Patent Description:
Some types of loudspeakers may include a driver unit (for generating sound waves) connected to an outwardly expanding horn (for propagating the generated sound waves). In some loudspeakers, sound waves uniformly travel from the driver unit as a point source through the horn and outward in all directions. However, the resulting wave shape of sound output by such loudspeakers may direct sound toward locations including those that do not include listeners (e.g., a ceiling area above the listeners) and/or cause undesirable interactions with adjacent loudspeakers in a directional array. The portion of the acoustical power of the loudspeaker utilized to radiate sound waves upward above the loudspeaker or to cause interference in the desired listener locations is largely wasted in such scenarios. Publication <CIT> discloses an acoustic transformer including at least one outer boundary wall. A plurality of inner walls are disposed within the outer boundary wall. The outer boundary wall and the inner walls define a substantially annular input opening divided by at least some of the inner walls into a plurality of circumferentially-spaced input sections. Each of the input sections has an inner circumferential side and an outer circumferential side. A substantially rectangular output opening is divided by at least some of the inner walls into a plurality of output sections. Each of a plurality of acoustic paths interconnects a respective one of the input sections with a respective one of the output sections. The acoustic paths maybe identical or individually unique in order to change the both the shape of the acoustic wavefront at the output and the energy distribution.

Embodiments are disclosed for a loudspeaker waveguide that achieves one or more of: providing substantially equal sound path lengths to create a flat and/or curved wave front from the exit of a compression driver, and providing a controlled cross-sectional area expansion rate from the inlet to the outlet of the waveguide. The above features may provide a loudspeaker output wave shape that propagates coherent sound waves in a controlled direction (e.g., toward an area of listeners), thereby reducing waste in sound output.

The disclosure may be better understood from reading the following description of non-limiting embodiments, with reference to the attached drawings, wherein below:.

In order to reduce the amount of sound directed from a loudspeaker to non-useful locations (e.g., areas away from a primary listening area, such as above the loudspeaker in some arrangements), a loudspeaker may be fitted with a horn that controls the propagation of sound to create a shape of sound output. For example, in an uncontrolled loudspeaker, a shape of the sound output may be spherical, or otherwise have equal sound radiation in all directions. Some loudspeakers may employ a waveguide or an array of waveguides to generate a substantially cylindrical output sound shape with controlled horizontal expansion and limited or no vertical expansion. However, other approaches to create such a sound output shape may utilize waveguides that use the vertical plane to create sound pathways having a similar or same length. The resulting waveguide may only feature in the horizontal plane a constant width from the inlet to the outlet of the waveguide, but differing (or more differing) path lengths in other planes. The present disclosure describes example waveguides and waveguide configuration techniques for waveguides that provide equal sound path lengths in substantially all directions to create equal length channels where sound can travel from a sound output source of the loudspeaker (e.g., an inlet of the waveguide) to a sound exit of the loudspeaker (e.g., an outlet of the waveguide). In this way, increased control may be provided over the sound propagation in relation to systems that utilize waveguides with equal path lengths in only one plane.

<FIG> is a projection view of a loudspeaker system <NUM>. <FIG> is a front view of the loudspeaker system <NUM>. The loudspeaker system <NUM> may include any device that converts input signals into sounds. For example, the loudspeaker system <NUM> may be configured to output sounds at a range of frequencies including those perceptible by a human ear (e.g., <NUM> to <NUM>).

The loudspeaker system may include a housing <NUM> that houses one or more audio-producing components. For example, in order to output sound in a wide range of frequencies, the loudspeaker system <NUM> may include a plurality of loudspeaker drivers (e.g., of different sizes). A largest size of loudspeaker driver includes woofers, which may reproduce low frequencies (e.g., about <NUM> or less). A medium-sized loudspeaker driver includes mid-range loudspeaker drivers, which may reproduce middle frequencies (e.g., about <NUM> to <NUM>). The smallest size of loudspeaker includes compression drivers, which may reproduce high frequencies (e.g., about <NUM> or more). Loudspeaker system <NUM> provides one example arrangement of loudspeakers, including a pair of woofers 104a and 104b (e.g., shown covered by a grill 105a and 105b, respectively, which may include a tight mesh that permits audible sound to pass through and prevents dust and debris from entering the housing <NUM>) positioned on opposing sides of at least one compression driver <NUM> within the housing <NUM>.

As shown in more detail in the front view of the loudspeaker system <NUM> of <FIG>, the compression driver <NUM> may include a waveguide <NUM> configured to control the propagation of sound from the mid-range loudspeaker out of the loudspeaker system <NUM>. For example, the waveguide <NUM> may be positioned in alignment with a slot or opening <NUM> of the housing <NUM>, such that sound exiting the waveguide may not encounter interference from internal surfaces of structural components of the housing <NUM>. In other words, the slot or opening <NUM> may be sized and shaped to allow outward-facing edges (e.g., edges facing a front exterior of the housing <NUM>) of waveguide <NUM> to be flush with either an interior surface of the housing in a region of the slot or opening, or the edges of the slot or opening. In the latter example, the slot or opening may be sized and shaped approximately equivalently to an outward-facing opening of the waveguide.

The vertical elongation of the slot or opening <NUM> (e.g., which may have a height, in the y direction, that is greater than a width, in the x direction) may control vertical expansion of sound waves. The short, horizontal span of the slot may provide minimal to no control over horizontal expansion of the sound waves. When having this rectangular shape, the slot or opening <NUM> may be referred to as a diffraction slot. The ratio of the vertical (e.g., y direction, or height) to horizontal (e.g., x direction, or width) dimensions of the slot or opening <NUM> may be any ratio that is greater than <NUM>, such as <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM>, etc. The external surface of the housing in the vicinity of the slot or opening <NUM> may be shaped to further control the expansion of sound waves exiting the waveguide <NUM>. For example, a mouth <NUM> may be formed by a portion of the front surface of the housing <NUM>, which curves forward (e.g., in the z direction) and outward (e.g., in opposing x directions from opposing sides of the opening <NUM>) from the opening and toward the grill 105a and 105b of the woofers 104a and 104b, respectively. The outward expansion of the mouth <NUM> may provide control over the horizontal and/or vertical expansion of the sound waves exiting the waveguide <NUM>.

