EP1078553A1

EP1078553A1 - Sound reproduction device working according to the bending wave principle

Info

Publication number: EP1078553A1
Application number: EP99952146A
Authority: EP
Inventors: Wolfgang Bachmann; Gerhard Krump; Hans-Jürgen Regl
Original assignee: Harman Audio Electronic Systems GmbH
Current assignee: Harman Becker Automotive Systems GmbH
Priority date: 1998-05-15
Filing date: 1999-05-14
Publication date: 2001-02-28
Anticipated expiration: 2019-05-14
Also published as: DE59906440D1; DE19821862A1; US6622817B1; WO1999060819A1; EP1078553B1

Abstract

The invention concerns the embodiment of panel loudspeakers working according to the bending wave principle. Said loudspeakers are generally formed by at least one acoustic panel (11) and at least one driver (12), the driver (12) being connected to the acoustic panel (11). When such acoustic panels (11) are used for reproducing low frequency audio signals, the acoustic panels (11) must be arranged in sufficiently large sound walls in order to exclude the occurrence of an acoustic short circuit between the front part and the back part of the panel. Apart from being costly, only one side of the sound walls is actively used for sound generation as a result of the separation of both acoustic panels (11). Hence, the invention aims at providing a panel loudspeaker (10) that does not require any additional sound walls in order to exclude the occurrence of an acoustic short circuit while at the same time enabling full utilization of the surface of the acoustic panel (11) for sound generation, This is achieved by arranging two of the acoustic panels (11.1, 11.2) at a distance (A) in relation to each other, by providing elements (13) connecting both acoustic panels (11.1, 11.2) and by arranging the drivers (12) on the sides of the acoustic panels (11.1, 11.2) facing each other. Due to the fact that, once connected, both acoustic panels (11.1, 11.2) vibrate in opposite directions, they mimic the principle of a breathing sphere or wall.

Description

description

SHALLW IEDERGABEARLANUNG UND DER B I EGEWELLENP RINZ IP

Technical field

The invention is concerned with the formation of sound reproduction arrangements which operate according to the bending wave principle, in particular with the improved utilization of the areas provided by such arrangements for sound generation.

State of the art

According to the prior art, sound reproduction arrangements are known which operate according to the bending wave principle. Such arrangements are essentially formed by a sound panel and at least one drive system, the sound panel being set in vibration when electrical audio frequency signals are supplied to the drive system (s). It is characteristic of such sound reproduction arrangements that "bending wave radiation" becomes possible from a lower limit frequency, the so-called critical frequency, the bending waves in the plane of the respective sound panel leading to sound radiation with a frequency-dependent direction. In other words, a section through a directional diagram created shows a main lobe, the direction of which is frequency-dependent.These ratios are fully valid for infinitely extended plates and absorber plates, while the ratios for the multi-resonance plates (also known as distributed mode loudspeakers) dealt with in this application are then significantly more complex because of the strong edge reflections Multi-resonance plates therefore stirs that the named main lobe with frequency-dependent direction is overlaid by a plurality of further such main lobes, so that a highly diversified directional diagram arises, which also is very frequency dependent. A typical characteristic of the multi-resonance plates dealt with here is that their directional diagrams on average tend to point away from the perpendicular. This behavior means that the room is more involved in the projection of the sound waves.

The sound panel is constructed according to the sandwich principle, in that two opposing surfaces of a very light core layer are each connected to a thin cover layer, for example by gluing. In order for the sound panel to have good sound reproduction properties, the material for the cover layer must have a particularly high expansion wave speed. Suitable cover layer materials are, for example, thin metal foils or fiber-reinforced plastic foils.

There are also special requirements for the core layer. So it is necessary that the materials that can be used initially have a low mass density and low damping. In addition, the materials for the core layer must have the highest possible shear modulus perpendicular to the surfaces that are provided with the cover layers. Finally, it is necessary that the materials that can be used for core layers have a very low modulus of elasticity in the direction in which the core layer formed from this material later has its greatest extent. These conditions, which at first glance are contradictory with regard to the last two requirements, are best met by a core layer which has a perforated structure with openings with a preferably small cross-section running between the two surfaces provided for the coating with the cover layers. In addition to the core layers with the perforated structure, rigid foams can also be used as core layer materials because, despite their isotropic material properties, they still have suitable shear and elasticity modules. It should not be left unmentioned in this context that when rigid foams are used as the material for the core layer, the cover layers have the task of producing the required anisotropic behavior of the sound panel.

