Phase plug for improving the directional response of a compression driver

Abstract

A phase plug for a compression driver includes a body having an entrance side with a front surface and an exit side with a back surface, the body disposed about a central axis. A plurality of channels are formed through the body from the entrance side to the exit side, each of the plurality of channels having an annular configuration with an entrance at the front surface, an exit at the back surface, and a path length between the entrance and the exit. The plurality of channels have unequal path lengths such that a sound signal propagating through the plurality of channels forms a convex wavefront at the exit side of the phase plug.

Description

Technical Field

[0001] The implementation scheme relates to a phase plug with an optimized configuration for improving the directional response of a compression driver. Background Technology

[0002] A compression driver generates an acoustic signal or sound wave through a vibrating diaphragm, which then propagates to a waveguide or horn via a phase plug. A thin layer of air (called a compression chamber) separates the diaphragm and the phase plug. Generally, compression drivers fall into two main categories: dome-shaped diaphragm-based drivers and ring-shaped diaphragm-based drivers. Typically, the compression driver has a circular outlet that matches the corresponding circular inlet of the horn. The outlet of the compression driver is actually the outlet of the phase plug, which acoustically connects the compression chamber and the horn at this point.

[0003] In a compression driver, the total area of ​​the phase plug inlets is significantly smaller than the diaphragm area. This is necessary to increase the load impedance of the diaphragm, thereby improving the efficiency of the compression driver. The fact that the phase plug inlet area is smaller than the diaphragm area increases the load impedance, thus matching the diaphragm's output impedance to the input impedance of the phase plug (followed by the horn or waveguide). This matched impedance maximizes the efficiency of the compression driver.

[0004] To maximize the efficiency of the compression driver, the total inlet area of ​​the phase plug is typically 6 to 10 times smaller than the diaphragm area. From a cross-sectional area perspective, the phase plug can be viewed as a small, short horn connecting the compression chamber and the compression driver outlet. Like a regular horn, the cross-sectional area should gradually increase from the inlet to the outlet to match the throat area of ​​the waveguide or horn attached to the compression driver outlet; otherwise, reflections and irregularities will occur in the SPL (sound pressure level) frequency response. Therefore, the area of ​​the phase plug inlet should not only be smaller than the diaphragm area but also smaller than the area of ​​the compression driver outlet.

[0005] The diameter of the compressor driver's outlet (and the corresponding throat diameter of the horn) determines the compressor driver's directivity control at high frequencies. Therefore, to control the directivity at the highest frequencies in the audio range and maintain a constant directivity response, it is desirable to keep the throat diameter small. However, considering the necessary extension of the phase plug region from the inlet to the outlet, this constraint may conflict with the requirement for a minimum outlet diameter. Summary of the Invention

[0006] In one or more embodiments, a phase plug for a compression driver includes a body having an inlet side with a front surface and an outlet side with a rear surface, the body being disposed about a central axis. A plurality of channels are formed through the body from the inlet side to the outlet side, each of the plurality of channels having an annular configuration, the annular configuration having an inlet at the front surface, an outlet at the rear surface, and a path length between the inlet and the outlet. The plurality of channels have unequal path lengths, such that acoustic signals propagating through the plurality of channels form a convex wavefront at the outlet side of the phase plug.

[0007] In one or more embodiments, one or more of the plurality of channels are circuitous and include a curved configuration between the inlet and the outlet. In one or more embodiments, for each of the plurality of channels, the radial distance from the inlet to the outlet to the central axis varies. In one or more embodiments, the path length of the plurality of channels increases from the first inner channel closest to the central axis to the outer channel furthest from the central axis.

[0008] In one or more embodiments, each of the plurality of channels is symmetrical about the central axis. In one or more embodiments, the inlets of the plurality of channels form concentric circles around the central axis on the front surface, and the outlets of the plurality of channels form concentric circles around the central axis on the rear surface. In one or more embodiments, for each of the plurality of channels, the area of ​​the inlet is smaller than the area of ​​the outlet, such that the cross-sectional area of ​​each channel increases from the inlet to the outlet.

[0009] In one or more embodiments, the front surface is convex. In one or more embodiments, the rear surface is generally flat. In one or more embodiments, the body includes a front portion including the front surface, an intermediate portion adjacent to the front portion, and a rear portion adjacent to the intermediate portion and including the rear surface, the front surface including a chamfer to overhang the intermediate portion, the diameter of the intermediate portion decreasing linearly tapered from the front portion to the rear portion, and the rear portion being generally cylindrical.