The loudspeaker system <NUM> illustrated in <FIG> provides just one example configuration of loudspeaker components in a housing. For example, the waveguide <NUM> may be included in a loudspeaker system with a different number, type, and/or arrangement of loudspeakers. The waveguide <NUM> may additionally or alternatively be used to propagate sound waves from a different type of loudspeaker (e.g., a loudspeaker configured to output sound at a different range of frequencies than compression driver <NUM>). As will be discussed in more detail below, the waveguide <NUM> and associated loudspeaker may be one of a plurality (e.g., an array) of similar or equivalent waveguides and associated loudspeakers in example loudspeaker systems.

<FIG> shows a projection view of an example loudspeaker <NUM>, including a driver unit <NUM> and a waveguide <NUM>. Loudspeaker <NUM> may be an example of high frequency loudspeaker/compression driver <NUM> of <FIG>, and waveguide <NUM> may be an example of waveguide <NUM> of <FIG>. The driver unit <NUM> may be a compressor driver and/or other sound source that generates and propagates sound waves toward the waveguide <NUM> responsive to electrical signal inputs provided to the driver unit. For example, the driver unit <NUM> may convert received electrical signals into acoustic energy through a sound-producing element, such as a fast-moving diaphragm. The acoustic energy may force the air mass within a region (such as a throat connecting the driver unit to the waveguide) toward the waveguide <NUM>. Pressure variations within the throat or other intermediary region may force the air mass to speed up and gain kinetic energy as the air mass passes through restrictions or other structural features of the throat. As the air mass moves into and through the waveguide <NUM>, the air mass may progressively expand as sound waves according to the contours of interior surfaces of the waveguide. Eventually, these sound waves may reach a listener, who may perceive the sound waves as audible sound.

The internal cross-sectional area of the waveguide <NUM> may generally increase in the z direction from the driver unit <NUM> to an outlet region <NUM> of the waveguide <NUM>. The waveguide <NUM> may include two outer shells 208a and 208b and two inner shells 210a and 210b that, when fit together as illustrated in <FIG>, provide substantially complementary sets of pathways for air to travel from the driver unit to the outlet region. For example, the sets of pathways created between the first outer shell 208a and the first inner shell 210a may be similarly or substantially equivalently sized and shaped to the sets of pathways created between the second outer shell 208b and the second inner shell 210b. More detail regarding the pathways will be provided below, with respect to <FIG>. The shells of the waveguide may be coupled together via a suitable coupling mechanism or combinations of coupling mechanisms, such as screws, bolts, welding, adhesion, etc. In the illustrated example, a plurality of threaded bolts <NUM> are used to couple the waveguide shells, where each bolt passes through all of the shells (e.g., passes from the first outer shell 208a, through the inner shells 210a/b, and to the second outer shell 208b).

The waveguide <NUM> may be coupled to the driver unit <NUM> via an inlet-side flange <NUM> positioned at an inlet region <NUM> of the waveguide. The inlet-side flange <NUM> may be formed by the joined outer and/or inner shells 208a-210b. The inlet-side flange <NUM> may provide a flush surface to which the driver unit may be mounted or otherwise coupled in order to produce a substantially air-tight seal between the driver unit and the waveguide. Accordingly, the inlet-side flange <NUM> may have a larger diameter and/or circumference than at least the portion of the driver unit <NUM> that is coupled to the waveguide <NUM>. The inlet-side flange <NUM> may also have a shape that is complementary to an output region of the driver unit (e.g., a region of the driver unit that is coupled to the flange), such as a generally circular, curved, and/or round shape. The perimeter region of the flange may not be coupled to the driver unit <NUM>, and may be either open or coupled to another component of an associated loudspeaker system (e.g., an internal feature of a housing of the loudspeaker system. For example, the inlet-side flange <NUM> may include one or more protrusions <NUM> that extend from points along the perimeter of the flange. The protrusions <NUM> may be solid or include holes, as illustrated, which may be used to couple to the flange to an additional component(s). The flange may also provide structural support for other portions of the waveguide in order to provide rigidity for the waveguide. For example, one or more structural supports <NUM> may extend from an outer surface <NUM> of the first outer shell 208a to a peripheral region of the inlet-side flange <NUM> (e.g., a peripheral region of a waveguide-facing surface of the inlet-side flange, opposite a driver-facing surface of the inlet-side flange).

The waveguide <NUM> may be coupled to a loudspeaker housing or other component of a loudspeaker system via an outlet-side flange <NUM>. The outlet-side flange <NUM> may be positioned opposite the inlet-side flange <NUM>, at the outlet region <NUM> of the waveguide, and may be formed by the joining of the outer and/or inner shells 208a-210b. The outlet-side flange <NUM> may be generally rectangular in shape and/or otherwise complementary to the shape of the outlet region <NUM> (e.g., the openings 221a and 221b for the sound pathways formed between complementary inner and outer shells). The outlet-side flange <NUM> may include one or more (e.g., two, in the illustrated example) protrusions <NUM> extending from sides of the generally rectangular perimeter of the flange. The illustrated protrusions <NUM> are curved and generally rectangular, extending first from a side of the flange, then curving to extend outward away from the outlet region <NUM> (e.g., in a substantially positive z-direction), and then curving slightly in an x-direction to create a slight hook shape. The protrusions <NUM> may thus provide a hook or notch for coupling to a complementary lip within a housing or other loudspeaker structure. In the illustrated example, opposing protrusions are provided on opposite sides of the outlet-side flange <NUM>. In other examples, a different number and/or shape of protrusions may extend from the outlet-side flange in order to couple to complementary surfaces of components of a loudspeaker system.

As discussed above, a waveguide that creates acoustic paths of substantially equal length in three-dimensional space provides increased control over a shape of sound output relative to waveguides that include acoustic paths that are only equal length in one two-dimensional surface (e.g., plane). <FIG> illustrate an example derivation of an air pocket for use in configuring a waveguide that provides the above-described paths with equal length in multiple planes. <FIG> shows a representation of an inlet region <NUM> of a waveguide and an outlet region <NUM> of a waveguide. For example, the inlet region <NUM> may correspond to an opening (or a portion of an opening) at the inlet region <NUM> of the waveguide <NUM> of <FIG> (e.g., the generally circular opening of the inlet region) and outlet region <NUM> may correspond to an opening (or a portion of an opening, such as a portion of opening 221a) at the outlet region <NUM> of the waveguide <NUM> of <FIG> (e.g., the generally rectangular opening of the outlet region). As shown, the inlet region <NUM> includes an inner circumference or perimeter <NUM> and an outer circumference or perimeter <NUM>, between which sound may enter an associated waveguide.

