Speaker unit

Abstract

A loudspeaker unit (1) has a loudspeaker frame (9) and two membranes (7, 8) arranged within the loudspeaker frame (9). The first membrane (7) radiates in a primary sound radiation direction (A) substantially perpendicular to a main plane (9a) of the loudspeaker unit (1). The second membrane (8) has a secondary sound radiation direction (B) different from the primary sound radiation direction (A). Two drive units (2) are located within the loudspeaker frame (9), attached to the two membranes (7, 8), and positioned coaxially to each other at the same height in the loudspeaker frame (9). An acoustic tube (6) provides a closed sound channel from the second membrane (8) along the secondary sound radiation direction (B) to a secondary surface (6a) of the loudspeaker unit (1), which secondary surface (6a) is in the same plane as the main plane (9a) of the loudspeaker unit (1).

Description

TECHNICAL FIELD

[0001] The present invention relates to a loudspeaker unit comprising a loudspeaker frame, two membranes arranged in the loudspeaker frame, a first membrane of the two membranes having a primary sound radiation direction substantially perpendicular to a main plane of the loudspeaker unit, and a second membrane of the two membranes having a secondary sound radiation direction different from the primary sound radiation direction, and two drive units located within the loudspeaker frame and attached to the first and second membranes, respectively. BACKGROUND

[0002] US patent publication US2010 / 0232637 discloses a loudspeaker apparatus having two opposing loudspeakers located in a loudspeaker cabinet, wherein the two loudspeakers are mechanically coupled and the loudspeaker cabinet is provided with an open portion.

[0003] US patent publication US2007 / 0154044 discloses a loudspeaker system having a plurality of spherical enclosures, each spherical enclosure housing a pair of (opposing) transducers.

[0004] US patent publication US2012 / 237077 discloses a opposed dual-vented bass loudspeaker system. A vented loudspeaker driver assembly is described that utilizes a loudspeaker driver having a pole piece that defines a vent hole therein that is not covered by a dust cap. The frame of the loudspeaker driver is configured to mount to a surface of a structure such that the pole piece of the driver is located within an interior space of the structure. The vented loudspeaker driver is configured for a back-to-back vented driver assembly in which sound from more than one loudspeaker driver is achieved within the footprint of only one driver and physical vibrations from the assembly are minimized.

[0005] US patent publication US5,821,471 discloses a loudspeaker enclosure having various configurations, e.g. for directing sound in the enclosure rearwardly to a front side of the loudspeaker.

[0006] International patent publication WO2019 / 086357 discloses a loudspeaker unit having two opposing moving membranes.

[0007] International patent publication WO02 / 052892 discloses a loudspeaker unit having a drive unit provided with an air channel. SUMMARY

[0008] The present invention aims to provide a loudspeaker unit having improved performance in terms of spatial efficiency, power and freedom of air displacement directionality compared to existing loudspeaker units. In another set of embodiments, the loudspeaker unit further provides improved cooling of electronic components of the loudspeaker unit.

[0009] According to the invention, there is provided a loudspeaker unit as defined above, wherein the first and second membranes are arranged in an opposite configuration in the loudspeaker frame, and the secondary sound radiation direction is opposite to the primary sound radiation direction, wherein the first and second membranes are coaxially aligned along the primary sound radiation direction and the opposite secondary sound radiation direction, and wherein the two drive units are positioned coaxially to each other at the same height in the loudspeaker frame and are consequently laterally displaced from the membranes in a side-by-side arrangement. The loudspeaker unit further comprises an acoustic tube providing a closed sound channel from the second membrane along the secondary sound radiation direction to a secondary surface of the loudspeaker unit, which secondary surface is located in the same plane as the main plane of the loudspeaker unit.

