EP1410680B1 - Planar loudspeaker - Google Patents

Abstract

The invention relates to a planar loudspeaker with a light, thin sounding board (2) which may be energised to give multiply reflected flexural waves, a frame (3), surrounding the sounding board (2) and holding the above in an articulated, shear-resistant manner, at least one driver (6, 7, 9, 10) connected to the sounding board (2) for energising the sounding board (2) and at least one bridge (13, 16, 18, 20, 22, 25), rigidly connecting the at least one driver (6, 7, 9, 10) to the frame (3), whereby the bridge or at least one of the bridges (13, 16, 18, 20, 22, 25) is connected to a damping board (14).

Description

The invention relates to a plate loudspeaker with a light, thin, to multiple reflected bending waves stimulable sound plate, a circumferential, the sound plate articulated holding frame, at least one connected to the sound board driver for exciting the sound panel and at least one at least one driver with the frame firmly connecting bridge.

From the US 5,701,359 For example, rigid panel loudspeakers are known which operate on the principle of the free piston, wherein the sound radiating surface ("membrane") is rigid (like a "piston"). This means that the sound radiating surface in the operating frequency range performs no appreciable bending vibrations and provided as a sound radiating surface rigid plate is free, so is open and not airtight enclosed by a housing.

Furthermore, for example, from the WO 97/09842 Multiresonanzplattenlautsprecher known, wherein occurring in the operating frequency range, weakly damped bending waves are reflected at the plate edge, so that as a result of the formation of standing waves, the membrane is a multiple resonator. Such multi-resonant panel loudspeakers are also referred to as "multi-resonant sound panels", "flexural wave loudspeakers" or "distributed mode speakers". Even with such speakers, the plate is usually free, so not part of a closed box.

The usual electrodynamic disk drivers (see for example DE 199 409 30 ) can be basically fixed floating on the plate, ie without support on a frame. The mass of the magnet system then forms the dynamic counter bearing for the application of force to the plate to be driven (principle of the "seismic mass").

If the plate is operated such that the plate normal is approximately perpendicular to the gravitational acceleration, then the heavy magnet systems of the drivers apply gravity to the plate via their corrugations. Due to the low strength of the beads, they will perform a creeping settlement motion with time due to gravity, resulting in an eccentric, irreversible maladjustment of the voice coils. Although such a setting also occurs in the case of horizontal mounting, such as ceiling panels, for example, the setting direction is not directed eccentrically (radially) but in the direction of the voice coil axis.

In order to prevent the destructive, eccentric creep effect, the drivers are fixed to so-called "bridges" in perpendicular to be operated plate speakers so that their weight can exert no shear force on the plate. These bridges ("trusses", "Gantries") are attached to frames, which in turn store the plate at the peripheral edge shear-resistant.

Due to the relatively large span, such a bridge will usually act as a leaf spring, which together with the mass of the fixed to the bridge driver forms a low-damping spring-mass vibration system. At the resonant frequency lying in the bass range, this vibration system (bridge resonator) will perform strong deflections without it noticeably radiate sound. The strong deflections in bridge resonance can overload the voice coil centering and lead to the destruction of the driver.

The object of the invention is therefore to provide a plate speaker with settlement protection, in which the dynamic side effects of such a settlement protection can be avoided.

The object is achieved by a panel loudspeaker according to claim 1. refinements and developments of the inventive concept are the subject of dependent claims.

Advantage of the invention is that a settlement protection is realized with relatively little effort, which has almost no harmful dynamic side effects. In addition, with the measure according to the invention an additional sound radiation is generated in an otherwise underserved low-frequency range.

This is achieved in a panel loudspeaker of the type mentioned in that the bridge or at least one of the bridges with a (preferably rigid) damper plate is connected or that the damper plate itself is a part of the bridge or at least one of the bridges. Thus, the bridge not only carries the driver or drivers, but also the damper plate.

The bridge resonance frequency can be tuned for example by mass adaptation. Namely, the bridge resonance is determined by the ratio of spring constant to total bridge mass with all elements attached thereto. Regardless of the attenuation given by the plate surface of the damper plate, by varying the plate thickness or the plate density of the damper plate, the mass can be adjusted so that the radiation contribution of the damper plate fits favorably into the acoustic spectrum of the multi-resonant panel loudspeaker.

Alternatively, for example, the bridge resonance frequency can be tuned by spring adaptation. Regardless of the given by the plate surface damping, the area moment of inertia and thus the spring constant can be adjusted by changing, for example, the cross-sectional profile of the bridge so that the resonance zone of the bridge fits favorably into the acoustic spectrum of the multi-resonant plate speaker.

Preferably, therefore, it can be provided that at least one bridge is designed as an air-permeable framework. But it can also be formed as an air-impermeable flat box cover at least one bridge.

