阅读说明：本技术 具有波导的指向式多路扩音装置 (Directional multi-channel loudspeaker with waveguide ) 是由 阿基·马基维塔 尤哈·霍尔姆 尤西·维桑恩 姆西亚马克·纳吉安 艾伯·玛蒂凯恩 于 2017-04-21 设计创作，主要内容包括：本发明涉及一种扩音装置(1),包括：外壳(2),其具有限定了内部空间(27)的前部(15)、侧部(21)和后部(25)；前部(15)形成为波导表面(8),在波导表面(8)的中心处包括至少一个驱动器(12,13),并且能够将扩音装置(1)的主声功率沿第一声轴(10)的方向辐射到环境空间26中；以及连接到外壳(2)的附加驱动器(4)。根据本发明,所述附加驱动器(4)连接在外壳(2)的内部,使得在所述内部空间(27)中形成了子空间(22),所述子空间(22)由所述驱动器(4)、位于驱动器(4)和前部(15)之间的间隔件(33)以及外壳(2)的前部(15)所限定；至少一个第一端口(20)适于从子空间(22)到环境空间(26)地通向所述外壳(2)的侧部(21)或后部(25)；至少一个谐振器(40)声学连接到所述子空间(22),所述谐振器(40)被调谐到所述子空间(22)的至少一个不想要的谐振。(the invention relates to a sound amplification device (1) comprising: a housing (2) having a front (15), sides (21) and a rear (25) defining an interior space (27); the front portion (15) is formed as a waveguide surface (8), comprises at least one driver (12, 13) at the center of the waveguide surface (8), and is capable of radiating the main acoustic power of the loudspeaker device (1) into the ambient space 26 in the direction of the first acoustic axis (10); and an additional drive (4) connected to the housing (2). According to the invention, the additional drive (4) is connected inside the housing (2) in such a way that a sub-space (22) is formed in the interior space (27), the sub-space (22) being defined by the drive (4), a spacer (33) between the drive (4) and the front (15) of the housing (2); at least one first port (20) adapted to open into a side (21) or a rear (25) of the housing (2) from a subspace (22) to an ambient space (26); at least one resonator (40) is acoustically connected to the subspace (22), the resonator (40) being tuned to at least one unwanted resonance of the subspace (22).)

1. A loudspeaker device (1) comprising:

a housing (2) having a front (15), sides (21) and a rear (25) defining an interior space (27),

The front part (15) is formed as a waveguide surface (8), comprises at least one driver (12, 13) in the center of the waveguide surface (8) and is capable of radiating the main acoustic power of the loudspeaker device (1) in the direction of the first acoustic axis (10), and

At least one additional drive (4) connected to the housing (2),

The additional drive (4) is connected inside the housing (2) in such a way that a sub-space (22) is formed in the interior space (27), the sub-space (22) being defined by the drive (4), a spacer (33) between the drive (4) and the front (15) of the housing (2),

At least one first port (20) adapted to open from a subspace (22) to an ambient space (26) to a side (21) or a rear (25) of the housing (2),

Characterized in that the sound amplifying device comprises

at least one resonator (40) acoustically connected to the subspace (22), the resonator (40) being tuned to at least one unwanted resonance of the subspace (22).

2. Loudspeaker device according to claim 1, characterised in that the resonator (40) is a resistive resonator with broadband properties.

3. Loudspeaker device according to claim 1 or 2, wherein the resonator (40) comprises an attenuating material (41), such as PES wool, open-cell foam, glass fibre, mineral wool, felt, or other fibrous or open-cell material or porous material, or alternatively any solid material which is manufactured in a spatial position such that the material has an open-cell or fibrous structure, wherein the cell size or fibre size is in the size range of 1 micrometer to 1 millimeter.

4. Loudspeaker device according to claim 1, characterised in that the resonator (40) is a reactive resonator, such as a panel resonator or a helmholtz resonator.

5. Loudspeaker device according to any of the preceding claims, wherein the subspace (22) has a width W and a length L such that the W/L ratio is in the range of 1.2-2.5, typically around 1.8.

6. Loudspeaker device according to any of the preceding claims, wherein the enclosure is metallic, typically aluminium, and the resonator (40) is an integral part of the enclosure (2).

7. Loudspeaker device according to any of the preceding claims, wherein the plane (31) of the front port (5) and the plane (32) of any of the first ports (20) have an angle a greater than 0 degrees, preferably greater than 45 degrees when the first port (20) is not on the rear portion (25).

