FIELD OF THE INVENTION The present invention relates to the audio devices, more specifically the invention provides an audio transducer, such as for generating an acoustic output in response to an electric input signal, especially a loudspeaker transducer suited for playback of audio signals, especially at higher audio frequencies. BACKGROUND OF THE INVENTION

In many loudspeakers designs, it is a problem to provide the desired angular sound dispersion covering e.g. a full horizontal 360° dispersion of acoustic energy, especially at higher audio frequencies.

This can be overcome by stacking separate audio transducers with separate diaphragms, however this is an expensive solution which further occupies space for the separate transducer structures. SUMMARY OF THE INVENTION

It may be seen as an object of the present invention to solve the above- mentioend problem. In a first aspect, the invention provides an audio transducer for generating an acoustic output in accordance with an electric input signal, comprising

- a diaphragm having a curved shape,

- an electrical conductor disposed on a surface on or integrated with the

diagphragm, wherein the electrical conductor extends in first and second zones at different locations of the diaphragm, wherein outer surfaces of the first and second zones face in different directions, and

- a magnet system arranged to provide a magnetic field in said first and second zones of the diaphragm, so as to move said first and second zones of the diaphragm in directions perpendicular to an extension of the diaphragm in the first and second zones (i.e. in a direction of their normal vectors) in response to the electric input signal being applied to the electrical conductor, so as to generate the acoustic output accordingly.

Such audio transducer is advantageous, since it is possible to implement a transducer capable of providing a pulsating movement of the diaphragm, thus radiating sound, also at high audio frequencies, with a pure monopole acoustic radiation pattern, e.g. covering a full 360° horizontal sound dispersion.

Still further, in a stereo version, the transducer can generate one stereo channel sound covering 180° dispersion, while covering the remaining 180° dispersion with the other stereo channel sound.

The transducer can be implemented with a diaphragm and electrical conductor(s) formed as a flexible printed circuit board which is shaped in the desired curved shape. The magnetic system can be implemented with permanent magnets shaped so as to provide a magnetic flux path which is parallel with the electrical conductor on the diaphragm.

In the following, preferred embodiments and features will be defined.

The magnet system is preferably arranged to provide a magnetic field which is parallel with or substantially parallel with the diaphragm in said first and second zones of the diaphragm. Preferably, the magnet system is arranged below an outer surface of the diaphragm. Hereby, it is possible to provide a design where the magnetic system is covered inside the transducer, namely below the diaphragm.

The diaphragm may be shaped so, and the electrical conductor may extend so on the diaphragm, that there exist first and second zones of the diaphragm, where normal vectors to outer surfaces of the first and second zones provide an angle of at least 20°, such as at least 30°, such as at least 40°, such as at least 90°, such as at least 120°. Hereby, the first and second zones can generate acoustic energy in different directions. Especially, the magnetic system may be arranged to generate magnetic fields in the first and second zones, such that acoustic contributions from the first and second zones of the diaphragm are in phase. This means sound generation as an acoustic monopole. With a dome shaped diaphragm, a pulsating sphere sound radiation can be implemented.

In preferred embodiment, the magnet system comprises a plurality of permanent magnets, e.g. neodymium magnets, arranged on a magnetic flux conducting yoke.

The electrical conductor may extend on the diaphragm and being arranged to interact with the magnetic system, so as to move the diaphragm perpendicular to its extension in response to the electric input signal across a majority of a total surface area of the diaphragm. By covering the majority of diaphragm area, it is possible to move the diaphragm in a uniform manner, so as to provide a pure monopole sound radiation up to high audio frequencies or above.

Preferably, the tranducer comprises a set of terminals arranged to receive the electrical input signal and being connected to respective ends of the electrical conductor.

The diaphragm may be made of a thin and flexible material. Especially, the diaphragm and the electrical conductor is constituted by a curved flexible printed circuit board. The diaphragm may be a monolithic foil being self-supported to at least substantially keep its shape without support. The diaphragm may be formed as one monolithic element with the electrical conductor disposed thereon or arranged inside said monolithic element.

