Directional multi-channel sound amplification device with waveguide

Abstract

The invention relates to a sound amplification device (1), comprising: a uniform housing (2) having a front part (15), a side part (21) and a rear part (25) defining an interior space (27); the front part (15) being formed as a waveguide surface (8), comprising at least one driver (12, 13) in the waveguide surface (8) and being capable of radiating the main sound power of the sound amplification device (1) in the direction of a first acoustic axis (10); an additional driver (4) connected to the housing (2), which is connected inside the housing (2) so that a sub-sound waveguide (27) is formed in the interior space (27); A subspace (22) defined by a driver (4), a spacer (33) between the driver (4) and the front (15), and the front (15) of the housing (2); at least one first port (20) adapted to lead from the subspace (22) to an ambient space (26) to a side (21) or rear (25) of the housing (2); at least one resonator (40) comprising at least one resonant cavity (46) acoustically connected to the subspace (22) and tuned to at least one unwanted resonance of the subspace (22). According to the invention, the resonator (40) is formed as a separate unit (51) connected to the uniform housing (2).

Description

Technical Field

[0001] The present invention relates to a sound amplification device and more particularly to a sound amplification device equipped with a waveguide. Background Art

[0002] In the prior art, especially sound amplification devices with two or more drivers (i.e. multi-way sound amplification devices) exhibit sound diffraction problems caused by discontinuities on the surface of the front baffle of the sound amplification device. 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 in which the surroundings of the tweeter have been formed as a continuous waveguide for high and medium frequency audio signals, or a continuous waveguide only for the tweeter and / or the midrange driver, or a continuous waveguide for a coaxial midrange-tweeter driver.

[0003] In this application, these kinds of sound 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 directivity of the sound energy can be achieved. However, the frequency range of the waveguide and the effectiveness of controlling the radiation directivity depend on the size of the waveguide, which is largely determined by the surface area covered by the waveguide and, therefore, also by the size of the front baffle of the sound reinforcement device. A small waveguide area limits the directivity control to the high frequency range, such as the range of tweeters only. A larger waveguide area allows the frequency range of the directivity control to be extended to lower frequency ranges, such as the frequency range of midrange drivers.

[0004] When designing a smaller sound reinforcement device, it is usually not possible to place all drivers (e.g. low frequency radiators, woofers) in the center of the waveguide, so the surface area occupied by these other drivers and themselves will limit the baffle area available for the waveguide, or additionally produce harmful diffraction of audio energy, which will result in a decrease in the quality of the audio signal audible to the listener.

[0005] In the prior art, attempts have been made to create a sound amplification device having one or more waveguides on the front side of the sound amplification device. The applicant of the present application has previously created various solutions such as those in European patent application 14168925.7 and international application PCT / FI2014 / 050757. In these applications, the following solution is proposed: the non-coaxial drivers are placed so that they do not interfere with the waveguide form formed on the front face of the housing, and if placed on the same surface (the front face of the housing), they can be covered with a material that, on the one hand, advantageously acts as a solid surface in the selected frequencies and limits the transmission of the frequencies emitted by the sound source for which the waveguide is designed, and on the other hand, allows the transmission of other frequencies, more specifically the frequencies radiated by the non-coaxial drivers (usually woofers).

[0006] Covering a low frequency driver may cause some problems with the dynamic performance of the driver, since the air volume movement of the driver requires sufficient openings to allow air to flow. Additionally, the subspace located in front of the woofer may induce undesirable resonances. Summary of the invention

[0007] According to the invention, at least some of the above problems are solved by acoustically connecting resistive or reactive resonators as separate elements of the cast housing to the subspace of the woofer, so that the overall volume of the loudspeaker is kept as small as possible. Advantageously, these resonators are at least partially located around the coaxial element. Furthermore, it is an object of the invention to improve the dynamic performance of the woofer.

[0008] More specifically, the sound amplification device according to the invention comprises: a uniform housing having a front, a side and a rear defining an interior space; the front being formed as a waveguide surface, comprising at least one driver located in the waveguide surface and capable of radiating the main sound power of the sound amplification device in the direction of a first acoustic axis; at least one additional driver connected to the housing, the additional driver being connected inside the housing so that a subspace is formed in the interior space, the subspace being defined by the additional driver, a spacer located between the additional driver and the front and the front of the housing; at least one first port adapted to lead from the subspace to an ambient space to a side or rear of the housing; and at least one resonator comprising at least one resonant cavity acoustically connected to the subspace, the resonator being tuned to at least one unwanted resonance of the subspace. Wherein the resonator is formed as a separate resonator unit connected to the uniform housing, the resonator unit being connected to the inner surface of the front of the housing.