[0010] Embodiments of the invention have a structure and mutual element orientation that allow to provide a self-balancing, more space-saving loudspeaker unit for double membrane units with air displacement direction limitations, such as car doors, ceiling speakers, TVs or any loudspeaker with single-sided air displacement limitations. BRIEF DESCRIPTION OF DRAWINGS

[0011] The invention will be discussed in more detail below with reference to the drawings, in which:

[0012] Figure 1 is a perspective view showing a loudspeaker unit according to an embodiment of the invention;

[0013] Figure 2 shows Figure 1 a top view of the shown loudspeaker unit embodiment;

[0014] Figure 3 shows Figure 2 a cross-sectional view of the shown loudspeaker unit embodiment along line III-III;

[0015] Figure 4 is a side view showing a loudspeaker unit according to another embodiment of the invention;

[0016] Figure 5 shows Figure 4 a top view of the shown loudspeaker unit embodiment;

[0017] Figure 6 shows Figure 5 a cross-sectional view of the shown loudspeaker unit embodiment along line VI-VI. DETAILED DESCRIPTION

[0018] The present application will be explained in detail, by reference to some example embodiments illustrated in the attached drawings that are intended to illustrate, not limit, the embodiments of the present application. The scope of the present application is defined by the appended claims and their technical equivalents. Those skilled in the art will understand that features, components, elements, etc. expressly identified as being for the purpose of illustrating the present application can be replaced by technical equivalents unless otherwise stated. Moreover, separate features of different embodiments can be combined, even if not explicitly shown or described in the specification, unless such a combination is physically not possible. The present application will be discussed in more detail below with reference to some drawings. The examples and embodiments described herein are for illustration and not limitation of the present application. Those skilled in the art will be able to design alternative embodiments without departing from the scope of the claims. The reference signs in brackets in the claims should not be interpreted as limiting the scope of the claims. Items described as separate entities in the claims or specification can be implemented as a single or multiple hardware items incorporating features of the described items.

[0019] It is to be understood that the application is only limited by the appended claims and their technical equivalents. In this document and its claims, the verb "comprise" and its conjugations are used in their non-limiting sense to mean that items following the word comprise, but not to the exclusion of items not specifically mentioned. Also, the indefinite article "a" or "an" referring to an element does not exclude the possibility that more than one of the element is present, unless the context clearly requires exclusivity. Thus, the indefinite article "a" or "an" is generally used to mean "at least one" or "one or more".

[0020] In the loudspeaker unit embodiments of the present application, two examples of which are shown in Figures 1 to 6 and discussed below, there are the following main elements (with the indicated reference signs and synonyms in brackets):

[0021] 1. loudspeaker unit (speaker, horn, loudspeaker device)

[0022] 2. drive unit (driver, motor)

[0023] 3. voice coil

[0024] 4. magnet assembly (at least two magnets)

[0025] 5. membrane suspension (surround, surround roll, flexible edge)

[0026] 6. acoustic tube (membrane tube)

[0027] 7. first membrane

[0028] 8. second membrane

[0029] 9. loudspeaker frame

[0030] In general, the present invention relates to a loudspeaker unit 1 comprising a loudspeaker frame 9, (at least) two membranes 7, 8, (at least) two drive units 2, and an acoustic tube 6. The two membranes 7, 8 are arranged in the loudspeaker frame 9, a first membrane 7 of the two membranes having a primary sound radiation direction A substantially perpendicular to a main plane 9a of the loudspeaker unit 1, and a second membrane 8 of the two membranes having a secondary sound radiation direction B different from the primary sound radiation direction A. Note that the first and second membranes 7, 8 are thus moving up and down along the indicated sound radiation directions A, B, but the sound from the loudspeaker has a direction away from the membranes 7, 8. The two drive units 2 are located within the loudspeaker frame 9 and attached to the two membranes 7, 8, the two drive units 2 being positioned coaxially to each other at the same height in the loudspeaker frame 9. The acoustic tube 6 is present and provides a closed sound channel from the second membrane 8 along the secondary sound radiation direction B to a secondary surface 6a of the loudspeaker unit 1, the secondary surface 6a lying in the same plane as the main plane 9a of the loudspeaker unit 1. The acoustic tube 6 is thus arranged to redirect the sound waves from the second membrane 8 to be radiated in the same plane as the first membrane 7.

[0031] In a more specific embodiment, the two membranes 7, 8 are arranged in opposite configuration in the loudspeaker frame, and the secondary sound radiation direction B is opposite (i.e. 180°) to the primary sound radiation direction A.