The transducer may comprise a hinge arranged along at least a part of an edge of the diaphragm and serving to attached the diaphragm to the (static) structure of the audio transducer. Especially, the hinge may be made of a foam, such as a cellular foam e.g. Poron™ or NBR rubber. The hinge serves to damp waves in the diaphragm which will otherwise be reflcted at the edge of the diaphragm. It may be preferred to use a cellular foam hinge on the edge as well as on a top portion of the diaphragm in case of a dome shaped diapghram. The electrical conductor may be formed by a suitable material, such as copper or aluminium. The electrical conductor may comprise a plurality of electrical conductors in parallel covering said first and second zones, so as to provide a suitable electrical impedance.

In a preferred embodiment, the diaphragm has a dome shape, such as a semi- spherical shape. The magnet system is preferably shaped to match a shape of the diaphragm, e.g. to provide a uniform air gap between magnetic poles and the electrical conductor on the diaphragm.

The magnet system preferably comprises a plurality of permanent magnets arranged on a magnetic flux conducting yoke. Especially, the plurality of permanent magnets may be arranged on the magnetic flux conducting yoke such that the magnetic system has magnetic north and magnetic south located below the diaphragm forming an alternating pattern separated by spaces. Especially, the electrical conductor is located in regions of the diaphragm being located above said spaces between magnetic north and south.

In one embodiment, the diaphragm has a dome shape, such as a semi-spherical shape, and wherein the electrical conductor forms a helical shaped path concentrically arranged on the diaphragm. Especially, the electrical conductor forms at least first and second concentric regions each comprising a plurality of helical loops arranged with a first distance, and wherein the first and second concentric regions are separated by a distance larger than the first distance.

Especially, the transducer comprises a plurality of separate (generally) ring shaped permanent magnets with different diameter, and being arranged below the diaphragm between said first and second concentric regions, wherein an inner radial surface and an outer radial surface a the ring shaped permanent magnets form respective magnetic poles. Preferably, the transducer comprises at least one set of ring shaped permanent magnets, wherein a first one of said set has magnetic north on its outer radial surface, and the second one of said set has magnetic north on its inner radial surface. Especially, a plurality of said sets of ring shaped permanent magnets may be arranged such that said first ones and said second ones are arranged in an alternating pattern and separated by spaces, and wherein a loop of the electrical conductor is arranged on the diaghragm in concentric regions corresponding to said spaces.

In another embodiment, the transducer comprises a second electrical conductor disposed on a surface on or integrated with the diagphragm, wherein the electrical conductor extends in first and second zones at different locations of the

diaphragm, wherein the third and fourth zones are located non-overlapping with the first and second zones, and wherein outer surfaces of the third and fourth zones face in different directions. Especially, the magnetic system may be arranged so as to move said third and fourth zones of the diaphragm in directions perpendicular to an extension of the diaphragm in the third and fourth zones in response to a second electric input signal being applied to the second electrical conductor, so as to generate a second acoustic output accordingly. Especially, the transducer comprises a first set of terminals connected to respective ends of the electrical conductor, and a second set of terminals connected to respective ends of the second electrical conductor, wherein the first and second set of terminals are arranged to receive electrical respective first and second electrical input signal, such as first and second electrical input signals representing respective stereo channels. Especially, the first and second zones are spatially separated from the third and fourth zones, and wherein the magnetic system is arranged so as to generate first and second acoustic outputs as respective first and second spatially different acoustic monopole outputs. In a preferred embodment, the diaphragm has a dome shape, such as a semi-spherical shape, and the transducer may comprise a plurality of permanent magnets shaped to match the dome shape of the diaphragm, and being arranged below the diaphragm, and wherein an outer surface and an inner surface of the permanent magnets form respective magnetic poles. Especially, the transducer may comprise at least one set of permanent magnets shaped to match the dome shape of the diaphragm, wherein a first one of said set has magnetic north on its outer surface, and the second one of said set has magnetic north on its inner surface. Especially, a plurality of said sets of permanent magnets may be shaped to match the dome shape of the diaphragm are arranged such that said first ones and said second ones are arranged in an alternating pattern and separated by spaces, and wherein a portion of the electrical conductor is arranged on the diaghragm in concentric regions

corresponding to said spaces. Especially, the permanent magnets shaped to match the dome shape of the diaphragm may extend from a centre portion of the dome shaped diaphragm to a base part of the dome shape of the diaphragm.