[0009] Significant advantages are achieved by means of the present invention.

[0010] By one embodiment of the present invention, the low frequency driver is covered, yet the resonance problems caused by the subspace of the woofer are suppressed. In some embodiments, this suppression can occur at multiple frequencies by multiple resonators tuned to different frequencies.

[0011] By means of the invention, the entire front surface of the loudspeaker can be formed as a continuous waveguide for midrange and high frequencies without any disruptive resonances occurring at the subspace of the bass driver, while the overall volume of the loudspeaker can be kept as small as possible. By this measure, the entire audio frequency range of 18-20,000 Hz can be directed precisely to a "sweet spot", and the rest of the sound energy is distributed to the listening room due to the fully waveguided form of the loudspeaker, so that the housing of the loudspeaker itself does not significantly influence the frequency response in directions other than the main direction.

[0012] In other words, in conventional sound reinforcement devices where the entire baffle is planar or only partially curved to act as a waveguide, signals formed in directions other than the "sweet spot" will be reflected in an uncontrollable manner by the walls of the listening room. However, the present invention provides an enclosure whose sound pressure is optimally distributed in all directions, thereby making the reflections from the walls sound natural to the human ear.

[0013] Because the resonator is a separate component, it can be made from different materials and with different manufacturing processes than the cast housing. This facilitates the manufacture of more delicate components, such as curved or spiral resonator cavities. In addition, this enables the production of different types of resonators for alternative drivers for the same cast loudspeaker housing. The material of the resonator can also be freely selected from plastic to wood, or even metal. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In the following, some preferred embodiments of the present invention are described with reference to the accompanying drawings, in which:

[0015] Figure 1 A front view of a sound amplification device according to the prior art is shown.

[0016] Figure 2 Shows Figure 1 A cross section of the sound amplification device is shown.

[0017] Figure 3 Shows Figure 1 A partial cross section of the sound amplification device shown.

[0018] Figure 4 A graph showing the frequency response of an inner cavity and a corresponding resonator of a woofer according to the prior art is shown.

[0019] Figure 5A cross section of a subspace of a woofer according to the prior art is shown.

[0020] Figure 6 A cross section through a second subspace of a woofer according to the prior art is shown.

[0021] Figure 7 A cross section through a third subspace according to the prior art is shown.

[0022] Figure 8a A front view of a woofer according to the prior art is shown.

[0023] Figure 8b Shows Figure 8a AA section view of the woofer shown.

[0024] Fig. 9 A cross section through a third subspace of a woofer according to the prior art is shown.

[0025] Fig.10 A front view of a sound amplification device according to an alternative embodiment of the prior art is shown.

[0026] Fig.11 Shows Fig. 9 A cross section of the sound amplification device is shown.

[0027] Fig.12 A front view of a sound amplification device according to the prior art is shown.

[0028] Fig.13 A view showing a sound amplification system according to a preferred embodiment of the prior art is shown.

[0029] Fig.14 A cross-sectional view of a sound amplification device according to a preferred embodiment of the prior art is shown.

[0030] Fig.15 A resonator unit according to the invention is shown.

[0031] Fig.16 A resonator unit according to the invention is shown connected to the front part of a housing inside a sound amplification device.

[0032] Fig.17 The sound amplifier device according to the invention is shown in a front view, wherein the resonator unit is indicated by dashed lines.

[0033] Fig.18 A further sound amplifier device according to the invention is shown in a front view, wherein the resonator unit is indicated by dashed lines. DETAILED DESCRIPTION

[0034] List of reference symbols used:

[0035] 1. Sound amplification device

[0036] 2 Housing

[0037] 3 waveguide drivers, can also be coaxial drivers or just tweeters

[0038] 4 woofers, low frequency drivers, additional drivers

[0039] 5 A front port (opening) of the woofer, the low frequency driver having an outer edge on the surface of the housing 2, which defines a plane of the edge of the front port

[0040] 6 Selective sound-transmitting layer

[0041] 7 Support structure of the selective sound-transmitting layer

[0042] 8 The three-dimensional waveguide surface is also the front surface of the housing 2 that radiates the main sound power. It has a smooth continuous surface and has an axially symmetrical feature around the center of the waveguide driver 3.