8. A loudspeaker arrangement according to any one of the preceding claims, comprising

A first driver (3) configured to generate a first frequency band (B1) and a corresponding first sound axis (10),

A second driver (4) configured to generate a second frequency band (B2) which is different from the first frequency band (B1) but may overlap in an intersection region, and the second frequency band (B2) has a second sound axis (11),

A housing (2) having a front (15), sides (21) and a rear (25) connected to the drivers (3, 4) and comprising a three-dimensional waveguide (8) on the front of the housing (2) and around the first driver (3), and

said three-dimensional waveguide (8) comprising a selectively acoustically transparent portion (6) that substantially acoustically reflects sound waves of a first frequency band (B1) propagating in a direction at an angle to said first acoustic axis,

The selectively acoustically transparent portion (6) being substantially transparent to sound waves of a second frequency band (B2) propagating through the selectively acoustically transparent portion (6) along the direction of the second sound axis (11),

Wherein the second driver (4) is located inside the housing (2) behind the selectively acoustically transparent portion (6).

9. loudspeaker device (1) according to any of the preceding claims, wherein the total area of the at least one first port (20) is typically 5-50% of the area of the front port (5), advantageously 10-20% of the area of the front port (5).

10. Loudspeaker device (1) according to any of the preceding claims, wherein the first port (20) is formed by a channel or guide leading to the rear (25) of the enclosure (2).

11. Loudspeaker device (1) according to any of the preceding claims, wherein the plane (32) of the first port (20) has an angle of 80-180 degrees with respect to the first sound axis (10).

12. loudspeaker device (1) according to any of the preceding claims, wherein the second sound axis (11) is not coaxial with the first sound axis (10).

13. Loudspeaker device (1) according to any of the preceding claims, wherein the second sound axis (11) is not parallel to the first sound axis (10).

14. Loudspeaker device (1) according to any of the preceding claims, wherein the selectively acoustically transparent part (6) is made of a porous material.

15. Loudspeaker device (1) according to any of the preceding claims, wherein the selectively acoustically transparent part (6) is made of a porous material, wherein the pores have a diameter of less than 1 mm.

16. Loudspeaker device (1) according to any of the preceding claims, wherein the selectively acoustically transparent part (6) is made of felt having a thickness of about 1-5 mm.

17. Loudspeaker device (1) according to any of the preceding claims, wherein the selectively acoustically transparent part (6) is made of open-cell plastic foam with a thickness of about 1-20 mm.

18. loudspeaker device (1) according to any of the preceding claims, characterised in that the selectively acoustically transparent part (6) covers the entire front surface (8) of the loudspeaker device except for the tweeter (12).

19. Loudspeaker device (1) according to any of the preceding claims, wherein the selectively acoustically transparent part (6) covers only the opening (5).

20. Loudspeaker device (1) according to any of the preceding claims, wherein the first driver (3) comprises two coaxial drivers (12, 13).

21. Loudspeaker device (1) according to any of the preceding claims, wherein the first driver (3) comprises only one driver (12, 13).

22. Loudspeaker device (1) according to any of the preceding claims, wherein the selectively acoustically transparent part (6) is made of metal.

23. Loudspeaker device (1) according to any of the preceding claims, wherein the selectively acoustically transparent part (6) is made of metal mesh.

24. Loudspeaker device (1) according to any of the preceding claims, wherein the selectively acoustically transparent part (6) is made of a multilayer metal mesh.

25. Loudspeaker device (1) according to any of the preceding claims, wherein the selectively acoustically transparent part (6) is made of a multilayer metal sheet with perforations.

26. Loudspeaker device (1) according to any of the preceding claims, characterised in that the selectively acoustically transparent portions (6) are made of sheets spaced from each other by 0.2-2 mm.

27. Loudspeaker device (1) according to any of the preceding claims, characterised in that the loudspeaker device (1) is a bass reflex loudspeaker device.

Technical Field

The present invention relates to a sound amplifying apparatus. More particularly, the present invention relates to a sound amplifying apparatus equipped with a waveguide.

More precisely, the invention relates to a loudspeaker device according to the preamble of claim 1.

