CZ58298A3 - Loudspeakers provided with panel-like acoustic radiating elements - Google Patents

Abstract

A panel-form loudspeaker (81) comprising a resonant distributed mode acoustic radiator having a periphery, a transducer (9) mounted to the radiator to excite distributed mode resonance in the radiator, and a frame (1) supporting the radiator, the transducer being coupled between the radiator and the frame to vibrate the panel to cause it to resonate to produce an acoustic output, characterised in that frame supports the radiator round its periphery and by resilient suspension means coupled between the frame and the radiator periphery.

Description

The present invention relates to loudspeakers, and more particularly to loudspeakers provided with panel acoustic radiating elements.

BACKGROUND OF THE INVENTION

Patent application GB-A-2262861 discloses a panel loudspeaker design comprising a multifunctional radiating element constituting a unit sandwich panel formed of two surface layers of material with a spatial core of a transverse lightweight structure, arranged such that its flexural stiffness ratio (CB) in all directions to the square of the mass of the panel per unit surface area (p) is at least 10, and which further comprises a fastener which supports the panel or attaches it to the carrier loosely and without damping, and further comprises an electromechanical excitation means associated with a panel that serves to drive multi-modal resonance in the radiator panel in response to an electrical input within the loudspeaker operating frequency band.

US-A-3,247,925 to VARNAKA discloses the importance of a low-frequency resonant panel loudspeaker mounted on a frame and excited by an electromagnetic transducer mounted on this frame.

SUMMARY OF THE INVENTION

The present invention uses members whose species, structure and

The arrangements are generally and / or obtainable from the description of our co-pending PCT Application No. WO97 / 09842, from the same date. Such members have the ability to maintain and propagate the input vibration energy by bending waves in the operating area or in the operating areas extending transversely to their thickness, often but not necessarily to their edges, these members being arranged with or without anisotropy of bending strength, with vibration components of the resonant modes distributed in this region, preferably for acoustic communication with the environment and with predetermined preferential locations in the region for locating the transducer, in particular for its operating or moving parts, which are effective with respect to acoustic vibration activity in this region and signals , usually electrical, corresponding to the acoustic content of this vibration action. The use is envisaged in the co-pending PCT Application No. V097 / 09842, from the same date, for these members as or in passive acoustic devices without converters, as reverberation or acoustic filtering or acoustic sounding of a room or room, and as or in active acoustic devices. with transducers, as in a remarkably wide range of sound sources or loudspeakers when powered by input signals to convert to said sound or as microphones when exposed to sound to convert it to other signals.

In particular, the present invention relates to active acoustic devices in the form of loudspeakers.

Said members are referred to as distributed radiation elements and are to be marked as in said PCT application and / or otherwise as specifically provided herein.

SUMMARY OF THE INVENTION The present invention is a panel loudspeaker, wherein the loudspeaker consists of a peripheral member capable of maintaining and propagating input vibration energy by bending waves in at least one operating area

Passing through transverse resonant modes, and predetermined to its thickness, with vibration components distributed at least in this region, preferred locations in the region for accommodating the transducer, the transducer being mounted on this member at one of these locations, for causing the member to vibrate, to derive its resonance, forming an acoustic radiating panel, producing an acoustic output during resonation. The loudspeaker further comprises a support frame supporting the panel around its periphery, further comprising a transducer disposed between the radiator panel and the support frame, and further comprising a resilient frame disposed between the carrier wound and the periphery of the radiator panel, the radiator panel having piston and resonance capability; and wherein the transducer is adapted to reciprocate the radiator panel. The support frame may have a portion surrounding the radiating panel. The resilient frame may be a resilient elastomer. The support frame may be provided with a base with a floor portion, a generally vertical portion extending from the floor portion, and a plurality of arms extending from the vertical portion, the distal ends of these arms being connected to the portion of the support frame surrounding the radiating panel. The radiation panel may be rectangular and the arms may extend near its corners. The drive can be mounted on or near the vertical part of the support frame. The transducer can be mounted in a bracket extending from the vertical. The speaker can be provided with a pair of symmetrically arranged transducers. The radiator panel may be formed by a light core disposed between a pair of high modulus light cover layers.

