EP0924959B1 - Sound reproduction arrangement - Google Patents

Description

Technical area

The invention relates to the arrangement of drive systems in sound reproduction arrangements which operate on the bending wave principle.

State of the art

According to the state, for example from the WO 97/09859 or the DE 21 12 516 In the art, there are known sound reproducing arrangements which operate on the bending wave principle. Such arrangements are essentially constituted by a panel and at least one drive system whereby the panel is vibrated when sound signals are supplied to the drive system (s). A characteristic feature of such sound reproduction arrangements is that bending wave radiation becomes possible from a critical lower cutoff frequency, with the bending waves along the plane of the respective panel leading to sound emission with a frequency-dependent direction. In other words, a section through a created directional diagram shows a main lobe whose direction is frequency-dependent. These ratios are fully valid for infinite plates and absorber plates, while the ratios for the multi-resonance plates treated in this application are significantly more complex because of the strong edge reflections. This complexity in multi-resonant plates stems from the fact that said main lobe is superimposed in a frequency-dependent direction by a plurality of further such main lobes, so that a highly fanned-out directional diagram arises, which is also very frequency-dependent. However, the multi-resonance plates and the absorber plates discussed here have in common that their directional diagrams on average tend to point away from the mid-perpendicular. This behavior causes the space to be more closely involved in the projection of the sound waves.

The 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. For the panel to have good sound reproduction properties, the material for the cover layer must have a particularly high expansion shaft speed. Suitable cover layer materials are, for example, thin metal foils or else fiber-reinforced plastic foils.

Also on the core layer special requirements are made. Thus, it is necessary that the usable materials initially have a low mass density and low attenuation. 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 in the sense of a main requirement that the materials which can be used for core layers have a very low modulus of elasticity in the direction in which later the respective core layer formed from this material has its greatest extent. These contradictory requirements with respect to the last two requirements are most likely to be fulfilled by a core layer which has a perforated structure with preferably small cross-section openings between the two surfaces provided for coating with the cover layers. In addition to the core layers with the hole 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. Not to mention in this context is that when using rigid foams as a material for the core layer, the outer layers have the task of producing the required anisotropic behavior of the panel.

In order to radiate sound waves by means of a panel as described above, it is necessary to connect the panel to a drive system which then waves the panel perpendicular to the plane of the deck views. In order to realize this, the prior art generally uses magnet systems which are also used to drive conventional loudspeakers. In order for these drive systems also bring about the necessary deformation of the panel for the radiation of bending waves, the drive systems are usually provided with a corresponding counter bearing. This counter bearing can be formed for example by a support structure which is arranged at a distance to one of the two cover sheets and receives the drive system. Apart from the fact that such a support structure not only increases the depth and weight of such arrangements, such support structures also require a considerable manufacturing effort. For this reason, it has been decided to connect the support structures acting as an abutment for the drive systems directly to the panel. The disadvantage here, however, that the associated with the panel support structures hinder the generation of bending waves in the panel and lead to a distorted sound reproduction. This is due to the fact that in comparison to the pure drive system such support structures because of the necessary attachment to the panel stiffen larger areas extending in the direction of the largest dimension of the panel. In addition, it is disadvantageous in such support structures that they do not fulfill the properties which are valid for the cover layers and the core layer.

It is therefore an object of the invention to provide a sound display device which overcomes the disadvantages of the prior art.

Presentation of the invention

This object is achieved with the feature combination specified in claim 1. Advantageous embodiments and further developments of the invention are the claims 2 to 8 can be removed.

The basic idea of the invention is to provide the panel with a recess and to arrange the drive system in this recess. If the sound reproduction device is formed in this way, the core layer itself can be used as an abutment for parts of the drive system. This has in addition to the advantage of weight and Bautiefeneinsparung also the advantage that both surfaces provided with the outer layers can be made uniform by the fully integration of drive systems within the panel. In addition, panels in which the drive systems are fully integrated in the panel or separated from the cover layer (s) from the environment can also be used without difficulty in rooms exposed to dirt or moisture. Finally, the weakening of the panel brought about by the recess also results in a particularly good impression of bending waves in the panel, so that the power required to produce the bending shaft is reduced or, with the same power, a vibrational behavior of the panel required for the bass reproduction can be brought about.