Background

In the prior art, especially loudspeakers with two or more drivers (i.e. multi-way loudspeakers) show sound diffraction problems caused by discontinuities on the front baffle surface of the loudspeaker. In fact, the high frequency driver (tweeter) is the most critical part in this sense. The applicant of the present application has created a solution where the surroundings of the tweeter have been formed as a continuous waveguide for high and mid audio signals, or a continuous waveguide for the tweeter and/or the mid driver only, or a continuous waveguide for the coaxial mid-tweeter driver.

In this application, these kinds of acoustic sources are called waveguide drivers, and they include any driver located at the center of this three-dimensional waveguide structure. With these solutions, good sound quality and accurate pointing of the sound energy can be achieved. However, the frequency range of the waveguide and the effectiveness of controlling the radiation direction depend on the size of the waveguide, which depends to a large extent on the surface area covered by the waveguide and therefore also on the size of the front barrier of the loudspeaker device. The smaller waveguide area limits the directional control to a high frequency range, such as only for tweeters. The larger waveguide area allows the frequency range of the directional control to be extended to lower frequency ranges, such as the frequency range of a midrange driver.

When designing loudspeakers of smaller size, it is not usually possible to center all drivers (e.g. low frequency radiators, woofers) in the waveguide, and therefore the surface area occupied by these other drivers and their own will limit the baffle area available for the waveguide, or additionally produce diffraction of unwanted audio energy, which can lead to a degradation of the quality of the audio signal audible to the listener.

Attempts have been made in the prior art to create a loudspeaker device having one or more waveguides at the front side of the loudspeaker device. The applicant of the present application has previously created a number of solutions such as those in european patent application 14168925.7 and international application PCT/FI 2014/050757. The following solutions are proposed in these applications: the non-coaxial drivers are placed so that they do not interfere with the form of the waveguide formed on the front face of the enclosure and, if placed on the same surface (the front face of the enclosure), they can be covered with a material that, on the one hand, can advantageously act as a solid surface in the selected frequencies and limit the transmission of the frequencies emitted by the sound source for which the waveguide is designed, and, on the other hand, can also allow the transmission of other frequencies, more particularly the frequencies radiated by the non-coaxial drivers, typically woofers.

Covering low frequency drivers may cause problems in the dynamic performance of the driver because the air volume displacement of the driver needs to be sufficiently open to allow air flow. In addition, the subspace located in front of the woofer may induce unwanted resonances.

Disclosure of Invention

According to the invention at least some of the above problems are solved by acoustically connecting a resistive or reactive resonator to the subspace of the woofer so that the total volume of the loudspeaker device is kept as small as possible. Advantageously, the resonators are located at least partially around the coaxial element. Furthermore, it is an object of the invention to improve the dynamic performance of a woofer.

More specifically, the loudspeaker device according to the invention is characterized by what is stated in the characterizing part of claim 1.

According to an embodiment of the invention the loudspeaker device comprises at least one resonator acoustically connected to said subspace, which is tuned to at least one unwanted resonance of said subspace.

THE ADVANTAGES OF THE PRESENT INVENTION

Significant advantages are obtained by the present invention.

With one embodiment of the invention, the low frequency drivers are covered, however the resonance problem caused by the sub-space of the woofer is suppressed. In some embodiments, the suppression may occur at multiple frequencies by multiple resonators tuned to different frequencies.

By means of the invention, the entire front surface of the loudspeaker device can be formed as a continuous waveguide for medium and high frequencies without any disturbing resonance at the subspace of the bass driver, while the total volume of the loudspeaker device can be kept as small as possible. By this measure the whole audio frequency range of 18-20000Hz can be directed exactly to one "optimum listening point" and the rest of the acoustic energy is distributed to the listening room due to the full wave guide form of the loudspeaker device, so that the enclosure of the loudspeaker device itself does not significantly influence the frequency response in other directions (with respect to the main direction).

In other words, in conventional loudspeakers where the entire baffle is planar or only partially curved as a waveguide, signals formed in other directions than the "sweet spot" will be reflected in an uncontrolled manner by the walls of the listening room. However, the invention provides a housing whose sound pressure is optimally distributed in all directions, whereby the reflection of the walls sounds natural to the human ear.

Drawings

Some preferred embodiments of the invention are described hereinafter with reference to the accompanying drawings, in which:

Fig. 1 shows a front view of a loudspeaker device according to a preferred embodiment of the invention.

Fig. 2 shows a cross-section of the loudspeaker device of fig. 1.

Fig. 3 shows a partial cross-section of the loudspeaker device shown in fig. 1.

figure 4 shows a graph of the frequency response of the internal chamber of a woofer and the corresponding resonator according to the invention.