Preferably, the damper plate has a smaller area than the sound plate. Furthermore, it is preferably provided that the damper plate is designed in a lightweight, very rigid sandwich design. Such a sandwich design is for example from the EP 0 924 959 known.

Furthermore, the connection points between the bridge (s) and damper plate can lie in the area of the nodal lines of the first two modes of vibration of the damper plate.

In a further development of the invention, at least one bridge consists of a prismatic rod, the bridge the not completely covered by the frame given, the sound plate opposite surface.

Furthermore, it can be provided that at least one bridge is designed as a regular lattice work and / or as a perforated plate.

In another embodiment of the invention, it is provided that at least one bridge is resilient and part of an airtight flat box, with all the outer components of this flat box itself are impermeable to air and are connected to each other impermeable to air. The flat box can have a bass reflex opening (also a bass reflex tube). In this case, at least one bridge may be formed as a rigid plate and be connected by a circumferential bridge bead with the damper plate.

In addition, a chamber can be attached to the flat box, wherein the chamber can also have a bass reflex opening (also a bass reflex tube). Alternatively, however, the chamber may also be airtight. Finally, the chamber may also have a passive radiator.

The plate loudspeaker according to the invention thus represents in its acoustic effect an asymmetrical two-plate loudspeaker, since the main, front-facing, the listener facing sound plate forms a multi-resonant acoustic sound plate, while the back, remote from the listener, smaller damper plate is acoustically a rigid plate.

The degree of damping can be adjusted directly over the surface of the damper plate. The larger the plate, the greater the damping achieved. An additional improvement The low-frequency sound radiation of the panel loudspeaker can be achieved in that the damper plate is designed as a rigid plate and thus not only damps the bridge resonance vibration, but also contributes to the sound radiation in the low frequency range. The low frequency range is always affected by the dipole short circuit in free multiresonance sound discs. The additional sound radiation partially compensates for this dipole short circuit.

A particular advantage of the asymmetrical two-plate loudspeaker lies in the simple drive technology. While well-known monopoly drivers (cf. DE 198 218 62 ) arranged back-to-back single drivers, alternatively arranged side-by-side single drivers or complicated double voice coil assemblies, according to the invention only at least one known conventional disk driver is needed.

If the frame carrying the bridge (s) and sound plate is acoustically open, then the compressed or decompressed air will flow through frame openings in an opposite pumping motion of the two different plates, thus causing pressure equalization.

If, on the other hand, the frame is sealed in such a way that the sound plate and damper plate form the radiating surfaces of an otherwise closed flat box, then the two plates work in opposite directions in the low frequency range. The arrangement of the two plates then forms a "low-monopole", ie a breathing ball with partially inactive zones.

As a preferred embodiment of such a flat box arrangement, it is ventilated in a controlled manner. For this purpose, one or more bass reflex openings are provided, through which the inside air can flow in the correct phase, so that a further improvement of the low-frequency behavior is achieved. The ventilation of the flat box at the same time avoids the unfavorable effect of too rigid air suspension.

Finally, in another preferred embodiment, the sealing of the rigid damper plate, which is not originally intended for sound radiation and is located in a plane with the rear flat box wall, can be formed as a sheet-like leaf spring, so that an increased emission surface is achieved with the associated increased radiation damping. This flat spring detunes the spring constant of the original bridge, which has to be considered in the resonance tuning.

Figur 1

eine erste bevorzugte Ausführungsform eines erfin- dungsgemäßen Plattenlautsprechers als freien, asym- metrischen Zweiplattenlautsprecher, bei dem die Dämp- ferplatte an einer Brücke befestigt ist,

Figur 2

eine zweite bevorzugte Ausführungsform eines erfin- dungsgemäßen Plattenlautsprechers als freien, asym- metrischen Zweiplattenlautsprecher, bei der die Dämp- ferplatte einen Teil der Brückenfunktion übernimmt,

Figur 3

eine dritte bevorzugte Ausführungsform eines erfin- dungsgemäßen Plattenlautsprechers als freien, asym- metrischen Zweiplattenlautsprecher, bei der die Brü- ckenstäbe eine Tellerfeder nachbilden,

Figur 4

eine vierte bevorzugte Ausführungsform als geschlos- sener, asymmetrischer Zweiplattenlautsprecher,

Figur 5

eine fünfte bevorzugte Ausführungsform eines erfin- dungsgemäßen Plattenlautsprechers als geschlossener, asymmetrischer Zweiplattenlautsprecher mit Bassre- flexöffnung,

Figur 6

eine sechste bevorzugte Ausführungsform eines erfin- dungsgemäßen Plattenlautsprechers als geschlossenen, asymmetrischen Zweiplattenlautsprecher mit starrer Plattenbrücke und Brückensicke und

Figur 8

eine siebte bevorzugte Ausführungsform eines erfin- dungsgemäßen Plattenlautsprechers als geschlossenen, asymmetrischen Zweiplattenlautsprecher mit zwei Kam- mern sowie mit starrer Plattenbrücke, Brückensicke und Bassreflexöffnung.