The sound panels are driven by drivers that

- as shown in DE-A-197 57 097 - either attached to the respective sound panel or integrated into it.

If, above all, low-frequency sound signals are to be reproduced with the acoustic panels, it has been shown that special measures must be taken to reduce the acoustic short circuit. In the simplest case, this can be achieved by means of a sufficiently large baffle in which the sound panel is installed. Apart from the fact that the baffle represents an additional cost factor, this measure also reduces the area of the sound panel that is potentially available for sound radiation.

The invention is therefore based on the object of specifying a sound panel which, with the same space requirement, reduces or excludes the acoustic short circuit and at the same time uses the surface of the sound panel available for sound radiation for increasing the sound level or expanding the frequency range. Presentation of the invention

This object is achieved with the features according to claim 1. Advantageous developments and further developments of the invention can be found in the dependent claims.

If two sound panels are arranged at a mutual distance A from one another and surrounded by a frame, a space is formed between the two sound panels and the frame, which separates the sound waves radiated into this room from the sound waves emitted by the two surfaces of the sound panels facing away from each other . If the drivers, which drive the two sound panels arranged at a mutual distance A, are controlled electrically in parallel, a monopole radiator is created which, thanks to the oppositely vibrating sound panels, ensures that the listening room is particularly well-sounded according to the principle of a breathing ball or wall.

If the sound energy emitted into the interior of the sound panels and the frame is also to be used for sound reinforcement in the listening room, the sound panels and / or the frame are to be provided with sound outlet openings. In this case, the space formed between the sound panels and the frame can be designed as a bass reflex volume and the respective sound outlet opening as a bass reflex opening. It is also possible to connect a transmission line to the sound outlet opening.

Already at this point it should be pointed out that the arrangement according to the invention is not only fixed on the pure bass reproduction. Rather, it is also possible to implement a combined arrangement in which one sound panel together with the space which has already been mentioned several times above is primarily designed for use in bass reproduction, while the other sound panel is then optimized for reproduction, for example in the mid / high range. The latter includes, according to claim 8, that the two sound panels are optimized in terms of material and / or dimensions for their respective transmission areas and can therefore also differ, for example, in terms of their thickness, the core layer material and / or the cover layers used. The fact that the sound panel, which is intended for bass reproduction, in contrast to the other sound panel, does not face the listener directly, is irrelevant, because the human ear has a poor location for frequencies below 100 Hz. If the drivers are arranged according to claim 2, the one driver which drives the one sound panel simultaneously acts as a counter bearing for the driver driving the other sound panel. Such a design is therefore particularly advantageous when the connected drivers, which drive the various sound panels, are operated electrically in parallel and thus oscillate in opposite directions.

The effort is further reduced if the connected drivers are designed as common drivers. Arrangements are to be understood here, whose common components and magnetic circuits contribute to driving both sound panels arranged at a mutual distance A.

If resilient elements are arranged at a distance A between the two sound panels, further stabilization of the two sound panels is achieved through mutual support. The springs can also be used to tune the sound panels due to their damping effect.

It is particularly advantageous if the drivers are not attached to the sound panels, but to the elements (frame and / or springs). This type of mounting of the drivers ensures that the bending wave propagation in the sound panels is not or only slightly impaired by mass loads or that the drivers do not cause any damping effects.

Brief presentation of the figures

Show it:

Figure 1 shows a sound reproduction arrangement in side section.

2 shows a section through a driver of a sound reproduction arrangement;

FIG. 3 shows a further illustration of an arrangement according to FIG. 2;

FIG. 4 shows a further illustration of an arrangement according to FIG. 2;

FIG. 5 shows a further illustration of an arrangement according to FIG. 2; and

6 shows yet another representation of an arrangement according to FIG. 2. Ways of completing the invention

The invention will now be explained in more detail with reference to the figures.

The side section shown in FIG. 1 shows a sound reproduction arrangement 10, which is essentially formed by a front sound panel 11.1, a rear sound panel 11.2, three drivers 12 and a frame 13.