The illustrated inlet circular sections <NUM> may be virtual points representing discrete points of entry of the overall sound path (e.g., from a driver unit) directed to the waveguide. The illustrated outlet circular sections <NUM> may be virtual points representing discrete points of exit of the overall sound path directed out of the waveguide. Accordingly, the virtual points on the inlet side of the waveguide may be located in a plane that is coplanar with an end or inlet-facing surface of the waveguide (e.g., flange surfaces of the waveguide shells). For illustrative purposes, points of entry of the sound path are only provided for a quarter section of the inlet of the waveguide, and corresponding points of exit of the sound path are thus provided for a quarter section of the outlet of the waveguide. For example, the outlet region <NUM> may correspond to an upper half of the opening 221a (or to another half of either opening 221a or 221b) of <FIG>. It is to be understood that similarly-configured sound paths and associated inlets and outlets may be provided for the remaining three quarters of the inlet region <NUM> and the outlet region <NUM>. For example, the sound paths for the illustrated quarter of the inlet region <NUM> may be repeated along each of the remaining three quarters of the inlet region (e.g., around the periphery of the inlet region) and directed to additional portions of the outlet region (e.g., to extend the outlet region to appear similar to the openings 221a and 221b of <FIG>).

The inlet circular sections <NUM> are illustrated as being distributed along an approximate sine wave curve <NUM> in the inlet region <NUM> (e.g., in a sinusoidal plane that is perpendicular to the sine wave curve <NUM> and/or a center of the sinusoidal curve formed at the inlet opening of the waveguide). When repeated in the remaining three quarters of the inlet region, the resulting curve may be a sine wave ring. The sine wave curve may be regular (e.g., where each peak-to-trough distance of the sine wave curve is substantially equal to one another, such that the distance between the inner circumference <NUM> and points of entry that are closest to the inner circumference is substantially equal to the distance between the outer circumference <NUM> and points of entry that are closest to the outer circumference <NUM>). In other examples, the sine wave curve may be irregular (e.g., where peak-to-trough distances vary along the curve). In still other examples, the inlet geometry (e.g., the distribution of the inlet circular sections <NUM>) may form a circular ring (e.g., substantially following the outer and/or inner circumference of the illustrated example inlet region <NUM>, such that the distances between the inner and/or outer circumference and each point of entry to the inlet are substantially equal). The outlet geometry may be configured as a vertical slot, where most or all of the outlet circular sections <NUM> are stacked on top of one another in a vertical direction (e.g., adjacent to and in contact with one another in the illustrated example), and a vertical dimension is larger than a horizontal dimension (e.g., between <NUM> and <NUM> times larger).

<FIG> shows another stage of configuration, in which three-dimensional splines <NUM> of equal (or substantially equal, such as within <NUM>%) length are placed between centers of corresponding inlet and outlet circular sections <NUM> and <NUM>. Additional circular sections <NUM> may be placed on normal planes distributed along the splines, the diameters of which are controlled by a curve representing a selected rate of expansion. In this way, the waveguide may be configured to accommodate a rate of expansion that is suitable for a given environment to produce a desired sound output shape, including a linear rate of expansion, an exponential rate of expansion, and/or any other rate of expansion that can be plotted on an X/Y plot.

In a computer modeling program, each circular section of a given path from inlet circular section to outlet circular section may be lofted (e.g., coupled via transitions along the splines <NUM>) to an adjacent circular section in the direction from inlet to outlet, as shown in <FIG>. In this way, conic lofts <NUM> may be formed along each path from a given inlet circular section to an associated outlet circular section.

As shown in <FIG> and <FIG>, cross section planes <NUM> (e.g., parallel in the z-axis) may be created, equally distributed along the z-axis (e.g., the axis directing from inlet region <NUM> to outlet region <NUM>) of the representation. Conic sections <NUM> may be created by intersecting the conic lofts <NUM> with the parallel cross section planes <NUM>. As shown in <FIG>, inner/outer circumferential splines <NUM>/<NUM> that are tangent to the conic sections may be constructed. Accordingly, rulings (e.g., median lines <NUM>) that project perpendicularly from the inner circumferential spline <NUM> through the center spline (e.g., spline <NUM> of <FIG>) and to the outer circumferential spline <NUM> may be constructed.

The rulings or median lines <NUM> may be lofted together into a complex, ruled surface <NUM>, which creates longitudinal splines/edges. As shown in <FIG>, the edges of the median surfaces may be used together with the inlet and outlet circular sections in a new loft to create the air space <NUM> of the waveguide. The final surfaces (e.g., inner surface <NUM> and outer surface <NUM>) may then be defined by the mesh composed of the longitudinal and circumferential splines. The air space <NUM> represents the gap formed between complementary shells of a waveguide, which may guide sound waves emitted from a driver unit coupled to the waveguide. For example, air space <NUM> may represent the shape of one half of the air gap between an opening of inlet region <NUM> of waveguide <NUM> and the opening 221a of outlet region <NUM> of waveguide <NUM> (between outer shell 208a and inner shell 210a) of <FIG>. As illustrated, the inlet region <NUM> of the air space <NUM> follows the curve of the inlet region <NUM> of <FIG> and the outlet region <NUM> of the air space <NUM> forms the shape of the outlet region <NUM> of <FIG>. Accordingly, near the inlet region <NUM>, the air space <NUM> includes a middle protrusion <NUM> corresponding to a peak of a sinusoidal wave, and two depressions <NUM> corresponding to troughs of the sinusoidal wave that the inlet region follows. With respect to a length of the air space <NUM> from the inlet region to the outlet region, the middle portion <NUM> of the air space generally protrudes relative to the inlet region. In the middle portion <NUM>, the protrusions and depressions of the inlet region <NUM> curve upward (e.g., to a first edge <NUM> of the air space <NUM>) in a stretched "S" shape, where an inclination toward the first edge <NUM> is greatest in the middle portion <NUM> of the air space. The protrusions and depressions of the inlet region <NUM> are smoothed toward the outlet region <NUM>, to form the generally rectangular shape of the outlet region.