[0010] In one or more embodiments, a compression driver includes a motor assembly disposed around a central axis and a diaphragm operably connected to the motor assembly along the central axis and having a concave surface. A phase plug is mounted to the motor assembly adjacent to the diaphragm along the central axis. The phase plug has a body having an inlet side and an outlet side. The inlet side has a convex front surface oriented toward the concave surface of the diaphragm, and the outlet side has a generally flat rear surface. The phase plug includes a plurality of annular channels formed through the body from the inlet side to the outlet side, through which an acoustic signal generated by the diaphragm propagates. Each of the plurality of annular channels includes an inlet at the front surface, an outlet at the rear surface, and a path length between the inlet and the outlet. The plurality of annular channels have unequal path lengths, such that the acoustic signal forms a convex wavefront at the outlet side of the phase plug.

[0011] In one or more embodiments, the motor assembly includes an annular magnet disposed between a top plate and a pole piece located on the front side of the compression drive.

[0012] In one or more embodiments, a horn driver includes a compression driver comprising a motor assembly disposed around a central axis and a dome-shaped diaphragm operably connected along the central axis to the motor assembly and having a concave surface. A phase plug is mounted to the motor assembly adjacent to the diaphragm along the central axis. The phase plug has a body having an inlet side and an outlet side, the inlet side having a convex front surface oriented toward the concave surface of the dome-shaped diaphragm, and the outlet side having a generally flat rear surface. The phase plug includes a plurality of annular channels formed through the body from the inlet side to the outlet side, through which an acoustic signal generated by the dome-shaped diaphragm propagates. Each of the plurality of annular channels includes an inlet at the front surface, an outlet at the rear surface, and a path length between the inlet and the outlet. The plurality of annular channels have unequal path lengths, such that the acoustic signal forms a convex wavefront at the outlet side of the phase plug. A horn is mounted to the compression driver adjacent to the outlet side of the phase plug. Attached Figure Description

[0013] Figure 1 This is a graph showing the relationship between coverage angle and frequency, illustrating the ideal directivity of a constant directivity horn of a compression driver. It is the containment angle (covering angle) between the walls of the horn;

[0014] Figure 2 It is a graph showing the relationship between coverage angle and frequency, illustrating the directional response of a conical horn with a finite throat diameter;

[0015] Figure 3 It is the far-field, axial SPL response diagram of the FEA model with an exponential model angle of the plane wavefront at the entrance;

[0016] Figure 4 This is a graph showing the normalized SPL response of the FEA model with an exponential model angle of the plane wavefront at the inlet at different angles;

[0017] Figure 5 This is a graph showing the far-field, axial SPL response of the FEA model with an exponentially shaped angle and a concave wavefront at the inlet.

[0018] Figure 6 This is a graph showing the normalized SPL response of the FEA model at different angles with an exponentially shaped wavefront at the inlet.

[0019] Figure 7 This is a graph showing the far-field, axial SPL response of an FEA model with an exponentially shaped angle and a convex wavefront at the inlet.

[0020] Figure 8 This is a graph showing the normalized SPL response of the FEA model with an exponentially shaped wavefront at the inlet at different angles;

[0021] Figure 9 This is a graph showing the far-field, axial SPL response of an exponentially oriented FEA model with four-channel phase plugs, a compression chamber, and an infinitely rigid diaphragm, where the path lengths of the phase plug channels are equal.

[0022] Figure 10 This is a graph showing the normalized SPL response of an FEA model with an exponential model angle, a four-channel phase plug, a compression chamber, and an infinitely rigid diaphragm at different angles, where the path lengths of the phase plug channels are equal.

[0023] Figure 11 This is a graph showing the far-field, axial SPL response of an exponential model FEA with a four-channel phase plug, a compression chamber, and an infinitely rigid diaphragm, where the path lengths of the phase plug channels are unequal and have been tuned to provide a convex wavefront at the inlet and optimize directivity.

[0024] Figure 12 This is a graph showing the normalized SPL response of an exponential model FEA with a four-channel phase plug, a compression chamber, and an infinitely rigid diaphragm at different angles, where the path lengths of the phase plug channels are not equal and have been adjusted to provide a convex wavefront at the inlet and optimize directivity.

[0025] Figure 13It is a perspective cross-sectional view of a phase plug having channels of unequal lengths according to one or more embodiments;

[0026] Figure 14 This is a cross-sectional view of the phase plug;

[0027] Figure 15 It is a perspective view of the phase plug of the channel at the entrance side according to one or more embodiments;

[0028] Figure 16 This is a plan view of the inlet side of the phase plug;

[0029] Figure 17 It is a perspective view of the phase plug of the channel at the outlet side according to one or more embodiments;

[0030] Figure 18 This is a plan view of the outlet side of the phase plug;

[0031] Figure 19 It is a cross-sectional view of a horn driver according to one or more implementation schemes;

[0032] Figure 20 It is an exploded view of a compression driver according to one or more implementation schemes;

[0033] Figure 21 A schematic diagram of an exponential wavefront model with equal channel lengths and convex wavefronts; and

[0034] Figure 22 This is a schematic diagram of an exponential type angle model with unequal channel lengths and convex wavefronts. Detailed Implementation

[0035] Detailed embodiments of the invention are disclosed herein as needed; however, it should be understood that the disclosed embodiments are merely examples of the invention that may be embodied in various and alternative forms. The drawings are not necessarily drawn to scale; some features may be enlarged or minimized to show details of specific components. Therefore, the specific structural and functional details disclosed herein should not be construed as limiting, but rather serve only as a representative basis for teaching those skilled in the art to employ the invention in various ways.