Overview of the drawings

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be explained in more detail with reference to the drawing, in which Fig. 1 schematically shows an exploded loudspeaker as described and claimed in our co-pending international application.

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No. 2a / 09842, Fig. 2a shows a partial sectional view of the loudspeaker according to line AA of Fig. 1, Fig. 2b is an enlarged view and a sectional view of the loudspeaker of Fig. 2a, showing two alternative constructions; 3a is a front elevational view of an exploded loudspeaker embodiment of the present invention; FIG. 3b is a side view of FIG. 3a; and FIG. 3c is a rear view of the loudspeaker of FIG. 3a.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a panel loudspeaker 81 of the type.

which is described and claimed in our international application no. VD97 / 09842, is provided with a rectangular co-ordinated from the same date and a support frame 1 surrounding its inner periphery with a flexible frame 3 supporting an unfolded sound emitting panel 2. 9, which is described in detail in our co-pending International Applications Nos. WO97 / 09859, WO97 / 09861 and WO97 / 09858, from the same date, and which is mounted fully and exclusively on this or in this panel 2, at a predetermined location , defined by x and y coordinates, the position of which is calculated as described in our co-pending International Application No. WO97 / 09842 from the same date, to send bending waves to the sound emitting panel, to induce panel resonation, to generate an acoustic output.

The transducer 9 is driven by a signal amplifier 10, for example a low-frequency amplifier, coupled to the transducer 9 via wires 28. The load and power requirement of the amplifier 10 may be quite normal, as with conventional cone loudspeaker types, with 86-88 dB / V sensitivity room conditions. The amplifier load impedance is strongly resistive at 6 ohms, with a load rating of 20 to 80 V.

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When the core of the panel and / or the cover layers are of metal, they may act as a heat sink to dissipate heat from the inverter coil and thus improve load capacity.

Figures 2a and 2b show typical cross-sections of the loudspeaker 81 of Figure 1. Fig. 2a shows that the supporting frame 1 surrounding the flexible frame 3 and the panel 2 are connected to each other by respective glued joints 20. Suitable materials for the supporting frame are lightweight frame structures, for example, picture frames of extruded metal, for example aluminum alloys or of plastics. Suitable materials for the flexible frame are resilient materials such as foam rubber and foam plastics. Suitable adhesives for glued joints 20 are epoxy, acrylic and cyanoacrylic adhesives, etc.

In Fig. 2b it is shown on an enlarged scale that the panel 2 is rigid, the light panel consisting of a core 22, for example a rigid plastic foam 97 of cross-linked polyvinyl chloride or a lightweight structure 98, ie a honeycomb structure of metal foil, plastics or the like. with chambers extending transversely to the plane of the panel 2, the core 22 being enclosed between opposing cover layers 21, for example of paper, cardboard, plastic or metal foil or sheet. When the cover layers 21 are plastic, they can be reinforced with fibers, for example carbon, glass, kevlar (RTM) or the like in a manner known per se, to increase their modulus.

The envisaged materials for the cover layers and reinforcement thus include carbon, glass, Kevlar (RTM), Nomex (RTM), ie, aramid and the like fibers in different layers and weaves, as well as paper, laminated paper, melamine and various synthetic plastic films and module such as Mylar (RTM), Kaptan (RTM), polycarbonates, phenolic plastics, polyesters or related plastics and fiber reinforced plastics, etc., and metal foils or sheets. Vectra grade research