Fig. 5 shows a cross-section of a subspace of a woofer according to the invention.

Fig. 6 shows a cross-section of a second subspace of a woofer according to the invention.

Fig. 7 shows a cross-section of a third subspace according to the present invention.

Fig. 8a shows a front view of a woofer according to the invention.

fig. 8b shows a cross-sectional view a-a of the woofer shown in fig. 8 a.

Fig. 9 shows a cross-section of a third subspace of a woofer according to the invention.

Fig. 10 shows a front view of a loudspeaker device according to an alternative embodiment of the invention.

Fig. 11 shows a cross section of a loudspeaker device according to fig. 9.

Fig. 12 shows a front view of a sound amplification apparatus according to another preferred embodiment of the present invention.

Fig. 13 shows a view of a loudspeaker system according to a preferred embodiment of the invention.

Fig. 14 shows a cross-sectional view of a sound amplifying apparatus according to a preferred embodiment of the present invention.

Detailed Description

List of terms used:

1 sound amplifying device

2 outer cover

3 waveguide driver, also coaxial driver or high pitch loudspeaker only

4 bass loudspeaker, low frequency driver, additional driver

5 front port (opening) of a woofer, the low frequency driver having an outer edge on the surface of the enclosure 2 defining the plane of the edge of the front port

6 Selective sound-transmitting layer

support structure for 7 selective sound-transmitting layer

8 three-dimensional waveguide surface, also the front surface of the housing 2 radiating the dominant acoustic power, has a smooth continuous surface and features axial symmetry around the center of the waveguide driver 3

Optimum listening point of 9 multi-loudspeaker device

10 first acoustic axis

11 second sound axis

12 high pitch loudspeaker

13 intermediate frequency driver

15 front part (wall) of the housing (which may also be a waveguide surface 8), front baffle part, which front part radiates the main acoustic power and comprises the waveguide surface 8 and has a plane 28 perpendicular to the first acoustic axis 10

Frequency band of B1 waveguide driver 3

B2 frequency band of non-coaxial driver 4

Cross band between C-band B1 and B2

depth of cavity of d-panel resonator

20 a first port, also a side opening, having an outer edge defining a plane of the first port on a surface of the housing

21 side part (wall) of the outer casing

22 subspace, which is also the front space of the woofer or low-frequency driver, is part of the interior space 27

width of W subspace

Length of L subspace

23 (front space) forming a spacer between the driver 4 and the housing 2, the tangent to the middle of the side wall 23 making an angle with the plane 28 of the front 15 different from zero, typically an angle of about 90 degrees

25 a rear portion of the housing having a plane defined by a tangent line formed in the middle of the rear portion 25 and generally parallel to the plane of the front portion 15; according to the invention, the plane of the rear portion 25 may have different angles

26 environment space

27 inner space of the housing 2

28 front plane

29 the plane of the side 21, determined by the tangent to the centre of the part

30 rear part, determined by the tangent to the centre of the part

31 front end 5 plane

32 the plane of the first port 20, the plane 31 of the front port 5 and the plane 32 of any one of the first ports 20 have an angle alpha greater than 0 degrees, preferably greater than 45 degrees when the first port 20 is not located on the rear portion 25

33 spacer, part of the space between the woofer and the front part 15, is an integral part of the housing 2, or is a separate element

34 reflective port

The angle between the plane 31 of the alpha front port 5 and the plane 32 of the first port 20

40 resonator

40' sub-resonator

Suppressing material for 41 resonator

43 frequency response of subspace

44 frequency response of the resonator

f₀Resonant frequency

Neck of 45 Helmholtz resonator

Inner cavity of 46 Helmholtz resonator

47 Bass speaker cover

48 cover tube

Panel of 50-panel resonator

According to fig. 1, a loudspeaker device 1 according to one embodiment of the invention comprises a coaxial waveguide driver 3 comprising a tweeter 12 and a midrange driver 13 surrounding it. The coaxial driver 3 is centered on the three-dimensional waveguide surface 8, also the front surface of the housing 2. The housing is typically made of cast metal, preferably aluminum. Other castable or moldable materials (e.g., lambda' ic composite materials) may also be used as the material for the housing.

the waveguide surface 8 radiates the main acoustic power of the driver 3. The waveguide 8 has a smooth continuous surface with features of axial symmetry around the center of the waveguide driver 3. Two bass drivers 4 are symmetrically located on both sides of the waveguide driver 3 and inside the enclosure 2, and a narrow port (opening) 20 (i.e., a first port) is formed right behind the waveguide surface of the bass speaker 4 so as to discharge the acoustic energy from the enclosure 2. In this embodiment, the first ports 20 are at the narrow front end of the housing 2 and are partly visible seen from the listening direction. In other words, the first port 20 is a U-shaped slot.

