CZ296166B6 - Inertial vibration transducer and loudspeaker in which such transducer is comprised - Google Patents

Abstract

In the present invention, there is disclosed an inertial vibration transducer (9) intended for exciting a radiating panel (2) and being capable to propagate, by bending waves, vibration energy generated by the transducer (9) within at least one acoustically active region extending perpendicularly to the radiating panel (2) width. The invented inertial vibration transducer (9) is characterized by a motor coil assembly comprising a tubular member (18) and a coil (13) rigidly fixed to the tubular member (18), and by a magnet assembly (15) disposed concentrically within the motor coil, and resilient means (19) supporting the magnet assembly for axial movement relative to the motor coil, the motor coil and tubular member (18) being adapted to be attached by means of adhesion means (16) to said radiating panel (2), as well as to a loudspeaker in which the invented transducer is comprised.

Description

The invention relates to a transducer, in particular a vibrating transducer for loudspeakers comprising panel acoustic radiating elements, and a loudspeaker comprising the transducer.

BACKGROUND OF THE INVENTION

GB-A-2262861 discloses a panel loudspeaker comprising a resonant multimode emitter consisting of a uniform composite plate comprising a cross-chamber core core that surrounds two shells, the plate having a bending strength ratio (b) in all directions to a cubic power of panel weight per unit area (μ) equal to at least 10, a fastener carrying or supporting said plate to the support body in a free, non-attenuated manner, and electromechanical excitation means designed to drive multi-mode resonance in the radiating plate in response to an electrical input within the working frequency range for the speakers.

US4506 117 discloses an electroacoustic transducer comprising an inertial mass adapted to be attached to a base plate of a panel to be vibrated.

Individual embodiments of the invention use acoustic members having the ability to not dampen and propagate the input vibration energy by bending waves in the acoustically active region or regions that extend perpendicularly to the thickness of the acoustic member frequently, but not necessarily, to the edges of said acoustic member. bending strengths such that the resonant modes of the bending wave vibrations distributed over the entire surface of the acoustic member in a favorable manner for acoustic communication with ambient air, and have predetermined advantageous positions in said acoustically active region for connecting an electromechanical transducer, in particular for its functionally active or moving parts effective depending on the acoustic vibration activity in said acoustically active region and on signals, usually electrical, corresponding to the acoustic measure of such vibration activity. Said acoustic elements are used as active acoustic devices with transducer means, including sound sources or loudspeakers with a remarkably wide frequency range, where input signals are applied to said sound, or microphones, which are exposed to sound which they convert to other signals.

In particular, the invention relates to active acoustic devices in the form of loudspeakers. The above-mentioned acoustic elements in these devices serve as acoustic radiators with distributed resonant modes.

SUMMARY OF THE INVENTION

SUMMARY OF THE INVENTION The present invention provides an inertial vibration transducer for generating an acoustic member, wherein the acoustic member is capable of undamped propagation of the vibration energy generated by the transducer in at least one acoustically active region perpendicular to the thickness of the acoustic member. the resulting resonant bending waveforms are distributed and at least one acoustically active region of the acoustic member has predetermined positions for connecting the transducer and the transducer is connectable to the acoustic member in one of these positions to supply vibration energy to the acoustic member and cause resonance of the acoustic member thus fulfilling the function of an acoustic emitter which, during said resonance, provides the acoustic output which is the essence

Characterized in that it comprises a coil attached to the tubular element, wherein at least one magnet is arranged concentrically with the coil axis and is supported by at least one resilient means for axially moving at least one magnet relative to the coil, the tubular element being attachable to the coil an acoustic member by means of an adhesive means.

The transducer according to the invention preferably comprises two resilient hinges arranged on opposite sides of the at least one magnet as a resilient means for axially moving the at least one magnet relative to the coil. Preferably, the axial ends of the tubular member are closed by caps which are connected to the elastic hinges. Preferably, the coil is attached to the inner wall of the tubular element. The tubular element to whose inner wall the coil is attached has a size and shape corresponding to the size and shape of the cavity of the acoustic member intended to receive the tubular element.

The axial ends of the tubular member may be closed by caps comprising resilient means for axially moving at least one magnet relative to the coil. Preferably, the caps comprise an annular groove as a resilient means for axially moving at least one magnet relative to the coil. Preferably said caps surround the magnetic shields.