[0036] One way to interpret the directivity response as a function of frequency is called beamwidth or coverage angle, which refers to the angle from the radiation axis to where the sound pressure level response decreases by 6 dB. Figure 1 The ideal beamwidth frequency response with a constant directivity horn is shown. Figure 1 medium to low Within the frequency range (wavelength greater than the diameter of the horn opening), directional control fails, and the horn becomes omnidirectional. This diagram corresponds to an assumption that the diameter of the horn's throat (and the corresponding compressor driver's outlet) is much smaller than the wavelength at the highest frequency. Therefore, directional control is achieved through the audio frequency range.

[0037] However, in reality, at least two factors influence directional responses. Figure 2 The directivity corresponding to the actual diameter of the horn throat is shown, taking into account the fact that the horn has a conical cross-section, where the improvement in directivity is related to the frequency range of "throat control". However, as shown, at low frequencies, the directivity response is adversely affected by the "waist effect". The beamwidth narrows between the frequency range where the horn antenna becomes omnidirectional and the frequency range where directivity is controlled by the horn walls. To avoid this narrowing, special measures can be taken, such as changing the angle of the horn walls.

[0038] At high frequencies, the diameter of the horn throat controls directivity, and the beamwidth narrows with increasing frequency, similar to the beamwidth of a piston. Therefore, to control directivity at the highest frequencies in the audio range and maintain a constant directivity response, a small throat diameter is desirable. However, from the perspective of phase plug region expansion, this limitation may conflict with the requirement for a minimum exit diameter. Typically, the standard exit diameter range for compression drivers with dome diaphragms is 1 inch to 2 inches, the latter belonging to compression drivers with large diaphragms (4 inches or larger). Horn control of directivity fails at approximately 16 kHz (for a 1-inch exit), 12 kHz (for a 1.5-inch exit), and 8 kHz (for a 2-inch exit).

[0039] In a compression actuator, the phase plug's function is to combine acoustic signals from different parts of the compression cavity and direct them to the actuator's outlet. Since the compression cavity is a hollow cavity with rigid walls, it exhibits acoustic resonance. The phase plug of a compression actuator with a dome-shaped diaphragm typically has multiple narrow annular grooves. Positioning n annular grooves at a specific diameter can suppress the first n radial resonant modes in the compression cavity.

[0040] In existing phase plugs, the acoustic channels typically have the same path length to allow acoustic signals to propagate from different parts of the compression chamber to the phase plug's outlet, thus generating a coherent plane wavefront. The purpose of this design is to ensure that acoustic signals from each of the channels arrive at the compressor driver's outlet simultaneously and in phase to avoid interference, hence the name "phase plug." Equal phase signals arriving at the phase plug's outlet imply a plane wavefront. However, this condition is not optimal from the perspective of improving directivity at high frequencies.

[0041] Therefore, the embodiments disclosed herein relate to a phase plug configuration that provides improved directivity response for compression drives at high frequencies, even for compression drives with large outlet diameters. Compared to previous phase plugs, the phase plug disclosed herein has an annular channel of unequal path lengths, thereby providing a progressive time delay at the channel outlet and producing a convex wavefront as further described below.

[0042] The following examples illustrate the effect of the wavefront shape and phase plug channel length at the inlet (outlet of the compression driver) of an exponentially type angle on its directivity at high frequencies. All FEA acoustic simulations with horns described below correspond to 2-Pi anechoic chamber boundary conditions. It should be understood that the model parameters and dimensions discussed below are not intended to be restrictive, but are chosen only to illustrate different phase plug and wavefront scenarios.

[0043] Figure 3 This is a graph showing the far-field, axial SPL response of an FEA model with an exponential horn angle and a plane wavefront at the inlet, assuming the acoustic system is uniformly excited at unit velocity across the entire frequency range of 200 Hz–20000 Hz. In the FEA model, the diameter of the horn inlet is 38 mm, the horn aperture diameter is 425 mm, and the horn length is 267 mm. Figure 4 This shows the normalized SPL response of the FEA model with an exponential model angle of the plane wavefront at the inlet at different angles relative to the axis, with model parameters and... Figure 3 The same applies as described in [the previous section]. A fourth-order high-pass Butterworth filter with a cutoff frequency of 1.0 kHz is applied to the response. As shown in the figure, for this plane wavefront, the directivity becomes significantly narrower above 10 kHz.