The outline of the woofer 4, as well as the subspace 22 of the woofer and the resonator 40 connected to the subspace 22 of the woofer are shown by means of dashed lines. The function of the resonator 40 is to suppress the resonance of the sub-space 22 of the woofer. These resonators 40 are partly located behind the coaxial driver 3 and each subspace 22 has two resonators on both sides of the coaxial driver 3. The subspace 22 has a width W and a height H such that the W/H ratio is about 1.8, typically in the range of 1.0-5. The resonator 40 is typically an integral part of the housing.

The resonator is dimensioned such that the longest dimension (here the length) is λ/4 or λ/2 of the wavelength to be suppressed. In other words, if the subspace 22 has an undesired resonance at the wavelength λ, the resonator should be λ/4 long. In the frequency domain, this means at resonance f₀Where λ is v/f₀Where v is the speed of sound. Advantageously, the resonator 40 is filled with a dampening material 41, such as PES wool, open-cell foam, glass fibre, mineral wool, felt, or other fibrous or open-cell or porous material, or may instead be made of any solid material that is fabricated in space such that the material has an open-cell or fibrous structure with the cell size or fibre size in the size region of 1 micron to 1 millimeter.

Referring to fig. 2, the resonator 40 may also be located at least partially behind the coaxial driver 3.

Referring to fig. 2 and 3, two woofers 4 symmetrically placed around the coaxial driver form an equivalent large woofer that radiates through port 20 along substantially the same acoustic axis 10 as the waveguide driver 3, even though the woofers have their respective acoustic axes 11.

In other words, the loudspeaker device 1 comprises a first driver 3 and a second driver 4, wherein the first driver 3 is configured to generate a first frequency band B1 and a corresponding first sound axis 10, and the second driver 4 is configured to generate a second frequency band B2, wherein the second frequency band B2 is different from the first frequency band B1 but may overlap in an intersection region, and the second frequency band B2 has a second sound axis 11. The housing 2 encloses said drivers 3, 4 and comprises a three-dimensional waveguide 8 on the front surface of the housing 2 and surrounding the first driver 3.

as described above, the second sound axis 11 of each woofer driver is not coaxial with the first sound axis 10, but the resultant axes of the plurality of symmetric woofers (equivalent woofer drivers) working together have the same sound axis as the coaxial driver (i.e., waveguide driver 3). However, such symmetry is not required in all embodiments of the invention. The acoustic axes 10 and 11 may be parallel, or non-parallel.

Referring to fig. 2 and 3, the woofer 4 is located within the enclosure 2 such that a sub-space 22 is formed in front of the woofer 4, which is bounded by the woofer 4 itself and the side walls 23. A resonator 40 is acoustically connected to the subspace 22. A suitable dampening material 41 may be used within the resonator 40 to further attenuate unwanted frequencies.

The side walls 33 of the sub-space (front space) 22 form a spacer between the driver 4 and the housing 2 to seal the sub-space 22 from the rest of the inner space 27 of the housing 2. More specifically, the interior space 27 is defined by the walls of the housing 2 (i.e., the front 15, side 21, and rear 25).

Typically, the first port 20 is oriented substantially orthogonally with respect to the first and second axes 10, 11, most preferably in the range of 60-120 degrees with respect to these axes. However, when the first port 20 is directed to the rear 25 of the housing 2, for example by a channel, the difference between the direction of the first port 20 and the axes 10 and 11 may even be 180 degrees.

The total area of the first ports 20 is a critical feature and therefore the first ports 20 may be a single type of first port 20 of only one for each woofer 4, as shown, or may be formed by a plurality of first ports 20, for example a grill of area corresponding to one single type of port.

The first ports 20 should not interfere with the three-dimensional waveguide surface 8, so they are advantageously located on the side 21 of the housing 2. Of course, these first ports 20 may be guided to the rear 25 of the housing 2 by suitable pipes or channels (not shown). In other words, the first port 20 forms an air passage leading to a region other than the three-dimensional waveguide 8 of the front portion 15 of the housing 2.