The transducer, e.g. part of its diaphragm, may further be used as microphone. Thus in some embodiments, at least one part of the diaphragm with an electrical conductor portion disposed thereon is arranged to serve as a microphone.

Especially, at least one of the first and second electrical conductors may be arranged to serve to generate an electrical output in accordance with an acoustic input to the diaphragm. Especially, said at least one of the first and second electrical conductors may be arranged to selectively serve to generate an electrical output in accordance with an acoustic input to the diaphragm. In a special embodiment, the diaphragm has a semipsherical shape, wherein four separately accessible electrical conductor portions each serve to cover a quarter of the diaphragm, wherein at least one of said four separately accessible electrical conductor portions is arranged to serve to generate an electrical output in accordance with an acoustic input to the diaphragm. In a second aspect, the invention provides a loudspeaker comprising

- at least one audio transducer according to the first aspect,

- an amplifier connected to the electrical conductor of the at least one audio transducer, and

- a cabinet,

wherein the audio transducer is arranged in or on a structure of the cabinet.

Especially, the at least one audio transducer is arranged to generate an acoustic output above a lower cut off frequency, such as a lower cut off frequency of 1-3 kHz, such as 2-5 kHz, such as 3-6 kHz, such as 3-8 kHz, such as 3-10 kHz.

The loudspeaker may comprise at least a second audio transducer arranged in or on a structure of the cabinet, and being arranged to generate an acoustic output below said lower cut off frequency. Especially, the loudspeaker may comprise a radio module arranged for wireless audio streaming, e.g. a radio module allowing audio streaming via wi-fi and/or Bluetooth or the like. Especially, the loudspeaker may be a portable loudspeaker, e.g. a battery powered portable loudspeaker.

The loudspeaker may comprise an amplifier circuit arranged to amplify an electrical signal generated by at least one electrical conductor part of the diaphragm, so as to generate an amplified electrical output in response to an acoustic input to the diaphragm. In such embodiment, the transducer, or part of it, is used as microphone, which can have several applications e.g. in a wireless stand-alone loudspeaker product, e.g. to capture voice from the user, e.g. for controlling one or more functions of the loudspeaker, e.g. to allow the user to perform a phone call using the loudspeaker. In a third aspect, the invention provides a method for generating an acoustic output in accordance with an electric input signal,

- providing a diaphragm having a curved shape,

- providing an electrical conductor on a surface of or integrated with the diagphragm in at least first and second zones at different locations of the diaphragm, wherein outer surfaces of the first and second zones face in different directions, and

- providing a magnetic field in said first and second zones of the diaphragm,

- applying the electric input signal to the electrical conductor, so as to move said first and second zones of the diaphragm in directions perpendicular to an extension of the diaphragm in the first and second zones, so as to generate the acoustic output accordingly.

In a fourth aspect, the invention provides a method for manufacturing an audio transducer according to the first aspect.

In a fifth aspect, the invention provides data representation of at least the diaphragm, such as the diaphragm and the electrical conductor, of the audio transducer according to the first aspect, so as to allow a 3D manufacturing device to manufacture said diaphragm or said diaphragm and the electrical conductor, such as manufacturing the diaphragm, and optionally also the electrical conductor thereon, by means of a 3D printer. Especially, said data may be represented on a tangible storage medium and/or in a computer readable memory. Especially, the manufacturing of the diaphragm may comprise and in-mold electronic technology, where the manufacturing comprises manufacturing the electrical conductor on the diaphragm surface or integrated with the diaphragm.

In a further aspect, the invention provides an audio transducer for generating an electric output signal in accordance with an acoustic input, comprising

- a diaphragm having a curved shape,

- an electrical conductor disposed on a surface on or integrated with the

diagphragm, wherein the electrical conductor extends in first and second zones at different locations of the diaphragm, wherein outer surfaces of the first and second zones face in different directions, and

- a magnet system arranged to provide a magnetic field in said first and second zones of the diaphragm, so that upon movement of said first and second zones of the diaphragm in directions perpendicular to an extension of the diaphragm in the first and second zones by an acoustic input, the electric output signal is being generated by the electrical conductor in accordance with the electric output signal. Thus, according to this aspect, the transducer can act as a microphone.