[0044] Figure 5 This is a graph showing the far-field, axial SPL response of an exponential horn-type FEA model with a concave wavefront at the inlet. In the FEA model, the diameter of the horn inlet is 38 mm, the horn aperture diameter is 425 mm, and the horn length is 267 mm. However, the model includes a concave wavefront with a curvature depth of 5 mm. As shown, the concave wavefront adversely affects the SPL response, resulting in a severe dip at 12 kHz. Figure 6 The normalized SPL response of an FEA model with an exponentially modulo angle at the inlet concave wavefront is shown at different angles relative to the axis, with the radius of the curvature arc being 5 mm. A fourth-order high-pass Butterworth filter with a cutoff frequency of 1.0 kHz is applied to the response. As shown in the figure, the SPL response of the concave wavefront is inferior to that of the plane wavefront.

[0045] Figure 7This is a graph showing the far-field, axial SPL response of an exponentially shaped FEA model with a convex wavefront at the inlet. In the FEA model, the diameter of the horn inlet is 38 mm, the horn aperture diameter is 425 mm, and the horn length is 267 mm. However, the model includes a convex wavefront with a convex profile height of 5 mm. Figure 8 This is a graph showing the normalized SPL response of an FEA model with an exponentially oriented angle at the inlet convex wavefront at different angles relative to the axis. The height of the curvature arc is 5 mm, and a 4th-order high-pass Butterworth filter with a cutoff frequency of 1.0 kHz is applied to the response. Compared to the plane wavefront and concave wavefront scenarios, the directivity response of the convex wavefront is significantly improved. As shown in the figure, the irregularity of the axial SPL response does not increase with the convex wavefront, but only slightly decreases around 20 kHz.

[0046] The preceding FEA model assumed the wavefront to be continuous. However, in reality, due to the finite number of channels in the phase plug, the wavefront is not continuous but discrete. Therefore, Figure 9 This is a graph showing the far-field, axial SPL response of an exponentially type-angle FEA model, where the wavefront profile is generated by four discrete channels. The FEA model includes a compression cavity and an infinitely rigid diaphragm oscillating at unit velocity. Figure 21 A schematic diagram of the exponential horn model and its convex wavefront W is shown. In the FEA model, the diameter of the horn inlet is 38 mm, the horn aperture diameter is 425 mm, and the horn length is 267 mm. Furthermore, the path lengths of the phase plug channels are equal, and similar acoustic signals exit all channels. Figure 10 It is shown Figure 9 The graph shows the normalized SPL response of the FEA model at different angles relative to the axis, with a 4th-order high-pass Butterworth filter with a cutoff frequency of 1.0 kHz applied to the response. As shown, the directional response is very similar to the response produced by a plane wavefront. Figures 3 to 4 ).

[0047] at last, Figure 11 This is the far-field, axial SPL response plot of an exponentially type-angle FEA model with a four-channel phase plug, a compression chamber, and an infinitely rigid diaphragm oscillating axially at unit velocity. In the FEA model, the horn inlet diameter is 38 mm, the horn aperture diameter is 425 mm, and the horn length is 267 mm. However, the path lengths of the phase plug channels have been adjusted to be unequal and to provide a convex wavefront with a curvature height of 5 mm. In this model, the convex wavefront is formed by introducing an asymptotic delay of 2.4 μs in the second (center-outward) channel, 6.6 μs in the third (center-outward) channel, and 11.8 μs in the outermost channel. Figure 22 The diagram shows the exponential model of the angular geometry and its convex wavefront W. Figure 12 It is shown Figure 11 The normalized SPL response of the FEA model at different angles relative to the axis is plotted, with a 4th-order high-pass Butterworth filter with a cutoff frequency of 1.0 kHz applied to the response. By comparison... Figure 10 Directional diagrams (with equal channel path lengths) and Figure 12 The figure shows that the directivity response of the model with unequal channel path lengths and a convex wavefront is significantly improved and optimized.

[0048] refer to Figures 9 to 10 The model, when the channel path lengths are equal (e.g., 34.2 mm each) and the phase plug channel entrance is located at the node of the fourth resonant mode, has the frequencies of the first four compression cavity resonants as follows: 4829 Hz, 8825 Hz, 12754 Hz, and 16720 Hz. The fifth resonant frequency is higher than the audio frequency range. The total area of ​​the annular channel entrance is:

[0049]

[0050] in It is the total area of ​​the entrances to all four circular passages.

