The present invention relates to a dynamic loudspeaker according to the preamble of claim 1 Acoustic sound is produced with a dynamic loudspeaker by feeding an electπc signal and power corresponding to sound to a voice coil of a loudspeaker driver from an amplifier The 5 voice coil moves in time with the signal The voice coil is fastened to a cone or diaphragm of the loudspeaker element and causes the diaphragm to move whereupon the surface of the diaphragm produces an acoustic sound wave corresponding to the electπc signal in the surrounding air The diaphragm efficiently Iransforms the movement of the voice coil into movement of air because the surface area of the diaphragm is large compared to that of the "• 0 voice coil

Generally, the cone element and voice coil of a loudspeaker must be lightweignt and very mobile in order to provide gooα sounα reproduction This is especially true in mε ireoie -ange vvhere voice frequencies are high and rapid accelerations of the diaphragm are required On the other hand, at bass frequencies the diaphragm that creates sound gener-

' 5 ally must be large and the voice coil correspondingly powerful, which means that the voice coil must withstand high heat and power This problem is usually solved by using a cross¬ over filter and two or more loudspeaker elements of different size, with each e-emeπt only producing sounds within its own frequency response range Such elements are called bass mid-range and treble elements Their cones are relatively soft and flexibly mounted to the 0 oody of the element As a result, velocities and accelerations directed to the cone are limited according to the buckling and stiffness characteπstics of the cone which are also affected by the a r pressure in the loudspeaker casing Furthermore, various surface waves tend to flow m th i cone which are discernible as distortion components in the sound produced by the loudspeaker

5 Several structures have been invented that differ from conventional loudspeakers The goal of the inventions has been to either decrease the size of the loudspeaker simplify the struc¬ ture or production process, or improve the quality of sound reproduction, etc. Decreasing the size and simplifying the structure of a loudspeaker improves its applicability, facilitates pro¬ duction and lowers costs The goal of improving the quality of sound reproduction is to 0 produce a loudspeaker that is suitable for many different applications and meets the quality requirements of each application with respect to sound reproduction Such quality require¬ ments are for example desired beam characteπstics, distortion, frequency response power etc In addition to the above factors, many solutions have attempted to produce all the

needed sound components with one loudspeaker element rather than with separate ele¬ ments This places major requirements on the structure of the loudspeaker Only in recent years has attention been paid to the external characteπstics of a loudspeaker such as design Still, there are many factors toward which little or no consideration is given Such factors are, for example, resistance to moisture, the possibility of covering the loudspeaker placement and integration of the loudspeaker In many applications the front cloth of the loudspeaker alone poses a major problem

In the following, non-conventional loudspeaker inventions whose characteristics are deter¬ mined by the details in each case are examined by means of a descπption of the pπor tech- nology

Hill's patent US 4,928 312 is a loudspeaker with a diaphragm consisting of three separate foam plastic panels The voice coil of the element is fastened to the center of the diaphragm Square zones are used in the diaphragm Imai Yanagishima and Kasai's patent US 4 720 867 is a bass loudspeaker intended for installation on the rear window shelf of an automobile The diaphragm of the loudspeaker element is a panel fastened to an opening in the shelf and connected to the voice coil of the dπver The structure is also equipped with a protective panel

Marquiss's patent US 4 385 210 is not actually a single element loudspeaker as it has separate drivers for bass and treble response The loudspeaker structure consists of a long, linear panel diaphragm equipped with an acoustic damper A speaker cloth covers the plane diaphragm

Bertagni's patent US 4 003 449 is a loudspeaker with a diaphragm that is asymmetrically cast from a lightweight material It is equipped with a separate treble element that is con¬ nected to the same diaphragm Ishikawa's patent 3 752,258 is a loudspeaker with a diaphragm that is cast of a lightweight material in a desired shape The structure is a modification of a conventional loudspeaker element and relates to a three-loudspeaker assembly that requires a flat, lightweight loud¬ speaker suitable for placement in different positions Bertagni's patent 3,596 733 is a loudspeaker with a diaphragm made of a thick, cellular polyurethane panel An driver is asymmetrically suspended behind the panel