[0043] 9 Sweet Spots for Multiple PA Installations

[0044] 10 First sound axis

[0045] 11 Second sound axis

[0046] 12 Tweeters

[0047] 13. Medium frequency driver

[0048] 15 The front part (wall) of the housing (which may also be the waveguide surface 8), the front baffle part, which radiates the main sound power and includes the waveguide surface 8 and has a plane 28 perpendicular to the first acoustic axis 10

[0049] B1 Frequency band of waveguide driver 3

[0050] B2 Non-coaxial driver 4 frequency band

[0051] C Crossover band between bands B1 and B2

[0052] d is the depth of the cavity of the panel resonator

[0053] 20 The first port, also a side opening, has an outer edge defining a plane of the first port on the housing surface.

[0054] 21 Side (wall) of housing

[0055] 22 Subspace, also the space in front of the woofer or low frequency driver, is part of the interior space 27

[0056] W is the width of the subspace

[0057] L is the length of the subspace

[0058] The side wall of the subspace 23 (front space) forms a spacer between the driver 4 and the housing 2. The angle between the tangent line of the middle of the side wall 23 and the plane 28 of the front part 15 is not zero, and is typically about 90 degrees.

[0059] 25 is 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 present invention, the plane of the rear portion 25 may have different angles.

[0060] 26 Environmental Space

[0061] 27 Internal space of housing 2

[0062] 28 Front plane

[0063] 29 The plane of the side portion 21 is determined by the tangent to the center of the portion

[0064] 30 The plane of the rear part, determined by the tangent to the center of the part

[0065] 31 Front port 5 plane

[0066] The plane 32 of the first port 20, the plane 31 of the front port 5 and any plane 32 of the first port 20 have an angle α greater than 0 degrees. When the first port 20 is not located on the rear portion 25, the angle α is preferably greater than 45 degrees.

[0067] 33 Spacer, part between the woofer and the front part 15, an integral part of the housing 2, or a separate element

[0068] 34 Reflection port

[0069] α Angle between the plane 31 of the front port 5 and the plane 32 of the first port 20

[0070] 40 Resonator

[0071] 40' Sub-Resonator

[0072] 41 Resonator Suppression Materials

[0073] 43 Frequency Response of Subspace

[0074] 44 Frequency response of a resonator

[0075] f0 Resonance frequency

[0076] 45 The opening or neck of a Helmholtz resonator

[0077] 46 Resonator or cavity of a Helmholtz resonator

[0078] 47 Woofer cover

[0079] 48 Cover tube

[0080] 50 Panel resonator panel

[0081] 51 Resonator Unit

[0082] 52 Connection lug

[0083] according to Figure 1 A prior art loudspeaker device 1 that can be used at least partially in the present invention comprises a coaxial waveguide driver 3, which comprises a tweeter 12 and a midrange driver 13 surrounding it. The coaxial driver 3 is located at the center of the three-dimensional waveguide surface 8, which is also the front surface of the housing 2. The housing is usually made of cast metal, preferably aluminum. Other castable or moldable materials (such as λtic composite materials) can also be used as the material of the housing.

[0084] The waveguide surface 8 radiates the main acoustic power of the driver 3. The waveguide 8 has a smooth continuous surface with an axially symmetrical feature 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 housing 2, and narrow ports (openings) 20 (i.e., first ports) are formed just behind the waveguide surface of the woofer 4 to release the acoustic energy from the housing 2. In this embodiment, these first ports 20 are located at the narrow front end of the housing 2, and these ports are partially visible from the listening direction. In other words, the first ports 20 are U-shaped grooves.

[0085] The woofer 4 is shown by dashed lines, as well as the outline of the woofer subspace 22 and the resonators 40 connected to the woofer subspace 22. The function of the resonators 40 is to damp the resonance of the woofer subspace 22. These resonators 40 are located partially 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, so that the ratio W / H is about 1.8, typically in the range of 1.0-5. The resonator 40 is usually an integral part of the housing.