Preferably, the tubular member to which the coil is attached is attachable to the face of the acoustic member.

According to a further preferred embodiment of the invention, the magnet is provided with two disc poles extending on opposite sides of the magnet, the edge of one of the poles extending inside the tubular element at a location adjacent to the inner wall of the tubular element. on the outside, a coil connected to the outer wall of the tubular element. Preferably, an elastic element is disposed between one of the pole pieces.

The converter according to the invention may also comprise two magnets between which a pole piece is arranged.

In a further preferred embodiment of the invention, the inertial vibration transducer comprises two complementary magnet and coil assemblies arranged on opposite faces of the acoustic member, and coupling means for connecting both assemblies to the acoustic member.

The present invention also provides a loudspeaker comprising an inertial vibration transducer as described above and an acoustic member capable of transiently dampening the vibration energy generated by the transducer in at least one acoustically active region perpendicular to the thickness of the acoustic member, the tubular element of the inertial vibration transducer is connected to the acoustic member by an adhesive means.

BRIEF DESCRIPTION OF THE DRAWINGS

BRIEF DESCRIPTION OF THE DRAWINGS The invention will become more apparent from the description of exemplary embodiments of the invention in which reference is made to the accompanying drawings, in which FIG. 1 schematically illustrates a distributed mode loudspeaker consisting of an electro-mechanical transducer and acoustic member performing acoustic radiator; Fig. 2b shows an enlarged cross-section of an acoustic element with distributed resonant modes of the same kind as shown in Fig. 2a, which also shows two alternative structures of the emitter.

Fig. 3 shows a cross-section of a first embodiment of a converter;

Fig. 4 shows a cross-section of a second embodiment of the inverter; Fig. 5a shows a cross-section of a third embodiment of the inverter; Fig. 5b shows a cross-section of a fourth embodiment of the inverter;

DETAILED DESCRIPTION OF THE INVENTION

In Fig. 1, a panel loudspeaker 81 is shown which comprises a rectangular frame 1 carrying a resilient joint 3 around an inner edge carrying an acoustic member 2 with distributed resonant modes. The transducer 9 is mounted on the acoustic member 2 or within the acoustic member 2 at a predetermined position defined by the x and y coordinates to excite the bending waveform in the acoustic member 2 to resonance the acoustic member 2 thus forming an acoustic radiator providing acoustic power during resonance of the acoustic member 2.

Said transducer 9 is driven by a signal amplifier 10, e.g., a low-frequency amplifier connected to the transducer by means of conductors 28. The load of the signal amplifier 10 and the power requirements may be quite normal, i.e. as with conventional conical loudspeakers with sensitivity of the order of 86-88 dB. / W at room load conditions. The impedance load of the amplifier has a very resistive character at 6 20 and a load capacity of 20 to 80 W. If the core of the panel and / or its sheath are made of metal, it serves as heat dissipation for the inverter to dissipate heat from the inverter's motor coil. and hence improve performance.

Figures 2a and 2b show typical cross-sections of the acoustic member 2 of the speaker 81 of Figure 1. From Figure 2a it is clear that the frame 1, the resilient joint 3 and the acoustic member 2 are bonded to each other by an adhesive 20. a lightweight frame, such as an image extruded frame of a metallic material, such as an aluminum alloy or plastic. Suitable materials for said resilient joint 3 may be resilient materials such as foam rubber and foamed plastic. Suitable adhesives 20 may be epoxy, acrylate and cyanoacrylate resins or other adhesives.

It can be seen from Figure 2b that the acoustic member 2 is formed by a rigid light panel having a core 22 made of eg rigid plastic foam 97 such as cross-linked polyvinyl chloride, or a cellular core 98 with a cellular structure such as e.g. A honeycomb core made of metal foil, plastic or other similar material, wherein the chambers of said cellular structure extend parallel to the thickness of the acoustic member 2 and are closed by opposing shells 21 made of a material such as paper, plastic or metal foil. . In case the casings are made of plastic, the casings can be reinforced in a known manner, for example by carbon, glass, Kevlar fibers, etc., to increase their modules.

