Compression driver with dome diaphragm and ring-shaped outlet

Abstract

A compression driver includes a dome diaphragm having a convex face and a concave face and a phase plug having a base portion with a first side and an opposite second side. The first side of the base portion is disposed adjacent the convex face of the diaphragm and defines a compression chamber between the diaphragm and the convex face. The base portion includes a plurality of channels extending through the base portion from the first side to the second side for sound waves to travel through the base portion, the plurality of channels converging to form an annular outlet of the compression driver.

Description

TECHNICAL FIELD

[0001] Embodiments relate to a compression driver for a transducer having a dome diaphragm and a ring-shaped outlet to a waveguide. BACKGROUND

[0002] Compression drivers can be divided into two groups: dome diaphragm based drivers and ring-shaped flexure diaphragm based drivers. Both types of drivers have their own strengths and weaknesses. Dome diaphragm drivers generally have a larger diaphragm area and thus provide higher sound pressure level (SPL) output. Large compression drivers based on dome diaphragms, where the voice coil diameter is 2 inches or larger, typically have a metal dome formed from titanium, aluminum, magnesium, or beryllium foil. The metal diaphragm is heavier than its polymer counterpart and can have a lower resonance, providing more efficient low frequency reproduction. However, it has a lower mass control velocity at high frequencies, and thus lower SPL output at high frequencies. This is typically compensated for by a high frequency breakup of the diaphragm. The breakup increases the overall output acceleration, and thus the in-phase component of the acceleration helps to increase the high frequency SPL output. However, this breakup is accompanied by an increase in non-linear distortion, including sub-harmonics and irregularities in the frequency response at high frequencies.

[0003] Most modern ring-shaped diaphragms are made from polymer films. The advantage of a ring-shaped diaphragm is that the moving portion of the diaphragm has a smaller radial dimension compared to a dome diaphragm with the same diameter of the moving voice coil. Ring-shaped diaphragm based drivers have a smaller radial compression chamber size, which is related to a higher radial resonance frequency. As the voice coil diameter increases, dome compression chambers have resonances starting at lower frequencies, and their number increases in the audio range. In contrast, ring-shaped diaphragm compression drivers can have a larger voice coil without increasing the radial dimension, with the same number of resonances in the compression chamber. However, the disadvantage of ring-shaped flexure diaphragm assemblies is that they have a smaller area compared to the area of an equivalent dome diaphragm assembly.

[0004] Both types of compression drivers typically have a circular outlet. The diameter of the outlet is related to the cross-over mode excited at the entrance of the corresponding horn or waveguide, and the directional control at high frequencies. In a regular constant directivity waveguide, the directional control is lost when the diameter of the driver outlet (equal to the diameter of the waveguide or horn entrance) is comparable to the wavelength of the radiated signal. The same effect is observed in waveguides used in line arrays, where a larger outlet diameter degrades the high frequency directional control.

[0005] In line arrays, the entrance of the waveguide is usually circular, while the exit of the waveguide is rectangular, with its vertical dimension significantly larger than its horizontal dimension. This way, a wide directivity is provided in the horizontal plane, while a narrow directivity is provided in the vertical plane. The goal of the waveguide in a line array is to transform the circular entrance into a rectangular exit, and to provide a "flat" wave front in the vertical plane, resulting in a cylindrical wave instead of a spherical wave when multiple line arrays are stacked vertically and a single or few waveguides form a very long vertically oriented radiator. This is achieved via a progressive time delay of the sound waves towards the middle of the vertically oriented exit, so that the time of arrival of the sound waves is equal along the vertical profile of the waveguide. In all such drivers with a circular exit and a corresponding circular entrance to the waveguide, the acoustic path must narrow to reach the exit of the driver, and then widen again in the waveguide, resulting in unnecessary redundancy. SUMMARY

[0006] In one or more embodiments, a compression driver includes a dome diaphragm having a convex face and a concave face and a phase plug having a base portion with a first side and an opposite second side. The first side of the base portion is disposed adjacent the convex face of the diaphragm and defines a compression chamber between the diaphragm and the convex face. The base portion includes a plurality of channels extending through the base portion from the first side to the second side so that sound waves travel through the base portion, the plurality of channels converging to form an annular exit of the compression driver.