The two sound panels 1 1.1, 11.2, which are arranged at a mutual distance A from one another, are connected to the frame 13 at their edges 14. Even if the connection between the frame 13 and the sound panels 11.1, 1 1.2 is designed as a rigid connection, in a different - not shown - example of embodiment between the frame 13 and the sound panels 1 1., 1 1.2 a corrugation - such as that in an under the filing date of this filing for the filing of the filing is shown. In room 15, which is enclosed by the two sound panels 1 1.1, 11.2 and the frame 13, two of the three drivers 12 are used back to back. These two completely identical drivers 12.1, 12.2, which are only shown schematically, are designed as ferrite systems in this exemplary embodiment and are connected to the respective sound panels 11.1, 1 1.2 via the voice coil carriers 26. If the voice coils of the two drivers 12.1, 12.2 are conductively connected to an audio signal source (all not shown), both sound panels 11.1, 11.2 are deformed in opposite directions. This deformation of the two sound panels 11.1, 11.2 causes the sound reproduction arrangement 10 to act like a breathing ball or wall.

For the sake of completeness, it should be pointed out that the sound reproduction arrangement 10 shown in FIG. 1 is designed as a bass reproduction arrangement. An acoustic short circuit between the surfaces of the two sound panels 11.1, 11.2 coupled directly to the listening room 16 is excluded because under the influence of the sound signals the two sound panels 11.1, 1 1.2 move in opposite directions with respect to the center line shown and the radiation emitted into the room 15 Sound energy is separated from the listening room 16 by the sound panels 11.1, 11.2 and the frame 13. If the sound energy radiated into the interior of the room 15 is also to be used for sound reinforcement in the listening room 16, the volume of the room 15 can be used as a so-called bass reflex volume, in that the interior of the room 15 by means of at least one Sound outlet opening 17 is connected to the listening room 16. 1, the sound outlet opening 17 is formed in the frame 13, in another embodiment (not shown), the sound outlet opening 17 can also be embedded in a sound panel 11.

In addition, a resilient element 18 is used in the interior of the room 15, which additionally supports the two sound panels 11.1, 11.2 arranged at a mutual distance A at the connection points 19 against one another. In addition to this supporting effect, the resilient element 18 can also exert a certain filtering effect on the sound waves to be emitted by the sound panels 1 1.1, 1 1.2.

12.3 denotes a driver which is embedded in the sound panel 1 1.2 and which is designed as a piezo driver. This driver 12.3 can be used, for example, to emit high-frequency sound signals from the sound panel 1 1.2. Since, in contrast to low-frequency sound waves, higher-frequency sound waves have a directional characteristic, the sound panel 1 1.2 having the driver 12.3 should face the listener in the listening room 16 directly to the sound reproduction arrangement 10.

In the exemplary embodiment according to FIG. 2, a sound reproduction arrangement 10 is shown in more detail. 2 that the two sound panels 1 1.1, 11.2 are each formed from a core layer 20 with a honeycomb structure and two cover layers 21. In addition, the drivers 12.1, 12.2, which drive the two sound panels 1 1.1, 11.2 according to FIG. 1, are designed as a common driver 12.4 in the exemplary embodiment according to FIG. 2. In detail, this is realized in such a way that a permanent magnet 22 with a ring shape is provided, the respective pole faces N, S of which are provided with a pole disk 23 in the form of a ring ring. In addition, the unit formed from the permanent magnet 22 and the pole disks 23 surrounds a pole 24 at a lateral distance. Since the common driver 12.4 is arranged in the center at a distance A between the two sound panels 11.1, 11.2, the present exemplary embodiments are two annular holding members 25 made of non-ferromagnetic material available. One holding member 25.1 connects the permanent magnet 22 to the pole 24, while the other holding member 25.2 is guided by permanent magnets 22 to the resilient elements 18 arranged at a lateral distance from the common driver 12.4 and is connected to the latter. This holding member 25.2 can also be connected to other drivers 12 and / or also to the edge 13 (FIG. 1) in another embodiment (not shown). For the sake of completeness, it should be pointed out that the holding members 25.1, 25.2 can be made of a resilient material and act like a leaf spring due to their parallel position to the sound panels 1 1.1, 11.2.

There are also two pot-shaped voice coil carriers 26 and each connected to one of the two sound panels 11.1, 11.2. The edges of the two voice coil carriers 26 are each provided with a voice coil 27 and dip into the gap between the pole 24 and the permanent magnet 22 and pole disk 23 unit.

If the sound reproduction device 10 of FIG. 2 as well as the arrangement of FIG. 1 are used as Baßanordnung and are in accordance with the above Ausfi ^'ihningen the two sound panels 1 1.1, respectively move in opposite directions 1 1.2 under the influence of sound signals, it is necessary that the current direction in the two voice coils 27 is different.