The envisaged sheath layers and reinforcements thus include carbon, glass, kevlar (RTM), nomex (RTM), ie, aramid, fibers in different layers and weaves, as well as paper, laminate, melamine, and various high modulus synthetic plastic films, such as mylar (RTM), captan (RTM), polycarbonate, phenolic, polyester plastic or related plastic, fiber reinforced plastic and metal foil. Based on Vectra liquid crystal quality research based on polymer thermoplastics, it has been found that polymer thermoplastics can be used for injection molding of ultra-thin coatings of small size, i.e. about 30 cm in diameter. This material itself constitutes an oriented crystalline structure in the injection direction, which is an advantageous direction for good propagation of high sound frequencies from the drive point towards the edges of the acoustic member 2.

-3GB 296166 B6

The additional molding of said or other thermoplastics allows the molding tools to have localization and registration features, such as grooves or rings for accurately positioning parts of the transducer, e.g., excitation coil and / or magnet hinge. In addition, in the case of a weaker core material, it may be advantageous to locally increase the thickness of the sheath, e.g. in a surface or ring with a diameter of up to 150% of the sensor diameter, in order to strengthen said surface and advantageously couple the vibration energy in the panel. In this way, the high frequency response can be improved for some softer foam materials.

The envisaged core layer has a honeycomb structure or a corrugated structure formed of aluminum alloy, Kevlar (RTM), nomex (RTM), reinforced paper or cardboard, and films of various synthetic plastics, as well as expanded or foamed plastic or fiber materials, even aerogel metals if they have a suitably low density. Some suitable core layer materials have a self-laminating capability in manufacture and / or have sufficient rigidity to fit between the sheath layers without lamination. The material for the core having a highly efficient cellular structure is known under the trade name Rohacell, which material may be suitable for forming a non-sheathed acoustic member. In practical terms, the aim is to achieve overall lightness and stiffness suitable for specific purposes, in particular by optimizing the individual contributions of lightness and stiffness provided by the core, sheath layers and transitions therebetween.

In several preferred embodiments of the acoustic member, sheaths of metal and metal alloys are used, or alternatively, the materials are reinforced with carbon fibers. These panel designs, as well as panel designs in which Aerogel alloy is used or in which the core has a honeycomb structure of metallic material, have high frequency dimming capability that is important for the acceptability of all electromagnetic energy emitting devices. Conventional cone-type panels or loudspeakers do not have the capability of said shielding.

In addition, preferred forms of piezoelectric transducers and electrodynamic transducers have negligible electromagnetic radiation or stray magnetic fields. Conventional loudspeakers have a large magnetic field, up to 1 m away, unless specific compensating countermeasures are taken.

Where it is important to provide or maintain shielding in a given application, the electrical connections may be made such that the conductive portions of a suitable DML panel, the electrically conductive foam, or the like interface can be used for attachment in the edge region.

The resilient joint 3 may damp the edges of the acoustic member 2 in order to prevent excessive movement of the edges of the acoustic member 2. In addition, additional damping means may be used, e.g., patch patches associated with the acoustic member 2 at selected positions to damp excessive movement of the acoustic member 2 The patches may be made of a bitumen-based material typically used in conventional loudspeaker enclosures, or a resilient or rigid polymeric sheet material. Some materials, especially paper and board, and some types of core materials may be self-attenuating. If desired, damping in the construction of the acoustic members 2 may be enhanced by the use of adhesives that are flexible and not stiff after curing.

Said effective selective damping comprises specific applications of the means to the acoustic member 2 comprising sheet material permanently associated with the acoustic member 2. The edges and corners may be particularly important for the dominant and less dispersible low frequency resonance modes of the bending wave of the acoustic member described in this application. The edge mounting of the damping means may advantageously lead to an acoustic member 2 with a completely framed sheet material, although at least its corners may often be relatively free for the desired extension of the acoustic

In the low frequency operation of the acoustic member 2, said fastening may be performed by means of adhesive or self-adhesive materials. Other forms of useful damping, particularly with respect to multiple minor effects and / or mid and high frequencies, may be accomplished by means of a suitable mass or masses attached to the sheet material at predetermined effective center positions within said area.

The above-mentioned acoustic member 2 is two-dimensional. The sound energy from the rear of the acoustic member 2 is not in a significant phase relation to the sound energy from the front of the acoustic member. This brings the advantage of the total sum of the acoustic power in a given space, the sound energy of uniform frequency distribution, the limited effect of reflecting and standing waves and good reproduction of natural space.

