Patent Application
20250142248
The invention relates to a coaxial loudspeaker.
Coaxial loudspeakers, which house both a high-frequency driver (tweeter) and a low/mid-frequency driver (woofer) along the same axis, offer the benefit of broad frequency range reproduction in a compact form.
Waveguides, commonly used in such loudspeakers containing a compression driver as the high frequency driver, direct the high-frequency sound pressure waves in a certain pattern and improve the impedance matching of the pressure at the compression driver diaphragm to the open air. Typical waveguides consist of an axis-symmetric continuous flare, or two different flare shapes with the same flare positioned opposite, so that the waveguide is symmetric in two dimensions. Often these waveguides are designed to achieve a specific directivity pattern in the vertical and horizontal planes on-axis in relation to the loudspeaker position.
Conventional waveguides typically have two dimensions of symmetry in the horizontal plane and the vertical plane, which limits their ability to achieve different directivity patterns at the bottom of the coaxial loudspeaker horizontal axis compared to the top of the horizontal axis when the coaxial loudspeaker is elevated with respect to the horizontal axis. As a result, the conventional designs cannot provide variety of directivity patterns in relation to the loudspeaker's height position.
Additionally, existing coaxial loudspeakers with moving waveguides—designed to move in sync with the woofer's cone diaphragm—might be prone to generating unwanted noise due to the movement of the waveguide.
The present invention addresses at least one of these drawbacks.
The above objective is achieved, and the present invention is defined by the appended claims.
A coaxial loudspeaker according to one example of the present disclosure and invention includes: first and second driver units that individually radiate sound from a same axis, the first driver unit comprising a cone diaphragm and being configured to output sound mainly in a first frequency range; the second driver unit being configured to output sound mainly in a second frequency range that is higher than the first frequency range, comprising: a fixed waveguide configured to guide the sound in the second frequency range from the second driver unit; wherein the fixed waveguide has a mouth part at an outer edge of the fixed waveguide, a throat part at one end, and at least three flared surfaces comprising a first flared surface, a second flared surface and a third flared surface each extending from the throat part to the mouth part of the fixed waveguide, wherein the at least three flared surfaces have different shapes from each other.
A coaxial loudspeaker according to an preferable example of the present disclosure and invention includes: first and second driver units that individually radiate sound from a same axis, the first driver unit comprising a cone diaphragm and a voice coil and being configured to output sound mainly in a first frequency range, the second driver unit being configured to output sound mainly in a second frequency range that is higher than the first frequency range, comprising: a moving waveguide configured to guide the sound in the second frequency range from the second driver unit, the moving waveguide being attached to, or integrated with, a main surface of the cone diaphragm so as to move in sync with the cone diaphragm; a tube element configured to guide the sound from the second driver unit to the moving waveguide; and a radial gap being formed between the tube element and the voice coil, wherein the moving waveguide has an extension portion positioned in the radial gap and movable within the radial gap and along the axis.
In one aspect of the present invention, a coaxial loudspeaker is capable of achieving varying directivity patterns at different positions of the horizontal axis when the loudspeaker is elevated. This results in improved directivity control and better overall acoustic performance.
In another aspect of the present invention, a coaxial loudspeaker is capable of reducing noise associated with moving waveguides.
Further advantages of the examples of the present invention are described in the following also with regard to the attached drawings.
The present invention is described, by way of examples and for solely helping understanding of the invention, with reference to the accompanying drawings, in which:
In more detail,
The first driver unit comprises a cone diaphragm 40 and is configured to output sound mainly in a first frequency range. The first driver unit may also be referred to as low frequency driver or woofer. The first driver unit may cover a range from 40 Hz to 2000 Hz.
The second driver unit is configured to output sound mainly in a second frequency range that is higher than the first frequency range. The second driver unit may cover a range from 0.5 kHz to 20 kHz, preferably a range from 1 kHz to 20 kHz, more preferably a range from 2 kH to 20 KHz.
The first driver unit may comprise a magnet 60 and a voice coil 70. The voice coil 70 is attached to the cone diaphragm 40, preferably to the radially inner end of the cone diaphragm 40. The voice coil 70 may be made of copper or aluminum wire wound around a cylindrical former. When an electrical audio signal flows through the voice coil 70, it creates a magnetic field that interacts with the permanent magnet 60, causing the cone diaphragm 40 to move along the axis Z.
