Loudspeaker with phase plug

Abstract

The loudspeaker (100) comprises: a magnetic assembly (1) defining a gap (T); a basket (4) containing the magnetic assembly (1); an audio coil (2) positioned in the gap (T); a cylindrical support (20) supporting the audio coil (2); and a diaphragm (3) connected to the cylindrical support (20) of the audio coil; the diaphragm (3) is annular and has an outer edge (35) connected to the basket (4) and an inner edge (36) around a central hole (30), and is connected to the central support (6); the diaphragm (3) has a concave annular channel (31) when viewed from above; the loudspeaker (100) also comprises an annular phase plug (9) positioned in the annular channel (31) of the diaphragm so as not to interfere with the movement of the diaphragm (3).

Description

Technical Field

[0001] The present invention relates to a loudspeaker with an acoustic type phase plug, and particularly to a loudspeaker with an annular diaphragm for high-frequency applications such as tweeters.

Background Art

[0002] U.S. Patent No. 1,690,840, U.S. Patent No. 2,058,208, British Patent No. 619,882, Japanese Patent Publication No. 57053198, Austrian Patent No. 382,281, and British Patent No. 2,099,659 disclose loudspeakers with annular diaphragms. Specifically, U.S. Patent No. 1,690,840 discloses a first annular diaphragm having a flat shape and a linear V-shaped shape. British Patent No. 619,882 is one of the initial documents that discloses an annular diaphragm with a curved V-shaped shape. On the other hand, Japanese Patent Publication No. 57053198 discloses different solutions for both linear and curved V-shaped shapes. British Patent No. 2,099,659 discloses the construction direction of the V-shaped shape. Furthermore, U.S. Patent No. 2,058,208 discloses the first curved annular diaphragm. Finally, Austrian Patent No. 382,281 discloses different solutions for the radial portion of the curved diaphragm.

[0003] A direct-radiating loudspeaker provided with an annular diaphragm (i.e., a diaphragm open at the center) is impaired in its function due to a decrease in effectiveness at high frequencies composed of 18 to 20 kHz. In order to solve such drawbacks, it is known to use a central phase plug disposed at the center of the annular diaphragm, i.e., a central phase plug disposed in the open portion of the annular diaphragm.

[0004] U.S. Patent No. 6,320,972, European Patent No. 1,351,546, Japanese Unexamined Patent Publication No. 2007325075, British Patent No. 2388488, and U.S. Patent No. 9,560,452 disclose loudspeakers with an annular diaphragm having a substantially conical central phase plug.

[0005] However, such prior art loudspeakers are hampered by several drawbacks. The central phase plug protrudes from the diaphragm; therefore, the loudspeaker has a large axial thickness.

[0006] Therefore, such loudspeakers cannot be used in automotive applications. In automotive applications, loudspeakers must be thin in order to be integrated into the vehicle body.

[0007] As shown in Figure 3 of U.S. Patent No. 6,320,972, the center phase plug increases the sound pressure level (SPL) only in a very narrow range of high frequencies consisting of 18–20 kHz. The center phase plug does not increase the SPL below 18 kHz or above 20 kHz.

[0008] Additionally, the central phase plug offers only limited advantages in terms of the transfer function for fundamental components measured off-axis. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] U.S. Patent No. 1690840 [Patent Document 2] U.S. Patent No. 2058208 [Patent Document 3] British Patent No. 619882 [Patent Document 4] Japanese Patent No. 57053198 [Patent Document 5] Austrian Patent No. 382281 [Patent Document 6] British Patent No. 2099659 [Patent Document 7] U.S. Patent No. 6320972 [Patent Document 8] European Patent No. 1351546 [Patent Document 9] Japanese Patent Publication No. 2007325075 [Patent Document 10] British Patent No. 2388488 [Patent Document 11] U.S. Patent No. 9560452 [Overview of the Initiative] [Problems that the invention aims to solve]

[0010] The object of the present invention is to eliminate the drawbacks of the prior art by providing a loudspeaker with a phase plug that is compact and, at the same time, can increase the SPL over a wider frequency range than prior art loudspeakers, both in-axis and out-axis relative to the loudspeaker.