For the sake of completeness, it should be pointed out that a permanent magnet 22 made of a rare earth alloy in the form of a neodymium alloy was used to provide a sufficiently large induction in the embodiment according to FIG. 2. To further increase the induction, further permanent magnets can be connected to the common driver 12.4, according to Faclimannic developments of the arrangement according to FIG. 2, for example by forming part 24.1 of the pole core 24 from a permanent magnetic material.

If, as in the exemplary embodiment shown in FIG. 2, the sound reproduction arrangement 10 has no sound outlet opening 17 which connects the room 15 to the listening room 16, the room 15 should be at least partially filled with a sound-absorbing material (not shown).

Finally, it should be mentioned that the pole 24 in the embodiment shown in FIG. 2 does not necessarily have to be connected to the permanent magnet 22 via the holding member 25.1, but can also be connected to the sound panels 11.1, 11.2 in another embodiment. To avoid damping, the connection between Polkem 24 and the sound panels 11.1, 1 1.2 should then be elastic.

FIG. 3 shows a common driver 12.4, which is modified compared to driver 12.4 according to FIG. 2. This driver 12.4 (FIG. 3) also comprises an annular permanent magnet 22 and two voice coil carriers 26 provided with voice coils 27. In contrast to the embodiment according to FIG. 2, the embodiment according to FIG O

so-called inference parts in the form of pole disks and poles can be dispensed with. Instead, in the arrangement according to FIG. 3, the conclusion is made exclusively via the air gap between the two poles N, S of the radially magnetized Daueπnagneten 22. In particular, this is solved so that the permanent magnet 22 is connected to the sound panel 11.2 via a holding member 25.3 . The voice coil 27 ', which is connected to the sound panel 11.2 via the voice coil support 26, is adjacent to the south pole S of the radially magnetized Daueπnagneten 22 with a narrow lateral distance, while the other voice coil 27 "with the other pole N of the Daueπnagneten 22 when the sound reproducing device 10 is at rest With regard to the different diameters of the two voice coils 27 ', 27 "and the resulting conditions, the sound reproduction arrangement 10 shown in FIG. 3 can be used to emphasize different frequency ranges of the two sound panels 11.1, 11.2 . Will the

3 with frequency ranges emphasized differently in both sound panels 11.1, 1 1.2, the two sound panels 11.1, 1 1.2 should be optimized for the respective frequency ranges with respect to the cover layers 21 and core layers 20.

In contrast to driver 12.4 according to FIG. 3, driver 12.4 according to FIG. 4 has pole disks 23, although the inference there between the two poles N, S of the Daueπnagneten 22 also takes place via the air gap. Therefore, the pole disks connected to the pole faces N, S of the axially magnetized Daueπnagneten 22 do not have a direct inference effect, but only contribute to a concentration effect of the field lines provided by the Daueπnagneten 22 on the voice coils 27 'and 27 ". In contrast to all previously described embodiments 4, the provision of a separate voice coil former is dispensed with. Instead, the voice coils 27 ', 27 "are connected to the edges 28 of cutouts 29, which are embedded in each of the two sound panels 11.1, ϊ 1.2. The driver 12.4 formed from the permanent magnet 22 and the two pole disks 23 is inserted at a distance A using the cutouts 29. The direct connection between the pole discs 23 and the sound panels 11.1, 11.2 takes place with the interposition of a holding member 25.4. For these holding members 25.4, which can also be provided by the respective sound panel 1 1.1 or 11.2 itself by a corresponding milling 29 in another embodiment (not shown), it is essential that they have the greatest possible lateral distance A "between the voice coils 27 '. , 27 "and the respective Have joints of the sound panels 1 1.1, 1 1.2 with the drivers 12 in order to achieve a particularly good force impression in the sound panels 1 1.1, 1 1.2.

For this reason in Fig. 3 also between the voice coil support 26, which is connected to the sound panel 11.2, and the sound panel 11.2, an additional holding member (not shown), which has a reduced diameter compared to the named voice coil support 26.

