Loudspeaker drive unit
The loudspeaker drive unit addresses the challenge of achieving excellent directivity and a small form factor by using a coaxial design with a deep throat waveguide, optimizing acoustic output without increasing baffle size.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- GENELEC OY
- Filing Date
- 2024-05-10
- Publication Date
- 2026-05-27
AI Technical Summary
Existing loudspeakers face a trade-off between achieving excellent directivity and a small form factor, as good directivity typically requires a larger physical size due to the difficulty in creating an effective waveguide with a small baffle.
A loudspeaker drive unit design featuring a coaxial arrangement of a bass-side frequency transducer and a high-frequency transducer, where the high-frequency transducer is mounted at the rear of an inner frame portion, forming a deep throat that serves as a waveguide, aligned with the low-frequency transducer's diaphragm to optimize directivity without increasing the baffle size.
This design achieves excellent directivity in a small form factor by minimizing reflective surfaces and optimizing the waveguide, resulting in a flatter acoustic output characteristic with fewer peaks and dips.
Smart Images
Figure 2026517001000001_ABST
Abstract
Description
Technical Field
[0006] , , ,
[0001] The present disclosure relates to an acoustic playback device. In particular, the present disclosure relates to a composite drive unit provided with a coaxial high-frequency drive unit in a mid-frequency driver.
Background Art
[0002] Loudspeakers are generally designed to produce only the frequencies intended to be reproduced, aiming for natural acoustic reproduction without coloring. Achieving as flat a response characteristic as possible is important, but it is equally desirable to give the driver excellent directivity for producing a clear sound image at the intended listening location. A clear sound image is produced when sound waves in a wide frequency band propagate to a focused location. This means that the low, mid, and high frequency bands are all radiated in the same direction with minimal scattering. However, good directivity typically comes at the trade-off of the physical size of the drive unit. This is because it is difficult to create an effective waveguide with a small baffle.
[0003] U.S. Patent Application Publication Nos. 2017111729A1 and 2017048610A1 disclose two examples of a composite loudspeaker drive unit characterized by coaxially arranging a compression driver as a high-frequency transducer inside a low-frequency transducer.
[0004] Therefore, there is a need for a loudspeaker drive unit that has excellent directivity and a small form factor.
Summary of the Invention
Means for Solving the Problems
[0005] The present invention is defined by the features described in the independent claims. Some specific embodiments are defined in the dependent claims.
[0006] According to a first aspect of the present disclosure, a loudspeaker drive unit having a frame is provided, the frame comprising an outer frame portion and an inner frame portion, the inner frame portion defining an opening and including a throat, the throat forming part of a waveguide. The loudspeaker drive unit also comprises a bass-side frequency transducer, the bass-side frequency transducer having a diaphragm, the diaphragm being suspended between the outer frame portion and the inner frame portion by an outer suspension element and an inner suspension element, respectively, thereby forming part of a waveguide. The loudspeaker drive unit further comprises a compression transducer as a bass-side frequency transducer, mounted on the inner frame portion.
[0007] Some embodiments of the loudspeaker drive unit may include one or more of the features listed below. - The high-frequency transducer is mounted at the rear of the inner frame section. - The throat defines the opening. - The output opening of the high-frequency transducer is aligned with the opening in the inner frame. - The throat includes the surface, which forms part of the waveguide. - The throat, suspension elements, and diaphragm are aligned tangentially. - The throat exhibits a waveguide surface that flares outward. - The waveguide surface is continuous and does not have axial protrusions exceeding 1 mm. - The distance in the acoustic axis direction between the high-frequency transducer and the low-frequency transducer is greater than or equal to the axial extension of the diaphragm of the low-frequency transducer in the acoustic axis direction of the drive unit. - The acoustic axes of the high-frequency transducer and the low-frequency transducer are aligned. - The outer and inner suspension elements suspend the diaphragm of the low-frequency transducer to the frame. - The outer and inner suspension elements form part of the waveguide. - The outer and inner suspension elements are not directly driven by the voice coil.
