 and 8 may be formed by insert molding (insert molding). The mass element may be disposed within a cavity of a mold. The cavity may then be filled with a flowable, curable material such that the cavity partially or completely comprises the mass element. And hardening or curing the flowable, curable material into a shape and elastomer suitable for use in a passive radiator suspension. Suitable materials include thermosetting, thermoplastic or curable materials such as closed-cell polyurethane foam. Insert molding positions the mass element 36 relative to the skin element 34 more accurately than other manufacturing methods. Because the mass element and the skin element can be aligned more accurately, a passive radiator less prone to sway mode vibrations due to misalignment of the passive radiator elements can be made. In addition, the passive radiator can be formed without using an adhesive, which eliminates a source of mechanical failure and reduces the manufacturing steps of depositing and curing the adhesive.

The embodiments in fig. 3A-8 may be combined. For example, the diaphragm assembly may comprise a non-skinned (non-skinned) honeycomb portion and a metal portion according to fig. 6 and a skin portion according to fig. 5; the diaphragm is relatively thick at the peripheral portion according to fig. 4B or 4C or both, and may have a discrete non-surrounding suspension element channel according to fig. 3A. Many other combinations are possible.

Various configurations and geometries may be formed in a variety of ways. For example, the embodiment of fig. 4B may be formed by metal forming or metal casting, or may be formed by removing material from a metal block or metal, plastic, or some other material. The embodiment of fig. 4C may be achieved by metal forming or metal casting, or by removing material from or adding material to a block of metal, plastic, or some other material.

It will be apparent to those skilled in the art that numerous uses of, and departures from, the specific apparatus and techniques described herein may be made without departing from the inventive concepts. The invention accordingly is to be construed as embracing each and every novel feature and novel combination of features disclosed herein and limited only by the spirit and scope of the appended claims.

Claims (16)

1. A passive acoustic radiator comprising:

a diaphragm for radiating acoustic energy, the diaphragm having a peripheral portion and a middle portion, wherein the peripheral portion is thicker than the middle portion;

a passive radiator suspension, the suspension comprising:

a skin element surrounding the diaphragm, the skin element including a surround for physically coupling the passive radiator to an acoustic enclosure and hermetically sealing the diaphragm and the acoustic enclosure, the surround having a width, wherein the width is non-uniform; and

a suspension element that is not hermetically sealed, non-encircling, and non-spider, wherein the non-encircling suspension element and the encircling member cooperate to control the motion of the diaphragm and support the weight of the diaphragm.

2. A passive acoustic radiator comprising:

a diaphragm for radiating acoustic energy;

a surround for hermetically sealing the diaphragm and the speaker; and

a plurality of discrete, non-surround, non-spider suspension elements for physically joining the diaphragm and the acoustic enclosure, wherein the non-surround suspension elements and the surround cooperate to control the motion of the diaphragm and support the weight of the diaphragm.

3. A passive acoustic radiator as claimed in claim 2, wherein each of the discrete suspension elements comprises a metal strip, each metal strip having one end constructed and arranged to engage the diaphragm and another end constructed and arranged to engage the acoustic enclosure.

4. A passive acoustic radiator as claimed in claim 2, wherein the plurality of discrete suspension elements and the surround are constructed and arranged to engage the diaphragm at a common point.

5. The passive acoustic radiator of claim 2, wherein the plurality of discrete suspension elements are mechanically bonded to the diaphragm at discrete points, and wherein the surround is bonded to the diaphragm along a continuous surface, wherein the continuous surface comprises the discrete points.

6. The passive acoustic radiator of claim 2, wherein the diaphragm is comprised of metal.

7. The passive acoustic radiator of claim 2, wherein the surround has a non-uniform width.

8. A passive acoustic radiator comprising:

a diaphragm for radiating acoustic energy;

a surround for hermetically sealing the diaphragm and the acoustic enclosure, wherein the surround is comprised of solid polyurethane; and

a plurality of discrete, non-encircling suspension elements, wherein the non-encircling suspension elements and the encircling member cooperate to control motion of the diaphragm and support the weight of the diaphragm.

9. A passive acoustic radiator as claimed in claim 8, wherein the discrete suspension elements comprise metal strips, each metal strip having one end constructed and arranged to engage the diaphragm and another end constructed and arranged to engage the acoustic enclosure.

10. The passive acoustic radiator of claim 8, wherein the plurality of discrete suspension elements and the surround are constructed and arranged to engage the diaphragm at a common point.

11. The passive acoustic radiator of claim 8, wherein the plurality of discrete suspension elements are mechanically bonded to the diaphragm at discrete points, and wherein the surround is bonded to the diaphragm along a continuous surface, wherein the continuous surface comprises the discrete points.

12. The passive acoustic radiator of claim 8, wherein the diaphragm has a non-uniform width.

13. A passive acoustic radiator comprising:

a diaphragm for radiating acoustic energy;

a surround for hermetically sealing the diaphragm and acoustic enclosure, wherein the surround has a non-uniform width; and

a plurality of discrete, non-encircling suspension elements, wherein the discrete suspension elements and the encircling member cooperate to control the motion of the diaphragm and support the weight of the diaphragm.

14. A passive acoustic radiator as claimed in claim 13, wherein the or each discrete suspension element comprises a metal strip, each metal strip having one end constructed and arranged to engage the diaphragm and another end constructed and arranged to engage the acoustic enclosure.

15. The passive acoustic radiator of claim 13, wherein the plurality of discrete suspension elements and the surround are constructed and arranged to engage the diaphragm at a common point.

16. The passive acoustic radiator of claim 13, wherein the discrete suspension elements are mechanically bonded to the diaphragm at discrete points, and wherein the surround is bonded to the diaphragm along a continuous surface, wherein the continuous surface comprises the discrete points.