The magnet 60 provides the necessary magnetic field for the voice coil 70 to operate. The magnet 60 may be a ferrite magnet. Preferably, the magnet 60 is a neodymium magnet. The interaction between the magnetic field generated by the voice coil 70 and the static field of the magnet 60 causes the voice coil 70 and, thus, attached cone diaphragm 40 to move along the axis Z.
The coaxial loudspeaker 100 may further include one or more pole pieces. The pole piece is configured to direct and focus the magnetic field of the magnet 60 to effectively interact with the voice coil 70. The one or more pole pieces may include a T-shaped pole piece (which is also referred as to a T-iron 80). The T-shaped pole piece 80 has a flat and radial part, sitting either on the upper side or the lower side of the magnet; and an axial part extending from the radially inner end of the radial part and along the axis Z. The one or more pole pieces may also include a magnetic guide plate 50 positioned on the other side of the radial part of the T-shaped pole piece 80 so that the magnet 60 is interposed between the magnetic guide plate 50 and the radial part of the T-shaped pole piece 80.
The shapes and locations of these additional components including the magnet 60, voice coil 70, and the pole piece 50 are not essential elements for the present inventions and may, thus, be changed or modified in accordance with certain requirements.
The second driver unit 10 may comprise similar components to the first driver units to output sound in the second frequency, such as a magnet, a voice coil and a diaphragm (not shown). The second driver unit may include a compression driver in which the radiating diaphragm is larger than a horn throat to increase the radiation resistance.
The coaxial loudspeaker 100 further comprises a fixed waveguide 30A. The fixed waveguide 30A is configured to guide sound in the second frequency range from the second driver unit 10. The fixed waveguide 30A has a mouth part 34 at the outer edge of the fixed waveguide 30A, a throat part 36 at one end, and at least three flared surfaces including a first flared surface S1, a second flared surface S2 and a third flared surface S3 each extending from the throat part 36 to the mouth part 34. The fixed waveguide 30A, therefore, defines a passage for channeling sound from the second driver unit 10. The flared shape is a shape in which the width or diameter of the passage gradually increases from the throat part 36 to the mouth part 34. At least three flared surfaces have different shapes S1, S2, S3 from each other.
In the illustrated example as shown in
Preferably, the flared surfaces S1, S2, S3 have different flare angles from each other, with respect to the axis Z. Preferably, the flared surfaces S1, S2, S3 are at least partially convex curved surfaces. In a case where each flared surface is a convex curved surface, the flare angle is defined between the axis Z and the tangent line of the flared surface, the tangent line extending from a point on the axis z at the throat part 36 as shown in
Additionally or alternatively, the arc lengths at the outer edges of the mouth parts 34 of the flared surfaces S1, S2, S3 may differ from each other. Preferably, there is substantially no discontinuity between the outer edges of the adjacent flared surfaces S1, S2, S3. In one embodiment, each junction between the adjacent flared surfaces S1, S2, S3 may form a ridge line, in other words, adjacent surfaces S1, S2, S3 may connect each other at less than 180 degrees of dihedral angle. Preferably, the primary dihedral angle between the first flared surface S1 and the second flared surface S2 ranges from 80 to 150 degrees, preferably from 100 to 140 degrees, and/or the primary dihedral angle between the second flared surface S2 and the third flared surface S3 ranges from 70 to 130 degrees, preferably from 80 to 120 degrees. This ensures that the surfaces S1, S2, S3 assume a different acoustic directivity from each other.
In a preferable arrangement, the coaxial loudspeaker further includes two or more radial waveguides 20A. Each radial waveguide 20A extends in the radial direction of the cone diaphragm 40 from the mouth part 34 to the outer edge of the cone diaphragm 40. Preferably, the mouth part 34 of the fixed waveguide 30A may interface with the radial waveguides 20A. There may be substantially no discontinuity between the surfaces of the radial waveguides 20A and the flared surfaces S1, S2, S3 of the fixed waveguide 30A.
The radial waveguides 20A may be attached to a surface of the cone diaphragm 40, which is on the other side of the magnet, preferably by adhesive. Alternatively, the radial waveguides 20A may be integrated with the cone diaphragm 40. This allows for the radial waveguides 20A to move in sync with the cone diaphragm 40.
Each radial waveguide 20A may extend in the radial direction from the mouth part 34 of the fixed waveguide 30A to the outer edge of the cone diaphragm 40. In other words, a tangent to the radially inner end of the radial waveguide 20A and a tangent to the radially outer end of the flared surfaces S1, S2, S3 of the fixed waveguide 30A are substantially coincident or parallel to each other.