A particularly good transmission power in low and midrange is achieved when the drive system is formed according to claim 2 of at least one permanent magnet, a voice coil bobbin and a voice coil.

The structure of a sound reproduction device is then particularly simple, who according to claim 3, the core layer has a honeycomb structure, wherein each honeycomb of a plurality of laterally connected and extending between the two cover layers walls is formed. In this case, it is possible for the walls exposed by the creation of the recess in the core layer to be one or a plurality of honeycombs To use voice coil bobbins. It should be noted at this point that the utilization of the core layer as a voice coil former is not limited to the honeycomb structure. Rather, the walls of the core layer forming circular or polygon structures and the walls, which are formed by the formation of a recess in a core layer of hard foam, in the same way usable.

The structure further simplifies that according to claim 4, the permanent magnet or magnets are connected directly or by means of holders with the core layer and the areas of the core layer, which are in direct physical communication with the permanent magnet or the holders, have a diameter D1 , which is larger than the diameter D2 of the voice coil. It should be noted at this point that the relation between the two diameters D1 and D2 is of crucial importance for the tuning of the panel. In particular, modifications of the diameter D2 are considerable, because these impendance changes and thus also influences the modal amplitudes result.

As claim 5 shows, the invention is not limited to the use of electromagnetic drive systems. Rather, piezoelectric drive systems can also be used if higher-frequency sound signals are to be transmitted. In order to realize a piezoelectric drive system, it is sufficient if the bottom of the recess is provided only with a piezoelectric disk.

If the drive system is realized by means of a disk of piezoelectric material, the side of the disk of piezoelectric material, which faces away from the ground, should be provided with a seismic mass in order to absorb counterforce.

In order to achieve a particularly good impression of force in the panel, according to claim 7, the bottom of the recess should be equipped with a pressure plate.

In order to improve the force impression in the panel, according to claim 8, at least the honeycomb, which axially and radially directly adjacent to the recess, should be foamed with a plastic material.

Short illustration of the figures

Figur 1

einen Schnitt durch ein Paneel;

Figur 2

einen Schnitt durch ein weiteres Paneel;

Figur 3

einen Schnitt durch ein weiteres Paneel; und

Figur 4

eine Schnitt durch ein weiteres Paneel.

Show it:

FIG. 1

a section through a panel;

FIG. 2

a section through another panel;

FIG. 3

a section through another panel; and

FIG. 4

a section through another panel.

Ways to carry out the invention

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

In FIG. 1 a section of a panel 10 is shown in side elevation. This panel 10 is formed by a core layer 11, an upper cover layer 12.1 and a lower cover layer 12.2. In this case, the two cover layers 12 are connected to opposite sides of the core layer 11. As in all other embodiments, also in this embodiment, the core layer 11 has a honeycomb structure, wherein each of these honeycomb 13 has a hexagonal cross-section. The respective honeycomb 13 forming and laterally interconnected walls 14 extend between the two cover layers 12. For the sake of completeness it should be noted that all embodiments shown in this application also have validity for core layers 11, which are formed from a rigid foam.

On the side of the core layer 11, which is connected to the lower cover layer 12.2, a recess 15 is milled. In this recess 15, a drive system 16 is used. This drive system 16 is formed by a so-called yoke arrangement 17.1- 17.4, a permanent magnet 18 and a provided with a voice coil 19 voice coil bobbin 20. The parts of the yoke assembly 17.1- 17.3 form a return pot. The permanent magnet 18 and the part 17.4 are inserted in the return pot formed from the parts 17.1-17-3. Furthermore, an air gap 21 is left in the unit of permanent magnet 18 and the parts of the yoke assembly 17.1- 17.4, in which the provided with the voice coil 19 voice coil bobbin 20 is immersed. In addition, a holder 22 is present, which is connected to the part 17.2 of the yoke arrangement and the core layer 11.