The loudspeaker of Heron's application publication WO 92/03024 is a panel to which an dπver is asymmetrically fastened The panel does not function as a piston-like vibrator, but wave-like

The present applicant's previous patent applications FI 915525 and PCT/FI92/00314 present a loudspeaker invention in which the d over's voice coil controls a plane diaphragm to pro¬ duce a sound wave The plane diaphragm is flexibly fastened to a loudspeaker casing The plane diaphragm usually becomes thinner closer to the voice coil The operating pπnαple is that the flexibility of the diaphragm changes as a function of the radius of the diaphragm, so that the higher the sound reproduced by the diaphragm, the smaller the area of the dia¬ phragm that vibrates At the lowest frequencies the whole plane diaphragm vibrates The loudspeaker also incorporates an acoustically damped and specially shaped rear chamber that affects the operation and tuning of the loudspeaker The plane diaphragm in said solu- tion is relatively stiff so even at low response frequencies no out-of-phase diaphragm vibra¬ tion is formed that could cause a drop in sound pressure at the response frequency

The new loudspeaker according to the present invention is characterized in that its plane-like loudspeaker diaphragm is a thin stiff panel with a relatively large surface area and it is part of another structure A benefit of a stiff diaphragm is that it does not readily form diaphragm nodes that lower the sound pressure but it vibrates in phase, i e the mechanical direction of movement at every point of the diaphragm is the same Therefore the loudspeaker can be constructed as a part of another structure, such as a door shelf wall, cabinet or other piece of furniture, component or device Thus, the loudspeaker can be manufactured and covered according to the requirements of the object it will be integrated into A further benefit is that the loudspeaker cannot necessarily be differentiated from the surrounding structure so the loudspeaker can be sold integrated into another product

Present equipment and methods of furniture manufacturers are suitable for producing the body components of a loudspeaker according to the present invention as the application of the integrated loudspeaker in a product requires only a machining component or structural modification of a component of the product, for example MDF sheets, which are currently commonly used as furniture material, are very suitable as the body and structural material of said loudspeaker The material can be quickly machined with automatic machines into sufficiently thin sheets that form the diaphragm of the loudspeaker Even thin sheets of the mateπal are mechanically sufficiently strong to withstand not only loudspeaker operation, but also normal handling and use of the component The loudspeaker diaphragm or body can be made from sheets of many different mateπals, such as MDF, plywood, hardboard, glued sheets and melamine laminated boards, and different types of composites, nets screens laminates or other structures The loudspeaker function of the above-mentioned compo¬ nents can also be enhanced by combining the basic components with auxiliary components

to achieve various objectives, such as an even response curve, changes in sensitivity, damping, different kinds of shields, design requirements, etc

A limitless amount of applications and optimized, advantageous embodiments for different needs can be built from a loudspeaker according to the present invention. For this reason, only a few essential embodiments are presented herein, in an attempt to illustrate the whole field with certain structural solutions and components. Furthermore, it must be noted that the presented solutions are ones that have been built to date and have provided practical expe¬ rience and test and measurement results. Actual questions of design and layout are not dealt with in detail at all, although they would further increase the vaπety of embodiments mentioned above and open new advantageous overall solution models and possibilities, especially for product and component designers, furnishers, mteπor decorators, architects, etc.

In the following, the loudspeaker is descπbed by pictuπng its structure and functioning with references to basic drawings of the loudspeaker, which present a few applications that the claims relate to The loudspeaker and its application possibilities are described in more detail with references to the following enclosed basic, application and structural drawings, in which figure 1 a ! is a basic diagram of the loudspeaker viewed from the front. b) is a cross-sectional view of the loudspeaker at the dπver and c) is an exaggerated cross-sectional view of the vibration of the loudspeaker diaphragm, figure 2 a • is a dipole and reflex application of the loudspeaker viewed from the front and b'ι is a cross-sectional view of the above at the driver. figure 3 a) is a diagram of a passive diaphragm application of the loudspeaker viewed from the front and b) is a cross-sectional view of the above at the dπver, and c; is a diagram of the above passive diaphragm and a lever mechanism of the driver, figure 4 a) is a diagram of a dipole application of the loudspeaker viewed from the front and b) is a cross-sectional view of the above at the driver, figure 5 a) is a diagram of a semi-dipole application of the loudspeaker viewed from the front and b) is a cross-sectional view of the above at the driver, figure 6 a) is a diagram of a two-sided semi-dipole application of the loudspeaker

viewed from the front and b) is a cross-sectional view of the above at the driver, figure 7 a) is a diagram of a cellular application of the loudspeaker viewed from the front and b) is a cross-sectional view of the above at the driver, figure 8 a) is a diagram of a panel application of the loudspeaker viewed from the front and b) is a cross-sectional view of the above at the driver, figure 9 a) is a diagram of a damping panel application of the loudspeaker and b) is a cross-sectional view of the above at the driver.