The invention will be explained in more detail with reference to the embodiments illustrated in the figures, wherein like elements are provided with the same reference numerals. It shows:

FIG. 1

a first preferred embodiment of a plate loudspeaker according to the invention as a free, asymmetrical two-plate loudspeaker, in which the damper plate is attached to a bridge,

FIG. 2

a second preferred embodiment of a plate loudspeaker according to the invention as a free, asymmetrical two-plate loudspeaker, in which the damper plate takes over a part of the bridge function,

FIG. 3

A third preferred embodiment of a plate loudspeaker according to the invention as a free, asymmetrical two-plate loudspeaker, in which the bridge bars simulate a disc spring,

FIG. 4

A fourth preferred embodiment as a closed, asymmetric two-plate loudspeaker,

FIG. 5

A fifth preferred embodiment of a plate loudspeaker according to the invention as a closed, asymmetrical two-plate loudspeaker with bass reflex opening,

FIG. 6

a sixth preferred embodiment of a plate loudspeaker according to the invention as a closed, asymmetrical two-plate loudspeaker with a rigid plate bridge and bridge bead and

FIG. 8

A seventh preferred embodiment of a plate loudspeaker according to the invention as closed, asymmetrical two-plate loudspeaker with two chambers and with a rigid plate bridge, bridge bead and bass reflex opening.

At the in FIG. 1 shown embodiment of a plate loudspeaker according to the invention in the form of an asymmetric two-plate loudspeaker 1 is provided as a sound panel 2, which is designed as a multi-resonant sound plate and is characterized in consequence of a low mass, high bending stiffness, low bending wave damping and a cantilever frame attachment. A rigid, mostly rotating frame 3 holds the sound plate 2 via a rotating plate bearing 4, as a shear-resistant joint acts. A bridge 13, for example, in the form of a slender prismatic rod is laterally (or rearwardly) connected via a rigid connection 8 with the magnet system 6 of a driver and at the same time at the distal ends of the magnet with the frame. As a result, the static load of the magnet system 6 is supported. An immersed in the annular gap of the magnet system 6 voice coil 7 is centered on the one hand via an inner bead 10 relative to the magnet system 6 and at the same time firmly connected to the sound plate 2. An outer bead 9 holds the static load of the magnet system 6 during speaker mounting. At the same time it represents a floating magnetic attachment, as it makes sense in horizontal operation. In a multi-resonant plate speaker, with substantially free storage of the frame 3 and / or the bridge contains 13 openings 11 (gaps) through which a pressure equalization of otherwise possible trapped air is ensured.

Based on this basic arrangement, the inventive, free, asymmetrical two-plate loudspeaker-1 has a damper plate 14, which is attached to the prepared bridge 13 of the sound panel 2 facing away. The large plate surface of the damper plate 14 is aligned approximately plane-parallel to the large plate surface of the sound plate 2.

FIG. 2 shows in section a further preferred embodiment of a designed as a free, asymmetrical two-plate loudspeaker 12 speaker plate according to the invention, wherein the damper plate 14 is attached directly to the magnet system 6. Relatively short bridge bars 16 connect the damper plate 14 with the frame 3. Thus, the damper plate 14 is a widened part of the bridge 15 formed from the bridge bars 16 and thus exercises the Function of the bridge 15 as a static weight relief. The large plate surface of the damper plate 14 is again aligned approximately plane-parallel to the large plate surface of the sound plate 2. Regarding the remaining elements, the in FIG. 2 shown embodiment with the in FIG. 1 illustrated embodiment match.

Starting from the two preceding embodiments shows FIG. 3 a further preferred embodiment of a plate loudspeaker according to the invention as a free asymmetrical two-plate speaker 17, wherein in contrast to the in FIG. 2 shown embodiment, only the bridge bars 16 are replaced by a rotating plate spring 18. The static function of the disc spring 18 is the same as that of the rods 16 in FIG FIG. 2 , but results in a different acoustic behavior. The sound panel 2 is in fact shielded against a possibly present, near building wall and thus forms a helpful measure against the undesirable "wall effect".

According to the embodiment FIG. 4 is a closed, asymmetrical two-plate speaker 19 is provided, in contrast to FIG. 3 all remaining ventilation openings 11 have been closed. The back, acting as a plate spring cover 20 consequently has no pores or openings. The caused by the cover 20 suspension is substantially hardened by the compression suspension of the trapped air.