That the bracket 22 -as in FIG. 1 is covered with the lower cover layer 12.2 is not necessary for the function of the sound reproducing assembly 10. If the lower cover layer 12.2 is omitted in another embodiment (not shown) in the region of the holder 22, it can, if it has a good thermal conductivity, also be used as a cooling plate for the drive system 16. For this purpose, the as Cooling plate-acting bracket 22 may also be provided with cooling fins (not shown).

Again FIG. 1 can be further removed by the puncturing, the honeycomb 13.1- 13.5, which adjoins the recess axially and radially directly, are foamed with a plastic material. As a result, the stability of the arrangement in the region of the drive system 16 is improved. In addition, a good introduction of force is ensured by the foaming of the honeycomb 13.2 and 13.4, since the voice coil bobbin 20 is coupled to the core layer 11 in the region of these honeycomb 13.2 and 13.4. Only for the sake of completeness it should be noted that the bottom 23 of the recess 15, even if the honeycomb 13.2 and 13.4 are filled with foam, in another embodiment not shown, even with a pressure plate 25 may be equipped.

FIG. 2 shows one opposite FIG. 1 In this embodiment, the drive system 16 inserted into the recess 15 is formed only by an annular permanent magnet 18 and a voice coil 19. The permanent magnet 18, which in contrast to the permanent magnet 18 according to FIG. 1 is radially magnetized to the center line shown is connected directly to the core layer 11. The voice coil 19 is to save a voice coil bobbin (20) directly connected to the creation of the recess 21 not milled (outer) wall 14 of the honeycomb 13.3 and dives together with the walls 14 of the honeycomb 13.3 in the recess 21.1 of the annular permanent magnet eighteenth one. Also in this embodiment, for reasons of stability, the honeycomb 13.2 - 13.4 filled with plastic material (shown dotted). In order to prevent damage to the lower cover layer 12.2 during operation of the panel 10, the lower cover layer 12.2 can furthermore be supported relative to the bottom 23 of the recess 15 by means of an intermediate piece 11 ', this intermediate piece 11' also being formed by the core layer 11 can.

In order to obtain a particularly good force impression in the core layer 11 or the panel, the voice coil bobbin 20 in the radial direction of the next and connected to the permanent magnet 18 areas of the core layer 11 have a diameter D1, which in this embodiment twice the diameter D2 of Voice coil carrier 20 and the voice coil 19 corresponds.

In FIG. 3 a sound reproduction device 10 is shown in which in the recess 15, a piezoelectric drive system 16 'is arranged. The drive system 16 'is made of a disk 24 of piezoelectric Material, a pressure plate 25 and a seismic mass 26 is formed. In this case, the pressure plate 25 is connected directly to the bottom 23 of the recess 15. At the side facing away from the upper cover layer 12.1 side of the pressure plate 25 includes the disc 24 of piezoelectric material. The seismic mass 26 is connected to the pressure plate 25 opposite side of the disc 24.

Whether in this case the disk 24 is designed as a so-called bending or thickness oscillator is of no significance for the sound reproduction arrangements in question, although the so-called flexural vibrators, in addition to the lower weight and a larger amplitude, are also much better adapted to the relevant application in terms of impedance.

Deviating from the other embodiments is in the embodiment according to FIG. 3 only the honeycomb 13.2. foamed (indicated by the punctuation).

For the sake of completeness, it should be noted that when using a FIG. 3 shown arrangement, the disc 24 of piezoelectric material can be connected to the core layer 11 even without interposing a pressure plate 25 when the core layer 11 and / or the foaming used has sufficient stability.

If an increase in loudness with simultaneous loss of broadband in the Fig. 3 shown drive assembly 16 'is desired, the disc 24 can be used without seismic mass 26.