[0008] This novel concept offers significant advantages. By designing the high-frequency transducer as a compression driver, the throat on the inner frame can be shaped relatively deeply in the dimension defined by the acoustic axis of the high-frequency transducer. As a result, the directivity of the throat's facade can be maximized. This means that the waveguide formed by the diaphragm assembly of the low-frequency transducer and the inner frame can be optimized to direct the acoustic output of the high-frequency transducer without increasing the size of the drive unit's baffle. In other words, this loudspeaker drive unit achieves excellent directivity in a small form factor.
[0009] Furthermore, the use of a compression driver allows the throat opening, and therefore the high-frequency transducer, to be positioned further away from the low-frequency diaphragm. This minimizes, or even eliminates, the reflective surface previously formed by the diaphragm of a dome tweeter positioned inside a relatively short throat in conventional designs. As a result, a drive unit that can be constructed in this way can achieve a flatter acoustic output characteristic with fewer peaks and dips caused by tweeter reflections.
[0010] The following describes exemplary embodiments in detail with reference to the attached drawings. The drawings are as follows: [Brief explanation of the drawing]
[0011] [Figure 1] Cross-sectional views of loudspeaker drive units according to at least some embodiments are shown. [Modes for carrying out the invention]
[0012] Figure 1 shows a loudspeaker drive unit 1000 according to an exemplary embodiment, shown detached from the enclosure (not shown) surrounding the loudspeaker. The drive unit 1000 includes a frame 400, which acts as a rigid reference for the drive's moving parts and houses the magnetic circuit 300. This example shows a composite drive unit 1000 hosting two transducers, namely a bass-side frequency transducer 100 that generates midrange and / or low-frequency bands, and a treble-side frequency transducer 200 that generates high-frequency bands. Such transducers 100, 200 are generally referred to as a midrange driver and a tweeter, respectively. The bass-side frequency transducer 100 is a cone-diaphragm assembly in a loudspeaker structure in the general sense. The treble-side frequency transducer 200 is a compression driver in a loudspeaker structure in the general sense as shown.
[0013] In the illustrated example, transducers 100 and 200 share an acoustic axis, and therefore the drive unit 1000 is a coaxial driver unit. Alternatively, transducers 100 and 200 may be offset to include two different acoustic axes, which may be parallel or inclined to each other. However, a coaxial structure is preferred for directivity. The orientation of the acoustic axis of transducers 100 and 200 or (in the case of a coaxial unit) the drive unit 1000 as a whole is defined by the direction of motion of the diaphragm of the diaphragm assembly, and this direction is defined by the dimension of the reciprocating motion of the voice coil assembly 120 that drives the diaphragm 110 of the low-frequency transducer 100. The acoustic axis should be understood as the intended primary direction of acoustic propagation of the drive unit, and / or the axis of symmetry along which the generated acoustic pattern follows. Alternatively, the acoustic axis may be understood as the axis on which the sum of the acoustic outputs of the drive unit is most ideal. Typically, the acoustic axis is the listening axis designed for the loudspeaker. The acoustic axis may, but does not have to be, the axis of symmetry of the low-frequency transducer 100.
[0014] The diaphragm 110 of the low-frequency transducer 100 is mounted to the frame between the outer frame portion 401 and the inner frame portion 402 of the frame 400. The outer frame portion 401 mounts the drive unit 100 to the enclosure surrounding it (e.g., a loudspeaker cabinet or wall in a flush-mount setup or another housing structure). The inner frame portion 402 houses the high-frequency diaphragm assembly 200. A magnetic circuit 300 is mounted to the frame 400 between the outer frame portion 401 and the inner frame portion 402. The magnetic circuit 300 includes a magnet 303 and a center pole 301 surrounding it with an annular gap 303 in between.