In order to provide the air space <NUM> in a wave guide, an outer shell is formed to follow the curvature of the outer surface <NUM> of the air space <NUM>, and an inner shell is formed to follow the curvature of the inner surface <NUM> of the air space <NUM>. Joining the outer shell to the inner shell will thus create an air gap having the properties of the air space <NUM>. For example, the air space <NUM> may form a half of the air gap introduced between outer shell 208a and inner shell 210a of <FIG>. Accordingly, half of the inner surface of outer shell 208a of <FIG> may follow the curvature of the outer surface <NUM> of air space <NUM>. Half of the outer surface of inner shell 210a of <FIG> may follow the curvature of the inner surface <NUM> of air space <NUM>. The remaining halves of the inner and outer shell surfaces may also follow the curvature of the air space <NUM> in a complementary manner. Accordingly, the description of these surfaces of the shells may also describe the surfaces of the air space <NUM>.

Turning now to <FIG>, an exploded view of the shells of waveguide <NUM> of <FIG> is shown including an outlet side (e.g., in outlet region <NUM>) of the shells. As shown, an interior surface <NUM> of outer shell 208a generally protrudes outward away from an exterior surface <NUM> of inner shell 210a. Since outer and inner shells 208b and 210b are substantially duplicates to outer and inner shells 208a and 210b (the waveguide is symmetric with respect to a central plane <NUM> disposed between the inner shells), an interior surface <NUM> of outer shell 208b generally protrudes outward away from an exterior surface <NUM> of inner shell 210b. It is to be understood that descriptions of the outer and inner shells 208a and 210a similarly apply to outer and inner shells 208b and 210b, respectfully. Likewise, the descriptions of outer and inner shells 208b and 210b similarly apply to outer and inner shells 208a and 210a, respectively. Accordingly, descriptions will be provided in the present disclosure for a given shell based on the views available in an associated figure, but will be understood to apply to the other shell of that type (e.g., inner or outer).

The shape of the interior surface <NUM> and the exterior surface <NUM> of the outer and inner shells, respectively, are continuous, smooth, undulating surfaces that provide an uninterrupted pathway (e.g., without obstruction) along the surface from the inlet region <NUM> to the outlet region <NUM> (e.g., from the sinusoidal curve of the inlet region to the rectangular exit of the outlet region). The interior surface <NUM> and the exterior surface <NUM> may not have any edges or corners. For example, the interior surface <NUM> and the exterior surface <NUM> may continuous and uninterrupted until the respective surface meets another surface, such as at a planar flange as described below, at a peripheral region.

<FIG> shows an isolated view of outer shell 208a. Seam <NUM> may represent a halfway point of a vertical (e.g., y) dimension of the shell. Accordingly, regions of the interior surface <NUM> of the outer shell 208a above the seam may follow the curvature of an outer surface of the air space <NUM> of <FIG> in some examples. Likewise, regions of the interior surface <NUM> of the outer shell 208a below the seam may also follow the curvature of the outer surface of the air space <NUM> of <FIG>, such that the outer shell is symmetric (or at least the interior surface <NUM> of the outer shell is symmetric) with respect to the seam <NUM>.

The interior surface <NUM> curves outward from the inlet region <NUM> toward the outlet region <NUM> to allow for vertical expansion of sound waves traveling along the surface. The curvature of the interior surface <NUM> in the y-direction changes more rapidly in the inlet region <NUM> than in the outlet region <NUM>. For example, the height of the interior surface (in the y-direction) may increase rapidly from the inlet region <NUM> to an approximate central region <NUM> (in the z-direction) and then may stay substantially the same from the central region <NUM> to the outlet region <NUM>. Accordingly, a perimeter <NUM> of the interior surface <NUM> may have a large slope in the y-direction from the inlet region <NUM> toward the central region <NUM> and a small or zero slope in the y-direction from the central region <NUM> toward the outlet region <NUM>.

The outer shell 208a may include a flange <NUM> that provides a surface for coupling the outer shell to a complementary inner shell (e.g., inner shell 210a) and/or other component of a loudspeaker. Flange <NUM> may include coupling mechanisms such as tabs <NUM>, which protrude from the flange and are configured to mate with a complementary structure on an associated inner shell, and holes <NUM>, which are configured to mate with a complementary structure on the associated inner shell. Hole <NUM> within interior surface <NUM> may provide a connection point for a bolt or other coupling mechanism used to hold the waveguide together.

As discussed above with respect to the air space <NUM>, the interior surface <NUM> may include dimples and/or protrusions that vary the width of the outer shell in the x-direction according to an arrangement of sound pathways to be created in the gap between the outer shell and the associated inner shell. For example, the width of the outer shell from the flange <NUM> to the exterior surface <NUM> (and/or to different regions of the interior surface <NUM>) may vary due to the dimples and/or protrusions. The width from the surface of the flange <NUM> to the interior surface <NUM> is lesser in regions near the perimeter <NUM> of the interior surface <NUM> than in regions toward a center of the interior surface. Further, the width from the surface of the flange to the interior surface is greater in regions following the outward-extending curves (e.g., peaks) of the sinusoidal inlet region <NUM> than in regions of the inward-extending troughs of the sinusoidal inlet region <NUM>.