The contour of each radial waveguide 20A may extend substantially continuously from the mouth part 34 of the fixed waveguide 30A to outer edge of the cone diaphragm 40 when the cone diaphragm 40 of the first driver unit is at rest. In other words, a tangent to the radially inner end of the radial waveguide 20A and a tangent to the radially outer end of the flared surface S1, S2, S3 of the fixed waveguide 30A are substantially coincident or parallel to each other. The radial waveguides 20A may therefore be considered to be a ‘moving’ waveguide as, in use, it is non-static.
At least one of the radial waveguides 20A has two or more different flared portions. In
The surfaces of the first flared portion A and the second flared portion B may have different curved surfaces from each other. The first flared portion A may extend in a substantially continuous radial direction from the first flared surface S1 of the fixed waveguide 30A to the outer edge of the cone diaphragm 40. The second flared portion B may extend in a substantially continuous radial direction from the second flared surface S2 of the fixed waveguide 30A to the outer edge of the cone diaphragm 40. That is, each of the first flared portion A and the second flared portion B corresponds to the first flared surface S1 and the second flared surface S2, respectively, where the intersection line between the first flared surface S1 and the first flared portion A is L1, and the intersection line between the second flared surface S2 and the second flared portion B is L2. Further, the intersection line between the third flared surface S3 and the cone diaphragm 40 is L3. Preferably, in the common plane of the intersection lines L1 and L2, the angle between the intersection line L1 and the intersection line L2 is 70 to 120 degrees, and/or in the common plane of the intersection lines L2 and L3, the angle between L2 and L3 is 90 to 150 degrees.
Preferably, the surfaces of the adjacent flared portions (e.g., the surfaces of the first and second flared portions A, B) are discontinuous from each other. The junction between two adjacent different-shape flared surfaces forms a ridge line. It means that there is a boundary between the flared surface of the first flared portion A and that of the second flared portion B. In other words, the curvature of adjacent flared portions A, B does not change continuously. Preferably, in one embodiment, the junction between the first flared portion A and the second flared portion B features at least one step or step structure. In other words, the thicknesses of the adjacent flared portions A, B at the junction differ from each other. This may create more reflection of sound. Preferably, the height of the junction interface, i.e., the height of the step between the adjacent first and second flared portions A, B gradually increases at least from the outer edge of the cone diaphragm 40 to the radially inner most, thickest position of the first flared portion A. This may create more distinctive variant of the reflection of sound.
Each radial waveguide 20A may be shaped in a circular sector in plan view, which has an outer arc, an inner arc and two radii connecting these two arcs. Preferably, each outer arc of the radial waveguide 20A is adjacent and aligned/flushed with the outer edge of the cone diaphragm 40.
Preferably, each radial waveguide 20A may contain or be made of foam polypropylene (FPP) material. Such a material is lightweight, which in turn has less adverse effect on the movement of the cone diaphragm 40, as well as easy to form. Each radial waveguide 20A may be attached to the surface of the cone diaphragm 40. If the surfaces of the first flared portion A and the second flared portion B are discontinuous from each other and/or the surfaces of the first and second flared portions A, B have different curve shapes, more reflection may be expected. Each of the first and second flared portion A, B has a different surface curvature. Preferably, the maximum surface curvature of the first flared portion A is greater than the maximum surface curvature of the second flared portion B. In addition, the central angle of the first flared portion A is greater than the central angle of the second flared portion B when viewed in the axis Z, i.e., in the top view.
Also, the coaxial loudspeaker 100 including the radial waveguide 20A, in combination with the fixed waveguide 30A can produce sound waves covering all ranges of audio sounds.
In this variant, the two radial waveguides 20A are asymmetrical to each other. The central angles of the two radial waveguides 20A may differ from each other, the radial waveguides 20A have a different number of flared portions, and/or the flared portions have different flared surfaces from each other. This arrangement may further offset the directivity of sounds from the on-axis plane.
In this variant, the coaxial loudspeaker 100B comprises more than two radial waveguides 20A. In
The fixed waveguide 30A has different flared surfaces including at least two first flared surfaces S1, four second flared surfaces S2 and two third flared surfaces S3.
Preferably, the one or more links D are made of the same material from that of the radial waveguides 20A. Preferably, both the radial waveguides and links D are made of foam polypropylene (FPP). Such a one-piece waveguide is easy to manufacture and easy to assemble to the cone diaphragm 40.