[0086] The resonator is dimensioned so 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 a wavelength λ, the resonator should be λ / 4 long. In the frequency domain, this means that at resonance f0 λ=v / f0, where v is the speed of sound. Advantageously, the resonator 40 is filled with a suppressing material 41, such as PES wool, open-cell foam, glass fiber, mineral wool, felt, or other fibrous or open-cell or porous material, or can be made of any solid material instead, which is manufactured in space so that the material has an open-cell or fibrous structure, where the pore size or fiber size is in the size region of 1 micron to 1 millimeter.

[0087] refer to Figure 2 , the resonator 40 can also be located at least partially behind the coaxial driver 3.

[0088] Reference Figure 2 and Figure 3 , the two woofers 4 placed symmetrically around the coaxial driver form an equivalent large woofer that radiates through port 20 substantially along the same acoustic axis 10 as the waveguide driver 3, even though the two woofers have their own acoustic axes 11.

[0089] In other words, the sound amplification device 1 includes 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 acoustic 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 a crossover region, and the second frequency band B2 has a second acoustic axis 11. The housing 2 surrounds the drivers 3 and 4, and includes a three-dimensional waveguide 8 located on the front surface of the housing 2 and surrounding the first driver 3.

[0090] As described above, the second acoustic axis 11 of each woofer driver is not coaxial with the first acoustic axis 10, but the composite axis of a plurality of symmetrical woofers (equivalent woofer drivers) working together has the same acoustic axis as the coaxial driver (i.e., the waveguide driver 3). However, this symmetry is not necessarily required in all embodiments of the present invention. The acoustic axes 10 and 11 may be parallel, or non-parallel.

[0091] Reference Figure 2 and Figure 3 , the woofer 4 is located in the housing 2 so that a subspace 22 is formed in front of the woofer 4, which is limited by the woofer 4 itself and the side walls 23. A resonator 40 is acoustically connected to this subspace 22. A suitable damping material 41 can be used in the resonator 40 to further attenuate unwanted frequencies.

[0092] The side walls 33 of the subspace (front space) 22 form a spacer between the driver 4 and the housing 2 to seal the subspace 22 relative to the rest of the interior space 27 of the housing 2. More specifically, the interior space 27 is defined by the walls of the housing 2, namely the front 15, the side 21 and the rear 25.

[0093] Typically, the first port 20 is oriented substantially orthogonally relative to the first axis 10 and the second axis 11, most preferably within a range of 60-120 degrees relative to these axes. However, when the first port 20 is directed to the rear 25 of the housing 2, for example by a passage, the difference between the direction of the first port 20 and the axes 10 and 11 may even be 180 degrees.

[0094] The total area of ​​the first port 20 is the key feature, so the first port 20 can be just one single first port 20 for each woofer 4, as shown, or can be formed by a plurality of first ports 20, such as a grille with an area corresponding to one single port.

[0095] 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 can be guided to the rear 25 of the housing 2 by suitable tubes or channels (not shown). In other words, the first ports 20 form air passages to areas other than the three-dimensional waveguide 8 of the front 15 of the housing 2.

[0096] Figure 4 The graph of FIG. 4 shows the frequency response of the subspace 22 of the woofer 4 (solid line), wherein there is a resonance at f0, Figure 4 Also shown is the corresponding frequency response (dashed line) of a resonator 40 acoustically connected to the subspace 22 , wherein the resonator 40 compensates for the undesired resonance of the subspace 22 .

[0097] Figure 5 An alternative embodiment is shown with two resistive resonators 40 of different lengths L for the two unwanted frequencies of the subspace. It is also possible to use one or two resistive broadband resonators, preferably filled with suppression material. In this case, the mechanical dimensions (length, width and depth) of the resonant cavity define one or more tuning frequencies of the resonator.

[0098] Figure 6An alternative embodiment with one reactive Helmholtz resonator 40 is shown. Typically, reactive resonators have a high quality factor and they are very efficient narrowband resonators. Also, if there are multiple sharp unwanted resonances, several such resonators can 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 as follows.

[0099] The resonance originates 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 cavity. The Helmholtz resonator can attenuate undesirable resonances close to the resonant frequency of the subspace 22. 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.

[0100]

[0101] Where f0 is 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.