[0011] Another objective is to provide a loudspeaker with a phase plug that is effective at high frequencies and minimizes harmonic distortion. [Means for solving the problem]

[0012] These objectives are achieved by the present invention with the characteristics of the attached independent claim 1.

[0013] Advantageous embodiments of the present invention will become apparent from the dependent claims.

[0014] Further features of the present invention will become more apparent from the following detailed description, which refers to embodiments as merely examples and therefore not limiting, as shown in the accompanying figures. [Brief explanation of the drawing]

[0015] [Figure 1] Axial perspective view of a loudspeaker with a curved V-shaped annular diaphragm provided with a phase plug according to the present invention. [Figure 2] Axial exploded perspective view of the loudspeaker in FIG. 1. [Figure 3] Schematic view of a linear V-shaped annular diaphragm together with a phase plug according to the present invention. [Figure 3A] Axial schematic view along the plane A-A of FIG. 3. [Figure 3B] Detailed view of the portion surrounded by the circle B in FIG. 3A. [Figure 4] Graph showing the axial frequency response (SPL as a function of frequency) of the loudspeaker in FIG. 1 and the same loudspeaker provided with the linear V-shaped annular diaphragm shown in FIG. 3, using multi-physics finite element analysis (FEA) simulation. [Figure 5] Graph showing the axial frequency response (SPL as a function of frequency) of a loudspeaker without a phase plug and a loudspeaker with a phase plug according to the present invention, using FEA simulation. [Figure 6] Graph showing the frequency response (SPL as a function of frequency) of a loudspeaker without a phase plug and a loudspeaker with a phase plug according to the present invention, using FEA simulation, in the case of a microphone placed off-axis at an angle of 30° with respect to the axis of the loudspeaker. [Figure 7] Graph showing the axial frequency response (SPL as a function of frequency) of a loudspeaker without a phase plug (dashed line) and a loudspeaker with a phase plug according to the present invention (solid line), using experimental tests. [Figure 8]This figure shows the total harmonic distortion (THD) at on-axis frequency (THD percentage as a function of frequency) for a loudspeaker, related to the graph in Figure 7, using experimental tests. [Figure 9] This graph shows the frequency response (SPL as a function of frequency) of a loudspeaker (SPL as a function of frequency) for a loudspeaker without a phase plug (dashed line) and for a loudspeaker with a phase plug according to the present invention (solid line), using experimental tests with a microphone positioned off-axis and tilted 30° relative to the loudspeaker axis. [Figure 10] This graph, using experimental testing, shows the THD percentage as a function of frequency, related to the graph in Figure 9. [Modes for carrying out the invention]

[0016] A loudspeaker according to the present invention will be described with reference to the drawings, which are shown in their entirety in reference no. 100.

[0017] The loudspeaker (100) comprises a magnetic assembly (1). The magnetic assembly (1) comprises a magnet (10) positioned between a lower electrode plate (11) and an upper electrode plate (12). The lower electrode plate (11) has a cup shape (U-shaped axial cross-section) with cylindrical side walls (13). The magnet (10) and the upper electrode plate (12) are disc-shaped and are housed in the lower electrode plate (11) with a gap, leaving an annular gap (T) between the outer surface (13) of the lower electrode plate and the upper electrode plate (12) superimposed on the magnet (10).

[0018] The audio coil (2) is wound around a cylindrical support (20) which is made entirely of a metallic material such as aluminum or titanium, or a plastic material such as polyimide (PI) or fiberglass. The audio coil (2) is positioned within the air gap (T) so that it can move within the air gap (T).

[0019] The cylindrical support portion (20) is connected to the diaphragm (3) so as to protrude downward from the diaphragm (3). The diaphragm (3) is an annular diaphragm. That is, the diaphragm (3) is open in the center and has a central hole (30). Thus, the diaphragm (3) has an outer edge portion (35) and an inner edge portion (36) around the central hole (30).