The graph of fig. 4 shows the frequency response (solid line) of the subspace 22 of the woofer 4, where f is₀Where there is one resonance, fig. 4 also shows the corresponding frequency response (dashed line) of the resonator 40 acoustically connected to the subspace 22, where the resonator 40 compensates for the undesired resonance of the subspace 22.

Fig. 5 shows an alternative embodiment with two resistive resonators 40, the lengths of the two resistive resonators 40 being different for the two unwanted frequencies of the subspace. One or two resistive broadband resonators may also be used, preferably filled with a suppressing material. In this case, the mechanical dimensions (length, width and depth) of the resonant cavity define the tuning frequency or frequencies of the resonator.

Fig. 6 shows an alternative embodiment with one reactive helmholtz resonator 40. Generally, reactive resonators have a high quality factor and they are very efficient narrow band resonators. Also, if there are multiple sharp unwanted resonances, several such resonators may be installed in one subspace 22. Such resonators are also tuned to one or more unwanted frequencies f₀. The dimensions of the helmholtz resonator are explained below.

The resonance arises from the effect of the acoustic air mass neck of the resonator 40 and the series resonant circuit formed by the acoustic compliance of the air volume of the resonator chamber. A helmholtz resonator may attenuate unwanted resonances of the subspace 22 near the resonance frequency. The neck-cavity system of the resonator 40 can be derived from the air volume of the resonator cavity and the diameter of the neck and its length.

Wherein f is₀Is the resonant frequency, c is the speed of sound, a is the cross-sectional area of the neck, L is the length of the neck, and V is the volume of the cavity.

Figure 7 shows an alternative embodiment with one reactive panel resonator as the resonator. The dimensions of this embodiment are determined in the following manner based on the depth d of the cavity and per unit mass of the panel 50.

The resonant frequency f of the panel resonator/film absorber is defined as follows:

Where m is the acoustic mass per unit area (kg/m) of the panel 50²) And d is the depth of the cavity.

The stiffness of the membrane fixation is negligible.

Fig. 8a shows a woofer 4 in a top view, which woofer 4 has a flat cover 47 and a short tube 48 forming a helmholtz resonator, wherein the tube is the neck and the space between the cover and the cone of the woofer forms the volume of the resonator. The a-a section of this solution is shown in fig. 8 b. The tuning principle is the same as in fig. 5 and 6.

Fig. 9 shows another alternative solution, in which a resonator 40 is formed between the front baffle portion 15 and the sub-space 22 of the woofer. If the opening to the subspace 22 is made as a tube, the resonator may be a resistive type resonator or a reactive type resonator without any neck. The tuning principle is the same as in the previous figures.

In general, the loudspeaker device according to the invention functions according to the well-known bass reflex principle, wherein the low frequency driver 4 is tuned by means of the compliance of the air volume contained within the enclosure 27 and the air volume contained within the reflex port 34 shown in fig. 2.

An embodiment of the present invention (fig. 10-11) may also be described in the following manner.

The sound amplifying device 1 comprises a housing 2 defining an inner space 27 and comprising a front baffle portion 15 (front), the front baffle portion 15 having a front port 5 for providing a fluid passage between the inner space 27 of the housing 2 and an ambient space 26, the inner space 27 further comprising a side portion 21 extending rearwardly from a periphery of the baffle portion 15. The side portions 21 form side walls of the housing 2. The housing also includes a rear portion 25, the rear portion 25 being generally substantially parallel to the front baffle portion 15 and forming a rear side of the housing 2. The loudspeaker device 1 further comprises a driver 4 connected to the enclosure 2 such that the driver 4 is arranged at a distance from the baffle portion 15 such that a sub-space 22 is formed inside the enclosure 2, such that the sub-space 22 is formed between the driver 4 and the baffle portion 15 by means of spacers 33, wherein said front port 5 serves as a front port between the sub-space 22 and the ambient space 28 of the enclosure 2. According to this embodiment, in the side portion 21 or the rear portion 25, a first port 20 is formed on the housing 2 to communicate the subspace 22 and the ambient space 26 with each other.

According to one embodiment of the invention shown in fig. 10, two woofer drivers 4 are located on either side of the waveguide driver 3 within the enclosure 2, and suitable ports (openings) 5 are formed for the woofers 4 so that acoustic energy can be output from the enclosure 2.

