EA001720B1 - Panel-form loudspeakers - Google Patents

Abstract

1. A panel-form loudspeaker comprising a resonant distributed mode acoustic radiator having a first and second transducers mounted on said radiator, a transducer mounted to the radiator to excite in said radiator bending waves to cause it to resonate to produce an acoustic output, wherein the first and second transducers are adapted to operate in different frequency ranges. 2. A panel-form loudspeaker according to claim 1, characterized in that the radiator has a cellular core sandwiched between skins. 3. A panel-form loudspeaker according to claim 3, characterized by a frame supporting the radiator and by a resilient suspension by which the radiator is attached to the frame. 4. A panel-form loudspeaker according to claim 3, characterized in that the frame surrounds the radiator and in that the suspension is attached to the edge of the radiator. 5. A panel-form loudspeaker according to any preceding claim, characterized in that the first and second transducers are mounted wholly and exclusively on the radiator. 6. A panel-form loudspeaker according to any preceding claim, characterized in that one of the transducers is electromagnetic. 7. A panel-form loudspeaker according to any preceding claim, characterized in that one of the transducers is piezoelectric. 8. A panel-form loudspeaker according to any preceding claim, characterized in that comprises a second transducer of a distributed mode being mounted by a resilient suspension on or in the first said transducer, wherein said radiator is mounted on the second transducer exciting in said second transducer bending waves to cause it to resonate to produce an acoustic output. 9. A panel-form loudspeaker according to claim 8, characterized in that the second transducer is mounted in an aperture in the first transducer. 10. A panel-form loudspeaker according to claim 8 or 9, characterized in that the second transducer is mounted wholly and exclusively on the second radiator.

Description

The invention relates to loudspeakers and, more particularly, to loudspeakers containing panel-shaped acoustic emitting elements.

State of the art

In OV-L-2262861 proposed panel-shaped loudspeaker containing:

a multi-mode resonant radiating element, which is an integral laminated panel formed by two shells of a material with a dividing core with a transverse cellular structure, the panel being made so that the stiffness ratio (B) in bending in all directions to the panel mass per unit surface area (μ) in the third degree equal to at least 10;

mounting means on which the panel rests or which secures the supporting body to it in a damping-free manner;

and electromechanical excitation means connected to the panel, which serves to excite multi-mode resonance in the emitting panel in response to an input electrical signal within the working frequency band of the loudspeaker.

In I8-L-3247925, the applicant, Warnak, proposed a loudspeaker with a low-frequency resonance panel mounted on a frame and excited by an electromechanical converter mounted on the frame.

SUMMARY OF THE INVENTION

Embodiments of the present invention use elements whose nature, structure and configuration are determined in general and / or in particular by our PCT application No. \ νϋ 97/09842 from the same date. Such elements are made with the ability to withstand and propagate the input vibrational energy using bending waves in the work area (work areas), passing across the thickness, often, but not necessarily, to the edges of the element (s); made with or without anisotropy of bending stiffness to provide vibration components in the resonant mode distributed over a specified area (specified areas) favorably for acoustic communication with the surrounding air; and have predetermined preferred places or zones within the indicated area for the means of the transducer, in particular its active or moving part (s) involved in creating acoustic vibrations in the specified area (s) and signals, usually electric, corresponding to the acoustic content of such vibrations. The areas of application of such elements are indicated in pending international application No. νθ 97/09842 from the same date, for example, as passive acoustic devices or their component parts without the use of transducer means, for example, for reverb or for acoustic filtering or for acoustic sounding of space or premises; as well as active acoustic devices or their component parts using transducer means, for example, in a wide enough range of sound sources or loudspeakers if they receive an input signal intended for conversion to the specified sound, or, for example, in microphones, if are exposed to sound that needs to be converted to other signals.

This invention relates in particular to active acoustic devices in the form of loudspeakers. The above elements are referred to herein as distributed-mode acoustic emitters and will be characterized as in the PCT application indicated and / or otherwise, as will be presented here.