While the sound or acoustic radiation from the acoustic member 2 is considerably non-directional, the percentage of phase-related information off-axis increases. To enhance the focus of artificial stereo listening, positioning the speaker at a height at which images are usually hung, that is, at the normal height of a standing person, gives the normal seated listener optimum stereo listening even when in a slightly deviated position speaker. Similarly, this triangular geometry left / right relative to the listener provides an additional angular component. In this way a good stereo effect is achieved.

This is another advantage for the group of listeners compared to conventional loudspeaker reproduction. Due to the actually dispersed nature of the acoustic panel acoustic radiation, the acoustic panel provides an acoustic volume which is not in any way subject to the square decrement rule for the equivalent point source. As a result, for listeners sitting off the loudspeaker axes or at a location not very suitable for listening, the field strength of the panel loudspeaker promotes a better stereo effect compared to conventional loudspeakers. This is because the listener located outside the center of action of all speakers does not suffer from two drawbacks, which are usually applied near the speakers. The first of these drawbacks lies in the excessively increased perceived loudness of the proximal speaker and, consequently, the second of these shortcomings, in the reduced perception of the loudness of the other speakers.

Also, another advantage of the flat light panel loudspeaker is its visual attractiveness, good sound quality and the requirement for only one transducer, and this loudspeaker does not require a crossover for the entire sound range for each panel diagram.

Giant. 3 shows an embodiment of a transducer 9 with a coil 13 completely disposed within a resonant mode distributed light, acoustic 2 comprising a core 22 coated on both sides of the bending wave housing (21) in the acoustic member 2.

The transducer 9 comprises a coil 13 which is embedded in an adhesive means 16 formed, for example, of an epoxy resin and arranged in the cavity space 29 of the core 22 of the acoustic member 2, and which surrounds the tubular element 18. členu 2.

In the part of the cavity 29 defined by the tubular element 18, a magnet assembly is mounted which includes a pair of opposing magnets 15 separated by a pole piece 14 and which is attached to the inner side of the jackets 21 of the acoustic member 2 by opposing flexible hinges 19 made of a rubber material. Thus, the magnets 15 and the pole piece 14 are concentrically disposed relative to the coil 13 and movable in the direction of the coil axis 13 on the resilient hinges 19.

During operation of the transducer 9 due to the axial movement of the magnet assembly relative to the coil 13, local elastic deformation of the acoustic member 2 occurs in the region between the magnet assembly and the

Thus, the excitation effect is increased by increasing the mass of the magnet assembly.

In operation of the transducer 9, at least at high frequencies, due to the mass of the magnet assembly being relatively greater compared to the mass of the acoustic member 2, the inertia of the magnet assembly tends to keep the magnet assembly stationary and to keep the acoustic member 2 relative to the magnet assembly condition.

Giant. 4 illustrates another embodiment of transducer 9 with coil 13 similar to transducer 9 shown in Figure 3 and disposed entirely within the inner portion of a rigid lightweight acoustic member 2 comprising a core 22 coated with sheath 21 to drive bending waves in the acoustic member 2. 9 with the acoustic member 2, the transducer 9 takes the form of a modular assembly. As can be seen from this figure, a suitable cavity 120 is provided in the acoustic member 2 for receiving the transducer 9.

Said transducer 9 comprises a coil 13 secured to the inner wall of the tubular element 18 by, for example, a solid adhesive 20, wherein the tubular element 18 forms the outer casing of the transducer 9 and is closed at opposite axial ends with light end caps 119 in the desired manner, e.g. by means of an adhesive 20.

The transducer module assembly 9 is adapted to be placed in the cavity 120 in the distributed resonant mode acoustic member 2 by moving in the direction of arrow A. This transducer assembly 9 is secured in the cavity 120 by adhesives.

In the cavity defined by the tubular member 18, a magnet assembly comprising a pair of opposing magnets 15 separated by a pole piece 14 is secured to the end caps 119 of the tubular member 18 by opposing resilient hinges 19 made of a rubber material such as foam rubber; adhesively bonded to the magnet assembly and the inner surfaces of the respective end caps 119.