[0007] In one or more embodiments, a transducer includes a compression driver including a dome diaphragm having a convex face and a concave face and a phase plug having a base portion with a first side and an opposite second side. The first side of the base portion is disposed adjacent the convex face of the diaphragm and defines a compression chamber between the diaphragm and the convex face. The phase plug has a hub portion extending outwardly from the second side of the base portion along a central axis, the hub portion having a first end and a second end and an outer surface. The base portion includes a plurality of channels extending through the base portion from the first side to the second side, the plurality of channels converging to form an annular exit of the compression driver. A shell is disposed on the base portion and has a first end and a second end and an inner surface, the hub portion and the shell together forming a waveguide having an entrance adjacent the compression driver and an exit to an ambient environment.

[0008] In one or more embodiments, a transducer includes a compression driver including a dome diaphragm having a convex face and a concave face, and a magnet assembly disposed adjacent the concave face of the diaphragm. The compression driver further includes a phasing plug having a base portion with a first side and an opposite second side, the first side of the base portion being disposed adjacent the convex face of the diaphragm and defining a compression chamber between the diaphragm and the convex face. The phasing plug has a hub portion extending outwardly from the second side of the base portion along a central axis. The base portion includes a plurality of channels extending through the base portion from the first side to the second side, the plurality of channels including concentric annular passages converging to form an annular outlet of the compression driver. A housing is disposed on the base portion, the hub portion and the housing together forming a waveguide, wherein the waveguide has an annular inlet adjacent the compression driver and a rectangular outlet to the ambient environment. BRIEF DESCRIPTION OF DRAWINGS

[0009] Figure 1 is a cross-sectional view taken along a vertical plane showing a transducer according to one or more embodiments;

[0010] Figure 2 is a cross-sectional view taken along a vertical plane showing a phasing plug and a waveguide of a transducer;

[0011] Figure 3 is a partial perspective view along a vertical plane showing a phasing plug and a dome diaphragm;

[0012] Figure 4 is a cross-sectional view taken along a horizontal plane showing a transducer according to one or more embodiments;

[0013] Figure 5 is a cross-sectional view taken along a horizontal plane showing a phasing plug and a waveguide of a transducer;

[0014] Figure 6 is a partial perspective view along a horizontal plane showing a phasing plug and a dome diaphragm;

[0015] Figure 7 is a perspective view of a transducer having a waveguide oriented along a vertical plane;

[0016] Figure 8 is a side view of the transducer of Figure 7

[0017] Figure 9 is a perspective view of a transducer having a waveguide oriented along a horizontal plane; and

[0018] Figure 10 is a side view of the transducer of Figure 9 ​​DETAILED DESCRIPTION

[0019] Detailed embodiments of the application are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the application which can be embodied in various alternative forms. The accompanying drawings are not necessarily to scale; some features can be exaggerated or minimized for the purpose of clarity. The specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the application.

[0020] Embodiments of the transducer disclosed herein include a dome diaphragm-based compression driver having a ring-shaped driver outlet and a waveguide having a corresponding ring-shaped inlet. Referring first to Figure 1 and Figure 4 , a cross-sectional view of a transducer 100 including a compression driver 102 and a waveguide 104 is shown. In one or more embodiments, the compression driver 102 includes a magnet assembly 106, which can include a ring-shaped permanent magnet 108 disposed between a ring-shaped top plate 110 and a back plate 112. The magnet assembly 106 provides a permanent magnetic field for electrodynamic coupling with a voice coil 114. The voice coil 114 is mechanically coupled to a diaphragm 116 and generates movement thereof to convert a received electrical signal into sound waves that propagate from the compression driver 102 toward the waveguide 104. In one or more embodiments, the diaphragm 116 has a dome configuration and is disposed coaxially with a central axis 118 above the magnet assembly 106.

[0021] As shown in Figures 1 to 6 , the compression driver 102 further includes a phasing plug 120 having a base portion 122 and a hub portion 124 extending outwardly or upwardly from the base portion 122, both of which are disposed coaxially about the central axis 118. The hub portion 124 has a first end 126 disposed proximate the base portion 122 and a second end 128 disposed distal from the base portion 122. The hub portion 124 can be integrally formed with the base portion 122 or can be attached to the base portion 122 by any suitable means. As an alternative to the solid hub portion 124 described herein, the interior of the hub portion 124 can instead be hollowed out to reduce weight and / or cost. The base portion 122 of the phasing plug 120 can be generally circular or can have any other suitable geometry. The phasing plug 120 can include a circumferential flange 130 for coupling or mounting (e.g., via bolts as shown in Figure 1 , Figure 4 and Figures 7 to 10 , the back plate 112 of the magnet assembly 106.