The invention is a panel-shaped loudspeaker having an element comprising a rigid light panel configured to withstand and propagate input vibrational energy through bending waves in at least one working region extending transverse to the thickness to create vibration components in resonance mode distributed over said at least one area, and having predetermined preferred places or zones within the specified area for the means of the Converter, and having the first and the second and second transducers installed on the specified element in two of the indicated places or zones for exciting the oscillations of the element, causing resonance with the formation of an acoustic emitter, which provides an output acoustic signal at resonance. The first and second converters can be made to work in different frequency ranges. The emitter may have a honeycomb core located between the shells. The loudspeaker may comprise a frame on which the emitter is mounted and an elastic suspension with which the emitter is attached to the frame. A frame can surround the emitter, and an elastic suspension can be attached to the edge of the emitter. The first and second converters can be installed completely and exclusively on the emitter. One of the transducers may be an electromagnetic transducer. One of the transducers may be a piezoelectric transducer. The panel-shaped loudspeaker may comprise a second element configured to withstand and propagate the input vibrational energy by means of bending waves in at least one working region extending transversely to the thickness to create oscillation components in the resonant mode distributed over said at least one area, and having predetermined preferred places or zones within the specified area for the means of the Converter, and having a Converter mounted on the specified element in the bottom of said seats or zones for the actuating member to oscillate in order to create resonance to form acoustic radiator which provides an output acoustic signal at resonance, the second member is mounted on or in the first said member, and the elastic suspension links the first and second elements. The second element may be installed in the hole in the first element. The second converter can be installed completely and exclusively on the second element.

Brief Description of the Drawings

The invention is schematically depicted as an example in the accompanying drawings, which show:

FIG. 1 - loudspeaker with distributed mode according to the description and claims of our invention pending international application No. νθ 97/09842;

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

FIG. 2b is an enlarged sectional view of a distributed mode emitter shown in FIG. Type 2a, with two alternative designs;

FIG. 3 is a schematic illustration of a first distributed mode speaker embodiment of the present invention;

FIG. 4 is a schematic illustration of a second distributed mode speaker according to the present invention;

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

FIG. 6 is a schematic diagram of a fourth embodiment of a distributed mode speaker according to the present invention;

FIG. 7 is a schematic illustration of a converter in perspective.

Preferred Embodiments

In FIG. 1 shows a loudspeaker 81 in the form of a panel according to the description and claims of our invention pending international application XVO 97/09842 with the same filing date, containing a rectangular frame 1 with an elastic suspension 3 located around its inner perimeter, on which an element in the form of a sound suspension is supported radiating panel 2 with a distributed mode. Converter 9, described in detail in our pending international applications νθ 97/09859, νθ 97/09861, νθ 97/09858 with the same filing date, is installed completely and exclusively on or in panel 2 in a predetermined location defined by the dimensions x and y, while the location is calculated, as described in our simultaneously pending international application νθ 97/09842 with the same filing date, to create bending waves in the panel in order to bring the panel into resonance to emit the output acoustic signal.

The converter 9 is excited by a signal amplifier 10, i.e. a low-frequency amplifier connected to the converter by conductors 28. The load and power requirements of the amplifier can be completely normal, similar to conventional diffuser speakers, with a sensitivity of approximately 86-88 dB / W under load conditions in an enclosed space. The total load resistance of the amplifier is mainly an active resistance of 6 ohms, the allowable power is 20-80 watts. If the core of the panel and / or shell is made of metal, they can serve as a heat sink for the converter to remove heat from the motor winding of the converter and thereby increase the allowable power.

In FIG. 2a and 2b show typical partial cross-sections of the speaker 81 of FIG. 1. As shown in FIG. 2a, frame 1, suspension 3 and panel 2 are interconnected by corresponding adhesive butt joints 20. A suitable material for the frame is a light frame, for example a frame for a picture of extruded metal, namely aluminum alloys, or plastic. Suitable materials for suspension are resilient materials such as, for example, foam rubber and foam plastic. Suitable adhesives for compounds 20 are epoxy adhesive, acrylic and cyanoacrylate adhesives, etc.