[0032] Figures 1 to 3 A first exemplary embodiment of the inventive loudspeaker unit 1 is shown. Figure 1 A perspective view of the loudspeaker unit 1 is shown, Figure 2 a top view is shown, and Figure 3 a cross-sectional view of the loudspeaker unit embodiment along Figure 2 line III-III in Fig. 1. The first membrane 7 is flexibly connected to the loudspeaker frame 9 using a membrane suspension 5 (or surround, surround roll, flexible edge) at the front surface of the loudspeaker unit 1, allowing the first membrane 7 to move up and down along the primary sound radiation direction A. The second membrane 8 is likewise flexibly connected using a similar membrane suspension 5', allowing the second membrane 8 to move in the direction of the secondary sound radiation direction B.

[0033] The loudspeaker frame 9 can be arranged as a combination of a top, a bottom, and four side walls, optionally provided with apertures to reduce the overall weight of the loudspeaker unit 1, as shown in the views of Figure 1 and Figure 3 Alternatively, the loudspeaker frame 9 can be provided as a combination of a scaffolding-like element, with appropriate attachment means for the elements of the loudspeaker unit 1. The main plane 9a is indicated in Figure 1 to coincide with the front surface of the loudspeaker unit 1, i.e. in the x-y plane of the indicated three-dimensional axes x, y, z.

[0034] In this embodiment, the secondary surface 6a is adjacent to the front surface of the speaker frame 9. The acoustic energy emitted from the second membrane 8 is redirected to the secondary surface 6a, and is thus arranged adjacent to the acoustic energy emitted from the first membrane 7 in the primary acoustic radiation direction A.

[0035] In Figure 3 a cross-sectional view, another embodiment is shown, in which the acoustic tube 6 has a first portion 6b arranged at a predetermined distance from the second membrane 8 along the secondary acoustic radiation direction B, and a second portion 6c arranged at one or more sides of the speaker frame 9. In the shown embodiment, a single second portion 6c is shown, but alternatively, second portions 6c are present at two, three, or even all four sides of the speaker frame 9. These chimney-like embodiments allow to maintain a very limited size of the speaker unit 1, but provide a highly efficient front-radiation arrangement.

[0036] Figures 4 to 6 A second exemplary embodiment of the inventive speaker unit 1 is shown. Figure 4 A side view is shown, and Figure 5 a cross-sectional view along line V-V is shown. Figure 4 A top view of the shown speaker unit 1. Figure 6 A cross-sectional view along line VI-VI of the shown speaker unit 1. Figure 5 A cross-sectional view along line VI-VI of the shown speaker unit 1.

[0037] In a set of embodiments similar to the one shown in Figures 4 to 6 the secondary surface 6a is located at the same position as the front surface of the speaker frame 9. The acoustic energy emitted from the second membrane 8 is redirected to multiple secondary surfaces 6a, 6a', and is thus arranged adjacent to the acoustic energy emitted from the first membrane 7 in the primary acoustic radiation direction A. In Figure 5 the shown embodiment, four secondary surfaces 6a, 6a' are arranged to be evenly distributed around the first membrane 7, allowing to still use the limited front surface area of the speaker unit 1.

[0038] As Figure 6 a cross-sectional view most clearly shows, in another embodiment, one or more of the (at least) two drive units 2 have an inner bore 2a, and a portion of the acoustic tube 6 is formed by the inner bore 2a of one or more of the two drive units 2. From Figure 5 a top view and Figure 6 a cross-sectional view, it is clear that in this embodiment, there are two diagonally positioned drive units 2 to drive the first membrane 7, providing a bore 2a in communication with the secondary surface 6a. Furthermore, there are two diagonally positioned drive units 2' to drive the second membrane 8, providing a bore 2a' in communication with the secondary surface 6a'. In this exemplary embodiment, the surface of the second membrane 8 (pointing in the secondary acoustic radiation direction B), the first portion 6b, the bores 2a, 2a', and the secondary orifices 6a, 6a' thus form the acoustic tube 6.

