EA002108B1 - Loudspeaker comprising panel-form acoustic radiating elements - Google Patents

Abstract

1. A panel-form loudspeaker comprising a resonant distributed mode acoustic radiator and drive means mounted to the radiator to excite bending waves, which causing it to resonate, provides an acoustic output and a baffle surrounding and supporting the radiator. 2. A panel-form loudspeaker according to claim 1, characterized by resilient suspension between the radiator and the baffle. 3. A panel-form loudspeaker according to claim 2, characterized in that the resilient suspension is of an elastomeric material. 4. A panel-form loudspeaker according to any preceding claim, characterised in that the baffle is formed as an enclosure having an open backed front box portion adapted to be mounted on a wall or the like. 5. A panel-form loudspeaker according to claim 5, characterised in that the front box portion (52) is adapted to be mounted to align with a cavity in the wall. 6. A panel-form loudspeaker according to any preceding claim, characterised in that the radiator comprises a lightweight core separating a pair of high modulus lightweight skins. 7. A panel-form loudspeaker according to any preceding claim, characterized by a subwoofer mounted to the baffle. 8. A panel-form loudspeaker according to any preceding claim, characterized by a tweeter mounted to the baffle.

Description

This invention relates to loudspeakers and, more particularly, to loudspeakers containing panel-shaped sound-emitting elements.

State of the art

Known by OV-A-2262861 is a panel-shaped loudspeaker containing an element of a resonant multi-mode emitter, which is a single sandwich panel made of two outer shells of material with a separating core of a transverse cellular structure, in which the panel is made in such a way that it has a bending stiffness ratio ( B), in all directions, to the cube of the panel mass per surface unit (μ) equal to at least 10;

fastening means, which is the support of the panel or secures it to the supporting body with freedom in the absence of damping, and electromechanical excitation means associated with the panel and designed to excite multi-mode resonance in the emitter panel when an electrical signal is applied to the input in the working frequency band for the loudspeaker.

I8-L-3247925 in the name of WARNACA discloses a low-frequency resonant panel loudspeaker mounted on the chassis and excited by an electromechanical converter mounted on the chassis.

Disclosure of invention

The implementation of this invention uses elements having the nature, structure and configuration, implemented in the General and / or specific implementation of the characteristics of our publication PCT XVO 97/09842, dated the same number as this application. These elements are configured to support and propagate the input vibrational energy by curving the waves in the working portion (s) extending in the transverse direction relative to the thickness, often, but not necessarily, to the edges of the element (s); they are configured with anisotropy of bending stiffness, or without anisotropy, in order to have resonant vibration components that are distributed over the indicated portion (s) in a way that is favorable for acoustic communication with the surrounding air; and have predetermined preferred locations or sites in the indicated area for the transducer means, especially the operationally active or moving part (s) thereof, which are effective with respect to the acoustic vibration activity in the indicated area (s) and signals, usually electric, corresponding to the acoustic content of this vibration activity. The types of application are assumed in the International Publication No. XVO 97/09842 of the same number, filed with this application as passive acoustic devices without or with a transducer, such as for reverb or for acoustic filtering, or for acoustic sounding of a space or premises; and as active acoustic devices with or in transducer means, such as in a significantly wide range of sound sources or loudspeakers, when input signals are converted to said sound, or such as microphones, to which sound is converted to other signals .

This invention specifically relates to active acoustic devices in the form of speakers.

The above elements are hereinafter referred to as distributed-mode acoustic emitters and are characterized in accordance with said PCT application and / or in another manner specifically specified herein.

The present invention is a panel-shaped loudspeaker characterized by an element configured to support and propagate input vibrational energy by bending waves in at least one working portion extending in the transverse direction relative to the thickness so as to have resonant vibration components distributed over said at least one area, and have predetermined preferred locations or sites within the specified area for means of the causative agent of vibration and having a vibration exciter installed on said element in at least one of the indicated locations or sites to give vibration to the element and cause it to resonate, forming an acoustic emitter that provides an acoustic output signal when resonating, and an acoustic screen surrounding and a carrier emitter. An elastic suspension can be provided between the acoustic screen and the emitter, and an acoustic screen that will carry the emitter. The elastic suspension can be made of elastomeric material. The vibration causative agent can be installed completely or exclusively on the emitter. The acoustic screen can be formed in the form of a housing having a front box-shaped portion open at the rear, which can be mounted on a wall or similar place. The front box part can be made flush with the cavity in the wall. The emitter may contain a lightweight core that separates a pair of high modulus lightweight outer shells. The subwoofer can be installed on the acoustic screen. The high-frequency speaker can be installed on the acoustic screen.