In FIG. 2b shows on an enlarged scale that panel 2 is a rigid lightweight panel having a core 22, namely of rigid foam 97, namely cross-linked polyvinyl chloride, or a cellular matrix 98, i.e. a honeycomb matrix made of metal foil, plastic, etc., with cells extending across the plane of the panel and enclosed in opposed shells 21, namely, paper, card tape, plastic, or metal foil or sheets. If the shells are made of plastic, then they can be reinforced with fibers, for example carbon, glass or Kevlar or the like, in a manner known per se to increase their modulus.

Thus, materials suitable for the manufacture of shell layers and reinforcements are carbon, glass, Kevlar, Nomex, i.e.

aramid, etc. fibers in different layers and weaves, as well as paper, multilayer paper, melamine and various high-modulus synthetic plastic films, such as Mylar, Kaptan, polycarbonate, phenolic, polyester and similar plastics and fiber-reinforced plastics, etc., and metal sheets or foil. Studies of the Vectra index of liquid crystal polymer thermoplastics show that they can be suitable for injection molding ultra-thin shells or smaller cases, for example up to 30 cm in diameter. This material itself forms an oriented crystalline structure in the direction of injection, which is the preferred orientation for a good distribution of the energy of the upper sound frequencies from the point of excitation to the perimeter of the panel.

In addition, such molding of these and other thermoplastics makes it possible to arrange in the form of means for indicating the position, for example, grooves or rings, for the exact location of the parts of the transducer, namely, the motor winding and the magnet supports. In addition, for some weaker core materials, it was calculated that it would be preferable to increase the shell thickness locally, namely, in an area or in a circle with a diameter equal to 150% of the diameter of the transducer, in order to strengthen this region and better transfer vibrational energy to the panel. At the same time, sensitivity at high frequencies can be improved with softer foams.

Suitable materials for core layers are cells or corrugations made from sheets of aluminum alloys or film, or Kevlar, Nomex, plain or multilayer paper, and various films from synthetic plastics, as well as expanded or foamed plastics or fibrous materials and even aerogel metals if they have a sufficiently low density. Some materials suitable for the manufacture of the core layer exhibit the beneficial effect of self-enveloping in their manufacture and / or have sufficient internal rigidity for use without layering the core layers. Highly efficient cellular core material is known under the trademark Rohacell (RoiassI). which may be suitable for the manufacture of an emitter panel and which does not have a shell. In practice, general lightness and rigidity are needed, suitable for a particular purpose, including optimizing the insertion of core layers and shells, as well as transitions between them.

In several of the preferred panel embodiments, shells of metal and metal alloys are used or, alternatively, carbon fiber reinforcement. They, as well as designs using aerogenic alloys or cores with metal honeycombs, have the properties of significant shielding of radio frequencies, which is important in a number of applications, taking into account electromagnetic compatibility. Conventional panel or diffuser loudspeakers do not have the inherent effect of shielding electromagnetic radiation.

In addition, preferred forms of piezoelectric or electrodynamic transducers have very low electromagnetic radiation or spurious magnetic fields. Conventional loudspeakers have large magnetic fields that extend to a distance of 1 m unless special compensating countermeasures are taken.

Where it is important to maintain shielding during use, electrical connections can be made to the conductive parts of the corresponding BMB panel, or an electrically conductive foam or similar interface can be used for installation on the edge.

Suspension 3 may damp the edges of the panel 2 to prevent excessive movement of the edges of the panel. In addition, or alternatively, additional damping can be applied, namely in the form of overlays attached to the panel at selected locations to dampen excessive movement to evenly distribute resonance throughout the panel. The pads can be made of bitumen-based material that is widely used in conventional loudspeakers, or can be made of resilient or rigid polymeric sheet material. Some materials, especially paper and carding tape, as well as some cores, can be self-damping. Where necessary, damping in the panel structure can be increased by using elastic adhesives instead of hard adhesives.