- 6 ·· ···· Liquid crystal polymer thermoplastics show that they can be useful for making ultra-thin coatings or coatings of smaller sizes, up to about 30 cm in diameter, by injection molding technology. This material itself creates an oriented crystalline structure in the injection direction, which is an advantageous orientation for propagating high-frequency energy from the excitation point to the panel perimeter. Injection of these and other thermoplastics further allows the positioning and aligning features such as grooves or rings to accurately position the components of the transducer, such as a coil and a magnet suspension, in the injection molding tools. It is further envisaged that some materials for the weaker cores would have the advantage of locally increasing the thickness of the cover, for example in the region of the annulus, up to 150¾ of the diameter to amplify this region and advantageously doubling in this way. Intended for core layers include industrially manufactured or corrugated sheet or foil construction of Kevlar (RTM), Nomex (RTM), cardboard and various synthetic also cellular or foam plastics or fibrous materials, even aerogel metals, provided they have a suitable low density. Some suitable core layer materials effectively exhibit useful self-contracting in their manufacture and / or otherwise have sufficient intrinsic rigidity for use without the need for lamination between layers. The high performance lightweight core material is known under the trade name Rohacel1, which may be suitable as a radiating panel, and which is free of covering layers. Practically speaking, the purpose is a lightweight and rigid material of a laminate, a transducer, a panel vibration energy, a material of aluminum alloy honeycomb material, uncoated P1 paper film, and generally or in particular including the best fit for special purposes, the benefit of the layers for cores and coatings and the transition between them. Some advantageous

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494 444 panel material compositions include metal and metal alloy coating layers with carbon fiber, alloy fleroge1 or alternatively reinforced and

As these materials, or with a metal honeycomb core, have important properties for radio frequency shielding, which should be of importance in some EMC (Electromagnetic Compatibility) applications. Conventional cone-type panels or loudspeakers do not possess intrinsic electromagnetic compatibility in shielding. In addition, preferred piezoelectric or electrodynamic transducers have negligible electromagnetic radiation or stray magnetic fields. Conventional loudspeakers have a large magnetic field, up to 1 m, unless specific compensating countermeasures are taken. Where it is important to maintain shielding during use, electrical connection of the conductive parts of the relevant DML (Data Manipulation Language) panel may be made, or an electrically conductive foam or similar interface may be used to connect the edges of the panel. The resilient frame 3 can damp the edges of the panel 2 to prevent excessive movement of these edges. Further or alternatively, additional damping, for example by means of damping pads glued to the panel at selected locations, may be used to damp excessive movements of the panel to ensure uniform distribution of resonance across the panel. The pads may be of a bitumen-based material typically used in a loudspeaker housing, or may be a flexible or rigid polymeric sheet material. Some materials, especially paper and board, and some cores may be self-damping. On request, damping can be increased by the construction of the panel by the use of flexible rather than rigid fixation adhesives.

This effective selective damping comprises specifically attaching the damping means to the panel, including its layers, which permanently bond to it. Margins and corners may be in particular

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- δ ”significant for the predominant and less dispersed types of panel vibration at low frequency. By attaching the damping means to the edges, a panel can be formed whose layers are fully framed, although its corners can often be relatively loose, it can be said for the desired expansion in low frequency operation. The connection can be made with adhesive or self-adhesive materials. Other types of useful damping means, particularly with respect to finer effects and / or mid and high frequencies, can be attached to the layers at predetermined intermediate positions in the region in the form of suitable materials.

The acoustic panel described is two-dimensional. The sound energy from his rear face is not strongly phased with the energy from his front face. This results in the benefit of the total sum of the acoustic power in the room, the distribution of sound energy at a uniform frequency, the reduced effects of reflected and standing waves, together with the advantage of excellent reproduction of the natural space and environment of the reproduced sound recording.

Although radiation from the acoustic panel is very non-linear, the percentage of phase information increases off-axis. For enhanced focus on artificial stereo, the position of the announcer, and images, at the usual height of a standing person, the advantage of a slight offset for a normally seated listener contributes to optimizing the stereo effect. Also, the triangular left / right geometry creates an additional angular component relative to the listener. Thus good stereo reception is achievable.

Compared to the reproduction of a conventional loudspeaker, there is another advantage for one group of listeners. The intrinsically dispersed nature of the acoustic panel's sound emission gives it a sound volume that is not governed by the law of indirect dependence on the square of the distance for the equivalent point source- Because the intensity with decreasing distance is much · 4 · 4 • 4 444 ·

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- 9 lower. than the law of indirect dependence on the square of distance. consequently, for off-center or poorly positioned listeners, the magnetic field strength of the panel speaker increases the stereo effect compared to conventional speakers. This is because an off-center listener does not suffer from the double problem caused by the proximity of the proximal speaker, first by increasing the volume from the proximal speaker excessively, and then lowering the volume from the proximal speaker accordingly.