[0039] In Figure 6 In the exemplary embodiment shown, the drive units 2, 2' each comprise a voice coil 3, 3' and a magnet assembly 4, 4'. The voice coils 3, 3' mechanically drive the first and second membranes 7, 8 via mechanical connection means 3a, 7a; 3a', 8a, respectively. In this embodiment, the membranes 7, 8 are implemented as flat surface membranes, but it is clear that other types of membranes can be used (e.g. conical membranes similar to the conical membranes shown in the embodiments) by suitable mechanical connection means to the voice coils 3, 3'. Figures 1 to 3 In the exemplary embodiment shown, the drive units 2, 2' each comprise a voice coil 3, 3' and a magnet assembly 4, 4'. The voice coils 3, 3' mechanically drive the first and second membranes 7, 8 via mechanical connection means 3a, 7a; 3a', 8a, respectively. In this embodiment, the membranes 7, 8 are implemented as flat surface membranes, but it is clear that other types of membranes can be used (e.g. conical membranes similar to the conical membranes shown in the embodiments) by suitable mechanical connection means to the voice coils 3, 3'.

[0040] In prior art loudspeaker systems, the principle of dual opposed drivers in the classical sense has been used, where the drivers are placed in a back-to-back position. The benefit of this architecture is that the opposing drivers can cancel the mechanical vibrations of the enclosure of the loudspeaker unit. Due to this cancellation, the enclosure is significantly less affected by the movements of the drivers even if the enclosure is relatively light, low in stiffness and / or small in relation to the drivers. The drawback of these early prior art systems employing back-to-back positioned drivers is that the footprint is constrained by at least twice the depth of the same drivers.

[0041] Gathering the drivers into coaxially positioned drive units 2 is an efficient way to reduce the minimum volume required in a loudspeaker design, as described for example in the present applicant's published patent application WO2019 / 086357, which is incorporated herein by reference. Further developments of loudspeaker devices that can have thin enclosures are described in the present applicant's international patent application WO2019 / 117706, which is also incorporated herein by reference. The drive units 2 applied in the embodiments of the present invention can also be implemented as the units described in international patent application WO2018 / 056814, which is also incorporated herein by reference.

[0042] Note that the damper and port solutions currently applied are not suitable for the above-mentioned gathered driver architecture. The variable distance between the membranes 7 when they are offset inwards (towards each other) creates problematic conditions for a static centering port, as is known for example from US patent publication US8,452,041.

[0043] Note that the acoustic tube 6 used in the embodiments of the present invention has a different function acoustically and mechanically than in a ported loudspeaker enclosure where the port is used as a way to enhance bass performance or provide a bandpass filter. Furthermore, the redirected air displacement is from one side of the membrane 8 that is in phase acoustically and out of phase mechanically with the side of the other membrane 7 that is moving in free air. The purpose of the acoustic tube 6 is to redirect the air displacement of the second membrane 8 with as little impact as possible on the acoustical output of the redirected membrane's air displacement.

[0044] The loudspeaker unit 1 can comprise a vented frame element, for example as a top plate of the loudspeaker frame 9, as shown in Figure 5 This vented frame element provides space for air displacement in free air space in the outwardly deflected direction A of the first membrane 7 closest to the vented frame element. An acoustic tube 6 or air guide is provided to redirect the air displacement from the second membrane 8 to a side not equal to the outwardly (outwardly means away from the loudspeaker unit 1) deflected direction B of the second membrane 8. The acoustic tube 6 provides a full air tight connection between the outwardly deflected direction of the second membrane 8 and free air. The acoustic tube 6 has a front surface opening towards free air (total orifice area of the secondary surface 6a) allowing sufficient air movement through without significant acoustic effects (band pass or bass boost effects).

[0045] According to the invention, various embodiments of a loudspeaker unit 1 are provided, wherein each of the plurality of drive units 2 comprises at least one voice coil 3 and a magnet assembly 4 having at least two magnets. In order to direct all air displacements towards a single surface or several surfaces providing the main sound radiation direction A, an acoustic tube 6 is used to redirect the acoustically in phase air displacement of at least one of the two membranes 7, 8 towards a surface 6a not equal to the acoustically in phase outwardly deflected direction of the membrane 8 whose air displacement is being redirected.