[0102] Figure 7 An alternative embodiment is shown having one reactive panel resonator as the resonator. The dimensions of this embodiment are determined based on the mass per unit of the panel 50 and the depth d of the cavity in the following manner.

[0103] The resonant frequency f of the panel resonator / film absorber is defined as follows:

[0104]

[0105] Where m is the acoustic mass per unit area of ​​the panel 50 (kg / m 2 ), d is the depth of the cavity.

[0106] The stiffness of the membrane fixation can be neglected.

[0107] Figure 8a A woofer 4 is shown in top view, having 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. Figure 8b The AA section of this solution is shown in Figure 2. Figure 5 and Figure 6 same.

[0108] Fig. 9Another alternative solution is shown, in which the resonator 40 is formed between the front baffle part 15 and the subspace 22 of the woofer. If the opening to the subspace 22 is made as a tube, the resonator can be a resistive or reactive resonator without any neck. The tuning principle is the same as in the previous figures.

[0109] Generally, the sound amplification device according to the invention functions according to the well-known bass reflex principle, wherein the low frequency driver 4 is driven by means of the air volume contained within the housing 27 and Figure 2 The compliance of the air volume contained within the reflection port 34 as shown is tuned.

[0110] An embodiment of the prior art that can be at least partially used in the present invention ( Figure 10-11 ) can also be described in the following way.

[0111] The loudspeaker device 1 comprises a housing 2 defining an interior space 27 and a front baffle portion 15 (front portion) having a front port 5 for providing a fluid passage between the interior space 27 of the housing 2 and an ambient space 26, the interior space 27 further comprising a side portion 21 extending rearwardly from the periphery of the baffle portion 15. The side portion 21 forms a side wall of the housing 2. The housing further comprises a rear portion 25 which is generally substantially parallel to the front baffle portion 15 and forms a rear side of the housing 2. The loudspeaker device 1 further comprises a driver 4 connected to the housing 2 such that the driver 4 is arranged at a distance from the baffle portion 15, thereby forming a subspace 22 inside the housing 2, such that the subspace 22 is formed between the driver 4 and the baffle portion 15 by a spacer 33, wherein the front port 5 serves as a front port between the subspace 22 and the ambient space 28 of the housing 2. According to this embodiment, a first port 20 is formed on the housing 2 in the side portion 21 or the rear portion 25 so that the subspace 22 and the ambient space 26 communicate with each other.

[0112] according to Fig.10 In one embodiment of the present invention shown, two woofer drivers 4 are located on either side of a waveguide driver 3 within a housing 2, and suitable ports (openings) 5 are formed for the woofers 4 so that sound energy can be output from the housing 2.

[0113] refer to Fig.11 The opening 5 is covered by an acoustically transparent layer 6 which forms part of a waveguide surface 8. If desired, the acoustically transparent layer 6 may be supported from below by support rods 7. The woofer driver 4 is typically spaced apart from the acoustically transparent layer 6.

[0114] Reference Fig.10Even though the two woofers 4 have their own acoustic axis 11 , they form an equivalent large woofer which radiates essentially along the same acoustic axis 10 as the waveguide driver 3 .

[0115] In other words, the sound amplification device 1 includes 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 acoustic 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 a crossover region, and the second frequency band B2 has a second acoustic axis 11. The housing 2 surrounds the drivers 3 and 4, and includes a three-dimensional waveguide 8 located on the front surface of the housing 2 and surrounding the first driver 3. The three-dimensional waveguide 8 includes a selective sound-transmitting portion 6, which can acoustically substantially reflect sound waves of the first frequency band B1 propagating in a direction at a certain angle to the first acoustic axis 10, and the waveguide portion 6 is substantially transparent to sound waves of the second frequency band B2 propagating through the waveguide portion 6 in the direction of the second acoustic axis, and the second driver 4 is located inside the housing 2 and behind the selective sound-transmitting portion 6.

[0116] As described above, the second acoustic axis 11 of each woofer driver is not coaxial with the first acoustic axis 10, but the composite axis of the multiple woofers (equivalent woofer drivers) working together has the same acoustic axis as the coaxial driver (i.e., the waveguide driver 3). However, this symmetry is not necessarily required in all embodiments of the present invention. The acoustic axes 10 and 11 can be parallel, or non-parallel.