Another advantage of the flat light panel speaker is that it is visually attractive, has good sound quality and requires only a transducer and not a speaker crossover for the full range of sound from each panel membrane.

FIG. 3 shows a panel loudspeaker 81 fixed to the floor, of the type generally illustrated in FIGS. 1 and 2, in which a light, rigid, rectangular distributed sound radiating panel 2 is mounted on a flexible frame 3 arranged around its periphery, wherein The support frame 1 is supported by a stand 23 provided with a floor-mounted base 83 carrying a vertical post 84 with four generally horizontal arms 85 connected by its distal ends 86 to respective corners 87 of the support frame 1. The loudspeaker is provided with a pair of symmetrically arranged transducers 9, which at one end are attached to the panel 2 and at the other end are mounted in brackets 88 on a vertical post 84 to drive the panel 2.

A pair of transducers 9 is located on the panel 2 at predetermined locations, as will be described hereinafter. The object of this arrangement is to control the excitation of the panel 2 by the piston method at low frequencies by counteracting the column 84, which together with the arms 85 acts as the carcass of the conventional loudspeaker unit, and further to vibrate the high frequency panel to derive its resonance

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acoustic output. Such an arrangement requires the flexible frame 3 to be compliant, i.e. like a disc arranged around a cone exciter of a conventional loudspeaker.

Industrial applicability

The panel loudspeaker according to the invention is relatively simple to manufacture and its flat configuration makes it easy for home use. It has a wide acoustic scattering angle compared to conventional loudspeaker types.

Claims (8)

PATENT CLAIMS A panel loudspeaker, characterized in that the loudspeaker (81) consists of a peripheral member (2) capable of maintaining and propagating the input vibration energy by bending waves in at least one operating region extending transversely to its thickness, with resonant mode vibration components distributed at least in this region, and with predetermined preferred locations in the region for locating the transducer, the transducer (9) being mounted fully and exclusively on the member at one of these vibration-generating locations to generate its resonance forming an acoustic radiating panel (2) providing an acoustic output during resonance, the loudspeaker further having a support frame (1) supporting the radiating panel (2) around its periphery, further comprising a transducer (9) disposed between the radiating panel (2) and the support frame (1) and is further provided with a resilient frame (3) for saving provided between the support frame (1) and the periphery of the panel (2), wherein the radiating panel (2) has a piston movement and resonance capability, and wherein the transducer (9) is adapted for the piston movement of the radiating panel (2). A panel loudspeaker according to claim 1, characterized in that the support frame (1) has a part surrounding the radiating panel (2). A panel loudspeaker according to claim 1 or 2, characterized in that the flexible frame (3) is made of an elastaer 44. ···· 4 4 4 4 A panel loudspeaker according to claim 2 or 3, if dependent on claim 2, characterized in that the support frame C1) is provided with a stand (23) having a base (C83) connected to the floor, and further provided generally a vertical portion (84) extending from the base (83) and further comprising a plurality of horizontal arms (85) connected by their distal ends (86) to a portion of the support frame (1) surrounding the radiating panel (2). A panel loudspeaker according to claim 4, characterized in that the radiating panel (2) is rectangular and the arms (85) extend near its corners. A panel loudspeaker according to claim 4 or 5, characterized in that the transducer (9) is mounted on or adjacent to the vertical part (84) of the support frame (1). A panel loudspeaker according to claims 4 to 6, characterized in that the transducer (9) is mounted in a yoke (88) extending from the vertical part (84). 8. Panel speaker, under 1 e claims 1 to 7, in y z n and no u jící s e team that is provided with a pair symmetrically arranged converters (9). 9. Panel speaker, according to claims 1 to 8, in y z n and no u s e by that radiation panel (2) it is formed by a light core (22) arranged between a pair of high-module lightweight cover layers (21).