Figure 1 is a diagrammatic presentation of a loudspeaker 1 according to the present inven¬ tion, which is made from an ft/IDF sheet or by machining or casting from some other suitable material. The loudspeaker includes a diaphragm 3 made from the same component and material, for example, and surrounded by a body 2. The diaphragm 3 of the loudspeaker 1 is essentially a plane, plane-like, gently curving, or otherwise shaped, thinly machined or otherwise formed part of the body structure 2 and it functions as a surface that produces sound, meaning that it moves when energized by an driver 4 according to the exaggerated drawing in figure 1c. The diaphragm 3 must move sufficiently over surface areas correspond¬ ing to desired frequencies, producing specific sound pressures in specific beams, i.e., the surface wave must advance sufficiently in the diaphragm. The diaphragm 3 can be ma¬ chined, components can be glued, laminated or cast to it. and it can be covered during the construction phase or later, according to the sound reproduction requirements of the loud¬ speaker. This may involve making various grooves, perforations and fill-ins. thinning and embedding that facilitate flexing of the diaphragm, or stiffeners that limit or damp bending, such as raised structural parts and material shapes. The diaphragm may be shaped so that the vibrating diaphragm part gets thinner closer to the voice coil, ending with rounding off at the body structure 2 of the loudspeaker. Rounding off has significance from the standpoint of the mechanical durability of the loudspeaker diaphragm and the manufacturing process, such as machining. The flexibility of the diaphragm and its fine and overall shape may change with the distance from the voice coil in a manner dictated by the characteristics of the sound reproduction. The diaphragm 3 may be simply machined in the finished loud¬ speaker or it may be covered, painted or laminated. Other additional structures may be necessary in different applications, such as damping materials or structures that are used to improve the efficiency, sensitivity, power capacity or other characteristics of the loudspeaker. The voice coil 5 of the driver 4 is joined to the diaphragm 3, transmitting the mechanical

kinetic energy of the dnver to the diaphragm In addition to the voice coil 5, the dπver con¬ sists of a magnet system 6 joined to the body 2 by means of a covering back pane! 8 or other device The voice coil 5 is wired to a connector 7 by means of leads glued to the diaphragm 3 An amplifier signal is conducted to the connector

5 In loudspeakers according to the present invention, the bodies diaphragms, castings, machinmgs, and backside spaces can be of any desired shape, and they may be part of the overall design of the loudspeaker The back panels may be embedded, rabbeted, or in¬ stalled on top of the loudspeaker body 2, depending on production and design requirements they may be panel-like or made from tubes for example The back pane! 8 may be the size 10 of the whole loudspeaker or a product such as a door whereupon the loudspeaker can be made from two panels fastened one on top of the other, for example

A loudspeaker according to the present invention can be used in different applications as a dipole, closed, or reflex loudspeaker if it is independently placed If the loudspeaker is integrated in a product or structure, such as furniture as a deer for example the structure 15 may have an open, partly open or closed space 9 behind the diaphragm 3 of the loud¬ speaker The space roa ^w contain a cloth and suitable dam ⁿ e ^r s c othe ^r fii'in ¹ " ¹ t 3 a^ects the operation of the loudspeaker The space also has an essential influence on the bass re¬ sponse of the loudspeaker, as it affects the sensitivity of movement cf the diaphragm 3

A loudspeaker according to the present invention can be constructed in pane! or glued sheet 20 doors or in other similar components, or directly in the frames cf furniture for example In the case of panel doors, the borders of the panels can function as border and connecting sur¬ faces of the diaphragm 3, unless the panel is of the same material as the diaphragm The component and panel borders or tπmwork can also easily hide flexible areas and other areas that loudspeaker functioning may require in certain applications