Referring to fig. 11, the opening 5 is covered by an acoustically transparent layer 6 forming part of the waveguide surface 8. The acoustically transparent layer 6 can be supported from below by support rods 7, if desired. The woofer driver 4 is typically spaced from the acoustically transparent layer 6.

Referring to fig. 10, even though the two woofers 4 have their own acoustic axes 11, they form an equivalent large woofer that radiates substantially along the same acoustic axis 10 as the waveguide driver 3.

In other words, the loudspeaker device 1 comprises a first driver 3 and a second driver 4, wherein the first driver 3 is configured to generate a first frequency band B1 and a corresponding first sound axis 10, and the second driver 4 is configured to generate a second frequency band B2, wherein the second frequency band B2 is different from the first frequency band B1 but may overlap in an intersection region, and the second frequency band B2 has a second sound axis 11. The housing 2 encloses said drivers 3, 4 and comprises a three-dimensional waveguide 8 on the front surface of the housing 2 and surrounding the first driver 3. The three-dimensional waveguide 8 comprises a selectively acoustically transparent portion 6 which is acoustically substantially reflective for sound waves in a first frequency band B1 propagating in a direction at an angle to the first sound axis 10, the waveguide portion 6 being substantially transparent for sound waves in a second frequency band B2 propagating through the waveguide portion 6 in the direction of the second sound axis, the second driver 4 being located inside the housing 2 behind the selectively acoustically transparent portion 6.

As described above, the second sound axis 11 of each woofer driver is not coaxial with the first sound axis 10, but the combined axes of the plurality of woofers (equivalent woofer drivers) working together have the same sound axis as the coaxial driver (i.e., waveguide driver 3). However, such symmetry is not required in all embodiments of the invention. The acoustic axes 10 and 11 may be parallel, or non-parallel.

Referring to fig. 10 and 11, the woofer 4 is located inside the enclosure 2 such that a sub-space 22 is formed in front of the woofer 4 and is defined by the woofer 4 itself, the side walls 23 and the selectively acoustically transparent layer 6. The subspace 22 is connected to a resonator 40, which is tuned to the unwanted frequencies generated by the subspace 22. The resonator 40 may be resistive or reactive. For resistive resonators, the rejection characteristic is of the broadband type. In other words, the frequency f around the center is generated by the resistive resonator₀are not as sharp as in a reactive resonator. The side walls 33 of the sub-space (front space) 22 form a spacer between the driver 4 and the housing 2, sealing the sub-space 22 from the rest of the inner space 27 of the housing 2. More specifically, the interior space 27 is defined by the walls of the housing 2 (i.e., the front 15, side 21, and rear 25).

In some embodiments of the invention, the selectively acoustically transparent layer 6 may be replaced by a mechanically protective grid, which in this case defines the subspace as well as the inner space 27. Advantageously, the first port 20 is formed in a side wall of the sub-space 22 and is connected with a side 21 of the enclosure 2 to optimize the operation of the woofer 4. Without these first ports 20, the performance of the woofer 4 may be compromised. The first port 20 may be located on either side 21, such as the shorter side 21 as shown, or the longer side 21.

Typically, the first port 20 is substantially orthogonal with respect to the first axis 10 and the second axis 11, most preferably in the range of 60-120 degrees with respect to these axes. However, when the first port 20 is directed to the rear 25 of the housing 2, for example by a channel, the difference between the direction of the first port 20 and the axes 10 and 11 may even be 180 degrees.

The area of these first ports 20 is typically 5-50% of the area of the openings 5 of the woofer 4, most advantageously in the range of 10-20% of the area of the openings 5 of the woofer 4. The total area of the first ports 20 is a critical feature and thus the first ports 20 may be a single type of first port 20, only one for each woofer 4, as shown, or may be formed by a plurality of first ports 20, for example a grid of areas corresponding to the single type of ports.

The first ports 20 should not interfere with the three-dimensional waveguide surface 8, so they are advantageously located on the side 21 of the housing 2. Of course, these first ports 20 may be guided to the rear 25 of the housing 2 by suitable pipes or channels (not shown). In other words, the first port 20 forms an air passage leading to a region other than the three-dimensional waveguide 8 of the front portion 15 of the housing 2.

Typically, the second driver 4 is located inside the housing 2 behind and spaced from the selectively acoustically transparent portion 6 such that a sub-space 22 is formed within the housing 2 and is separated from the interior space 27 by the driver 4 and a side wall 23, the side wall 23 forming a spacer between the driver 4 and the front portion 15 of the housing 2.