The specified selective damping includes a special application to the panel, including its sheet material, of means permanently associated with it. Edges and corners can be especially important for the dominant and less dispersed low-frequency modes of panel vibrations. The fastening on the edges of the damping means can advantageously control a panel whose said sheet material is completely enclosed in a frame, although its angles can often be relatively free, for example, for desirable extension of the frequency response towards lower frequencies. Fixing can be done with adhesive or self-adhesive materials. Other types of useful damping, in particular with the aim of achieving finer effects and / or mid and higher frequencies, can be carried out using a suitable mass or masses attached to predefined effective localized positions of the specified area.

The panel described above is bidirectional. Sound energy from the back does not have a strong connection with the phase of sound energy on the front side. Therefore, there is the advantage of the total summation of acoustic power in the room, sound energy with a uniform distribution of frequencies, the reduced effects of reflected and standing waves, and the advantage of excellent reproduction of natural space and surroundings when playing sound recordings.

While the radiation from the acoustic panel is mainly non-directional, the percentage of phase-related information increases off-axis. For improved focusing of the apparent stereo display, the location of the speakers, like the pictures, at the normal height of a standing person, gives the advantage of being moderately off-axis for a normally sitting listener, which optimizes the stereo effect. Similarly, a triangular left / right arrangement with respect to the listener provides an additional angular component. This way you can get a good stereo effect.

In addition, there is an additional advantage for a group of listeners compared to playback with conventional speakers. The intrinsic diffuse nature of sound emission from the acoustic panel gives the sound a volume that does not obey the law of inverse proportionality to the square of the distance from the equivalent point source. Since the decrease in intensity depending on the distance is much smaller than in accordance with the law of inverse proportionality to the square of the distance, therefore, for listeners located outside the center and inconveniently located listeners, the intensity field of the panel speaker provides a stronger stereo effect compared to conventional speakers. This is because off-center listeners do not suffer from a double problem due to their proximity to the closer speaker: firstly, from an excessive increase in volume from the nearest speaker and, secondly, from a corresponding decrease in volume from a more distant speaker.

Thus, flat, lightweight panel speakers have the advantages of an attractive appearance, good sound quality and the presence of only one transducer, as well as the absence of cross-modulation in the entire sound range from each panel diaphragm.

In FIG. 3 shows a panel-shaped loudspeaker 81, generally similar to the loudspeaker of FIG. 1 and 2, in which the panel 2 with distributed modes is made, in general, with a rectangular hole 82 inside its borders, in which a second sound-emitting panel 4 with distributed modes is installed with an elastic suspension 3 located between the respective panels. Panel 4 is made in the same way as panel 2, i.e. with a central core 22 separating the shells 21. The panel 4 is excited by its own transducer 9, installed completely and exclusively on or in the panel 4 in a predetermined place to create a high-frequency acoustic signal, while the panel 2 is excited by a separate transducer 9 to create an output acoustic signal of a lower frequency, so that the loudspeaker can cover the full acoustic spectrum. This arrangement can be useful if losses in panel material tend to attenuate high frequencies. Each panel can have more than one transducer installed to improve sound quality.

In FIG. 4 shows how a distributed mode panel 2 according to the present invention shown, for example, in FIG. Type 1 and 2, using a pair of 70, 71 converters. The smaller of the transducers 70 is a high frequency piezoelectric transducer, namely the one shown in FIG. 7 types, and the larger of the 71 transducers is an electrodynamic transducer, namely, according to our international applications pending XVO 97/09859, AO 97/09861, AO 97/09858.