[0051] parameter It is calculated from the expression (2) for the maximum efficiency of the compression driver.

[0052]

[0053] in For voice coil resistance, where c is the air density and c is the speed of sound. The effective area of ​​the diaphragm, and This is the force factor driving the motor.

[0054] Total area of ​​phase plug outlet Equal to the nominal outlet area of ​​the compression drive Subtract the area of ​​the phase plug's partition wall :

[0055]

[0056]

[0057] in This refers to the exit area of ​​each passageway. (Area) This is derived from the ratio of the entrance area to the exit area:

[0058]

[0059]

[0060] Constants A, B, and C were obtained by solving the boundary value problem using FEA. (The outlines of each channel are shown.) This was obtained by applying the following conditions to each channel:

[0061]

[0062] in It is the outline of the exponential type angle. It is the value of the channel cross section along coordinate x. It is the exponential type angle parameter, and L is the length of the i-th channel. For the case where all channels have the same path length, L = 34.2 mm. Figures 11 to 12 The configuration shown has improved directivity, and the optimized path length of the channel is, for example: 34.0 mm 34.9 mm 36.3 mm 38.1 mm.

[0063] The comparison of the above axial and non-axial SPL frequency responses shows that, for Figures 11 to 12 The model shown, with unequal channel path lengths and convex wavefronts, exhibits a significant improvement in directivity response at high frequencies. This approach does not meet the general requirement of maintaining equal channel path lengths. Although the improved directivity response leads to a slight increase in irregularity in the SPL frequency response, this irregularity can be balanced using a simple FIR filter while still maintaining improved directivity.

[0064] Therefore, now refer to Figures 13 to 20 The diagram shows a phase plug 100 for the compression driver 200 and the horn driver 300, which has unequal channel path lengths for forming a convex wavefront, such as... Figures 11 to 12 The FEA model is shown.

[0065] First refer to Figures 13 to 14 and Figures 19 to 20 The image shows a cross-sectional view of the phase plug 100. In one or more embodiments, the phase plug 100 is configured to have a diaphragm 202 (such as a dome diaphragm, see below). Figures 19 to 20The compression driver 200 includes a body 102 having an inlet side 104 facing the diaphragm 202 and a front surface 106 that may be generally convex to conform to the contour of the generally concave surface 204 of the diaphragm 202. The phase plug 100 also includes an outlet side 108, the rear surface 110 of which may be generally flat in one or more embodiments.

[0066] While the dome-shaped diaphragm 202 has been shown and described, it should be understood that the geometry of the phase plug 100 can be customized for virtually any diaphragm, and the phase plug 100 can be acoustically coupled to said diaphragm. For example, the geometry of the phase plug 100 can be customized for diaphragms having convex, concave, parabolic, spherical (e.g., hemispherical), conical, planar, polygonal, and other geometries.

[0067] like Figures 13 to 15 and 19 to Figure 20 As shown, the body 102 of the phase plug 100 may include a front portion 112, a middle portion 114, and a rear portion 116 formed around a central axis 118. The front portion 112 includes a front surface 106 and is generally shaped to match the shape of the diaphragm to which it is to be placed. In embodiments disclosed herein, the front portion 112 is generally convex, wherein the outer periphery 120 of the front portion 112 may include a chamfer 122. The middle portion 114 is formed adjacent to the front portion 112, and in one or more embodiments, its diameter decreases linearly tapering as the central axis 118 is laterally moved away from the front portion 112. The middle portion 114 begins at the chamfer 122 such that the middle portion 114 is disposed radially inward from the front portion 112, wherein the front portion 112 partially overhangs the middle portion 114. The rear portion 116 is formed adjacent to the middle portion 114 and may be generally cylindrical, wherein the rear portion 116 includes a rear surface 110. However, it should be understood that the phase plug 100 is not limited to this configuration, and modifications to the dimensions and proportions of the front portion 112, the middle portion 114, and the rear portion 116 of the phase plug 100 as described herein are entirely conceivable.

[0068] The phase plug 100 can be formed in various suitable ways, including forming the phase plug 100 as a single body 102, or alternatively, wherein two or more portions 112, 114, 116 of the phase plug 100 are formed separately and then subsequently joined together to form the body 102. In one or more embodiments, the phase plug 100 can be made of a plastic material.