[0015] The diaphragm assembly of the low-frequency transducer 100 is suspended from the outer frame portion 401 by an outer suspension element 114. The outer suspension element 114 surrounds the diaphragm 110 and connects the diaphragm 110 to the frame 400 of the drive unit 1000, and this connection is flexible so that the diaphragm 110 can reciprocate and translate axially, that is, move back and forth in a direction parallel to the acoustic axis. In other words, the outer suspension element 114 is a flexible structure that allows the diaphragm 110 to repeatedly move in the primary acoustic direction of the drive unit 1000, and to return to the rest position after being displaced in the primary acoustic direction by the voice coil. In other words, the suspension element is not directly driven by the voice coil. The outer suspension element 114 may be made as an annular member. Suitable materials include rubber, foamed plastic or Styrofoam®, fabric, special fabric, thermoplastic elastomer, urethane, and silicone. The outer suspension element 114 may be made of the same material as the primary vibrating diaphragm 110, but may be loosened or otherwise modified to have elasticity that allows for the translation of the diaphragm 110. Whatever the structure and material of the outer suspension element 114 may be, its role is to allow the intended movement of the diaphragm 110. Therefore, preferably, the outer suspension element 114 is constructed to allow for the axial translation of the diaphragm 110, to support the diaphragm 110 in the radial dimension so as not to tilt, to seal the inside of the diaphragm 110 to the outside so as not to cause acoustic short circuits, and / or to provide a return force that returns the diaphragm 110 to its rest position.
[0016] The diaphragm 110 has a frustoconical shape as understood in this art. Figure 1 shows a cross-section along the acoustic axis, and as shown in this figure, the cross-sectional shape of the diaphragm 110 extends away from the acoustic axis along its contour, which has a component in the direction of the acoustic axis and a component that crosses the acoustic axis. In other words, the diaphragm 110 is an annular plate that extends in the radial dimension when viewed in a cross-section along the acoustic axis of the diaphragm assembly. In this context, the term “radial” means the dimension or contour that extends from the acoustic axis of the diaphragm assembly along a straight or curved path at any angle other than 0 and 180 degrees relative to the acoustic axis. Thus, the radial dimension is defined by the path formed at a continuous point of the diaphragm 110 that extends away from the acoustic axis toward the outer rim of the diaphragm 110 when viewed in a cross-section along the acoustic axis. Therefore, it can be understood that the flare shape of the diaphragm 110 is radial, since the virtual extensions of the cross-sectional shape of the diaphragm converge on the acoustic axis of the diaphragm assembly (for example, at the same point on the acoustic axis).
[0017] As described above, the diaphragm 110 has a roughly frustoconical shape. In this context, the term “cone” should be understood not only as a mathematical cone, but also as a cone as understood in the field of loudspeaker manufacturing. Therefore, this expression also includes curved diaphragms, non-rotationally symmetric diaphragms, and those made into frustocones. Accordingly, the suspension elements 113, 114 and the diaphragm 110 are tangentially aligned to produce a continuous outer surface of the diaphragm assembly formed by the suspension elements 113, 114 and the diaphragm 110. In this context, the term “continuous” should be understood not only as mathematical continuity, but also as a surface as understood in the field of loudspeaker manufacturing, including surfaces that exhibit small axial deviations that are of little (i.e., immeasurable) or no (i.e., meaningless) to the output of the diaphragm assembly or drive unit. That is, the suspension elements 113, 114 and the diaphragm 110 have the same flare direction. Of course, there may be some deviation in the tangential alignment of each shape. For example, in Figure 2, a small ridge is shown at the joint between the suspension elements 113, 114 and the diaphragm 110. Such a small ridge would theoretically cause tangential misalignment, but if it is minute (i.e., does not cause a measurable effect on the acoustic output), it should be ignored. The continuous outward flare of the diaphragm assembly causes the baffle to form an effective waveguide for the high frequencies generated by the high-frequency transducer 200.