For example, regions <NUM> may have a greater width than regions <NUM>. Furthermore, regions of the interior surface <NUM> extending from the regions <NUM> toward the outlet region <NUM> may generally have a greater width than regions of the interior surface <NUM> extending from the regions <NUM> toward the outlet region <NUM>. For example, a protrusion 1020a at a bottommost one of regions <NUM> may begin at a peak 1016a of the sinusoidal inlet region <NUM>, then curve toward the bottom of perimeter <NUM> of the interior surface while extending generally in the z-direction toward the central region <NUM> to midpoint 1016b of the protrusion 1020a. Thus, the protrusion 1020a follows a similar curve to the perimeter <NUM> in the inlet-to-central region. The protrusion 1020a may curve slightly back toward the seam <NUM> while extending from the midpoint 1016b to an endpoint 1016c (e.g., toward the outlet-side flange <NUM>). The amount of deformation caused by the protrusion (e.g., the width from the surface of the flange <NUM> to the interior surface <NUM> in regions of the protrusion 1020a) may vary along the length of the protrusion (e.g., in the general z-direction, from inlet to outlet of the waveguide), but may be consistently greater than the width from the surface of the flange <NUM> to the interior surface <NUM> in regions adjacent to the protrusion (e.g., in regions of dimples 1022a and 1022b). A similar protrusion may be present as indicated at 1020b. Furthermore, the protrusions and dimples present below the seam <NUM> may be repeated symmetrically above the seam <NUM> as well. The interior surface may have a substantially equal width taken at all points along the y-direction at the intersection of the interior surface and the outlet-side flange <NUM>.

The intersection of the interior surface <NUM> and the outlet-side flange <NUM> may form an opening edge or perimeter <NUM>. As illustrated, the opening edge or perimeter <NUM> may form three sides of a rectangle that has at least one curved edge (two curved edges 1026a and 1026b in the illustrated example). Between the curved edges 1026a/b, the opening edge or perimeter <NUM> may be substantially flat (e.g., extend substantially straight in the y-direction). A fourth remaining side of the rectangle (e.g., which forms the opening 221a of <FIG>) is provided by an edge of the complementary inner shell 210a, described below with respect to <FIG>.

<FIG> shows an isolated view of the inner shell 210a. Seam <NUM> may represent a halfway point of a vertical (e.g., y) dimension of the shell. Accordingly, regions of the exterior surface <NUM> of the inner shell 210a above the seam may follow the curvature of an inner surface of the air space <NUM> of <FIG> in some examples. Likewise, regions of the exterior surface <NUM> of the inner shell 210a below the seam may also follow the curvature of the inner surface of the air space <NUM> of <FIG>, such that the inner shell is symmetric (or at least the exterior surface <NUM> of the inner shell is symmetric) with respect to the seam <NUM>. The exterior surface <NUM> curves outward from the inlet region <NUM> toward the outlet region <NUM> to allow for vertical expansion of sound waves traveling along the surface. The curvature of the exterior surface <NUM> in the y-direction changes more rapidly in the inlet region <NUM> than in the outlet region <NUM>. For example, the height of the exterior surface (in the y-direction) may increase rapidly from the inlet region <NUM> to an approximate central region <NUM> (in the z-direction) and then may stay substantially the same from the central region <NUM> to the outlet region <NUM>. Accordingly, a perimeter <NUM> of the exterior surface <NUM> may have a large slope in the y-direction from the inlet region <NUM> toward the central region <NUM> and a small or zero slope in the y-direction from the central region <NUM> toward the outlet region <NUM>.

The inner shell 210a may include a flange <NUM> that provides a surface for coupling the inner shell to a complementary outer shell (e.g., outer shell 208a), a complementary inner shell (e.g., inner shell 210b), and/or another component of a loudspeaker. Flange <NUM> may include coupling mechanisms such as notches <NUM>, which cut into the flange toward the perimeter <NUM> of the exterior surface and are configured to mate with a complementary structure on an associated outer and/or inner shell (e.g., tabs <NUM> of <FIG>), and holes <NUM>, which are configured to mate with a complementary structure on the associated outer and/or inner shell. Hole <NUM> within exterior surface <NUM> may provide a connection point for a bolt or other coupling mechanism used to hold the waveguide together.

As discussed above with respect to the air space <NUM>, the exterior surface <NUM> may include dimples and/or protrusions that vary the width of the inner shell in the x-direction according to an arrangement of sound pathways to be created in the gap between the inner shell and the associated outer shell. For example, the width of the inner shell from the surface of the flange <NUM> to the exterior surface <NUM> in a given region may vary due to the dimples and/or protrusions. The width from the surface of the flange <NUM> to the exterior surface <NUM> is lesser in regions near the perimeter <NUM> of the exterior surface <NUM> than in regions toward a center of the exterior surface. Further, the width from the surface of the flange to the exterior surface is greater in regions following the outward-extending curves (e.g., peaks) of the sinusoidal inlet region <NUM> than in regions of the troughs of the sinusoidal inlet region <NUM>.

For example, regions <NUM> may have a greater width than regions <NUM>. Furthermore, regions of the exterior surface <NUM> extending from the regions <NUM> toward the outlet region <NUM> may generally have a greater width than regions of the exterior surface <NUM> extending from the regions <NUM> toward the outlet region <NUM>. Accordingly, the protrusions 1120a, 1120b, and 1120c may be formed, extending from the peaks in regions <NUM>, while the dimples 1122a, 1122b, and 1122c are formed adjacent to the protrusions and extending from the troughs in regions <NUM>. The waveguide may have a greatest width between flange <NUM> and exterior surface <NUM> in a region indicated at <NUM>, which may extend from the top region of the waveguide to the bottom region of the waveguide (e.g., in the y-direction) along a curve that generally follows the sinusoidal curve of the inlet region <NUM>.

The exterior surface may have a substantially equal width taken at all points along the y-direction at the intersection of the exterior surface and the outlet region <NUM>. Further, the width of the waveguide between the flange <NUM> and the exterior surface <NUM> may generally decrease from a central region <NUM> toward outlet region <NUM>, until the width is substantially zero (e.g., the flange <NUM> is flush with the exterior surface <NUM>) at a perimeter <NUM> of the inner shell 210a. In this way, the protrusions and dimples may smooth in the midpoint regions indicated at <NUM> and flatten in the end regions indicated at <NUM>. The change in width from the flange <NUM> to the exterior surface <NUM> may be greater between the region <NUM> and the regions <NUM> than between the regions <NUM> and the regions <NUM>. The perimeter <NUM> may form a remaining fourth side of the rectangle of the outlet opening (e.g., as discussed above with respect to <FIG>) when the inner shell is coupled to an associated outer shell (e.g., outer shell 208a of <FIG>).