[0020] The diaphragm (3) is very thin and durable, and is made of aluminum foil, processed silk or other woven fabric, or plastic film.

[0021] Referring to the figure, when viewed from above, the diaphragm (3) has a concave ring shape, which means that the diaphragm has an annular channel (31) having a bottom (32), a first wall (33) extending from the bottom (32) to the inner edge (36) around the central hole (30), and a second wall (34) extending from the bottom (32) to the outer edge (35).

[0022] In Figures 1 and 2, when viewed from above, the first wall (33) and the second wall (34) of the diaphragm have a curved convex shape. In addition, the first wall (33) and the second wall (34) have different lengths.

[0023] Referring to Figures 3A and 3B, when viewed in an axial cross-section, the annular channel (31) has a shape that can be substantially represented as a V-shape (hence the term "V-type") with its vertex separated at the bottom (32) of the channel, that is, as a triangle with low angles (α1, α2) of 30 to 50°, preferably 35 to 45°. An angle (γ) of 80 to 100°, preferably 93°, is provided between the first wall (33) and the second wall (34).

[0024] The annular channel (31) has a depth (H) equal to the height of the triangle formed in the cross-section of the annular channel. Figures 3A and 3B show a diaphragm with an isosceles triangle shape, but this triangle does not have to be isosceles, the sides of the triangle may be of different lengths, and it may be curved rather than straight.

[0025] The cylindrical support portion (20) of the audio coil has an upper edge portion (21) that is attached to the bottom portion (32) of the annular channel in the diaphragm (3). In this way, the cylindrical support portion (20) of the audio coil is positioned axially with respect to the diaphragm (3).

[0026] The magnetic assembly (1) is placed in a basket (4) which is shaped like a cup with an open top. The basket (4) has an upper rim (40). The upper ring (5), which is an integrated part with the basket, is attached to the upper rim (40) of the basket.

[0027] The central support (6) is attached to the upper electrode plate (12) and protrudes upward and axially from the upper electrode plate. The central support (6) has a conical shape with its tip cut off. The tongue (60) protrudes downward from the central support and is coaxially engaged with the hole (15) in the upper electrode plate (12).

[0028] The central support (6) is made of a plastic material such as polycarbonate, and in some cases acrylonitrile butadiene styrene (ABS) is added.

[0029] The peripheral portion (7) connects the upper ring (5) of the basket to the outer edge (35) of the diaphragm. When viewed from above, the peripheral portion (7) is convex and ring-shaped.

[0030] The central edge (8) connects the central support (6) to the inner edge (36) of the diaphragm around the central hole (30) of the diaphragm. When viewed from above, the central edge (8) is convex and ring-shaped.

[0031] In this way, the diaphragm (3) vibrates due to the axial movement of the sound coil (2) in the air gap, thereby causing the loudspeaker to generate sound.

[0032] The central support (6) and basket (4) are intended to support the diaphragm (3). The shape and volume of the central support (6) and basket (4) affect the volume of the total harmonic chamber beneath the diaphragm (3), and therefore also affect the frequency response of the loudspeaker.

[0033] The loudspeaker (100) is equipped with a ring-shaped phase plug (9). The phase plug (9) is positioned in the annular channel (31) of the diaphragm so as not to interfere with the movement of the diaphragm (3). The function of the phase plug (9) is to compress and adjust the sound waves generated by the vibration of the diaphragm (3) in order to achieve better performance in terms of SPL at high frequencies.

[0034] The phase plug (9) is made of plastic material such as polycarbonate or polycarbonate with added ABS.

[0035] The phase plug (9) is supported by a number of brackets (50) connected to the upper ring (5) of the basket.

[0036] Each bracket (50) is in the shape of a curved rigid element and protrudes radially inward from the upper ring (5) of the basket.