Brief Description of the Drawings

The invention is schematically illustrated by way of example in the accompanying drawings, in which FIG. 1 is a diagram of an element with distributed mode in accordance with the statement and formula of our International Publication AO 97/09842, jointly filed with this application from the same date;

FIG. 2a is a partial section along line AA of FIG. one;

FIG. 2b is an enlarged sectional view of a distributed mode emitter of the type depicted in FIG. 2a, and depicting two alternative designs;

FIG. 3 is a diagram of a first embodiment of a distributed mode speaker in accordance with this invention;

FIG. 4a is a perspective view of a second embodiment of a distributed mode speaker according to the present invention;

FIG. 4b is a partial sectional view of the loudspeaker of FIG. 4a;

FIG. 5a is a perspective view of a third embodiment of a distributed mode speaker according to the present invention;

FIG. 5b is a partial sectional view of the speaker of FIG. 5a.

BEST MODES FOR CARRYING OUT THE INVENTION

In FIG. 1 shows a panel-shaped loudspeaker (81) of the type described in our co-filed International Publication AO 97/09842 of the same number, containing a rectangular frame (1) supporting an elastic suspension (3) around its inner periphery that carries a sound-emitting panel (2) with distributed mode.

A transducer (9) of the type, for example, described in detail in our jointly filed International Publication AO 97/09859, AO 97/09861, AO 97/09858 of the same number, is installed completely and exclusively on or in a sound-emitting panel (2) at a specified location defined by the dimensions x and y; the position of this location is calculated in accordance with the method described in our jointly filed International Publication AO 97/09842 of the same number to direct the bending waves into the panel and cause the sound-emitting panel to resonate to emit an acoustic output.

The converter (9) is driven by a signal amplifier (10), for example, an audio frequency amplifier connected to the converter via wires (28). The requirements for the amplifier in terms of load and power can be quite ordinary, similar to ordinary conical loudspeakers, with a sensitivity of about 86-88 dB / W in loaded room conditions. The total load resistance of the amplifier is mainly active at 6 ohms with a processed power of 20-80 watts. In cases where the core of the panel and / or the outer shells are made of metal, they can be used as a heat sink for the converter in order to remove heat from the motor winding of the converter and thereby improve energy transfer.

FIG. 2a and 2b depict partial typical cross-sections of the speaker (81) of FIG. 1. FIG. 2a shows that the frame (1), the suspension (3) and the sound-emitting panel (2) are connected by corresponding glued joints (20). Suitable frame materials may be a lightweight frame material, such as extruded metal photo frame material, such as aluminum alloy or plastic. Suitable suspension materials include resilient materials such as foam rubber and foam. Suitable adhesives for compounds (20) include epoxy adhesives, acrylic and cyanoacrylate adhesives, etc.

FIG. 2b shows on an enlarged scale that the sound-emitting panel (2) is a rigid lightweight panel having a core (22), for example, of rigid foam (97), for example, of structured polyvinyl chloride or a cellular matrix (98), i.e. a cellular matrix of metal foil, plastic, or the like; while the cells are located across the plane of the panel and are enclosed between opposite outer shells (21), for example, of paper, cardboard, plastic or metal foil or metal sheet. In cases where plastic is used for the outer shell, it can be reinforced with fibers, for example, carbon, glass, Kevlar (registered trademark (TK)) or similar materials by methods known per se to increase their modulus.

The proposed materials and fittings for the outer shell thus include carbon, glass, Kevlar (TK), Nomex (TK), i.e. fibers of aromatic polyamide in various layers and woven materials, as well as paper, laminated plastics with filler from bonded paper, melamine and various high-modulus films of synthetic plastics, such as Mylar, captan, polycarbonate, phenolic or polyester plastics, and fiber-reinforced plastics, etc., and a metal sheet and foil. A study of the Vectra index of thermoplastics from liquid crystalline polymers shows that they can correspond to injection molding of ultrathin outer shells or small shells up to about 30 cm in diameter. This material self-forms an oriented crystal structure in the direction of injection - the preferred orientation for a good distribution of the energy of the upper sound frequencies from the excitation point to the perimeter of the panel.

Such additional molding for these and other thermoplastics enables the moldings to have such topological elements of location and alignment, such as grooves or rings for the precise placement of converter parts, for example, motor windings and magnetic suspensions. It is estimated that, in addition to weaker core materials, it is advisable to have local increases in the thickness of the shells, for example, in a section or in an annular space up to 150% of the diameter of the transducer, in order to reinforce this section and effectively bind vibration energy to the panel. Thus, the high frequency response will be improved by softer foam materials.