[0046] The combination of the loudspeaker frame 9, the two membranes 7, 8 and the drive units 2, 2' of the embodiments of the invention can be placed in a loudspeaker cabinet with at least one acoustic tube 6 enabling the two membranes 7, 8 to displace air into free air (i.e. outside of the loudspeaker unit 1) wherein the air displacement of at least one membrane 8 is directed through the acoustic tube 6 towards a side of the loudspeaker unit 1 not equal to the outwardly deflected direction of the membrane 8 being redirected.

[0047] In another embodiment, the first membrane 7 and the second membrane 8 are conical (see Figures 1 to 3 Embodiment). This will provide an efficient loudspeaker unit 1 in terms of obtainable sound pressure level and further loudspeaker characteristics. Additionally, a flat shaped protective cover in the form of a mesh or plane of light weight material can be added. In an alternative embodiment, the first membrane 7 and the second membrane 8 are flat (see Figures 4 to 6 Embodiment).

[0048] In order to obtain an even more efficient loudspeaker unit 1, in another embodiment, the acoustic tube 6 has an inner surface arranged to guide sound waves. This can be obtained by for example using a suitable (plastic) material with appropriate acoustic properties.

[0049] In another embodiment, the loudspeaker unit 1 has an interior space bounded by the loudspeaker frame 9 and the two membranes 7, 8, in which the two drive units 2 are located. The voice coil 3 and the magnet assembly 4 of the drive units 2 are then isolated from the ambient air and from the sound waves generated by the membranes 7, 8.

[0050] In another embodiment, in order to obtain a highly efficient loudspeaker unit 1, in which the second membrane 8 also significantly contributes to the sound generated by the loudspeaker unit 1, the smallest cross section of the sound channel 6 is greater than 1 cm 2 This size limit will provide a sufficiently low acoustic damping to obtain a sufficiently high sound pressure level emitted from the secondary surface 6a.

[0051] Alternatively or additionally, in another embodiment, the smallest width of the sound channel 6 is chosen to be greater than 5 mm. For example, the width w of the secondary surface 6a as indicated in the embodiment shown in Figure 1 or Figure 5 the diameter d of the secondary surface 6a, 6a' in the embodiment can be chosen to be greater than 5 mm. For sound waves, the smallest dimension of an acoustic tube is most relevant for obtaining a sufficiently low acoustic damping.

[0052] With regard to the first two embodiments, it is noted that in alternative embodiments in which the loudspeaker unit 1 is a very small loudspeaker unit, the smallest cross section and / or the smallest width can even be smaller.

[0053] In yet another embodiment, the front surface area of the secondary surface 6a is at least 10% of the front surface area of the second membrane 8. This has the effect that a sufficiently high portion of the acoustic energy generated by the second membrane 8 is directed towards the front side of the loudspeaker unit 1 and contributes to the total sound pressure level that can be generated by the loudspeaker unit 1.

[0054] In order to enable the loudspeaker unit 1 of the present invention to be applied in many applications (e.g. car door, ceiling speaker, in- television device, etc.), the total height h (see Figure 1 and Figure 4 of the loudspeaker unit 1 of the embodiments shown is substantially equal to or smaller than four times the maximum peak-to-peak excursion of each of the (at least) two membranes 7, 8. The specific structure of the embodiments of the present invention using coaxially positioned drive units 2 (i.e. side-by-side arranged, laterally displaced from the membranes 7, 8) allows to keep the thickness dimension of the loudspeaker unit 1 within this limit.

[0055] In a further advantageous embodiment, the loudspeaker unit 1 of the present invention also provides for an improved cooling of the internal or external components of the loudspeaker unit 1 (e.g. the (at least) two drive units 2, but also one or more electronic components 2 for driving the two drive units). In order to obtain this effect, at least a part of the acoustic tube 6 is made of a thermally conductive material.

[0056] With reference to the above mentioned Figure 3 and Figure 6 The acoustic tube 6 has a first portion 6b arranged at a predetermined distance from the second membrane 8 along the secondary sound radiation direction B and a second portion 6c arranged at one or more sides of the speaker frame 9. A single second portion 6c is shown, but the second portion 6c can also represent two, three or even all four sides of the speaker frame 9.