[0117] Reference Fig.10 and Fig.11 , the woofer 4 is located inside the housing 2 so that the subspace 22 is formed in front of the woofer 4 and is defined by the woofer 4 itself, the side walls 23 and the selectively sound-transmitting 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 can be resistive or reactive. For a resistive resonator, the suppression characteristics are of a broadband type. In other words, the notch around the center frequency f0 generated by the resistive resonator is not as sharp as in a reactive resonator. The side walls 33 of the subspace (front space) 22 form a spacer between the driver 4 and the housing 2, sealing the subspace 22 relative to the rest of the internal space 27 of the housing 2. More specifically, the internal space 27 is defined by the walls of the housing 2, namely the front 15, the side 21 and the rear 25.

[0118] In some embodiments of the invention, the selectively acoustically transparent layer 6 can be replaced by a mechanically protective grille which in this case defines the subspace as well as the inner space 27. Advantageously, first ports 20 are formed in the side walls of the subspace 22 and are connected to the sides 21 of the housing 2 to optimize the operation of the woofer 4. Without these first ports 20, the performance of the woofer 4 may be impaired. The first ports 20 can be located on any of the sides 21, for example the shorter side 21 as shown in the figure, or the longer side 21.

[0119] Typically, the first port 20 is substantially orthogonal relative to the first axis 10 and the second axis 11, most preferably within a range of 60-120 degrees relative to these axes. However, when the first port 20 is directed to the rear 25 of the housing 2, for example by a passage, the difference between the direction of the first port 20 and the axes 10 and 11 may even be 180 degrees.

[0120] The area of ​​these first ports 20 is typically 5-50% of the area of ​​the opening 5 of the woofer 4, most advantageously in the range of 10-20% of the area of ​​the opening 5 of the woofer 4. The total area of ​​the first ports 20 is the key feature, so the first ports 20 can be just one single first port 20 for each woofer 4, as shown, or can be formed by a plurality of first ports 20, for example a grid with an area corresponding to that of a single port.

[0121] 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 can be guided to the rear 25 of the housing 2 by suitable tubes or channels (not shown). In other words, the first ports 20 form air passages to areas other than the three-dimensional waveguide 8 of the front 15 of the housing 2.

[0122] Typically, the second driver 4 is located inside the housing 2, behind and separated from the selectively sound-permeable portion 6, so that a subspace 22 is formed inside the housing 2 and is separated from the interior space 27 by the driver 4 and the side wall 23, and the side wall 23 is formed as a spacer between the driver 4 and the front 15 of the housing 2.

[0123] For the selectively sound-transmitting layer 6, "substantially reflective" means reflecting or absorbing at least 50-100% of the sound energy, preferably in the range of 80-100%.

[0124] In the same manner, "substantially transparent" means at least 50-100% transparency of acoustic energy, preferably in the range of 80-100%.

[0125] Further advantageous properties of the selectively acoustically permeable layer 6 are presented below.

[0126] The thickness of layer 6 is advantageously:

[0127] □-Felt, about 1-5 mm thick

[0128] □-Open-cell plastic foam, about 1-20 mm thick, with a pore size less than 1 mm

[0129] □-Thin fabric as layer 6 or part of layer 6.

[0130] The layer 6 should attenuate the acoustic radiation of the waveguide driver 3, which means typically frequencies above 600 Hz.

[0131] In other words, layer 6 should have an acoustic impedance (or absorption) as a function of frequency, and thus act as an acoustic filter in the following manner:

[0132] - The sound from the woofer driver 4 is low-passed - The high frequencies from the waveguide driver 3 are attenuated (e.g. by oscillation or absorption with high losses), resulting in strong reflections of mid- and high-frequency sound waves

[0133] - High reflectivity for high frequencies of driver 3

[0134] Advantageously, the layer 6 is formed with holes or pores or a combination thereof in the following manner:

[0135] - If using a single layer 6, the diameter of the hole should be less than 1mm

[0136] - If multiple layers 6 are used, holes with a diameter less than 1 mm are possible

[0137] - Also, if multiple layers 6 are used, holes with diameters larger than 1mm are possible (not tested yet)

[0138] - Microstructures like felt and open-cell plastic are possible. The properties of the ideal material for layer 6 are as follows:

[0139] - Breathable (=porous)

[0140] - Low acoustic losses up to the crossover frequency C (woofer 4)

[0141] - High acoustic reflectivity slightly above the crossover frequency C

[0142] - Known materials that meet the above conditions:

[0143] □Felt, about 1-5 mm thick

[0144] □Open-cell plastic foam, about 1-20 mm thick, with a pore size less than 1 mm

[0145] The layer 6 may cover the front part of the loudspeaker device (excluding the tweeter 12 ), or only the hole 5 .