FIG. 5 shows in section an asymmetric two-plate bass reflex speaker 21 formed according to the invention plate speakers. In contrast to the embodiment according to FIG. 4 here is just a bass reflex tube 23 inserted into an opening in the frame 3. This results in a further possibility of tunable, low-frequency filling of the sensitivity spectrum in addition to the bridge resonance.

The embodiment according to FIG. 6 is different from the one in FIG. 5 shown embodiment in that an inventive asymmetric two-plate loudspeaker 24 starting from the embodiment according to FIG. 5 a rigid plate bridge 25 and a bridge bead 26, wherein the damper plate 14 is vibrationally connected via the bridge bead 26 with the plate bridge 25. The plate bridge 25 is attached to the frame 3.

In the FIG. 7 shown in section preferred embodiment of a plate loudspeaker according to the invention as a closed, asymmetrical two-plate two-chamber loudspeaker 27 comprises starting from the embodiment according to FIG. 6 in addition to the rigid plate bridge 25 and the bridge bead 26, a second chamber 28, which is equipped with a bass reflex tube 29. The second chamber 28 adjoins the rear end of the two-plate two-chamber loudspeaker 27, that is to say the side of the two-plate two-chamber loudspeaker 27 enclosing the damper plate 14. Instead of using a bass reflex tube 29, however, the second chamber 28 may also be closed or have a passive radiator 29.

Claims (17)

1. A planar diaphragm loudspeaker including a light, thin sounding plate (2), which is excitable by multiply reflected bending waves, a peripheral frame (3), which holds the sounding plate (2) in an articulated and shear-resistant manner, at least one driver (6, 7, 9, 10) connected to the sounding plate (2) for exciting the sounding plate (2) and at least one bridge (13, 16, 18, 20, 22, 25) rigidly connecting one of the at least one driver (6, 7, 9, 10) to the frame (3), characterised in that the bridge or at least one of the bridges (13, 16, 18, 20, 22, 25) is/are connected to a damping plate (14) or that the damping plate (14) itself is a component of the bridge or at least one of the bridges (13, 16, 18, 20, 22, 25).
2. A planar diaphragm loudspeaker as claimed in claim 1, characterised in that the damping plate (14) is of rigid construction.
3. A planar diaphragm loudspeaker as claimed in claim 1 or 2, characterised in that at least one bridge (13, 16, 18, 20, 22, 25) is constructed in the form of an air-permeable bar structure.
4. A planar diaphragm loudspeaker as claimed in claim 1 or 2, characterised in that at least one bridge (13, 16, 18, 20, 22, 25) is constructed in the form of an air-impermeable flat box cover.
5. A planar diaphragm loudspeaker as claimed in one of the preceding claims, characterised in that the damping plate (14) has a smaller area than the sounding plate (2).
6. A planar diaphragm loudspeaker as claimed in one of the preceding claims, characterised in that the damping plate (2) is of light, very bending-resistant sandwich construction.
7. A planar diaphragm loudspeaker as claimed in one of the preceding claims, characterised in that the connecting points between the bridge(s) (13, 16, 18, 20, 22, 25) and the damping plate (14) are situated in the region of the node lines of the first two modes of oscillation.
8. A planar diaphragm loudspeaker as claimed in one of the preceding claims, characterised in that at least one bridge consists of a prismatic bar, wherein the bridge does not completely cover the surface, which is predetermined by the frame (3) and is situated opposite the sounding plate.
9. A planar diaphragm loudspeaker as claimed in one of the preceding claims, characterised in that at least one bridge is constructed in the form of a regular lattice.
10. A planar diaphragm loudspeaker as claimed in one of the preceding claims, characterised in that at least one bridge is constructed in the form of a perforated plate.
11. A planar diaphragm loudspeaker as claimed in one of the preceding claims, characterised in that at least one bridge (20, 22) is resiliently flexible and part of an air-tight flat box, wherein all the external components of this flat box are air-impermeable and are connected together in an air-impermeable manner.
12. A planar diaphragm loudspeaker as claimed in claim 11, characterised in that the flat box has a base reflex opening/base reflex tube (21).
13. A planar diaphragm loudspeaker as claimed in claim 11, characterised in that at least one bridge (25) is constructed in the form of a rigid plate and is connected to the damping plate (14) by a peripheral bridge bead (26).
14. A planar diaphragm loudspeaker as claimed in claim 11, 12 or 13, characterised in that a chamber (28) is attached to the flat box.
15. A planar diaphragm loudspeaker as claimed in claim 14, characterised in that the chamber (28) has a base reflex opening.
16. A planar diaphragm loudspeaker as claimed in claim 14, characterised in that the chamber (28) is air-tight.
17. A planar diaphragm loudspeaker as claimed in claim 14, characterised in that the chamber (28) has a passive emitter (23).

Images