[0018] The diaphragm has an outer surface 115 that propagates sound along the acoustic axis X of the diaphragm assembly 100, and an inner surface 116 on the opposite side of the outer surface 115. The voice coil assembly 120 is attached to the inner surface 116 of the diaphragm 110. More specifically, the voice coil assembly 120 is attached to the inner peripheral portion 112a of the diaphragm 110. The voice coil assembly 120 is also suspended from the drive unit frame 400 and is aligned with the magnetic gap 303 by a spider.
[0019] The inner frame portion 402 of the frame 400 operates as a mounting point for the center edge of the diaphragm 110 and further houses the high-frequency transducer 200. The inner frame portion 402 includes an opening 404, which is defined by a throat 403, and the throat 403 is a surface visible from the outside. The opening 404 provides a path for the sound of the output of the high-frequency transducer 200. The output opening of the high-frequency transducer 200 is aligned with the opening 404 of the inner frame portion 402. In this way, the composite drive unit 1000 becomes coaxial.
[0020] The high-frequency transducer 200 is a compression driver.
[0021] The high-frequency transducer 200 is mounted at the rear of the inner frame portion 402. As a result, when viewed along the acoustic axis of the drive unit 1000, the foremost part of the high-frequency transducer 200 is behind the rearmost part of the diaphragm 110 of the low-frequency transducer 100. The distance in the acoustic axis direction between the high-frequency transducer 200 and the low-frequency transducer 100 may be greater than or equal to the axial extension line of the diaphragm 110 of the low-frequency transducer 100 when viewed along the acoustic axis of the drive unit 1000. Therefore, the throat 403 is significantly deeper compared to conventional composite drive units.
[0022] The throat 403 is shaped to be tangentially aligned with the diaphragm assembly. That is, the throat 403, the suspension elements 113, 114, and the diaphragm 110 essentially form a continuous surface, which serves as a waveguide for sound waves emitted from the high-frequency transducer 200. Thus, the throat 403 can present a waveguide surface that flares outward when viewed along the acoustic axis of the high-frequency transducer 200. This waveguide surface is preferably as smooth and continuous as possible to minimize sound diffraction. Therefore, it is preferable to tangentially align each component of this waveguide, namely, the throat 403, the suspension elements 113, 114, and the diaphragm 110. In particular, the waveguide surface preferably does not include any non-negligible lips or other protrusions that would break the continuity. If possible, it is preferable to finish any seams along the waveguide surface such that the axial displacement does not exceed 1 mm.
[0023] Of course, the disclosed embodiments of the present invention are not limited to the specific structures, processing procedures, or materials disclosed herein, and extend to equivalents that would be understood by those skilled in the art. Further, of course, the terms used herein are for the purpose of describing particular embodiments only and are not intended to be limiting.
[0024] References to one embodiment or an embodiment throughout this specification mean that the particular features, structures, or characteristics described in relation to that embodiment are included in at least one embodiment of the present invention. Thus, the appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment.
[0025] Multiple items, structural elements, compositional elements, and / or materials used herein may be included in general lists for convenience. However, these lists should be interpreted as if each element in the list were individually identified as a distinct and unique element. Accordingly, each element in such lists should be interpreted as a de facto equivalent of any other element in the same list, based solely on their presence in a general group, unless otherwise indicated. Furthermore, various embodiments and examples of the invention may be referred to herein in conjunction with alternative forms with respect to their various components. Naturally, such embodiments, examples, and alternative forms should not be interpreted as de facto equivalents of each other, but should be considered distinct and independent expressions of the invention.
[0026] Furthermore, the described features, structures, or properties may be combined in any suitable manner in one or more embodiments. The description so far has provided various specific details, such as examples of length, width, and shape, to ensure a full understanding of embodiments of the present invention. However, as those skilled in the art will understand, the present invention can be implemented without one or more of these specific details, or with other methods, components, materials, etc. In other examples, well-known structures, materials, or operations are not illustrated or described in detail, so as not to obscure aspects of the present invention.