In FIG. 4 is one of the FIG. 1 similar embodiment shown. Deviating from this, only the drive system 16 inserted into the recess 15 is configured. This is formed by two permanent magnets 18.1, 18.2, a yoke plate 17.5 and a voice coil 19. The two permanent magnets 18.1, 18.2, which like the permanent magnet 18 according to FIG. 1 are magnetized toward the center line shown are connected to two opposite sides of the yoke plate 17.5 with this. The permanent magnet 18.1 is fixed to the bottom 23 of the recess 15.

Since the same poles (N or S) of the two permanent magnets 18.1, 18.2 with respect to the center line in opposite directions, a magnetic drive system 16 is simulated, which according to FIG. 2 with the magnetized in the radial direction permanent magnet 18 corresponds.

In contrast to the statements according to the Figures 1 and 2 but is in FIG. 4 the voice coil 19 is not connected to the bottom 23 of the recess 15, but with the recess 15 in the radial direction limiting side surfaces 28, which are formed by the foaming shown dotted.

If necessary, in another - not shown-embodiment between the side surface 27 and the voice coil 19 and a separate voice coil bobbin 20 may be arranged. The latter also implies that such a voice coil bobbin 20 - similar to in FIG. 2 - consists of honeycomb 13 forming walls 14 directly.

How the particular Figures 2 and 4 clarify, the recess 15 and the mutual Zentierung of voice coil 19 and magnet system 17; 18 are used when the recess 15 is equipped with corresponding steps 27. As in the embodiment according to FIG. 2 the voice coil bobbin 20 is formed by the wall 14 of the honeycomb 13.3, that this honeycomb 13.3 is left standing during the milling of the recess, automatically results in the proper mutual assignment of voice coil bobbin 20 and voice coil 19 to the permanent magnet 18, if this as in FIG. 2 shown its end position has taken on the step 27 in the recess 15. Should in the embodiment according to FIG. 4 the recess 15 also for centering of the voice coil 19 and magnet system 17; 18 are used, the bottom 23 with a step 27 '(shown in phantom) should be provided, in which then the permanent magnet 18.1 can engage when the magnet system 17, 18 has taken its final position in the recess 15.

Claims (7)

1. A sound reproduction system with a panel (10), which is constituted substantially by a core layer (11) and an upper and a lower cover layer (12.1, 12.2), wherein the two cover layers (12) cover the core layer (11) at opposite surfaces and with a driver (16), which is connected to the panel (10) and causes it to oscillate under the influence of sound signals, wherein the core layer (11) has a recess (15) and the driver (16) is integrated exclusively into this recess (15), characterised in that the core layer itself acts as the support for parts of the drivers (16).
2. A sound reproduction system as claimed in Claim 1, characterised in that the driver (16) is constituted by at least one permanent magnet (18), a moving coil carrier (20) and a moving coil (19).
3. A sound reproduction system as claimed in Claim 2, characterised in that the core layer (11) has a honeycomb structure, wherein each cell (13) of this honeycomb structure is defined by a plurality of laterally connected walls (14) extending between the two cover layers (12) and that the moving coil carrier (20) is constituted by walls (14) of the cells (13) constituting the core layer (11).
4. A sound reproduction system as claimed in Claim 1, characterised in that the driver (16) is constituted by a piezo-electric disc (24) and that this disc (24) is connected to the base (23) of the recess (15).
5. A sound reproduction system as claimed in Claim 4, characterised in that the side of the disc (24) of piezo-electric material remote from the base (23) of the recess (15) is provided with a seismic mass (26).
6. A sound reproduction system as claimed in Claims 1 to 5, characterised in that the base (23) of the recess (15) has a pressure plate (25).
7. A sound reproduction system as claimed in Claims 1 to 6, characterised in that at least the cells (13) of the core layer (11), which directly adjoin the recess (15) axially and radially, are filled with a foamed plastic material.

Images