[0022] Referring to Figure 1 , Figures 3 to 4 and Figure 6The dome diaphragm 116 has a concave lower surface 132 and a convex upper surface 134. In contrast to a typical compression driver with a dome diaphragm, where the acoustic signal is guided by a phase-modulation plug adjacent to the dome's concave surface, in one or more embodiments disclosed herein, the acoustic signal can enter the phase-modulation plug 120 from the convex surface 134 of the dome diaphragm 116. The base portion 122 of the phase-modulation plug 120 includes a first side 136 facing the convex surface 134 of the diaphragm 116 and an opposing second side 138 facing the waveguide 104. The first side 136 may be generally concave, complementary to the convex surface 134 of the diaphragm 116, while the second side 138 may be generally planar. It should be understood that any directional terms used herein are merely for indicating the relative positions of the various components of the transducer 100 and are not intended to be limiting.

[0023] like Figures 1 to 6 As shown, the base portion 122 of the phase-modulating plug 120 also includes at least one channel 140, which serves as a passageway extending from the first side 136 to the second side 138 through the base portion 122, through which sound waves generated by the diaphragm 116 can travel. A compression chamber is defined in the space between the convex surface 134 of the diaphragm 116 and the first side 136 of the phase-modulating plug base portion 122. In practice, the height of the compression chamber can be very small (e.g., about 0.5 mm or less), resulting in a small volume of the compression chamber. Actuation of the diaphragm 116 generates a high sound pressure level acoustic signal within the compression chamber, and this signal travels as a sound wave through the channel 140 through the base portion 122 of the phase-modulating plug 120. In a non-limiting embodiment, sound-absorbing material may be disposed below the concave surface 132 of the diaphragm 116 to mitigate any air resonance in the cavity.

[0024] As described herein, a plurality of channels 140 may be configured as an annular pathway arranged circumferentially around a central axis 118, forming concentric circles near the convex surface 134 of the diaphragm 116. The channels 140 may be positioned at concentric radii to block radial acoustic modes excited in the compression chamber. The channels 140 are used to transmit sound waves from all regions of the convex surface 134 of the diaphragm 116 through a phase-modulation plug 120 into the waveguide 104. Each channel 140 has a first end 142 adjacent to the convex surface 134 of the diaphragm 116 and communicating with the compression chamber, and a second end 144 located at a second side 138 of the base portion 122. Each channel 140 may have substantially similar lengths from its first end 142 to its second end 144, wherein the second ends 144 of the channels 140 converge to form an annular outlet 146 to the compression driver 102, such that each sound pulse arrives in the waveguide 104 as a coherent wavefront.

[0025] like Figures 1 to 10As shown, the hub portion 124 is disposed within a housing 150 having a first end 152 disposed at or attached to the phase plug 120 (e.g., at the second side 138 of the base portion 122) and a second end 154 disposed at a distance from the base portion 122. The hub portion 124 and the housing 150 together form the waveguide 104. More specifically, an outer surface 156 of the hub portion 124 and an inner surface 158 of the housing 150 can collectively define the waveguide 104 and provide a path for the propagation of acoustic waves from an entrance 160 of the waveguide 104 to an exit or exit aperture 162 of the waveguide 104. In the assembled waveguide 104, the exit aperture 162 can generally be aligned with the hub portion 124. The waveguide 104 can be used to control the directivity (i.e., the sound pressure coverage over a particular listening area) of acoustic waves propagating from the transducer 100 into the surrounding environment and increase the reproduced SPL in a particular frequency range. The housing 150 can include a generally flat flange 164 that surrounds the exit 162, which can be generally circular as described herein, which can be used to couple the transducer 100 to a transducer housing or other components of a speaker system.

[0026] The waveguide entrance 160 can be a continuous annular ring formed by the outer surface 156 of the hub portion 124 at its first end 126 and the inner surface 158 of the housing 150 at its first end 152. The waveguide exit 162 can be implemented as a rectangular exit aperture disposed at the second end 154 of the housing 150, with a smaller dimension in the horizontal plane and a larger dimension in the vertical plane. This configuration provides a wide directivity response (wider dispersion) in the horizontal plane and a narrower dispersion in the vertical plane, which generally meets the requirements for horn driver directivity in practical applications. The requirement for narrow directivity in the vertical plane is especially important in line array applications, in which the entire array comprises many independent systems that form a vertical wave front that is close to a cylindrical sound wave to avoid unwanted dispersion of acoustic energy in the vertical plane and increase the coverage distance.