[0146] Layer 6 can also be formed as a metal structure, for example with one or more layers of mesh or grid, depending on the above requirements for porosity and frequency characteristics. Such a structure can be formed, for example, by a stack of perforated metal sheets or plates with a thickness of about 0.2-2 mm. The properties of this 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 apertures can generally vary from about 0.3-3 mm. The spacing between the sheets or plates is generally about 0.2-2 mm.

[0147] The above-described metal structure is advantageous because its characteristics can be freely adjusted and external characteristics such as color can be selected without restriction.

[0148] The crossover frequency C is usually as follows:

[0149] - Low frequency f<600Hz (output range of woofer)

[0150] - High frequency f>600Hz (midrange and / or tweeter output range)

[0151] According to the present invention, in combination with a large waveguide 8:

[0152] - The woofer 4 is placed behind the waveguide surface 8

[0153] - Two or more (eg 4) woofers 4 may be used to obtain directivity, the woofers may be placed symmetrically with respect to the coaxial driver

[0154] Likewise, embodiments with only one woofer are possible, but no low frequency directivity is achieved beyond those benefits resulting from the size of the woofer's air moving surface combined with the size of the front baffle of the loudspeaker housing.

[0155] In an alternative embodiment of the invention, the selectively permeable portion 6 may be replaced by a mechanical protection barrier having no full characteristic of selective permeability.

[0156] according to Fig.12 , the resonator can be divided into a plurality of independent sub-resonators 40', each sub-resonator having its own resonant frequency.

[0157] Fig.13 A typical positioning of a sound amplification device 1 according to the invention is shown, wherein the sound amplification device is directed towards the listening position, i.e. the sweet spot 9. Due to the fact that the entire front surface of the housing 2 is formed as a waveguide 8, a very good directivity can be achieved. Furthermore, the waveguide form 8 distributes all frequencies uniformly in all directions in the listening room, so that reflections from walls, ceiling and floor do not lead to sound coloration. Fig.13Also shown are the front 15 , the side 21 and the rear 25 of the housing 2 of the loudspeaker device 1 .

[0158] exist Fig.14 , a sound amplification device is shown in which a suppression material 41 is located in a resonant cavity 40. In this figure, only the upper cavity 40 is filled with the material, but in reality, both the upper cavity and the lower cavity 40 will be filled with the suppression material.

[0159] according to Fig.15 The resonator unit 51 is usually made of plastic. Other materials such as moldable wood or metal may also be used. Fig.15 The side of the resonator 51 is shown, which will be connected to the front plate 15 of the cast housing. The connection is usually made by screws passing through the connecting lugs 52. The resonator unit is usually tapered so that the highest part of the unit is located close to the center of the resonator opening 45, and the edges of the unit 51 are correspondingly lower. Because the resonator unit 51 is separate from the larger cast metal housing, a delicate structure can also be achieved. In this case, the resonant cavity is made significantly curved in order to obtain the desired length L of the resonant cavity in the smallest possible overall size of the resonator unit 51.

[0160] Fig.16 The resonator unit 51 is shown connected to the cast metal housing, in particular to the front part 15 of the housing, so that the resonator opening 45 is directed towards the coaxial driver comprising the tweeter 12 and the midrange driver 13. Thus, the opening 45 of the resonator unit 51 is directed away from the first port 20 of the sound amplification device. Fig.16 Also visible is the suppression material 41 located in the cavity and extending to the opening 45 of the cavity.

[0161] Fig.17 and 18 An embodiment of a resonator unit is shown in dashed lines.Only one resonator unit 51 is shown per loudspeaker device, but of course there is also a second resonator unit at the bottom of each loudspeaker device.

[0162] Combination Figures 15 to 18 The dimensions of the resonant cavity 46 can be determined in accordance with the principles described in conjunction with other figures, especially Figure 4-9 Same as described.