<FIG> shows an exploded view of the waveguide <NUM> of <FIG> including an inlet region <NUM> of the waveguide shells. As shown, the peaks and troughs at an inlet region of the inner shells 210a and 210b may be complementary to the peaks and troughs at the inlet region of the outer shells 208a and 208b, respectively. As further shown, the inlet flange <NUM> of <FIG> may have an outer shell portion and an inner shell portion. For example, outer shell 208a may include an outer flange portion <NUM> and inner shell 210a may include an inner flange portion <NUM>. Each flange portion may include substantially planar surfaces for coupling to a drive unit or other sound-producing source. Outer and inner shells 208b and 210b may similarly include flange portions that together form the flange <NUM>.

<FIG> shows the waveguide <NUM> of <FIG> joined together to create sound paths 1302a and 1302b for sound to travel from a driver unit into the waveguide at an inlet region <NUM>. As illustrated, each sound path inlet 1304a and 1304b is formed by edges or perimeters of the inlet-side flange portions <NUM> and <NUM>. Accordingly, the sound path inlets 1304a and 1304b may each form a continuous semi-circular curve that follows the substantially sinusoidal curvature of the inlet regions of the shells. When joined as shown in <FIG>, the sound path inlets may form a continuous undulating ring (e.g., extending around an annulus of the opening at the inlet) that is only interrupted at a top and a bottom of the ring by the inlet surfaces of the inner shells. Each sound path inlet may have a top termination point <NUM> and a bottom termination point <NUM> defined by the intersection between complimentary outer and inner shells. Along the undulating path of the sound path inlets 1304a and 1304b (e.g., around the ring formed by the sound path inlets), the sound path inlets may have a substantially equal width (e.g., distance between the edge of the outer shell portion <NUM> and the edge of the inner shell portion <NUM> at a given location around the inlet curve).

<FIG> show an additional or alternate example waveguide <NUM> including outer shells 1402a and 1402b joined together (<FIG>) and inner shells 1502a and 1502b joined together (<FIG>). The waveguide <NUM> may be similar to waveguide <NUM> of <FIG> and <FIG> in some examples. For example, waveguide <NUM> may have an inlet region <NUM> that is similar to inlet region <NUM> of waveguide <NUM> of <FIG>. However, in the example shown in <FIG>, the inlet region <NUM> of the inner shells may include protrusions <NUM> at peaks of the sinusoidal curve at the inlet region. The protrusions <NUM> may be used to couple the inner shells to associated outer shells 1402a and 1402b, respectively.

<FIG> show different cross sections taken through the waveguide <NUM> of <FIG> at different heights (e.g., in the y-direction), as viewed from the inlet region <NUM> of the waveguide. <FIG> show different cross sections taken through the waveguide <NUM> of <FIG> at different heights (e.g., in the y-direction), as viewed from the outlet region <NUM> of the waveguide. In each set of cross sectional views, the sound paths <NUM> increase in width (e.g., in the x-direction, where the width of the sound paths is the distance between the interior surface of the outer shell and the exterior surface of the inner shell of a given outer-inner shell pair, such as outer shell 208a and inner shell 210a, at a particular location along the sound path in a generally z-direction from inlet region <NUM> to outlet region <NUM> of the waveguide and at a particular location along a generally y-direction from top to bottom of the waveguide). However, the degree to which the widths change varies at different cross sectional heights. For example, as shown in <FIG> and <FIG>, the paths <NUM> are wider toward a bottom <NUM> of the waveguide than toward a top of the waveguide (e.g., opposite of the bottom <NUM> in the y-direction). In this way, the distance between the inner shells and the associated outer shells is greater in bottom section views than in higher section views. Furthermore, the paths <NUM> are wider in a middle region <NUM> of the waveguide (in an x-direction) than at the inlet region <NUM>. As shown in <FIG> and <FIG>, the paths <NUM> extend below openings in the inlet region.

As shown in <FIG>, the top of the sound paths at cross-sectional plane through an approximate middle of the height of the waveguide may generally increase in width in the direction from the inlet region <NUM> to the outlet region <NUM>. For example, the peripheral edge of the exterior surface <NUM> in the region of the cross-section shown in <FIG> is substantially linear from the inlet region <NUM> to a mid-point <NUM>. The peripheral edge of the exterior surface <NUM> then curves inward toward the inner shell 210b until reaching the outlet region <NUM>. The peripheral edge of the interior surface <NUM> of the outer shell 208a curves out slightly from the inlet region <NUM> to a midpoint <NUM> then curves in slightly to the outlet region <NUM>. The inward curvature of the interior surface <NUM> is lesser than the inward curvature of the exterior surface <NUM>, thereby increasing the width of the sound path 1302a. As the shells are symmetrical, a substantially same curvature is provided for outer and inner shells 208b and 210b as described above for outer and inner shells 208a and 210a.

As shown at <NUM>, a central region of inner shells 210a and 210b may be hollowed out to decrease weight and/or cost of the waveguide and/or to promote resiliency of the shells. One or more webs <NUM> may separate openings in order to provide additional structural integrity for the waveguide and/or to provide a structural surface to which another portion of the waveguide and/or loudspeaker may be coupled to the inner shell. Similarly, external cutouts <NUM> may be formed on the outer shell to reduce weight and/or cost of the waveguide and/or to promote resiliency of the shells. One or more supports <NUM> may protrude from sections of the external surface of the outer shells to provide structural stability and/or to provide a structural surface to which another portion of the waveguide and/or loudspeaker may be coupled. Protruding ring <NUM> may extend from an inlet-facing surface of the inner shells 210a and 210b, and may serve as a key or other coupling mechanism to couple the waveguide to a drive unit or other sound source.

In <FIG>, which shows a cross-section of the waveguide <NUM> at a lower height than that of <FIG>, the curvature of the inner shell <NUM> is more dramatic (e.g., changes by a greater amount) along the path from the inlet region <NUM> to the outlet region <NUM> relative to the curvature of the inner shell <NUM> at the cross-sectional height illustrated in <FIG>. For example, from the inlet region <NUM> to a mid-point <NUM>, the edge of the exterior surface <NUM> curves outward (e.g., toward outer shell 208a). From the mid-point <NUM> to the outlet region <NUM>, the exterior surface <NUM> curves inward (e.g., toward inner shell 210b) by a greater amount than the exterior surface <NUM> at the higher cross-section of <FIG>. The curvature of the interior surface <NUM> of the outer shell <NUM> at the cross-section shown in <FIG> is similar to that of the interior surface <NUM> at the cross-section shown in <FIG>, with a slightly larger radius of curvature. However, the more dramatic curvature of the exterior surface <NUM> results in an overall increased sound path width relative to the sound paths at the cross-section shown in <FIG>. The openings <NUM> in the inner shells 210a and 210b are shown to be larger at the lower cross-section of <FIG> than the higher cross-section of <FIG>.