[0027] The profiles of the outer surface 156 of the hub portion 124 and the inner surface 158 of the housing 150 can be “shaped” and improve the wave front to be flatter at the exit (exit aperture 162) of the transducer 100. The shape of the hub portion 124 has different profiles in the vertical and horizontal planes, which can provide time alignment and correspondingly a flat wave front in the vertical plane at the exit aperture 162. In modern waveguides, which are commonly used in line arrays, the vertical directivity is controlled by the phase and time relationship of the acoustic signals radiated at different vertical points within the waveguide 104. The typical goal is to radiate equally in time and in phase over the vertical dimension of the rectangular exit aperture 162, which provides a “flat” wave front in the vertical plane.

[0028] As Figures 1 to 6As shown, the shape of the inner surface 158 of the housing 150 and the outer surface 156 of the hub portion 124 is a continuous, smooth, contoured surface that provides an uninterrupted path from the waveguide inlet 160 to the waveguide outlet 162. The transition of the air path from the annular outlet 146 of the compression driver 102 and the corresponding annular waveguide inlet 160 to the rectangular outlet aperture 162 can be provided by the custom shape of the hub portion 124, which begins at the first end 126 with a generally circular cross-section and then transitions to a blade-like shape at the second end 128. The waveguide 104 is symmetrical about both a vertical plane Figures 1 to 3 and Figures 7 to 8 ) and a horizontal plane Figures 4 to 6 and Figures 9 to 10 ).

[0029] Along the vertical dimension of the waveguide 104, the region of the hub portion 124 below the transition point 166 can follow one curvature, while the region of the hub portion 124 above the transition point 166 can follow another curvature. In this way, the hub portion outer surface 156 and the housing inner surface 158 can protrude further outward from the central axis 118 near the transition point 166 than below or above the transition point 166, where the transition point 166 can have any suitable location between the waveguide inlet 160 and the waveguide outlet 162. For example, referring to Figures 4 to 6 which depicts a cross-sectional view along a horizontal plane, the outer surface 156 of the hub portion 124 can be substantially linear from the waveguide inlet 160 to the transition point 166. The outer surface 156 can then curve inward until terminating in a blade-like shape at the second end 128 of the hub portion. The inner surface 158 of the housing 150 can curve slightly outward from the waveguide inlet 160 to the transition point 166, and then can curve slightly inward until reaching the waveguide outlet 162. The inward curvature of the inner surface 158 is less than the inward curvature of the outer surface 156, thereby increasing the cross-section or width of the annular waveguide path 170.

[0030] Accordingly, the waveguide 104 provides an annular path 170 for sound waves to travel from the annular waveguide inlet 160 to the rectangular outlet aperture 162. The inner cross-sectional area or width of the annular path 170 generally increases from the inlet 160 to the outlet 162 of the waveguide 104. The waveguide 104 controls the propagation of sound waves by providing a substantially equal sound path length from the outlet 146 of the compression driver 102, providing a controlled cross-sectional area expansion rate from the inlet 160 to the outlet 162 of the waveguide 104.

[0031] In the embodiments disclosed herein, the use of a dome diaphragm provides a larger effective area than a ring diaphragm, thereby increasing the maximum SPL output of the compression driver. Furthermore, the dome diaphragm has a relatively low resonant frequency; this combination of characteristics makes the transducer well-suited for bidirectional linear arrays. Additionally, the smaller cross-sectional size of the acoustic path improves directional control at high frequencies compared to drivers with circular exits. Finally, the ring-shaped interface between the compression driver and the waveguide offers the significant advantage of a very short driver-waveguide assembly. In drivers with circular exits, the acoustic path narrows to reach the exit and then begins to widen again in the waveguide. However, in the transducer disclosed herein, the acoustic path gradually widens from the phase-tuning plug through the waveguide, thus omitting the redundant "narrowing-widening" phase and allowing for a shorter assembly.

[0032] While exemplary embodiments have been described above, they do not imply that these embodiments describe all possible forms of the invention. In fact, the wording used in this specification is descriptive rather than limiting, and it should be understood that various changes can be made without departing from the spirit and scope of the invention. Furthermore, features of various embodiments can be combined to form other embodiments of the invention.