->C Generally, no special measures or components are required to center the voice coil in the air gap of the magnet in a loudspeaker according to the present invention, because the stiff diaphragm and body structure facilitate precise centeπng. The voice coil is glued to the diaphragm 3. to which leads are installed for a connector 7, which is usually installed in the body, so that leads do not have to be connected to the back panel duπng installation

30

Figure 2 shows a practical loudspeaker structure in which a perforated panel 10 equipped with an driver 4 is fastened to the loudspeaker body 2 in place of the back panel 8 The

perforated panel 10 forms a combination dipole and reflex structure for the backside wave of the diaphragm In pπnciple, the dimensions of the diaphragm and its location-specific ampli¬ tude of movement define the beam and response characteπstics of the loudspeaker The amount, shape and surface area of the holes in the perforated panel 10 define the dipole and reflex tuning of the loudspeaker The perforated panel must be mechanically sturdy enough to keep the vibration of the driver 4 at a minimum unless said vibration is exploited in the dynamic operation of the loudspeaker The pressure vaπation of the backside space 9 of the loudspeaker generates air flow in the backside space both inward and outward The air flow may move or transport dust, which is not desirable in kitchen cabinet applications, for example Therefore said structure is most suitable in places where dust will not pose a problem The backside space 9 of the loudspeaker may contain suitable damping mateπal that affects the sensitivity and other sound reproducing characteristics of the loudspeaker as well as the dust problem

In the loudspeaker construction of figure 3, a thin stiff panel or passive diaphragm 20, is installed in the body 2 of the loudspeaker in the direction of the diaphragm 3 The passive diaphragm, as a thin panel together with the diaphragm structurally forms an closed casing for the loudspeaker but it functionally forms a dipole This is because the passive diaphragm 20 does not sever the acoustic short in the structure at low frequencies However, at mid- range and treble frequencies the loudspeaker functions as if it were closed The principle is that the passive diaphragm 20 moves duπng sound reproduction as a diaphragm controlled by the voice coil, or in the same phase and same direction so no pressure change occurs inside the loudspeaker In pπnciple, the passive diaphragm produces the same acoustic wave as the back of the diaphragm 3 would in a free space A benefit of this structure is that although it is closed, it functions like a dipole loudspeaker at low frequencies An dnver bridge 21 , from which the driver 4 is suspended, may be located between the diaphragm 3 and the passive diaphragm 20 The dπver bπdge 21 may be stiff or it may be integrated with the passive diaphragm 20 or be a part of it An driver bridge 21 joined with the passive diaphragm 20 is also stiff, but the adjoining diaphragm part is flexibly connected to it or the passive diaphragm part made of the same mateπal is thinned for flexibility near the dπver bπdge 21

The loudspeaker according to the present invention shown in figure 3 may also be equipped with a special dπver bπdge 22 as shown in pπnαple and as an example in figure 3c which has an dπver lever mechanism 26, which is connected to the dπver 4 by means of flexible connecting surfaces 23, to the dπver bridge 21 by means of flexible connecting surfaces 24

and to the passive diaphragm 20 by means of flexible connecting surfaces 25 The purpose of the lever mechanism 26 is to function as an aid duπng the dynamic operation of the loudspeaker by conserving the natural inertia energy of the dπver, which would otherwise be lost The structure of the driver bridge 22 may be panel-like and it may also be a cast com- ponent, and also equipped with separate connecting joints that correspond to the connecting surfaces 23 - 25 The lever mechanism 22 turns the acceleration and motion of the driver in the opposite direction and transfers its kinetic energy to kinetic energy of the passive dia¬ phragm 20. improving the bass response of the loudspeaker The mechanism can be tuned to the desired range of self-resonance according to the desired response characteristics of the loudspeaker It is essential that, duπng the operation of the loudspeaker the passive diaphragm 20 is forced to move at low frequencies in the same phase and direction as the diaphragm 3 along its whole surface Thus, the diaphragm 3 and passive diaphragm 20 produce acoustic waves of opposite phase into the surroundings with respect to each other just as a no ^r ma! dipole loudspeaker does A further benefit o^ this loudspeaker structure is that it is constructed from only thin panels and furthermore that it is air and dust tight The other backside space characteπstics of this embodiment of the loudspeaker are the same as in the previous loudspeaker structures