In order to reduce the magnetic resistance and to increase the driving force, a driver 12.4 modified compared to FIG. 4 is shown in FIG. 6. This driver 12.4 is essentially formed by three axially magnetized permanent magnetic disks 22.1 to 22.3, two pole disks and a return rotor 30. The two pole faces N, S of the Daueπnagneten 22.2 are connected to the two pole disks 23. In addition, on each side of each pole disk 23, which is not connected to the Daueπnagneten 22.2, another Daueπnagnet 22.1, 22.3 attached and connected so that on each side of the two pole disks 23, which with the Daueπnagneten 22.2, 22.1 and 22.3, 22.1 are connected, the same poles N or S act. 6 that the Daueπnagnete 22.2 and 22.3, which are directly connected to the bottoms 31 of the cutouts in the sound panels 1 1.1, 11.2, have a reduced diameter compared to the pole discs 23. If the embossing of bending waves in the sound panels 1 1.1, 1 1.2 is to be further improved, another holding example (not shown) between the respective base 31 and the permanent magnet 22.1, 22.2 can also have a holding member (25.4) opposite, as shown in FIG. 4 the permanent magnets 22.1 and 22.3 of reduced diameter are arranged.

In order to reduce the magnetic resistance of the return path, the arrangement of the pole disks 23 and the Daueπnagneten 22.1 to 22.3 is inserted into a return path 30, which surrounds the arrangement with a lateral distance. The two, provided with the voice coils 27 ', 27 ", and immerse in the voice coil supports 26 acting on the two sound panels 1 1.1, 11.2, also dip into this annular gap. The yoke roller 30 is connected to the edges 28 of the bevel 29 in the sound panels 1 1.1, 11.2. In addition, a damping element 33, indicated by the punctuation, is inserted between the bottom 31 and the end faces 32 of the return tube 30, which reduces the damping otherwise emanating from the return tube 30. Only for the sake of completeness should it be pointed out that the use of the return tube 30 does not conform to driver training Fig. 6 is limited, but can also be used with a corresponding modification in an arrangement according to FIG. 4. If a direct connection, shown in FIG. 6, between the common driver 12.4 and the return circuit 30 with the sound panels 11.1, 11.2 is to be dispensed with, an attachment, as explained in conjunction with FIG. 2, can also alternatively be provided via resilient elements 18 and corresponding holding members 25 can be realized.

5 shows two sound panels 11.1, 11.2 arranged at a mutual distance A, each of which has a driver 12.1, 12.2 and a voice coil support 26 with a voice coil 27 ', 27 "arranged thereon. The mutual arrangement of driver 12.1, 12.2 and voice coil support 26 or voice coil 27 ', 27 "is selected such that the voice coil 27", which is physically connected to the sound panel 11.1, engages in the driver 12.2, which is connected to the sound panel 1 1.2 and is pot-shaped, and the voice coil 27' engages in the driver 12.1 on the sound panel 1 1.1. The mutual support of the two drivers 12.1., 12.2, which is not present in FIG. 5, is compensated for by the fact that the drivers 12.1, 12.2 or better their Daueπnagnete 22 as seismic masses provide a sufficient counter bearing.

Claims

Expectations

1. Sound reproduction arrangement

with at least one sound panel 1 1.1, 11.2, which is formed by a core layer 20 and at least one cover layer 21, and

with at least one driver 12, which is attached to the sound panel 11 or integrated in it,

characterized,

that two of the sound panels 11.1, 11.2 are arranged at a mutual distance A from one another,

that elements 13 are present which connect the two sound panels 11.1, 11.2, and

that the drivers 12 are arranged on the sides of the sound panels 11.1, 11.2, which face each other.

2. Sound reproduction arrangement according to claim 1,

characterized,

that at least one driver 12.1 of a sound panel 11.1 is connected to a driver 12.2 of the other sound panel 11.2.

3. Sound reproduction arrangement according to claim 2,

characterized,

that the connected drivers 12.1, 12.2 of both sound panels 11.1, 11.2 are designed as common drivers 12.4.

4. Sound reproduction arrangement according to one of claims 1 to 3,

characterized,

that the element 13, which connects the two sound panels 11.1, 11.2, a Ralimen 13, which is connected to the edges 14 of the sound panels 11.1, 11.2.

5. Sound reproduction arrangement according to one of claims 1 to 4,

characterized,

that resilient elements 18 are present and

that these resilient elements 18 are arranged between two mutually facing sides of the sound panels 1 1.1, 11.2 arranged at a mutual distance A.

6. Sound reproduction arrangement according to one of claims 1 to 5,

characterized,

that at least one of the sound panels 11.1, 11.2 and / or the element 13 has at least one sound outlet opening 17.

7. Sound reproduction arrangement according to one of claims 1 to 6,

characterized,

that the drivers 12 are connected to the elements 13, 18.

8. Sound reproduction arrangement according to one of claims 1 to 7,

characterized,

that the cover layers 21 and / or core layers 20 of the two sound panels 11.1, 11.2 differ from one another in terms of material and / or dimensions.