It is to be understood that the invention can be implemented in various ways, and that the above-mentioned preferred features and embodiments may be mixed in any way.

BRIEF DESCRIPTION OF THE FIGURES

Embodiments of the invention will be described in more detail in the following with regard to the accompanying figures. The figures show one way of implementing the present invention and is not to be construed as being limiting to other possible embodiments falling within the scope of the attached claim set.

Figs, la and 2b show sketches of a section of the diaphragm and magnetic system to illustrate the basic function of the audio transducer according to the invention, Fig. 2 shows an exploded 3D view of parts of a preferred embodiment with a dome shaped diaphragm,

Figs. 3a-3d show various view of a of the embodiment of Fig. 2,

Figs. 4a-4c show various views of diaphragm and electrical conductor

configuration of the embodiment of Figs. 2 and 3a-3d,

Fig. 5 shows an exploded 3D view of parts of another preferred embodiment with a dome shaped diaphragm,

Figs. 6a-6d show various view of a of the embodiment of Fig. 5,

Figs. 7a and 7b show different views of diaphragm and electrical conductor configuration of the embodiment of Figs. 5 and 6a-6d,

Fig. 8 show different 3D sketches of possible diaphragm shapes,

Fig. 9 shows steps of a method embodiment,

Figs. 10-12 show various views of an embodiment suitable for stereo reproduction and/or suitable to be used both as loudspeaker and as a microphone, and

Fig. 13 shows a simple circuit diagram indicating a possible connection of a electrical conductor of the diaphragm to allow at least a part of the transducer to serve as microphone.

DETAILED DESCRIPTION OF EMBODIMENTS Figs, la and lb show sketches of sections of an audio transducer embodiment for generating an acoustic output in accordance with an electric input signal.

In Fig. la a part of the flexible diaphragm DM with a curved shape is seen. It has an electrical conductor CD disposed on its surface, indicated here leading current in a direction perpendicular to the paper. The electrical conductor CD extends in first and second zones Zl, Z2 at different locations of the diaphragm, wherein outer surfaces of the first and second zones Zl, Z2 face in different directions, illustrated with the dashed arrows indicating normal vectors to the diaphragm in the first and second zones Zl, Z2. A magnet system MS is arranged to provide a magnetic field in said first and second zones Zl, Z2 of the diaphragm DM. Hereby, the first and second zones Zl, Z2 of the diaphragm DM is caused to move in directions perpendicular to an extension of the diaphragm DM in the first and second zones Zl, Z2 (indicated by bold double arrows) in response to the electric input signal being applied to the electrical conductor CD, so as to generate the acoustic output accordingly.

Thus, one single conductor is used to provide a magnetic motor effect to portions of the diaphragm which serves to generate acoustic energy in different directions, thereby enabling a monopole sound generation.

Fig. lb shows a section sketch of an embodiment in more detail than Fig. la, and with indication of magnetic flux lines in a configuration of a magnetic system where three permanent magnets Ml, M2, M3 are visible, and which are arranged on one common yoke Y. The magnetic poles for each of the magnets Ml, M2, M3 are indicated as ^λ Ν' and 'S'.

As seen, magnetic flux lines are parallel with the diaphragm DM, and thus the electrical conductor portions CD_1 and CD_2 on the diaphragm DM in the respective zones Zl, Z2, thereby leading current perpendicular to the paper plane with a direction indicated by Y (current direction out of the paper plane) and ^λ χ ' (current direction into the paper plane). Due to the opposite direction of the current and the opposite directions of the magnetic flux in the two zones Zl, Z2, the electrical conductor CD_1, DC_2 will move the diaphragm as indicated on Fig. lb, indicated by dashed arrows on each conductor segment, namely perpendicular to the diaphragm surface in different directions indicated by the non-parallel dashed lines in the respective zones Zl, Z2.