In <FIG>, which shows a cross-section of the waveguide <NUM> at a lower height than that of <FIG>, the curvature of the inner shell <NUM> is less dramatic (e.g., changes by a lesser amount) along the path from the inlet region <NUM> to the outlet region <NUM> relative to the curvature of the inner shell <NUM> at the cross-sectional heights illustrated in <FIG>. For example, from the inlet region <NUM> to a mid-point <NUM>, the edge of the exterior surface <NUM> curves outward (e.g., toward outer shell 208a). From the mid-point <NUM> to the outlet region <NUM>, the exterior surface <NUM> curves inward (e.g., toward inner shell 210b) by a lesser amount than the exterior surface <NUM> at the higher cross-section of <FIG>. The curvature of the interior surface <NUM> of the outer shell <NUM> at the cross-section shown in <FIG> is more dramatic than that of the interior surface <NUM> at the cross-section shown in <FIG>, with a much larger radius of curvature. The combined lesser radius of curvature of the exterior surface <NUM> and the greater curvature of the interior surface <NUM> results in an overall increased sound path width relative to the sound paths at the cross-section shown in <FIG>. Similar relative path widths and surface curvatures to those shown in <FIG> are illustrated in <FIG>.

<FIG> show an outlet-side view and an inlet side view, respectively, of an example waveguide <NUM> coupled to a driver unit <NUM> in a loudspeaker <NUM>. The waveguide <NUM> may be an example of waveguide <NUM> of <FIG>, and some or all of the above description of waveguide <NUM> may apply to waveguide <NUM>. The driver unit <NUM> may be an example of driver unit <NUM> of <FIG>, and some or all of the above description of driver unit <NUM> may apply to driver unit <NUM>. As shown, the driver unit <NUM> may include outlet openings <NUM> configured to output sound waves to the waveguide <NUM>. The outlet openings <NUM> may be shaped and positioned similarly to inlet openings <NUM> of the waveguide <NUM>. In the illustrated example, the outlet openings <NUM> may be discontinuous, with solid material positioned between sections of a sinusoidal ring, whereas inlet openings <NUM> of the waveguide <NUM> may be continuous to form an uninterrupted sinusoidal ring. Similarly-paired openings may be used in example configurations with circular inlet openings of the waveguide.

<FIG> shows an example configuration of a loudspeaker <NUM> including a waveguide <NUM> coupled to a driver unit <NUM>. The waveguide <NUM> may be an example of waveguide <NUM> of <FIG>, and some or all of the above description of waveguide <NUM> may apply to waveguide <NUM>. The driver unit <NUM> may be an example of driver unit <NUM> of <FIG>, and some or all of the above description of driver unit <NUM> may apply to driver unit <NUM>. As shown, the outlet region <NUM> of the waveguide <NUM> is coupled to a mouth <NUM> of the loudspeaker. The mouth <NUM> may be an example of mouth <NUM> of <FIG>, and the description of mouth <NUM> may apply to mouth <NUM>. For example, the mouth <NUM> may provide a surface for guiding sound output by the waveguide <NUM>. <FIG> shows a cross sectional view of the loudspeaker <NUM>, illustrating sound wave paths <NUM> that travel through the waveguide <NUM> and out toward the mouth <NUM>. The cross sectional view of <FIG> also illustrates a coupling mechanism <NUM> by which the waveguide <NUM> may be coupled to a housing <NUM> of the loudspeaker associated with the mouth <NUM>. The coupling mechanism <NUM> may also help to align the openings at the outlet region <NUM> with the mouth <NUM> such that each edge or periphery 2406a and 2406b of the outer shells 2408a and 2408b, respectively, is flush with an edge or periphery <NUM> of the mouth <NUM>. In this way, the mouth <NUM> may not impede the flow of sound directly at the exit of the waveguide.

<FIG> shows an example loudspeaker <NUM> including an array of waveguides <NUM> positioned within a housing <NUM>. In the illustrated example, the array of waveguides are stacked vertically and directly adjacent to one another (e.g., with no intervening air and/or structure). In other examples, other arrangements may be used to produce a selected sound output shape and pattern. The waveguides <NUM> may be examples of waveguide <NUM> of <FIG>, and some or all of the above description of waveguide <NUM> may apply to waveguides <NUM>.

The above-described loudspeaker systems may reduce the amount of sound directed from a loudspeaker to non-useful locations (e.g., areas away from a primary listening area, such as above the loudspeaker in some arrangements), by employing waveguides that provide equal sound path lengths in substantially all directions to create equal length channels where sound can travel from a sound output source of the loudspeaker (e.g., an inlet of the waveguide) to a sound exit of the loudspeaker (e.g., an outlet of the waveguide). The technical effect of these features is that increased control may be provided over the sound propagation in relation to systems that utilize waveguides with equal path lengths in only one plane, resulting in increased sound production efficiency for a given listening area.