[0037] The basket (4), upper ring (5), and bracket (50) may be made of plastic for economic convenience. However, to facilitate the dissipation of heat generated by the magnetic assembly (1), the basket (4), and optionally the upper ring (5) and bracket (50), may be made of a thermally conductive material such as aluminum. In this case, it is possible to achieve a higher dispersion of heat generated by the sound coil (2), which is mainly propagated by conduction through the magnetic assembly (1), reducing overheating of the loudspeaker and obtaining a higher average power of the loudspeaker.

[0038] Referring to Figure 3A, the thickness (h) of the phase plug (9) is less than the depth (H) of the annular channel (31) in the diaphragm. Therefore, the phase plug (9) does not occupy any space above the diaphragm (3) and thus does not increase the axial thickness of the loudspeaker. For example, the thickness (h) of the phase plug can be approximately 0.6 to 0.8 of the channel depth (H) in the diaphragm; therefore, the difference between the channel depth (H) in the diaphragm and the thickness of the phase plug can be in the range of 0.5 to 1.2 cm.

[0039] When viewed in an axial cross-section, the phase plug (9) has a schematic triangular shape with a base (90) and two sides (91, 92). As shown in Figures 1 and 2, if the diaphragm has curved walls, the sides (91, 92) of the phase plug will be curved like the walls (33, 34) of the diaphragm and will not be straight.

[0040] Referring to Figure 3B, the base angles (β1, β2) of the triangle formed in the cross-section of the phase plug are 20-30%, preferably 25%, larger than the base angles (β1, β2) of the triangle formed by the cross-section of the annular channel (31) in the diaphragm, and the triangle defined by the first wall (33) and the second wall (34) of the diaphragm. Therefore, the base angles (β1, β2) of the triangle in the cross-section of the phase plug are 40-60°, preferably 45-55°, relative to the base angles (β1, β2) of the annular channel (31) in the diaphragm, which are 30-50°, preferably 35-45°. The base (90) of the phase plug is positioned at the base of the triangle formed by the cross-section of the annular channel (31) in the diaphragm. The basket bracket (50) is connected to the base (90) of the phase plug.

[0041] The sides (91, 92) of the phase plug are inclined with respect to the first wall (33) and the second wall (34) of the diaphragm by angles (β1, β2) set at 7 to 15°, preferably 11°.

[0042] The inclination of the sides (91, 92) of the phase plug relative to the diaphragm walls (33, 34) is made to form a sequence with hyperbolic extension.

[0043] Figure 4 shows the results of an FEA simulation regarding the difference between the frequency response of a loudspeaker with a straight V-shaped annular diaphragm (dashed line) and the frequency response of a loudspeaker with a curved V-shaped annular diaphragm (solid line).

[0044] Figure 5 shows the results of FEA simulations for the frequency response of a loudspeaker with an annular diaphragm without a phase plug and a loudspeaker with an annular diaphragm with a phase plug. The dashed line shows the SPL as a function of frequency for the loudspeaker without a phase plug. The solid line shows the SPL as a function of frequency for the same loudspeaker with a phase plug according to the present invention.

[0045] As clearly shown in the graph in Figure 5, in the frequency range of 7-20 kHz, a loudspeaker with a phase plug has a better frequency response (as SPL) than a loudspeaker without a phase plug.

[0046] Figure 6 shows the results of FEA simulations performed on a loudspeaker with an annular diaphragm without a phase plug and a loudspeaker with an annular diaphragm with a phase plug. This test was conducted by placing a microphone on an axis tilted at 30° with respect to the loudspeaker axis, and the SPL was measured in decibels detected by the microphone. The dashed line shows the measured SPL as a function of frequency for the loudspeaker without a phase plug. The solid line shows the measured SPL as a function of frequency for the same loudspeaker with a phase plug according to the present invention.