Proposed core materials include honeycomb structures or corrugations of sheet or foil made of aluminum alloy, or Kevlar (TK), nomex (TK), plain or bonded paper and various films of synthetic plastic, and also foamable plastics or foams , or cellulosic materials, even aerogel metals, if they have a corresponding low density. Some appropriate core materials have a useful property on their own to create a shell during their manufacture, and / or in other cases have sufficient intrinsic rigidity so that they can be used without forming a core between the shells. A well-known cellular core material is known under the trade name Rojasell, which can be used as a sound-emitting panel and which does not have shells. The practical task is to achieve general lightness and rigidity that would correspond to a specific task, especially to optimize the distributions from the core and shells and the transitions between them.

Some preferred panel formulations employ metal and alloy outer shells or carbon fiber reinforcement. Both of these compositions and also designs with a core made of an airgel alloy or of metal cells will have significant properties of radio frequency shielding, which is important in some types of electromagnetic compatibility. Conventional panel or cone loudspeakers do not have their own EMC shielding properties.

In addition, the preferred form of piezoelectric or electrodynamic transducers has negligible electromagnetic radiation or stray magnetic fields. Conventional loudspeakers have a significant magnetic field up to 1 m long, unless special countermeasures are taken to compensate them.

In cases where it is important to shield the device, the electrical connection can be made to the conductive parts of the corresponding panel of the speaker with a distributed mode or electrically conductive foamy material, or a similar interconnect can be used to mount the edge.

Suspension (3) can dampen the edges of the sound-emitting panel (2) to prevent excessive edge movement of the panel. Additionally, or alternatively, damping can be applied, for example, as separate overlays associated with the panel in selected positions to damp excessive movement to evenly distribute resonance across the panel. The individual pads may be from a material based on bitumen, commonly used in conventional loudspeaker housings, or may be resilient or rigid polymer sheet material. Some materials, especially paper or cardboard, and some inner layers can be self-damping. If desired, damping can be increased in the construction of panels by the use of elastically cured, rather than rigidly cured, adhesive materials.

The specified effective selective damping contains a special application on the panel, including its sheet material, of means that are constantly associated with it. Edges and corners can be of particular importance for the dominant and less scattered modes of low-frequency vibration of their panels. Edge fastening of damping means can have a useful result in a panel whose sheet material is completely framed, although their angles can often be relatively free, for example, to the right degree for working with lower frequencies. This attachment can be carried out by adhesive or self-adhesive materials. Other types of expedient damping, in particular from the point of view of finer sound effects and / or medium or higher frequencies, can be the corresponding mass or masses attached to the sheet material at predetermined effective mid-localized positions of the indicated section.

The sound emitting panel described above is bidirectional. The energy of sound from the rear does not have a strong phase relationship with the energy from the front. Therefore, there is the advantage of the total summation of the acoustic power in the room, the sound energy of a uniform frequency distribution 002108, the reduced effect of the reflected and standing waves, along with the advantage of better reproduction of natural space and surroundings in reproduced sound recordings.

Although the radiation from the sound emitting panel is mainly non-directional, the percentage of phase-related information increases in the direction from the axis. To improve the focus of the artificial stereo image, loudspeakers, like pictures, are placed at the usual height of a standing person, which gives the benefit of moderate off-axis placement for a normally sitting listener, optimizing the stereo effect. Similarly, the triangular left / right geometry relative to the listener provides an additional angular component. This way you can get a good stereo effect.

There is one more advantage for a group of listeners compared to playback using a conventional speaker. The intrinsic characteristics of the scattering of radiation from a sound-emitting panel give it a sound volume that does not obey the law of inverse squares of distance for an equivalent point source. Due to the fact that the decay intensity with a distance is much lower than that provided by the law of inverse squares, as a result of this, for the out-of-center and poorly placed listeners, the field strength for the panel loudspeaker contributes to a better stereo effect compared to conventional loudspeakers. This is because the off-center listener is not affected by the double problem of proximity to a closer speaker; firstly, an excessive increase in volume from a closer loudspeaker; and secondly, a corresponding decrease in volume from a farther loudspeaker.

Another advantage of a flat, lightweight panel-shaped loudspeaker is its good appearance, good sound quality and that it requires only one transducer and does not require transition for full range sound from each diaphragm of the panel.

FIG. 3 depicts a first embodiment of a panel mode distributed mode speaker (81) of the general type depicted in FIG. 1 and 2, and in which the frame (1) is replaced by a panel of an acoustic screen (6), for example, a medium-density fiberboard with a rectangular hole (82), in which a sound-emitting panel with a distributed mode (2) is installed with its elastic in the middle pendant (3). A converter (9) of the type described in our jointly filed International Publication AO 97/09859, AO 97/09861, AO

97/09858 from the same number, is installed completely or exclusively on the sound-emitting panel (2) to impart vibration to the panel in order to cause its resonance in order to obtain an acoustic output.