In Fig. lb, the electrical conductor is shown having 5 parallel or substantially parallel conductor paths CD_1, CD_2 in respective zones Zl, Z2, and as seen, the electrical conductor portions CD_1, CD_2 are located on the diaphragm surface in the spaces between the magnets, so as to be positioned where the magnetic flux lines are parallel with the diaphragm in order to cause a magnetic force on the diaphragm which is parallel with the normal to the surface of the diaphragm, thereby generating an acoustic output if an audio signal is applied to the electrical conductor. It is to be understood that the electrical conductor portions CD_1, CD_2 may be connected in series, thus forming one single electrical conductor. However, if preferred, The two electrical conductor portions CD_1, CD_2 may be implemented as two separate electrical conductors on which the same audio signal is applied. In the following illustrations, the configuration of the electrical conductor on the diaphragm will be shown by examples.

Figs. 2, 3 and 4 illustrate various drawings of one embodiment arranged for generating a mono acoustic output in response to an audio signal applied to one set of electrical terminals with +/- polarity connecting one single electrical conductor disposed on a diaphragm foil.

Fig. 2 shows an exploded view of the full transducer with all major parts present.

Front panel A and housing parts E constitute together the outer shell which have a twofold purpose. A shields the diaphragm from ambient impact and at the same time permits diffusion of sound. Front panel A in conjunction with housing parts E constitutes a mechanical base for both magnets D and dome shaped foil diaphragm B with electrical conductor disposed on its surface. Front panel A and housing parts E serve to hold the parts in place during operation. Rivets F act as clamps holding front panel A and housing parts Etogether securing the transducer.

Hinges on the diaphragm B of cellular foam serve to act as dampers, which in other words, is intended to minimize any unwanted harmonic vibrations occurring as breakup of the diaphragm B becomes more pronounced at still higher frequencies. These breakups will manifest themselves as standing waves and the hinges B made from cellular foam will minimize the reflection of these waves. This will reduce harmonic distortion yielding an improved response. The magnetic system with generally ring shaped magnets D arranged on a matching common yoke serving to provide magnetic flux lines parallel with the diaphragm B in the 4 annular loops of the electrical conductor. Referring to Figs. 3a-3d, the transducer embodiment from Fig. 2 is seen in top view (Fig. 3d), a side view (Fig. 3c), and a section cut A-A (Fig. 3b). In Fig. 3a, a section cut A-A is shown where the magnet rings A, B, C, D, E and their magnetic orientations are indicated. The cut-out show that each magnet is a full ring and with the configuration with alternating polarity, an alternating magnetic field that is uninterrupted thus maximizing the flux needed for operation. The polarity of the magnetic field is constructed as normal to the magnet surface. This ensures a normal force on the diaphragm when a signal conducting current is introduced in the electrical conducting portions being arranged in loops on the diaphragm in spaces between the magnets A, B, C, D, E. Bottom magnet A and top magnet E have cut-out holes to accommodate for lead wires carrying the alternating signal to the electrical conductor on the diaphragm.

Section A-A in Fig. 3b shows the transducer assembly collapsed when compared to Fig. 2. Foam hinges N and H are glued to the diaphragm J for support of the diaphragm J during operation. Magnets K are placed on top of the housing part I comprising interconnecting parts forming a yoke made from iron. The magnetic system forms a magnetic path for the all field lines as to reduce any stray field and making the magnetic field between the magnet rings K as intense as possible. By extracting a flat diaphragm into a curved shape, here a dome shape, a diaphragm suited for high frequency sound reproduction is possible, e.g. with a diameter of such as 1-3 cm, such as 1-8 cm, since the entire dome shape contributes to generate acoustic output by moving in-phase. The dome shaped diaphragm can be made in one piece and lateral self-supporting. E.g. by etching aluminium electrical conducting lanes (wires) on a thin poly-carbon material, a wide area of the dome diaphragm can be filled with electrical current conductors and thus producing the normal-force intended for converting motion into the air for making sound. Figs. 4a-4c show the dome shaped diaphragm of the embodiment of Figs. 2 and 3. As the dome is a half sphere and intentionally ridged, it can acoustically be equated to a pulsating sphere. Preferably, the dome shaped diaphragm has slits in the diaphragm dome to accommodate movement in both directions in/out. Please refer to Fig. 4b, where four slits E are seen, extending from the dome top D to the lower edge of the diaphragm. These slits E are placed to reduce stress in the diaphragm material when forces are applied to thereto through interaction between current and the magnetic field from the magnetic system thus changing the radius of the diaphragm slightly. At audio frequencies above 2 kHz the necessary displacement of the diaphragm is in the order of 20 μηη. Thus there is no visible displacement taking place. In the specific embodiment, the dome has a diameter of 50 mm.