[0069] Figures 15 to 16 The inlet side 104 and front surface 106 of a phase plug 100 according to one or more embodiments are shown, and Figures 17 to 18The exit side 108 and rear surface 110 of a phase plug 100 according to one or more embodiments are shown. In the embodiment shown herein, the phase plug 100 includes five solid segments 124 that are at least substantially concentrically aligned with each other relative to a central axis 118 extending from the inlet side 104 to the outlet side 108. The segments 124 collectively form the front surface 106 and rear surface 110 of the phase plug 100. Extending radially outward from the central axis 118, the segments 124 may include a central segment 124a, a first inner segment 124b, a second inner segment 124c, a third inner segment 124d, and an outer segment 124e, wherein the height of the segments 124 relative to the central axis 118 decreases smoothly and gradually from the central segment 124a to the outer segment 124e. The outer segment 124e defines the overall outer periphery and surface of the body 102 of the phase plug 100. It should be understood that the number of segments 124 depicted herein is merely exemplary and not intended to be limiting.

[0070] In one or more embodiments, segment 124 is symmetrical about central axis 118. In other words, segment 124 is symmetrical about the entire diameter of phase plug 100 along any radial axis perpendicular to and intersecting central axis 118. Except for the central segment 124a, which may have a generally circular cross-section, the other segments 124 may have generally annular cross-sections. However, the geometry (e.g., shape, width, spacing, etc.) of segment 124 along rear surface 110 may differ from its geometry at front surface 106. Thus, as phase plug 100 moves laterally along central axis 118 from front surface 106 to rear surface 110, the geometry of segment 124 can transition from a first geometry to a second geometry.

[0071] like Figures 13 to 18 As best shown, adjacent segments 124a-124b, 124b-124c, 124c-124d, and 124d-124e are separated by channels 126 through which acoustic signals (sound waves) can propagate. Channel 126 may be generally annular and extends through the body 102 from the front surface 106 to the rear surface 110, spanning the length of the phase plug 100 (e.g., measured along the central axis 118). Each channel 126 has an inlet 128 at the front surface 106 (inlet side 104) of the phase plug 100 and an outlet 130 at the rear surface 110 (outlet side 108).

[0072] In the illustrated embodiment, four channels 126 may be provided: a first inner channel 126a, a second inner channel 126b, a third inner channel 126c, and an outer channel 126d. In one or more embodiments, the channel inlets 128 may be evenly distributed on the front surface 106 of the phase plug 100, wherein the inlets 128 form concentric circles. In other embodiments, the spatial distribution of the channel inlets 128 on the front surface 106 may be asymmetrical. In one or more embodiments, the channel outlets 130 are generally circular along the rear surface 110 of the phase plug 100, again forming concentric circles. As with segment 124, the number of channels 126 shown is merely exemplary and not intended to be limiting. Figures 17 to 18 As shown, one or more bridging members 132 that extend at least partially radially across the channel 126 can be provided as spacer supports for the section 124.

[0073] like Figures 13 to 14 As shown, according to one or more embodiments, channels 126 have unequal path lengths. Path length can be defined as the length of a particular channel 126 from its inlet 128 to its outlet 130, or the distance an acoustic signal (sound wave) travels along the channel 126 from its inlet 128 to its outlet 130. In one or more embodiments, the path length increases from the first inner channel 126a to the second inner channel 126b, to the third inner channel 126c, and to the outer channel 126d. Compared to the first inner channel 126a, these unequal path lengths result in a gradual delay in the acoustic signal reaching the channel outlet 130 of the second inner channel 126b, the third inner channel 126c, and the outer channel 126d, wherein the delay in the outer channel 126d is greater than the delay in the third inner channel 126c, and the delay in the third inner channel 126c is greater than the delay in the second inner channel 126b. The unequal path lengths and the gradual delay of the acoustic signal reaching the channel outlet 130 create a convex wavefront at the outlet side 108 of the phase plug 100, thereby improving directivity at high frequencies, as described above. Figures 11 to 12 The explanation given.

[0074] In one or more embodiments, each channel 126 is symmetrical about the central axis 118. In other words, the channel 126 is symmetrical about the entire diameter of the body 102 of the phase plug 100 along any radial axis perpendicular to and intersecting the central axis 118. As the channel path length of each successive channel 126 further away from the central axis 118 increases, the channel geometry also becomes more circuitous and / or exhibits increased curves or curvature with respect to each successive channel 126 further away from the central axis 118. More specifically, refer to... Figures 13 to 14The tortuous geometry and / or curvature of channel 126 increases from the first inner channel 126a to the second inner channel 126b, to the third inner channel 126c, and to the outer channel 126d. In one or more embodiments, for any given channel 126, the portion of channel 126 with the greatest curvature is located within the front portion 112 of the body 102 of the phase plug 100.