The transducers 70, 71 are excited by an amplifier 10 connected in parallel to the respective transducers with an intermediate connection of the step-up transformer 72 and the matching resistance 73 in the piezoelectric transducer circuit, since it requires a relatively high voltage. If necessary, more than one transducer 70 and / or transducer 71 can be used to improve sound quality.

In FIG. 5 shows how a distributed mode panel 2 according to the present invention, namely, shown in FIG. 1 and 2 of the type, using a pair of transducers 70, 74, the transducer 70 being a high-frequency piezoelectric transducer, namely, shown in FIG. 7 types, and transducer 74 is a low-frequency piezoelectric transducer, namely according to our pending international application AO 97/09861. The position means that the Converter 74 is weighted with additional mass to increase its inertia. The converters 70, 71 are excited by an amplifier 10, with which they are connected in parallel, with an intermediate inclusion of resistances 78 to create a frequency separation circuit. If necessary, more than one transducer 70 and / or transducer 74 can be used to improve sound quality.

In FIG. 6 shows how a distributed mode panel 2 according to the present invention, namely, shown in FIG. Types 1 and 2, using a pair of 68, 69 electrodynamic transducers according to our international applications pending SHO 97/09859, SHO 97/09861, SHO 97/09858.

Converter 68 is a high frequency driver and therefore has a low inductance, while converter 69 is a low frequency driver and therefore has a high inductance.

Converters 68, 69 are driven in parallel by an amplifier 10, with which they are connected in parallel, with a capacitor 77 connected in the converter circuit 68 as a frequency divider to direct most of the high-frequency signal to converter 68. More than one converter 68 and / or converter 69 can be used if necessary. to enhance sound quality.

In FIG. 7 shows a transducer 9 for a panel 2 with distributed modes in the form of a crystalline bending disk piezoelectric sensor 27 mounted on a disk 118, for example, of brass, which is attached to the surface of the panel 2, for example, by means of an adhesive joint 20. In operation, an acoustic signal supplied by conductors 28 to the transducer 9, leads to the bending of the piezoelectric disk 27 and thereby to local elastic deformation of the panel 2 to start the bending waves in the panel.

Claims (10)

CLAIM 1. A panel-shaped loudspeaker, characterized in that it comprises a distributed-mode acoustic emitter, on which a first transducer and a second transducer are mounted, which excite bending vibrations in said acoustic emitter, which, by causing resonance in the acoustic emitter, produce sound, the first and second transducers being made for work in various ranges of frequencies. 2. The panel-shaped loudspeaker according to claim 1, characterized in that the acoustic emitter comprises a honeycomb core enclosed between the outer layers of the shell. 3. The panel-shaped loudspeaker according to claim 2, characterized in that it comprises a frame that supports the acoustic emitter, and an elastic suspension, through which the emitter is connected to the frame. 4. The panel-shaped loudspeaker according to claim 3, characterized in that the frame surrounds the acoustic emitter, and the suspension is attached to the edge of the emitter. 5. The panel-shaped loudspeaker according to any one of claims 1 to 4, characterized in that the first and second transducers are installed completely and exclusively on an acoustic emitter. 6. The panel-shaped loudspeaker according to any one of claims 1 to 5, characterized in that one of the transducers is an electromagnetic transducer. 7. The panel-shaped loudspeaker according to any one of claims 1 to 6, characterized in that one of the transducers is a piezoelectric transducer. 8. The panel-shaped loudspeaker according to any one of claims 1 to 7, characterized in that it comprises a second distributed-mode acoustic emitter mounted by means of an elastic suspension on the first acoustic emitter or in the first acoustic emitter, wherein a converter exciting in said second is mounted on the second acoustic emitter acoustic emitter bending vibrations, which, causing resonance in the acoustic emitter, provide sound generation. 9. The panel-shaped loudspeaker according to claim 8, characterized in that the second acoustic emitter is installed in the hole in the first acoustic emitter. 10. The panel-shaped loudspeaker according to claim 8 or 9, characterized in that the second transducer is installed on completely and exclusively on the second acoustic emitter.