[0057] To prevent too much heat from accumulating within the speaker frame 9 when the speaker unit 1 is in operation, embodiments are provided in which the acoustic tube 6 (e.g. the first portion 6b and / or the second portion 6c) comprises a thermally conductive material. This embodiment allows for dissipation of heat generated in the speaker frame 9 by the two drive units 2 through, for example, an improved thermal conductivity to be achieved by the first portion 6b and the second portion 6c of the acoustic tube 6. Alternatively or additionally, the acoustic tube 6 can now also be used to cool externally mounted components (e.g. electronic components) by using the moving air inside the acoustic tube 6 during operation (even if the actual volume is limited, there is still an exchange of thermal energy via the air moving in the acoustic tube 6. In this embodiment, the first portion 6b and the second portion 6c now therefore act as a heat sink for the speaker unit 1.

[0058] It is noted that since the second portion 6b can comprise one, two, three or all four sides of the speaker frame 9, it is possible to achieve a desired level of heat dissipation by choosing which of the one, two, three and / or four sides should comprise the thermally conductive material.

[0059] The thermal performance of the speaker unit 1 can be improved by considering embodiments in which the acoustic tube 6 also has a third portion 6d as shown in Figure 3 and 6 The third portion 6d is arranged at a predetermined distance from the second membrane 8 opposite or in front of it. This third portion 6d can be seen as a back side / wall of the speaker unit 1 extending substantially parallel to the second membrane 8, and wherein this back side is circumferentially connected to the first portion 6b and the second portion 6c. The third portion 6d can then also comprise a thermally conductive material and act as a heat sink to further dissipate heat generated by the speaker unit 1 or external components mounted on the third portion 6d in advantageous embodiments.

[0060] By considering the above, a combined embodiment can be envisaged in which the acoustic tube 6 also has a third portion 6d arranged at a predetermined distance from the second membrane 8 opposite it, and wherein the first portion 6b, the second portion 6c and / or the third portion 6d comprise a thermally conductive material.

[0061] In an exemplary embodiment, the thermally conductive material exhibits a thermal conductivity of at least 100 W / m*K. Thus, when the first portion 6b, the second portion 6c, and / or the third portion 6d comprise, for example, aluminum or copper, a thermal conductivity of at least 100 W / m*K can be achieved.

[0062] In an embodiment, as shown in Figure 3 and Figure 6 The one or more electronic components 10a, 10b, 10c can include a speaker amplifier, filter circuitry, power supply, and / or any other electronics required by the speaker unit 1. The components 10a, 10b, 10c are shown as internally mounted (i.e., within the acoustic tube 6), but in further embodiments, the components 10a, 10b, 10c are mounted to an external surface of the acoustic tube 6.

[0063] As the one or more electronic components 10a, 10b, 10c can generate heat, embodiments are contemplated in which the one or more electronic components 10a, 10b, 10c are mounted in thermal contact with the acoustic tube 6 (e.g., on the first portion 6b, the second portion 6c, and / or the third portion 6d, each of which accordingly comprise a thermally conductive material). This embodiment effectively allows the one or more electronic components 10a, 10b, 10c to use the acoustic tube 6 as a heat sink, with heat from the one or more electronic components 10a, 10b, 10c being dissipated through the thermally conductive first portion 6b, second portion 6c, and / or third portion 6d.

[0064] Notably, in embodiments in which the one or more electronic components 10a, 10b, 10c are mounted internally within the acoustic tube 6 on the thermally conductive first portion 6b, second portion 6c, and / or third portion 6d, air cooling of the one or more electronic components 10a, 10b, 10c can also occur. Thus, as the speaker unit 1 is in use, movement of air through the acoustic tube 6 will cool the one or more electronic components 10a, 10b, 10c disposed therein. Note that this air cooling also occurs when none of the first portion 6b, second portion 6c, and / or third portion 6d are thermally conductive.

[0065] In yet further embodiments, another portion of the speaker unit 1 that is in thermal contact with the acoustic tube 6 (e.g., a front surface of the speaker frame 9) can also be made of a thermally conductive material, thereby allowing external components requiring cooling to be mounted thereon.

[0066] The application has been described above with reference to a number of exemplary embodiments as shown in the drawings. Modifications and alternative implementations are possible, and include departures from the details described herein that fall within the scope of the attached claims.