Embodiment 2 differs from Embodiment 1 in that the coaxial loudspeaker 200 includes an isolated or independent fixed waveguide 30B having a flared hone structure. In Embodiment 2, parts that are common to Embodiment 1 are denoted by the same reference symbols, and descriptions thereof are omitted. Further, features that are different from Embodiment 1 are mainly described.
The isolated fixed waveguide 30B has a mouth part 34A at the outer edge of the fixed waveguide 30B, and a throat part 36A at one end. As shown in
This arrangement allows different directivity patterns not only in the vertical and horizontal axis, but also in the horizontal plane at any elevated degrees in between.
Preferably, the height of the mouth part 34A of the fixed waveguide 30B is at least more than half the height of the cone diaphragm 40. More preferably, the height of the mouth part 34A of the fixed waveguide 30B is equal to or higher than the height of the cone diaphragm 40. Accordingly, a wider dispersion can be achieved.
As shown in
As further illustrated in
Preferably, junctions between two adjacent different-shape flared surfaces are formed by smooth surfaces. In other words, the curvature of adjacent flare surfaces changes continuously.
The lower end of the fixed waveguide 30B may be attached to the pole piece of the first driver unit, e.g., to the T-iron 80.
Preferably, the mouth part 34A of the fixed waveguide 30B has a flared surface design extending from the throat part 36A of the fixed waveguide 30B, along the main surface of the cone diaphragm 40, whilst maintaining a certain gap with respect to the main surface of the cone diaphragm 40. In other words, there is a space between the cone diaphragm 40 and the fixed waveguide 30B.
This embodiment achieves different directivity patterns not only in the vertical and horizontal axis, but also in the horizontal plane at any elevated degrees in between, by just a one-piece fixed waveguide, because the shape of the fixed waveguide 30B is unique and without 2 planes of symmetry.
Preferably, the fixed waveguide 30B has a one-piece structure. The unique 3D shape of the fixed waveguide 30B is symmetric in one plane only which allows different directivity patterns in the horizontal plane at different elevations to the horizontal axis, as well as the vertical plane. The fixed waveguide 30B may be shaped as a flared horn with a narrow entrance and a wider exit, like trumpet shape.
The throat part 36A of the fixed waveguide 30B constitutes the small-slit aperture AP which is symmetric in one plane only. The asymmetry creates different patterns of directivity at different angles of elevation to the horizontal plane and affects mostly the high frequency range.
The fixed waveguide 30B comprises at least three different-shape flared surfaces S1, S2, S3. When the coaxial loudspeaker 200 is elevated with respect to the horizontal plane, the combination of the three different-shape flared surface S1, S2, S3 achieves two different horizontal directivities and affect mostly the mid-range, preferably 500-2000 Hz.
The combination of these three different-shape flared surfaces within a one-part fixed waveguide 30B form a unique design with only one plane of symmetry, ensuring different horizontal directivities across the frequency range when the loudspeaker is elevated with respect to the horizontal plane.
In this variant, the isolated fixed waveguide 30B has a mouth part 34A at the outer edge of the fixed waveguide 30B, and a throat part 36A at one end. As shown in
The moving waveguide 20B has a main body portion 24A (mouth part) that is attached to the surface of the cone diaphragm 40 or integrated with it and an extension portion 26A (throat part), which is a portion that is apart from the main surface of the cone diaphragm 40. The extension portion 26A is positioned in the radial gap. For example, at least a portion of the extension portion 26A is located between the voice coil 70 and the tube element 90, allowing the extension portion 26A to be movable within the radial gap and along the axis Z. In other words, the extension portion 26A can move up and down in the radial gap, and the moving waveguide 20B can move in sync with the cone diaphragm 40. The extension portion 26A guides the movement of the cone diaphragm 40 along the axis Z, suppressing unwanted diaphragm movement and noise due to the increased diaphragm weight with the movable waveguide 20B. The extension portion 26A may also function as a stopper of the cone diaphragm 40, which is particularly beneficial when transporting the loudspeaker. Damage to the diaphragm during transportation can be reduced or prevented. The moving waveguide 20B, together with the tube element 90, can help guide and transmit the sound from the second driver unit 10. Also, the coaxial loudspeaker 300, including the moving waveguide 20B, in combination with the tube element 90, can produce sound waves covering all ranges of audio sounds.