[0027] The embodiments described above illustrate the principles of the present invention in one or more specific applications. However, as will be apparent to those skilled in the art, various modifications can be made to the form, usage, and details of the implementation without exercising inventive ability and without departing from the principles and concepts of the present invention. Accordingly, the present invention is not limited except as defined by the claims described below.
[0028] In this document, the verbs “to comprise” and “to include” are used as open limitations, neither excluding nor requiring the existence of features not described. Features described in dependent claims may be freely combined with each other unless otherwise specified. Furthermore, naturally, the use of “a” or “an,” i.e., the singular form, does not exclude plurality throughout this document. [Explanation of symbols]
[0029] 100 Low-frequency transducer 110 diaphragm 113 Internal suspension element 114 External suspension elements 115 Exterior 116 Inner self 120 Voice Coil Assembly 200 High-frequency transducer 300 Magnetic Circuits 301 Magnet 302 Center Pole 303 Gap 400 frames 401 Outer frame section 402 Inner frame section 403 Throat 404 Opening 1000 Drive Unit
Claims
1. A frame (400), the frame (400) includes an outer frame portion (401) and an inner frame portion (402), the inner frame portion (402) includes an opening (404) and a throat, the throat forming part of a waveguide, the frame (400) and A low-frequency transducer (100) is provided, the low-frequency transducer (100) includes a diaphragm (110), the diaphragm (110) is suspended between the outer frame portion (401) and the inner frame portion (402) by an outer suspension element (114) and an inner suspension element (113), respectively, thereby forming part of the waveguide, the low-frequency transducer (100), A compression transducer, comprising a high-frequency transducer (200) attached to the inner frame portion (402), A loudspeaker drive unit (1000) including the above.
2. The loudspeaker drive unit (1000) according to claim 1, wherein the high-frequency transducer (200) is mounted on the rear of the inner frame portion (402).
3. The loudspeaker drive unit (1000) according to claim 1 or 2, wherein the throat (403) defines the opening (404).
4. The loudspeaker drive unit (1000) according to any one of claims 1 to 3, wherein the output opening of the high-frequency transducer (200) is aligned with the opening (404) of the inner frame portion (402).
5. The loudspeaker drive unit (1000) according to any one of claims 1 to 4, wherein the throat (403) includes a surface, and the surface forms part of the waveguide.
6. The loudspeaker drive unit (1000) according to any one of claims 1 to 5, wherein the outer suspension element (114) and the inner suspension element (113) suspend the diaphragm (110) of the low-frequency transducer (100) from the frame (400) and form part of the waveguide.
7. The loudspeaker drive unit (1000) according to any one of claims 1 to 6, wherein the outer suspension element (114) and the inner suspension element (113) are not directly driven by a voice coil.
8. The loudspeaker drive unit (1000) according to any one of claims 1 to 7, wherein the throat (403), the suspension elements (113, 114), and the diaphragm (110) are aligned tangentially.
9. The loudspeaker drive unit (1000) according to any one of claims 1 to 8, wherein the throat (403) exhibits a waveguide surface that flares outward.
10. The waveguide surface is continuous and there are no axial protrusions exceeding 1 mm, as described in any one of claims 1 to 9 (1000).
11. The loudspeaker drive unit (1000) according to any one of claims 1 to 10, wherein the distance in the acoustic axis direction between the high-frequency transducer (200) and the low-frequency transducer (100) is greater than or equal to the axial extension line of the diaphragm (110) of the low-frequency transducer (100) in the acoustic axis direction of the drive unit (1000).
12. The loudspeaker drive unit (1000) according to any one of claims 1 to 11, wherein the acoustic axis of the high-frequency transducer (200) and the acoustic axis of the low-frequency transducer (100) are aligned.