Figs. 4a, 4b and 4c all show the electrical conductor forming a helical shaped path or lane concentrically arranged on the diaphragm. The electrical conductor is preferably made of an aluminium lane or path disposed on the diaphragm material. In the shown embodiment the electrical conductor is formed by one single path forms concentric regions each comprising a plurality of helical loops arranged with a first distance, and wherein the first and second concentric regions are separated by a distance larger than the first distance. Hereby, a plurality of electrical conductor loops are arranged on the diaghragm in concentric regions matching the space between magnets of the magnetic structure, as can be seen in Fig. lb, Fig. 2 as well as Figs. 3a and 3b. In the speicifc example shown, each of four concentric regions comprise 8 loops of parallel of substantially parallel conducting lanes arranged at a distance of 0.2 mm, wherein the lanes have a width of 0.45 mm. The distance between the concentric regions of loops is at least 5 times, such as at least 10 times, the distance between the loops or lanes in each region of loops. The lanes or loops in each region form a gentle slope. The electrical conductor can in principle be formed by one single helical path, as shown, or it can be formed by two separately twisted helical paths running in parallel. The choice may depend on the tolerances of the impedance.

Fig. 4b shows a top view of the diaphragm dome, where terminals A, B of respective electrical conducting paths arranged for carrying current in parallel can be seen, and the direction is alternated to follow the fields lines of the alternating magnetic field presented in Figs, lb and 3a. C shows one of two terminal leads ending in opposite terminals either A or B, hereby connecting one of the two helically shaped electrical conductor paths on the diaphragm dome. D indicates a hole made for connection to the terminals A, B electrically and support by the foam hinges shown in Fig. 2.

The embodiment in the foregoing is especially suitable as an audio tweeter in a loudspeaker including one or more audio transducers arranged to generate lower audio frequencies. The transducer in the forgoing allows a high degree of sound dispersion due to its working principle, even at high audio frequencies, and even in version which are quite large compared to a traditional dome tweeter. The reason is that its working principle allows a 360° horizontal sound dispersion.

Referring now to Figs. 5-7, another embodiment with a dome shaped, or flat dome shaped, diaphragm is shown. Whereas the embodiment described in the foregoing is a mono transducer, the embodiment in Figs. 5-7 is configured to functions as a stereo transducer, i.e. it has two separate electrical conductors arranged to receive respective audio input signals, and the two electrical conductors are spatially arranged on the dome shaped diaphragm to allow generation of a first audio channel acoustic output to one side, and generation of a second audio channel acoustic output to the opposite side, thus allowing generation of an acoustic stereo image. Most of the physics and layout is similar to the mono transducer embodiment already described, and thus an emphasis on differences will be made in the following.

Fig. 6a shows a section B-B serving to illustrate the configuration of the magnetic system comprising permanent magnets and their magnetic poles indicated by ^λ Ν' and 'S' arranged on a an iron yoke structure D. The yoke structure D splits the design in four equal sections each of these are identical in terms of the magnetic structure. By splitting the magnetics into multiple sections, it is possible to convert the 360° mono transducer described in the foregoing into a 360° stereo transducer and getting a Left/Right/Left/Right stereo channel output arrangement

Fig. 5 shows an exploded view of the stereo transducer, where the permanent magnets D are seen to be rotated 90° vertical in contrast to the mono version, and the magnets D are arraonged on a common yoke structure E which forms the base of the transducer. Of course the electrical conductors on the diaphragm are configured, as previously descried, in spaced between the alternating magnets, so as to allow the magnetic flux lines to interfere with a current in the electrical conductor according to the general principle explaind in relation to Fig. lb. The diaphragm B has been divided into four separate parts, which is further seen in Figs. 7a and 7b, and here slits E are seen to separate the four separate parts, and the division is also clamped to the iron housing and thus stretching of the material is possible. In addition, this division makes it possible to remove any incoming vibrations from adjacent parts of the diaphragm. This in turn reduces harmonic distortion. Again, in Fig. 5, cellular foam hinges C are used in the top and on the edge part of the diaphragm.