[0075] refer to Figures 13 to 14 and Figure 16 In one or more embodiments, the cross-sectional areas of the channel inlets 128 may be approximately equal to each other. However, as Figures 13 to 14 As shown, in a non-limiting embodiment, the cross-sectional area of ​​the channel outlet 130 can decrease from the first inner channel 126a to the outer channel 126d, but other configurations are conceivable. Due to the tortuous nature of each channel 126, the outlet 130 of each channel 126 can be closer to the central axis 118 than the inlet 128 of each channel 126. Typically, the cross-sectional area of ​​each channel 126 increases from its inlet 128 to its outlet 130, such that the sum of the cross-sectional areas of the channel outlets 130 can approximate the area of ​​the inlet of the connected waveguide or horn 302, as described below. The number of channels 126 can be selected based on the number of resonant modes of the compression cavity within the audio frequency range, and the inlet 128 of the channel 126 can be located on the inlet side 104, corresponding to the node of the highest-order resonance of the compression cavity within the audio frequency range.

[0076] Figure 19 It is a cross-sectional view of a horn driver 300 including a compression driver 200 according to one or more embodiments, and Figure 20 This is an exploded view of a compression driver 200 according to one or more embodiments. As shown, the compression driver 200 includes a motor assembly 206 disposed around a central axis 118, a diaphragm 202 operatively connected to the motor assembly 206 along the central axis 118, and a compression cavity (not shown) disposed between a phase plug 100 and the diaphragm 202. A voice coil 208 is mechanically connected to the diaphragm 202 such that induced motion in the voice coil 208 can be transmitted to the diaphragm 202, thereby generating an acoustic signal (sound wave). These acoustic signals are then guided via the compression cavity to a channel 126 of the phase plug 100, propagating from the channel inlet 128 to the channel outlet 130 to form a convex wavefront at the outlet side 108 of the phase plug 100.

[0077] In the illustrated embodiment, the motor assembly 206 may include an annular magnet 210 disposed between a top plate 212 and a pole piece 214 located at the front side 216 of the compression driver 200. Figure 19As shown, in one or more embodiments, the phase plug 100 may be mounted to the pole piece 214, wherein the pole piece 214 may have a configuration complementary to the body 102 for receiving the body 102 therein. The voice coil 208 may be made of copper, aluminum, or other conductive materials or combinations thereof, and the magnet 210 may be a permanent magnet made of a hard ferromagnetic material, including but not limited to ferrite, neodymium alloy, AlNiCo alloy, or alloys thereof. It should be understood that the configurations of the compression driver 200 shown and described herein are provided as examples only and are not intended to be limiting.

[0078] The horn driver 300 includes a horn 302 having an enlarged cross-sectional area that flares outward in at least one dimension from a throat 304 to an opening 306, although other horn types are also conceivable. The throat 304 may be positioned close to the exit side 108 of the phase plug 100, allowing acoustic signals exiting the phase plug 100 to enter the throat 304, propagate through the horn 302, and exit through the opening 306. The horn driver 300 may include a rear housing 308 that at least partially surrounds the compression driver 200 and provides a stable mounting structure to which the components of the compression driver 200 can be secured.

[0079] In the horn driver 300, an acoustic signal is directed to the horn 302 through the acoustic channel 126 of the phase plug 100. Along its unequal path length, the total cross-sectional area of ​​the channel 126 gradually increases toward the channel outlet 130 at the outlet side 108 of the phase plug 100, at least approximately matching the area of ​​the horn inlet (e.g., throat 304).

[0080] The phase plug 100 disclosed herein can be used in the compression driver 200 and the horn driver 300 to alleviate the problems inherent in previous phase plug designs with equal channel path lengths as described above. The unequal path lengths of the channels 126 and the resulting convex wavefront exiting from the exit side 108 of the phase plug 100 and entering the horn 302 provide better directivity at high frequencies.

[0081] It should be understood that various modifications can be made to the configuration of the phase plug 100 disclosed herein, such as, but not limited to, the dimensions (e.g., width, height, length), relative positions, and curvatures of the multiple channels 126. Variations of the channel pattern and the number of channels 126 disclosed herein are also fully contemplated, as are scaling and modifications of the phase plug 100, such as depending on the specific compression driver 200 and horn driver 300 to which it is coupled.

[0082] While exemplary embodiments have been described above, they are not intended to describe all possible forms of the invention. Rather, the terms used in this specification are descriptive rather than restrictive, and it should be understood that various changes may be made without departing from the spirit and scope of the invention. Furthermore, features of various embodiments can be combined to form further embodiments of the invention.

Claims

1. A phase plug for a compression driver, the phase plug comprising: The main body includes an inlet side with a front surface and an outlet side with a rear surface, and the main body is arranged around a central axis; as well as Multiple channels are formed through the body from the inlet side to the outlet side. Each of the multiple channels has an annular configuration with an inlet at the front surface, an outlet at the rear surface, and a path length between the inlet and the outlet. The multiple channels have unequal path lengths, such that acoustic signals propagating through the multiple channels form a convex wavefront at the outlet side of the phase plug.