Claims

1. A compression drive, comprising: A dome-shaped diaphragm having a convex surface and a concave surface; and A phase-modulating plug having a base portion having a first side and an opposing second side, wherein the first side of the base portion is disposed adjacent to the convex surface of the diaphragm and defines a compression chamber between the diaphragm and the convex surface, the second side of the base portion being generally planar and including an annular outlet of the compression driver, the base portion including a plurality of channels extending from the first side through the base portion to the second side for sound waves to travel through the base portion, the plurality of channels converging at the second side to form the annular outlet of the compression driver.

2. The compression driver of claim 1, wherein the plurality of channels comprises concentric ring pathways.

3. The compression driver of claim 1, wherein each of the plurality of channels has substantially similar lengths from its first end to its second end.

4. The compression driver of claim 1, wherein the first side of the base portion is generally concave.

5. The compression driver of claim 1, further comprising a magnet assembly disposed adjacent to the concave side of the diaphragm.

6. The compression driver of claim 1, wherein the phase-shifting plug has a hub portion extending outward from the second side of the base portion along a central axis.

7. The compression driver of claim 6, wherein the hub portion has a generally cylindrical cross-section at a first end near the base portion and transitions into a blade shape at a second end located at a distance from the base portion.

8. A transducer comprising: A compression driver, the compression driver comprising: A dome-shaped diaphragm having a convex surface and a concave surface; and A phase-shifting plug having a base portion having a first side and an opposing second side, wherein the first side of the base portion is disposed adjacent to the convex surface of the diaphragm and defines a compression chamber between the diaphragm and the convex surface, the second side of the base portion being generally planar and including an annular outlet of the compression actuator, the phase-shifting plug having a hub portion extending outwardly along a central axis from the second side of the base portion, the hub portion having a first end and a second end and an outer surface, the base portion including a plurality of channels extending from the first side through the base portion to the second side, the plurality of channels converging at the second side to form the annular outlet of the compression actuator; and A housing is disposed on the base portion and has a first end, a second end, and an inner surface. The hub portion and the housing together form a waveguide having an inlet adjacent to the compression driver and an outlet to the surrounding environment.

9. The transducer of claim 8, wherein the outer surface of the hub portion and the inner surface of the housing together define an annular path for acoustic waves to travel through the waveguide.

10. The transducer of claim 9, wherein the cross-sectional area of ​​the annular path increases from the inlet to the outlet of the waveguide.

11. The transducer of claim 8, wherein the waveguide inlet is an annular ring formed by the outer surface of the hub portion at the first end of the hub portion and the inner surface of the housing at the first end of the housing.

12. The transducer of claim 8, wherein the waveguide outlet comprises a rectangular outlet hole located at the second end of the housing.

13. The transducer of claim 8, wherein the waveguide port is substantially aligned with the second end of the hub portion.

14. The transducer of claim 8, wherein the hub portion has a generally cylindrical cross-section at the first end and transitions into a blade shape at the second end.

15. The transducer of claim 8, wherein the plurality of channels comprises concentric ring pathways.

16. The transducer of claim 8, wherein each of the plurality of channels has substantially similar lengths from its first end to its second end.

17. The transducer of claim 8, wherein the first side of the base portion is generally concave.

18. The transducer of claim 8, further comprising a magnet assembly disposed adjacent to the concave side of the diaphragm.

19. The transducer of claim 8, wherein the housing includes a generally flat flange surrounding the waveguide port for coupling the transducer to a loudspeaker system.

20. A transducer comprising: A compression driver, the compression driver comprising: A dome-shaped diaphragm having a convex surface and a concave surface; A magnet assembly, the magnet assembly being disposed adjacent to the concave surface of the diaphragm; and A phase-shifting plug having a base portion having a first side and an opposing second side, wherein the first side of the base portion is disposed adjacent to the convex surface of the diaphragm and defines a compression chamber between the diaphragm and the convex surface, the second side of the base portion being generally planar and including an annular outlet of the compression actuator, the phase-shifting plug having a hub portion extending outwardly along a central axis from the second side of the base portion, the base portion including a plurality of channels extending from the first side through the base portion to the second side, the plurality of channels including concentric annular passages converging at the second side to form the annular outlet of the compression actuator; and A housing is disposed on the base portion, and the hub portion and the housing together form a waveguide having an annular inlet adjacent to the compression driver and a rectangular outlet leading to the surrounding environment.

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