Such an acoustic screen may have the effect of improving the amplitude-frequency characteristics of the speaker in the lower frequency region.

FIG. 4 shows a second embodiment of a loudspeaker (81) according to the present invention. The loudspeaker comprises a box-shaped case (8) having an upper part (148), a lower part (149), sides (150), a rear part (151) and a front part (152). The front part (152) of the housing (8) consists of a rigid lightweight sound-emitting panel (2) with a distributed mode of the type described with reference to FIG. 1 and 2 and containing a core (22) enclosed between opposing outer shells (21). The sound-emitting panel (2) is supported on the housing (8) by means of a surrounding elastic suspension (17), which may be, for example, a strip of latex rubber. Sound absorbing cladding may be provided in the housing.

A transducer (9), for example, of the types described in our jointly filed publication AO 97/09859, AO 97/09861, AO 97/09858 of the same number, is installed completely or exclusively on the inwardly facing surface of the sound emitting panel (2) at a predetermined location in accordance with our jointly filed International Publication AO 97/09842 of the same number, for imparting vibration to the panel in order to cause its resonance and obtaining an acoustic output.

The housing (8) can be formed with windows (109), for example, on one side (150), to improve the performance of the speaker in the low frequency region. In any case, the use of the housing (8) may make the speaker unidirectional, which may be desirable in some circumstances.

FIG. 5 depicts yet another embodiment of a loudspeaker (81) according to the present invention and is generally similar to the embodiment described with reference to FIG. 4.

The loudspeaker comprises a box-shaped case (8), consisting of a front box-shaped part (52) having an open rear side, configured to be mounted on a wall and installed flush with the cavity (110) in the wall, for example, in a half-timbered wall, to reduce the thickness of the loudspeaker case while ensuring the benefits of a larger enclosure. The front surface (51) of the front box part consists of a rigid lightweight sound-emitting panel (2) with a distributed mode containing a core (22) enclosed between the opposite outer shells (21). The sound-emitting panel (2) is supported on the housing (8) by means of a surrounding elastic suspension (17) made, for example, of a strip of latex rubber. Thus, the loudspeaker is, in general, a loudspeaker of the type described above with reference to FIG. 1 and 2.

A transducer (9), for example, of the types described in our jointly filed International Publication SHO 97/09859, SHO 97/09861, SHO 97/09858 of the same number, is installed completely or exclusively on the inwardly facing surface of the sound-emitting panel (2) in a predetermined location in accordance with our jointly filed International Publication SHO 97/09842 of the same number, to impart vibration to the panel in order to cause its resonance in order to obtain an acoustic output.

Industrial applicability

The loudspeakers of the present invention are relatively easy to manufacture and can be made with a relatively small thickness or with an obviously small thickness compared to conventional loudspeakers. The speakers of the present invention have a wide scattering angle compared with conventional piston speakers. In cases where the sound-emitting panel is made of metal foil or it has an outer shell of these materials, the loudspeaker can be shielded from radio frequency radiation.

Claims (8)

CLAIM 1. A panel-shaped loudspeaker, characterized in that it comprises a distributed acoustic emitter, a transducer mounted on said acoustic emitter and exciting bending vibrations in it, which cause resonance in said acoustic emitter to produce sound, and an acoustic screen that surrounds and supports said acoustic emitter. 2. The panel-shaped loudspeaker according to claim 1, characterized in that it comprises an elastic suspension located between the acoustic emitter and the acoustic screen. 3. The panel-shaped loudspeaker according to claim 2, characterized in that the elastic suspension is made of elastomeric material. 4. The panel-shaped loudspeaker according to any one of claims 1 to 3, characterized in that the acoustic screen is made in the form of a housing with a front box-shaped section open at the rear, made to be installed on a wall or in a similar place. 5. The panel-shaped loudspeaker according to claim 4, characterized in that the front box part is configured to be flush with the cavity in the wall. 6. The panel-shaped loudspeaker according to any one of claims 1 to 5, characterized in that the emitter comprises a lightweight core enclosed between a pair of lightweight outer shells with a high module. 7. The panel-shaped loudspeaker according to any one of claims 1 to 6, characterized in that a loudspeaker is installed on the acoustic screen for reproducing low frequencies. 8. The panel-shaped loudspeaker according to any one of claims 1 to 7, characterized in that a loudspeaker is installed on the acoustic screen for reproducing high frequencies.