By "substantially reflective" with respect to the selectively acoustically transparent layer 6 is meant reflecting or absorbing at least 50-100% of the acoustic energy, preferably in the range of 80-100%.

In the same way, "substantially transparent" means at least 50-100% transparent, preferably in the range of 80-100%, to acoustic energy.

Other advantageous properties of the selectively acoustically transparent layer 6 are presented below.

The thickness of the layer 6 is advantageously:

Felt, about 1-5mm thick

Open-cell plastic foams, about 1 to 20mm thick, with pore diameters of less than 1mm

A tissue as layer 6 or part of layer 6.

The layer 6 should attenuate the acoustic radiation of the waveguide driver 3, which means that frequencies above 600Hz are typical.

In other words, the layer 6 should have an acoustic impedance (or absorption) as a function of frequency and therefore act as an acoustic filter in the following way:

Low-pass sound from woofer driver 4-attenuation (e.g. caused by oscillations or absorption with high losses) for high frequencies from waveguide driver 3, resulting in strong reflection of sound waves of medium-high frequencies

High reflectivity for high frequencies of the driver 3

Advantageously, the layer 6 forms holes or pores or a combination thereof in the following way:

If a single layer 6 is used, the diameter of the hole should be less than 1mm

If a plurality of layers 6 is used, holes with a diameter of less than 1mm are feasible-likewise, if a plurality of layers 6 is used, holes with a diameter of more than 1mm are feasible (not yet tested)

Isomicrostructures like felt and open-pored plastic are feasible

the properties of the ideal material for layer 6 are as follows:

-breathable (═ porous)

Low acoustic losses up to cross-over frequency C (woofer 4)

High acoustic reflectivity slightly above the crossover frequency C

Known materials meeting the above conditions:

Felt, about 1-5mm thick

open-cell plastic foam about 1-20mm thick with a cell size of less than 1mm

The layer 6 may cover the front of the loudspeaker (not including the tweeter 12) or only the hole 5.

The layer 6 may also be formed as a metal structure, e.g. with one or more layers of mesh or grid, depending on the above requirements for porosity and frequency characteristics. Such a structure may be formed, for example, from a stack of perforated metal sheets or plates having a thickness of about 0.2-2 mm. The properties of such a stack can be adjusted by the arrangement (distribution) of the holes or apertures, the percentage of holes or apertures (openness) and the spacing between the plates. The diameter of the holes or bores can vary generally from about 0.3 to 3 mm. The spacing between the sheets or plates is typically about 0.2-2 mm.

The above-described metal structure is advantageous in that its characteristics can be freely adjusted, and external characteristics such as color can be selected without limitation.

The crossover frequency C is typically as follows:

Low frequency f <600Hz (output range of woofer)

High frequency f >600Hz (output range of midrange and/or tweeter)

According to the invention, in combination with a large waveguide 8:

The woofer 4 is placed behind the waveguide surface 8

Two or more (e.g. 4) woofers 4 may be used to obtain directivity, which may be placed symmetrically with respect to the coaxial driver

Also embodiments with only one woofer are possible, but no low frequency directivity is obtained, except for those benefits brought about by the combination of the size of the air moving surface of the woofer and the size of the front barrier of the housing of the loudspeaker device.

In an alternative embodiment of the invention, the selectively permeable section 6 may be replaced by a mechanical protective grid that does not have the full characteristics of selective permeability.

according to fig. 12, the resonator may be divided into a plurality of independent sub-resonators 40', each having its own resonance frequency.

Fig. 13 shows a typical positioning of a loudspeaker device 1 according to the invention, wherein the loudspeaker device is directed to a listening position, i.e. an optimum listening point 9. Very good directivity can be achieved due to the fact that the entire front surface of the housing 2 is formed as the waveguide 8. In addition, the waveguide form 8 distributes all frequencies evenly in all directions in the listening room, and therefore reflections from walls, ceilings and floors do not cause acoustic staining. Fig. 13 also shows the front 15, side 21 and rear 25 of the enclosure 2 of the loudspeaker device 1.

In fig. 14 a sound amplification device is shown in which a suppressing material 41 is located in the cavity 40. In this figure, only the upper chamber 40 is filled with the material, but in practice both the upper and lower chambers 40 will be filled with the inhibiting material.