[0047] As clearly shown in the graphs in Figures 7 and 9, experimental tests conducted on samples constructed based on FEA studies confirmed the results in Figures 5 and 6 obtained from FEA simulations. Additionally, the solid lines in the graphs in Figures 8 and 10 indicate that the annular phase plug did not increase the THD level, but rather significantly increased the SPL.

[0048] Therefore, the loudspeaker with an annular phase plug according to the present invention has a better frequency response in the frequency range of 7 to 20 kHz, that is, in a significantly wider frequency range than the 18 to 20 kHz obtained using the prior art loudspeaker equipped with a central phase plug.

[0049] Equivalent modifications can be made to embodiments of the present invention by those skilled in the art without departing from the scope of the present invention as specified in the attached "Claims".

Claims

1. A loudspeaker (100), A magnetic assembly (1) defining the air gap (T), A basket (4) containing the magnetic assembly (1), A sound coil (2) is placed in the aforementioned gap (T). A cylindrical support portion (20) that supports the aforementioned sound coil (2), A diaphragm (3) connected to the cylindrical support portion (20) of the sound coil, having an annular outer edge portion (35) connected to the basket (4), and an inner edge portion (36) around a central hole (30) connected to a central support portion (6) located in the magnetic assembly (1), Equipped with, The diaphragm (3) has a concave annular channel (31) when viewed from above. The loudspeaker (100) includes a ring-shaped phase plug (9) positioned in the annular channel (31) of the diaphragm (3) so as not to interfere with the movement of the diaphragm (3). Loudspeaker (100).

2. The loudspeaker (100) according to claim 1, wherein the phase plug (9) has a thickness (h) smaller than the depth (H) of the annular channel (31) in the diaphragm, so that the phase plug (9) does not occupy any space above the diaphragm (3).

3. The loudspeaker (100) according to claim 2, wherein the difference between the height (H) of the annular channel (31) in the diaphragm and the pressure (h) of the phase plug is 0.5 to 1.2 cm.

4. The loudspeaker (100) according to any one of claims 1 to 3, wherein the annular channel (31) of the diaphragm comprises a bottom (32), a first wall (33) extending from the bottom (32) to the inner edge (36) around the central hole (30), and a second wall (34) extending from the bottom (32) to the outer edge (35), and the cylindrical support portion (20) of the sound coil is mounted on the bottom (32) of the annular channel in the diaphragm so as to protrude downward and axially from the diaphragm.

5. The loudspeaker (100) according to claim 4, wherein the annular channel (31) of the diaphragm has a substantially V-shaped axial cross-section, with the apex being cut off at the bottom (32) of the channel.

6. The loudspeaker (100) according to claim 5, wherein the annular channel (31) of the diaphragm has a triangular axial cross-section and has triangular base angles (α1, α2) of 30 to 50°.

7. The loudspeaker (100) according to claim 6, wherein the phase plug (9) has a substantially triangular axial cross-section.

8. The loudspeaker (100) according to claim 7, wherein the phase plug (9) has an upward-facing base (90) and two side edges (91, 92) that converge downwards.

9. The loudspeaker (100) according to claim 8, wherein the base angles (β1, β2) of the triangle formed in the cross-section of the phase plug are 20 to 30% smaller than the respective base angles (α1, α2) of the triangle formed in the cross-section of the annular channel (31) in the diaphragm and defined by the first wall (33) and the second wall (34).

10. The loudspeaker (100) according to claim 9, wherein the sides (91, 92) of the phase plug are inclined with respect to the first wall (33) and the second wall (34) of the diaphragm, respectively, and the inclination of the sides (91, 92) of the phase plug with respect to the walls (33, 34) of the diaphragm is such that it forms a sequence with hyperbolic expansion.

11. The loudspeaker (100) according to any one of claims 1 to 10, wherein the phase plug (9) is supported by a plurality of brackets (50) connected to the upper ring (5) of the basket.

12. The loudspeaker (100) according to claim 11, wherein each bracket (50) is in the form of a curved rigid element that protrudes radially inward from the upper ring (5) of the basket.

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