The moving waveguide 20B may feature a flared horn structure, with its outer edge of the main body portion 24A generally extending in a substantially continuous radial direction from the extension portion 26A of the moving waveguide 20B and attached to the surface of the cone diaphragm 40 or integrated with it. The moving waveguide 20B is arranged to move in sync with the cone diaphragm 40. The flared horn structure is shaped like a conical cylinder with a narrow entrance and a wider exit, like trumpet shape.
In Embodiment 3 of the present invention, the extension portion 26A of the moving waveguide 20B is positioned in the gap between the tube element 90 and the voice coil 70. The function of the tube element 90 is similar to the fixed waveguide, and the tube element 90 is used to propagate high-frequency sound from the second driver unit 10 to the moving waveguide 20B.
Preferably, the main body portion 24A of the moving waveguide 20B comprises at least three different-shape flared surfaces, each extending from the extension portion 26A to the outer edge of the main body portion 24A. As a result, the combination of these three different-shape flared surfaces within a one-part main body of the moving waveguide 20B form a unique design with only one plane of symmetry and ensure that different horizontal directivities can be maintained across the frequency range when the loudspeaker is elevated with respect to the horizontal plane.
Preferably, the moving waveguide 20B is made of paper material, e.g., pulp material. Additionally or alternatively, the thickness of the moving waveguide 20B may be 1 mm or less than 1 mm. This allows a lightweight and compact loudspeaker. The moving waveguide 20B may be attached by glue bounding, which is commonly used for dust cover attachment.
Alternatively, the moving waveguide 20B may contain or be made of foam polypropylene (FPP) material. This allows a lightweight and robust loudspeaker.
In this variant, at least two moving waveguides 20B are arranged to each other. The two moving waveguides 20B are connected each other by one or more links D. The two moving waveguides are thus integrated into one piece. Preferably, the height of the main body portion 24A of the moving waveguide 20B is at least more than half the height of the cone diaphragm 40. The moving waveguides 20B are arranged to surround a mouth part 92 of the tube element 90 and a junction between the tube element 90 and the moving waveguides 20B features at least one step structure 91 which is generated by the thickness of the tube element 90. This may create more reflection of sound.
Preferably, the one or more links are made of the same material from that of the moving waveguides 20B. Preferably, both the moving waveguides and links D are made of foam polypropylene (FPP). Such a one-piece waveguide is easy to manufacture and easy to assemble to the cone diaphragm 40.
Preferably, at least one moving waveguide 20B has at least one recessed structure on the side facing the cone diaphragm 40. This allows the weight of the moving waveguides 20B to be reduced without affecting the desired acoustic properties. Preferably, each moving waveguide 20B has two or more recessed structures on the side facing the cone diaphragm 40, e.g., a first recessed structure 201 and a second recessed structure 202. More preferably, the two or more recessed structures 201, 202 in each moving waveguide 20B are adjacent to each other in the radial direction of the cone diaphragm 40. More preferably, the recessed volume of the first recessed structure 201 located radially outwards is greater than the recessed volume of the second recessed structure 202 located radially innerwards. The volume and location of such recessed structures 201, 202 may be designed to ensure balanced weight distribution among the two or more moving waveguides 20B, and thus weight uniformity of the cone diaphragm 40 including the waveguides 20B. Notably, the surfaces of the first recessed structure 201 and the second recessed structure 202 both do not come into contact with the surface of the cone diaphragm 40.
In this variant, the tube element 90 may be inserted and positioned within the axial part of the T-iron 80. Thus, the extension portion 26A of the moving waveguide 20B (i.e., lower part of the moving waveguide 20B) is positioned in the gap between the tube element 90 and the axial part of the T-iron 80. The function of the tube element 90 is similar to the fixed waveguide, and the tube element 90 is used to propagate high-frequency sound from the second driver unit 10 to the moving waveguide 20B. The extension portion 26A may also function as a stopper of the cone diaphragm 40, which is particularly beneficial when transporting the loudspeaker. Damage to the diaphragm during transportation can be reduced or prevented.
Similarly to the recessed structures 201, 202 in the embodiment of
Preferably, the tube element 90 further has a radial extending structure (disc structure) 90A, which is used to secure the tube element 90 to the T-iron 80.
This application claims priority of U.S. Provisional Application No. 63/595,057 filed on Nov. 1, 2023 under 35 U.S.C. § 119 (e), the entire contents of all of which are hereby incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| 63595057 | Nov 2023 | US |