Figure 4 shows an embodiment of a loudspeaker which the back pane! 8 perforated pane! 10 and passive diaphragm 20 cf the above-mentioned different loudspeaker structures have been left out whereupon the loudspeaker 1 forms a dipole structure If it is realized in a cabinet door for example a nearly closed casing is formed that prevents an acoustic short ^τ he thinning of the pane! that forms the diaphragm can be shaped according to vibration and design requirements The driver 4 is suspended from the body 2 by means of a separate module or driver bridge 31 which usually is constructed of the same material as the loud- speaker body 2, but which may be constructed of metal, such as tubes The benefit of the driver bridge 31 being a separate module is that it can be quickly joined to a ready-made body and furthermore, it can be joined later to a pre-formed door structure, for example, whereupon the complete unit forms a functioning furniture loudspeaker This has marketing significance The dπver bπdge 31 is located in the direction of and close to the diaphragm 3 Flexible foam rubber seals can be located between edges of the driver bridge 31 and the diaphragm 3 making the structure hygienic and providing acoustic damping of the dia¬ phragm 3 and preventing mechanical contact between the diaphragm 3 and driver bπdge 31 at high-powered bass frequencies The diaphragm 3 can be advantageously covered or coated with paint, varnish, laminate, or required additional structures duπng the machining stage As a consequence, in making a furniture loudspeaker, a finished product, such as a

door, can be modified to become a loudspeaker by installing a separate module or dπver bπdge 31, that fits into vaπous standard products in production The method simplifies the production process and reduces the need to transport product components, if the module is made in its own production facility The voice coil must be centered carefully to make it easy to install the module. Therefore, a spider, which is a mechanism consisting of small, flexible tube or panel components, can be joined to the magnet system of the driver 4 The voice coil is connected to the spider whereby the voice coil can be advantageously centered in the air gap of the magnet The spider can be either outside or inside the voice coil and it can be connected directly to the cylindπcal wall of the voice coil or to the end panel of the voice coil, which is still used in connecting the voice coil to the diaphragm The spider may consist of stiffer, lever-like or jointed components, whereby the voice coil is centered and connected and also prevented from being installed in a crooked position This is beneficial duπng instal¬ lation and also duπng the dynamic operation of the loudspeaker

Figure 5 presents a dipole structure of a loudspeaker 1 according to the present invention in which the above-mentioned dipole structure is halved so that it operates in part like a dipole and in part like a closed or reflex loudspeaker The structure has a modified back panel 40 that is connected to the loudspeaker body 2 elsewhere, but having a wide opening, or reflex tube 41 at the bottom The tube 41 is filled with a flexible mateπal, such as a foam rubber sealing mateπal 42, that suitably allows air to pass through, allowing the reflex tuning of the loudspeaker to be adjusted and also improving the hygienic quality of the loudspeaker The dπver 4 is suspended from the back panel 40 which together with the loudspeaker body 2 orms the reflex tube 41 The suspension of the driver from the back panel 40 can be stiff flexible or flexible over part of its surface as shown in figure 3, whereupon the back panel 40 also functions as a passive diaphragm

Figure 6 shows a modification of the loudspeaker structure, or loudspeaker 1 , of figure 5, in which said dipole structure is two-sided, in other words, the reflex tube 41 is also on the other side of the example structure A benefit is the greater sensitivity of movement of the dia¬ phragm, which improves the efficiency of bass response The other detailed characteπstics are the same as in the loudspeaker of figure 5 This structure also makes it possible to modify the beam of sound, because the freedom of movement of the diaphragm 3 can be defined as desired Thus, a diaphragm that is wide in the vertical direction and narrow in the hoπzontal direction produces a sound beam that is wide in the hoπzonta! direction and narrow in the vertical direction, so the loudspeaker is suitable for sound reproduction in

different types of public halls, for example In such a case the loudspeaker is a pillar loud¬ speaker