The systems and methods described above also provide for a waveguide for a loudspeaker, the waveguide including an outer shell, and an inner shell coupled to the outer shell, a first end of the inner shell and a first end of the outer shell forming a first continuous ring defining a periphery of an inlet opening to an air gap between an interior surface of the outer shell and an exterior surface of the inner shell, a second, opposite end of the inner shell and a second, opposite end of the outer shell forming a second continuous ring defining a periphery of an outlet opening of the air gap, each of a plurality of three-dimensional paths between virtual points at the inlet opening of the air gap and virtual points at the outlet opening of the air gap having a substantially equal path length. In a first example of the waveguide, the first continuous ring may additionally or alternatively form a substantially sinusoidal curve and the virtual points at the inlet opening of the air gap may additionally or alternatively be located along the sinusoidal curve within the first continuous ring and in a plane that is coplanar with the first end of the inner shell and perpendicular to a center of the first continuous ring. A second example of the waveguide optionally includes the first example, and further includes the waveguide, wherein the second end of the inner shell forms a first side of a rectangle, and the second end of the outer shell forms remaining three sides of the rectangle. A third example of the waveguide optionally includes one or both of the first example and the second example, and further includes the waveguide, wherein the rectangle includes at least one rounded edge. A fourth example of the waveguide optionally includes one or more of the first through the third examples, and further includes the waveguide, wherein each of the exterior surface of the inner shell and the interior surface of the outer shell forms a continuous, smooth surface having a plurality of convex protrusions and a plurality of concave depressions. A fifth example of the waveguide optionally includes one or more of the first through the fourth examples, and further includes the waveguide, wherein each of the plurality of paths have an equal path length extending between a virtual inlet plane and a virtual outlet plane, where the first continuous ring lies on the virtual inlet plane and the second continuous ring lies on the virtual outlet plane. A sixth example of the waveguide optionally includes one or more of the first through the fifth examples, and further includes the waveguide, wherein the first continuous ring is adapted to be coupled to a driver unit that produces sound waves for propagation through the waveguide.

The above-described systems and methods also provide for a loudspeaker including a driver unit, and a waveguide coupled to the driver unit, the waveguide comprising an outer shell and an inner shell coupled to the outer shell, a first end of the inner shell and a first end of the outer shell forming a first continuous ring defining a periphery of an inlet opening to an air gap between an interior surface of the outer shell and an exterior surface of the inner shell, a second, opposite end of the inner shell and a second, opposite end of the outer shell forming a second continuous ring defining a periphery of an outlet opening of the air gap. In a first example, each of the exterior surface of the inner shell and the interior surface of the outer shell may additionally or alternatively form a continuous, smooth surface having a plurality of convex protrusions and a plurality of concave depressions. A second example of the loudspeaker optionally includes the first example, and further includes the loudspeaker, wherein the first continuous ring forms a substantially sinusoidal curve. A third example of the loudspeaker optionally includes one or both of the first example and the second example, and further includes the loudspeaker, wherein the second end of the inner shell forms a first side of a rectangle, and the second end of the outer shell forms remaining three sides of the rectangle. A fourth example of the loudspeaker optionally includes one or more of the first through the third examples, and further includes the loudspeaker, wherein the driver unit includes a plurality of outlet openings forming the sinusoidal curve. A fifth example of the loudspeaker optionally includes one or more of the first through the fourth examples, and further includes the loudspeaker, wherein each of a plurality of paths between virtual points at the inlet opening of the air gap and virtual points at the outlet opening of the air gap having a substantially equal path length. A sixth example of the loudspeaker optionally includes one or more of the first through the fifth examples, and further includes the loudspeaker, wherein each of the plurality of paths have a linear rate of expansion from the inlet side of the waveguide to the outlet side of the waveguide. A seventh example of the loudspeaker optionally includes the first through the sixth examples, and further includes the loudspeaker, wherein each of the plurality of paths have an exponential rate of expansion from the inlet side of the waveguide to the outlet side of the waveguide.

The above-described systems and methods also provide for a loudspeaker system including a plurality of driver units, and a plurality of waveguides, each of the waveguides coupled to one of the plurality of driver units, each of the waveguides comprising a first and second outer shell coupled to one another, and each of the waveguides comprising a first and second inner shell coupled to one another and positioned between the first and second outer shells, each of the outer and inner shells extending from an undulating ring at an inlet region of the waveguide to a rectangular opening at an outlet region of the waveguide via a continuous smooth surface having a plurality of convex protrusions and a plurality of concave depressions, the convex protrusions and concave depressions of an exterior surface of each first inner shell being positioned over convex protrusions and concave depressions of the interior surface of a respective complementary first outer shell to form an air gap between each complementary first inner shell and first outer shell. In a first example, the plurality of waveguides may additionally or alternatively be arranged in a vertical array on top of one another within a housing of the loudspeaker system. A second example optionally includes the first example, and further includes the loudspeaker system, wherein each of a plurality of paths between points at the inlet opening of the air gap and points at the outlet opening of the air gap having a substantially equal path length. A third example optionally includes one or both of the first and the second examples, and further includes the loudspeaker system, wherein the undulating ring at the inlet region of the waveguide forms a sinusoidal curve. A fourth example optionally includes one or more of the first through the third examples, and further includes the loudspeaker system, wherein the outlet side of the first inner shell forms a side of the rectangular opening, and the outlet side of the first outer shell forms remaining three sides of the rectangular opening rectangle, and wherein the interior surface of the first outer shell protrudes in a middle region of the waveguide relative to peripheral regions of the waveguide.

The description of embodiments has been presented for purposes of illustration and description. Suitable modifications and variations to the embodiments may be performed in light of the above description or may be acquired from practicing the methods. The described systems are exemplary in nature, and may include additional elements and/or omit elements. <FIG> are shown to scale, although other relative dimensions may be used, if desired.

Claim 1:
A waveguide (<NUM>) for a loudspeaker (<NUM>), the waveguide (<NUM>) comprising:
an outer shell (208a, 208b); and
an inner shell (210a, 210b) coupled to the outer shell (208a, 208b), a first end of the inner shell (210a, 210b) and a first end of the outer shell (208a, 208b) forming a first continuous ring defining a periphery of an inlet opening (<NUM>) to an air gap (<NUM>) between an interior surface (<NUM>, <NUM>) of the outer shell (208a, 208b) and an exterior surface (<NUM>, <NUM>) of the inner shell (210a, 210b), a second, opposite end of the inner shell (210a, 210b) and a second, opposite end of the outer shell (208a, 208b) forming a generally rectangular area defining a periphery of an outlet opening (221a, 221b; <NUM>) of the air gap (<NUM>), each of a plurality of three-dimensional paths (<NUM>) between virtual points (<NUM>) at the inlet opening (<NUM>) of the air gap (<NUM>) and virtual points (<NUM>) at the outlet opening (221a, 221b; <NUM>) of the air gap (<NUM>) having a substantially equal path length,
characterized in that the inner shell (210a, 210b) and the outer shell (208a, 208b) are two separate parts, wherein the outer shell comprises a first and a second outer shell (208a, 208b) that are coupled to one another, and the inner shell comprises a first and a second inner shell (210a, 201b) that are coupled to one another.