Thus, the magnets 15 and the pole piece 14 are mounted concentrically relative to the coil 13 and are axially movable on the resilient hinges 19. During operation of the transducer 9, local elastic deformation of the acoustic member 2 occurs and hence vibration of the acoustic member 2 as in the embodiment of the transducer 9 shown in FIG. 3, so that the transducer 9 drives bending waves in the acoustic member 2.

In the embodiment of Fig. 5a, the transducer 9 comprises complementary double-acting drivers located on opposite sides of the acoustic member 2 for driving bending waves in a rigid light resonant mode acoustic member 2 comprising a core 22 surrounded by opposite shells 21 to cause resonance of the acoustic member 2.

In this embodiment, the coils 13 are attached, e.g., by adhesives, to the outside of the tubular member 18 to form the coil assemblies that are rigidly connected, e.g., epoxy adhesive means 16, to opposite surfaces of the sheaths 21 of the radiating acoustic member 2. Magnets 15 are closed between pairs of pole pieces 14, one of which is disc-shaped and its edge is near the inner wall of each tubular element 18 and the other has a peripheral flange 162 arranged to surround the coil 13 externally.

The coupling means 93, which is generally cylindrical in shape, is arranged to extend freely through the aperture 129 in the acoustic member 2. The coupling means 93 comprises opposed generally complementary portions each provided with a head 95 which acts against the axial end of the respective exciter. from said pair of transducers of transducer 9 to couple said exciters together. Said complementary portions of the coupling means 93 are rigidly connected to each other

-6GB 296166 B6 with threaded complementary parts 160, 161. The connecting means 93 can be made of any suitable material, such as plastic.

In the embodiment of Fig. 5a, the transducer 9 is firmly clamped at a location adjacent to the aperture 129 but is coupled to the acoustic member 2 by elastic members 17 made, for example, of foam rubber and arranged near the aperture 129 in the acoustic member 2 in the same manner as 3 and 4, whereby the transducer 9, due to the inertial effects induced by the combined mass of the respective exciters, drives bending waves in the acoustic member 2.

The embodiment of the transducer 9 in Fig. 5b is generally similar to the embodiment of Fig. 5a, except that in the embodiment of Fig. 5b the transducer 9 is intended to be mounted on only one side of the acoustic member 2. The magnets 15 and the pole piece 14 are therefore the surface of the acoustic member 2 by means of an elastic element 17 made, for example, of rubber, and attached to the edge of the flange 162 of the outer pole piece 14.

Giant. 5c shows an embodiment of a transducer 9 of the same type as shown in FIG. 5b and intended to be simply applied to the surface of the acoustic member 2. The transducer 9 is therefore secured by a tubular element 18, adhesive means 16 and elastic element 1 to a thin substrate 147 provided. on the outside a self-adhesive layer by means of which the transducer 9 can be attached to the acoustic member 2 in the desired position.

The transducer 9 in FIG. 6 is a low profile device and can be substantially concealed within the resonant mode distributed acoustic member 2. The transducer 9 comprises a tubular element 18 adapted to be fastened by means of an adhesive means 16 in a corresponding opening of the acoustic member

2. A coil 13 is attached to the inside of said tubular element 18 by means of, for example, adhesives, to form a coil assembly. Opposite axial ends of the tubular element 18 are closed by disc-shaped resilient caps 59 made, for example, of rubber and other similar materials and provided with an annular groove 136 disposed at the edge of said lids 59 to form a groove-like edge similar to that used with conventional conical loudspeaker drivers. The edges of said lids 59 are secured to the axial ends of the tubular member 18, for example by snapping the respective portions of these members by means of adhesives or some other suitable means. The central portions of the caps 59 defined by said annular grooves 136 carry a magnet assembly therebetween comprising a pair of opposing magnets 15 between which a pole piece 14 is inserted. The outer faces of the magnets 15 are secured to the central portions of the caps 59, thereby magnets 15 and the pole pieces 14 are arranged concentrically with respect to the coil 13 and are capable of limited axial movement relative to the coil 13.

The magnet assembly is shielded by disc-shaped magnetic shields 121 mounted on annular elastic members 17 mounted on the acoustic member 2 to prevent or reduce the scattering magnetic field surrounding the acoustic member 2 at a location adjacent to said transducer 9.