If the loudspeaker must reproduce mainly speech frequencies, it may be small, and the physical size of the body and diaphragm can be the same and the diaphragm can be of suitable mateπal of even thickness, such as plywood, which is fastened to the dπver body or the place of installation If the diaphragm is fastened by its side edges, for example, the diaphragm tends to vibrate in a flexing manner in line with the voice coil, which is a typical operating mode of the diaphragm If the response characteristics of the loudspeaker require tuning, it can be done by means of the above-mentioned modifications by machining, casting, laminating, etc If the above-mentioned structure is realized directly in a wall panel its reflex openιng(s) can be located near the ceiling and/or floor In such a case the dia¬ phragm structure of the loudspeaker may be only a small part of the body structure Fur- thermo ^r e if e g , the wall structure or backside space of the diaphragm allow, the reflex openings can be left out, whereupon the loudspeaker is closed On the other hand if the surface area of the loudspeaker body or diaphragm is large from the standpoint of an acous¬ tic short the edge of the diaphragm or the body of the loudspeaker can be completely open

The diaphragm 3 of the loudspeaker of figure 7 is of cellular construction, in that between two hard and thin or otherwise discernable structures there is lightweight and/or softer ate- rial that separates the surfaces from each other and stiffens the structure The intermediate material may be paper that is glued or cast by its edges to the diaphragms, or urethane styrofoam, composite mateπa! foam plastic or other filler The cell and support structure of the diaphragm 3 can be made in desired forms that differ noticeably from a plane surface Furthermore the thickness, mass and other structure of the diaphragm 3 or cell can vary or remain the same according to the desired response and beam charactenstics The driver 4 of the loudspeaker can be suspended from a separate dπver bπdge 51 , which can be fas¬ tened directly to the diaphragm by means of a flexible suspension Said driver bridge 51 may be similar in pπn ple to the above-mentioned dπver bπdge 22 whereupon the inertia of the mass of the dπver is exploited at bass frequencies in that the large mass of the dπver-bπdge structure 4 - 51 actuates the lightweight diaphragm 3 by means of the voice coil

Figure 8 presents a modification of the above-mentioned loudspeaker, or a panel modifica¬ tion in which an dnver bπdge 51 is connected to a construction sheet or panel or similar sheet of varying or even thickness, such as plywood or hardboard The loudspeaker forms a dipole with a sufficiently large surface area that it can be suspended from the ceiling of the

listening area at a suitable distance from the listeners and the walls. On the other hand, the sheet modification, having a large surface area, can be used to divide a room or part of a room, whereupon it produces sufficient sound in both directions, and an acoustic short will not occur. The surface wave of the large diaphragm can be modified by means of lamination, etc., if necessary.

Figure 9 presents a modification of the above-mentioned loudspeaker, or a damping panel modification, in which between the back panel 61 and diaphragm 3 there is a soft, thick damping material 62 that may be cloth, mineral wool, cotton, etc., on which the diaphragm is suspended. The diaphragm may be of suitable material, such as plywood, hardboard, etc. The material keeps the driver and voice coil centered with respect to each other, or centering is done by other means, such as by using a spider or other mechanical device, regardless of the location of the loudspeaker. The material 62 is a tuning element for the loudspeaker, so it is a reflex loudspeaker. As the diaphragm 3 is supported throughout by the damping mate¬ rial, the diaphragm 3 may be thin, and it nevertheless will not easily cause nodes in the surface wave of the diaphragm that lower the sound pressure.

The present invention is not limited to the embodiments presented above, but they can be varied within the limits of the enclosed claims. Thus, for example, the diaphragm 3 does not have to be plane-like, but it can include other shapes or be part of another structure. In principle, the diaphragm 3 of a loudspeaker according to the present invention may consist of several functional components. For example, the diaphragm 3 can be joined to a flexible edge instead of a solid body structure. The flexible edge allows a large amplitude of move¬ ment that is needed to reproduce low, powerful bass sounds. Still, said flexible edge can be of the same material or component as the diaphragm 3. The flexible edge can be con¬ structed into the diaphragm material or it can be a separate component made of a different material. The diaphragm material can be chosen from many suitable and durable materials, such as plywood, wood, MDF sheets, HDF sheets, other fiberboards, cloths, fabrics, plastics, composite materials, and even metals.