Claims

1. A loudspeaker unit (1), comprising: Speaker frame (9); Two diaphragms (7, 8) are arranged in the loudspeaker frame (9), wherein the first diaphragm (7) has a primary sound radiation direction A that is substantially perpendicular to the main plane (9a) of the loudspeaker unit (1), and the second diaphragm (8) has a secondary sound radiation direction B that is different from the primary sound radiation direction A. Two drive units (2) are located within the speaker frame (9) and are respectively attached to the first diaphragm (7) and the second diaphragm (8). The first diaphragm (7) and the second diaphragm (8) are arranged in a relative configuration within the speaker frame (9), and the secondary acoustic radiation direction B is opposite to the primary acoustic radiation direction A. Wherein, the first membrane (7) and the second membrane (8) are coaxially aligned along the primary acoustic radiation direction A and the opposite secondary acoustic radiation direction B, and The two drive units (2) are coaxially positioned at the same height within the speaker frame (9), and are subsequently laterally displaced from the two diaphragms (7, 8) in a side-by-side arrangement; and An acoustic tube (6) provides a closed channel from the second diaphragm (8) along the secondary acoustic radiation direction B to the secondary surface (6a) of the loudspeaker unit (1), wherein the secondary surface (6a) and the main plane (9a) of the loudspeaker unit (1) are located in the same plane. The acoustic tube (6) includes: The first part (6b) is arranged along the secondary acoustic radiation direction B; The second part (6c) is disposed on at least one side of the speaker frame (9); and The third part (6d) is arranged at a predetermined distance opposite to the second membrane (8). The acoustic tube (6) forms an airtight connection between the second diaphragm (8) and the loudspeaker frame (9) in the main acoustic radiation direction A.

2. The loudspeaker unit (1) according to claim 1, wherein, The third part (6d) forms the rear wall of the speaker unit (1) and extends substantially parallel to the second diaphragm (8).

3. The loudspeaker unit (1) according to claim 1, wherein, The third part (6d) is connected to the first part (6b) and the second part (6c).

4. The loudspeaker unit (1) according to claim 1, wherein, The secondary surface (6a) is adjacent to the front surface of the speaker frame (9).

5. The loudspeaker unit (1) according to claim 1, wherein, The secondary surface (6a) is located at the same position as the front surface of the speaker frame (9).

6. The loudspeaker unit (1) according to claim 1, wherein, The first membrane (7) and the second membrane (8) are conical or flat.

7. The loudspeaker unit (1) according to claim 1, wherein, The acoustic tube (6) has an inner surface arranged to guide sound waves.

8. The loudspeaker unit (1) according to claim 7, wherein the acoustic tube (6) is composed of a material having acoustic properties, the material being configured to guide sound waves through the acoustic tube (6).

9. The loudspeaker unit (1) according to claim 7 or 8, wherein, The acoustic tube (6) is made of plastic material.

10. The loudspeaker unit (1) according to claim 1, wherein, The loudspeaker unit (1) has an internal space defined by the loudspeaker frame (9) and the two membranes (7, 8), and the two drive units (2) are located in the internal space.

11. The loudspeaker unit (1) according to claim 1, wherein, The minimum cross-section of the acoustic tube (6) is greater than 1 cm. 2 .

12. The loudspeaker unit (1) according to claim 1, wherein, The minimum width of the acoustic tube (6) is greater than 5 mm.

13. The loudspeaker unit (1) according to claim 1, wherein, The front surface area of ​​the secondary surface (6a) is at least 10% of the front surface area of ​​the second membrane (8).

14. The loudspeaker unit (1) according to claim 1, wherein, At least a portion of the acoustic tube (6) is made of a thermally conductive material.

15. The loudspeaker unit (1) according to claim 14, wherein, The thermally conductive material exhibits a thermal conductivity of at least 100 W / m*K.

16. The loudspeaker unit (1) according to claim 14, further comprising one or more electronic components (10a, 10b, 10c) for driving the two drive units (2), and wherein, The one or more electronic components (10a, 10b, 10c) are mounted in thermal contact with the acoustic tube (6).

17. The loudspeaker unit (1) according to claim 14, wherein, The first part (6b), the second part (6c) and / or the third part (6d) include thermally conductive material.

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