[0163] Typically, the uniform loudspeaker housing 2 is made by casting or molding metal, plastic or wood material.

Claims

1. A sound amplification device (1), comprising: a uniform housing (2) having a front portion (15), side portions (21) and a rear portion (25) defining an interior space (27), The front part (15) is formed as a waveguide surface (8), comprises at least one driver (12, 13) located in the waveguide surface (8) and is capable of radiating the main sound power of the loudspeaker device (1) in the direction of a first acoustic axis (10), and at least one additional drive (4) connected to the housing (2), The additional drive (4) is connected to the interior of the housing (2) so that a subspace (22) is formed in the interior space (27), the subspace (22) being defined by the additional drive (4), a spacer (33) between the additional drive (4) and the front part (15), and the front part (15) of the housing (2), at least one first port (20) adapted to open to the side (21) or rear (25) of the housing (2) from the subspace (22) to the ambient space (26), and at least one resonator (40) comprising at least one resonant cavity (46) acoustically connected to the subspace (22), the resonator (40) being tuned to at least one unwanted resonance of the subspace (22), It is characterized in that The resonator (40) is formed as a separate resonator unit (51) connected to the homogeneous housing (2), and The resonator unit (51) is connected to the inner surface of the front portion (15) of the housing (2).

2. The sound amplification device according to claim 1, characterized in that: The resonator unit (51) is made of plastic, wood or metal.

3. The sound amplification device according to claim 1 or 2, characterized in that: The resonator unit (51) comprises one or more curved cavities (46) having an opening (45).

4. The sound amplification device according to claim 1 or 2, characterized in that: The opening (45) of the resonator unit (51) faces away from the first port (20) of the sound amplification device.

5. The sound amplification device according to claim 1 or 2, characterized in that: The resonator (40) is a resistance resonator with broadband characteristics.

6. The sound amplification device according to claim 1 or 2, characterized in that: The resonator (40) comprises a damping material (41).

7. The sound amplification device according to claim 6, characterized in that: The attenuating material is PES wool, open cell foam, fiberglass, mineral wool or felt, or other fibrous or open cell material or porous material, or any solid material which is manufactured in a spatial position so that the material has an open cell or fibrous structure, wherein the pore size or fiber size is in the size range of 1 micron to 1 mm.

8. The sound amplification device according to claim 1 or 2, characterized in that: The resonator (40) is a reactance resonator.

9. The sound amplification device according to claim 1 or 2, characterized in that: The subspace (22) has a width W and a length L, such that W / L is in the range of 1.2-2.

5.

10. The sound amplification device according to claim 9, characterized in that: W / L equals 1.

8.

11. The sound amplification device according to claim 1 or 2, characterized in that: The front portion has a front port (5), and a plane (31) of the front port (5) and a plane (32) of any one of the first ports (20) have an angle α greater than 0 degrees.

12. The sound amplification device according to claim 11, characterized in that: When the first port (20) is not on the rear portion (25), the angle α is greater than 45 degrees.

13. The sound amplification device (1) according to claim 1 or 2, characterized in that: The at least one driver is configured to generate a first frequency band (B1) and a corresponding first acoustic axis (10), and the additional driver is configured to generate a second frequency band (B2) and a corresponding second acoustic axis (11), wherein the second acoustic axis (11) is not coaxial with the first acoustic axis (10).

14. The sound amplification device (1) according to claim 13, characterized in that The second acoustic axis (11) is not parallel to the first acoustic axis (10).

15. The sound amplification device (1) according to claim 1 or 2, characterized in that: The at least one drive comprises two drives (12, 13) which are coaxial with each other.

16. The sound amplification device (1) according to claim 1 or 2, characterized in that: The at least one drive comprises only one drive (12, 13).

17. The sound amplification device (1) according to claim 1 or 2, characterized in that: The sound amplification device (1) is a bass reflex sound amplification device.

18. The sound amplification device (1) according to claim 1 or 2, characterized in that: The uniform shell (2) is made by casting or molding metal, plastic or wood material.

19. The sound amplification device (1) according to claim 1 or 2, characterized in that: The uniform shell (2) is made by machining metal, plastic or wood material.

20. The sound amplification device (1) according to claim 1 or 2, characterized in that: The at least one driver (12, 13) is located in the center of the waveguide surface (8).

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