Although in the above embodiments of the transducer, the coil assembly is shown attached to the acoustic member 2 and the magnet assembly shown to be resiliently attached to the acoustic member 2, it is understood that this arrangement can be reversed such that the magnet assembly is attached to said acoustic member 2 and the coil assembly is resiliently suspended. In this case, the magnet assembly will be made to be relatively light, and the coil assembly will be made to be relatively heavy to increase the excitation effect.

Claims (14)

An inertial, vibration transducer (9) for actuating an acoustic member (2), the acoustic member (2) being capable of bending waves to transmit the vibration energy generated by the transducer (9) undamped in at least one acoustically active region perpendicular to the acoustic member thickness. (2), wherein in said at least one acoustically active region of the acoustic member (2), the resulting resonant bending waveform modes are distributed, and in said at least one acoustically active region of the acoustic member (2) there are predetermined positions for connecting the transducer (9) and transducer (9) is connectable to the acoustic member (2) in one of these positions to provide vibration energy to the acoustic member (2) and to cause resonance of the acoustic member (2), thereby acting as an acoustic radiator providing acoustic output during said resonance; characterized in that it comprises a coil (13) attached to the tubular an element (18), wherein at least one magnet (15) is arranged concentrically with the axis of the coil (13) and is supported by at least one resilient means for axially moving at least one magnet (15) relative to the coil (13), 18) is attachable to the acoustic member (2) by means of an adhesive means (16). An inertia vibratory transducer according to claim 1, characterized in that it comprises two resilient hinges (19) arranged on opposite sides of the at least one magnet (15) as a resilient means for axially moving the at least one magnet (15) relative to the coil (13). An inertia vibratory transducer according to claim 1 or 2, characterized in that the axial ends of the tubular element (18) are closed by caps (119) which are connected to the resilient hinges (19). An inertia vibratory transducer according to any one of claims 1 to 3, characterized in that the coil (13) is attached to the inner wall of the tubular element (18). Inertial vibration transducer according to one of claims 1 to 4, characterized in that the tubular element (18), to whose inner wall a coil (13) is attached, has a size and shape equal to the size and shape of the cavity (120) of the acoustic member (2). intended to receive the tubular element (18). An inertia vibratory transducer according to claim 1, characterized in that the axial ends of the tubular element (18) are closed by caps (59) comprising resilient means for axially moving at least one magnet (15) relative to the coil (13). An inertia vibratory transducer according to claim 6, characterized in that the caps (59) comprise an annular groove (136) as an elastic means for axially moving at least one magnet (15) with respect to the coil (13). An inertia vibratory transducer according to claims 6 and 7, characterized in that it comprises a magnetic shield (121) surrounding the lids (59). An inertia vibratory transducer according to any one of claims 1 to 4, characterized in that the tubular element to which the coil (13) is attached is attachable to the face of the acoustic member (2). An inertia vibrating transducer according to claim 9, characterized in that the magnet (15) is provided with two disc-shaped pole pieces (14) arranged on opposite sides of the magnet (15), the edge of one of these pole pieces (14) being located inside the tubular element. (18) at a location adjacent to the inner wall of the tubular element (18) and the edge of the second pole piece (14) is formed by a flange (162) surrounding the coil (13) externally connected to the outer wall of the tubular element (18). -8EN 296166 B6 An inertia vibratory transducer according to claim 10, characterized in that an elastic element (17) is disposed between one of the pole pieces (14) and the face of the acoustic member (2). An inertia vibratory transducer according to any one of claims 1 to 9, characterized in that it comprises two magnets (15) between which a pole piece (14) is arranged. An inertia vibratory transducer according to claim 1, characterized in that it comprises two complementary assemblies of magnets (15) and a coil (13) arranged on opposite faces of the acoustic member (2), and coupling means (93) for connecting both assemblies to the acoustic member. (2). A loudspeaker characterized in that it comprises an inertial vibration transducer (9) according to any one of claims 1 to 13 and an acoustic member (2) which is capable of bending waves to transmit the vibration energy generated by the transducer (9) in at least one acoustically active. a region extending perpendicular to the thickness of the acoustic member (2), the tubular element (18) of the inertial vibration transducer (9) being connected to the acoustic member (2) by an adhesive means (16).