2. The phase plug of claim 1, wherein one or more of the plurality of channels are circuitous and include a curved configuration between the inlet and the outlet.

3. The phase plug of claim 1, wherein for each of the plurality of channels, the radial distance from the inlet to the outlet to the central axis is varied.

4. The phase plug according to claim 1, wherein the path length of the plurality of channels increases from the first inner channel closest to the central axis to the outer channel furthest from the central axis.

5. The phase plug of claim 1, wherein each of the plurality of channels is symmetrical about the central axis.

6. The phase plug of claim 1, wherein the inlets of the plurality of channels are formed in concentric circles around the central axis on the front surface, and the outlets of the plurality of channels are formed in concentric circles around the central axis on the rear surface.

7. The phase plug of claim 1, wherein for each of the plurality of channels, the area of ​​the inlet is smaller than the area of ​​the outlet, such that the cross-sectional area of ​​each channel increases from the inlet to the outlet.

8. The phase plug according to claim 1, wherein the front surface is convex.

9. The phase plug of claim 1, wherein the rear surface is substantially flat.

10. The phase plug of claim 1, wherein the body comprises a front portion including the front surface, an intermediate portion adjacent to the front portion, and a rear portion adjacent to the intermediate portion and including the rear surface, the front surface including a chamfer to overhang the intermediate portion, the diameter of the intermediate portion decreasing linearly tapered from the front portion to the rear portion, and the rear portion being generally cylindrical.

11. A compression drive, comprising: A motor assembly, wherein the motor assembly is arranged around a central axis; A diaphragm, operably connected to the motor assembly along the central axis and having a concave surface; as well as A phase plug is mounted to the motor assembly adjacent to the diaphragm along the central axis. The phase plug has a body with an inlet side and an outlet side. The inlet side has a convex front surface oriented toward the concave surface of the diaphragm, and the outlet side has a generally flat rear surface. The phase plug has a plurality of annular channels formed through the body from the inlet side to the outlet side. Acoustic signals generated by the diaphragm propagate through the plurality of annular channels. Each of the plurality of annular channels has an inlet at the front surface, an outlet at the rear surface, and a path length between the inlet and the outlet. The plurality of annular channels have unequal path lengths, such that the acoustic signal forms a convex wavefront at the outlet side of the phase plug.

12. The compression drive of claim 11, wherein one or more of the plurality of annular channels are circuitous and include a curved configuration between the inlet and the outlet.

13. The compression driver of claim 11, wherein for each of the plurality of channels, the radial distance from the inlet to the outlet to the central axis is varied.

14. The compression driver of claim 11, wherein the path length of the plurality of annular channels increases from the first inner channel closest to the central axis to the outer channel furthest from the central axis.

15. The compression driver of claim 11, wherein each of the plurality of channels is symmetrical about the central axis.

16. The compression driver of claim 11, wherein the inlets of the plurality of channels are formed in concentric circles around the central axis on the front surface, and the outlets of the plurality of channels are formed in concentric circles around the central axis on the rear surface.

17. The compression driver of claim 11, wherein for each of the plurality of annular channels, the area of ​​the inlet is smaller than the area of ​​the outlet, such that the cross-sectional area of ​​each annular channel increases from the inlet to the outlet.

18. The compression drive of claim 11, wherein the motor assembly includes an annular magnet disposed between a top plate and a pole piece located on the front side of the compression drive.

19. The compression actuator of claim 11, wherein the body comprises a front portion including the front surface, an intermediate portion adjacent to the front portion, and a rear portion adjacent to the intermediate portion and including the rear surface, the front surface including a chamfer to overhang the intermediate portion, the diameter of the intermediate portion decreasing linearly tapered from the front portion to the rear portion, and the rear portion being generally cylindrical.

20. A horn driver comprising: A compression driver, the compression driver comprising: A motor assembly, wherein the motor assembly is arranged around a central axis; A dome-shaped diaphragm, operably connected to the motor assembly along the central axis and having a concave surface; and A phase plug, mounted adjacent to the diaphragm along the central axis to the motor assembly, the phase plug having a body having an inlet side and an outlet side, the inlet side having a convex front surface oriented toward the concave surface of the dome-shaped diaphragm, and the outlet side having a generally flat rear surface, the phase plug having a plurality of annular channels formed through the body from the inlet side to the outlet side, through which an acoustic signal generated by the dome-shaped diaphragm propagates, each of the plurality of annular channels having an inlet at the front surface, an outlet at the rear surface, and a path length between the inlet and the outlet, the plurality of annular channels having unequal path lengths such that the acoustic signal forms a convex wavefront at the outlet side of the phase plug; and A horn, which is mounted to the compression driver adjacent to the outlet side of the phase plug.

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