Fig. 7b shows terminal endings A, B, C, D of the electrical conductors are indicated. These endings A, B, C, D will be folded and isolated from each other and fed through a hole in the top part of the diaphragm to allow external connection of the transducer.

As the 360° stereo audio transducer embodiment suggests, there exists another parameter for harnessing advantages of the geometry, namely scalability. By changing both diameter and/or the height of the mechanical structure, it is possible to change the size of the tweeter to accommodate many design constraints. Thus, apart from serving as a high audio frequency transducer, versions with larger diaphragms may serve as well as midrange transducers.

Fig. 8 shows a variety of different curved diaphragm shapes as alternative to the shown dome.

Fig. 9 shows steps of a method embodiment for generating an acoustic output in accordance with an electric input signal.

Step A: providing a diaphragm having a curved shape.

Step B: providing an electrical conductor on a surface of or integrated with the diagphragm in at least first and second zones at different locations of the diaphragm, wherein outer surfaces of the first and second zones face in different directions.

Step C: providing a magnetic field in said first and second zones of the diaphragm, and finally

Step D: applying the electric input signal to the electrical conductor, so as to move said first and second zones of the diaphragm in directions perpendicular to an extension of the diaphragm in the first and second zones, so as to generate the acoustic output accordingly.

Figs. 10-12 show various views of an embodiment which is suited as a

loudspeaker for stereo audio reproduction, just as the embodiment shown in Figs. 5-7, and the magnet structure and principal diaphragm shape is seen to be the same. However, in the embodiment of Figs. 10-12, a mechanically absorbing material C (preferably a cellular foam such as Poron™ or NBR rubber) serves to reduce mechanical vibrations from one part of the diaphragm to enter the adjacent diaphragm part. Compared to the corresponding material C in Figs. 5 and 6, the material C embodiment of Figs. 10-12 is shown to divide the

semispherical diaphragm into four quarter parts each covering an angular portion of 90° of the semisphere, since the material C has a top portion, a bottom portion and four radial connecting portions, where the diaphragm rests. This divides the diaphragm into four mechanically separated parts which can be accessed separately by respective audio signals being applied to the respective electrical conducting portions.

It is futher appreciated that the transducer embodiment in Figs. 5-7 as well as in Figs. 10-12 are also suited for use as a microphone, i.e. where the transducer is used in reverse compared to as a loudspeaker. Further, it is appreciated that the transducer design can be used partly as a loudspeaker and partly as a

microphone, even at the same time, if desired, since some electrical conductor parts on the diaphragm may serve as loudspeaker coils, while other electrical conductor parts on the diaphragm serve as a microphone coils. Thus, at the same time, some parts of the diaphragm may have separately accessible conductors which can be used to generate acoustic waves in response to an applied audio signal, while other parts of the diaphragm may have separately accessible conductors which can be used to capture acoustic waves and generate an audio signal in response. Still further, one electrical conductor part and the

corresponding diaphragm part can selectively serve, at one time, as a

loudspeaker, and at another time, as a microphone.

When serving as a microphone, an incoming acoustic pressure wave will move the diaphragm which is electrical conducting in a magnetic field. In accordance with Faraday and Lorentz equations, but in reverse, a force will be converted to a voltage by a current flowing in the conductor on the diaphragm, e.g. in the form of an aluminum wire etched onto the diaphragm. The diaphragm design can be made very light weight, and this allows the diaphragm to be suited as a

microphone as well as a loudspeaker. Therefore, there is no need for a different mechanical design for the transducer to work as a microphone. All necessary adjustments or alterations can be made purely electrically outside the transducer itself. This means that the electrical terminals will experience either a low impedance - in normal use as a loudspeaker - or a high impedance, which is then the microphone mode. In embodiments where two or more different parts of the diaphragm are used as separate microphones, it is possible to apply a signal processing algorithm to the respective output signals from the separate microphone, and to determine a direction of an incoming acoustic signal. Thus, e.g. it may be possible to locate an incoming voice signal relative to the transducer, and thus relative to a device, e.g. a wireless loudspeaker device with the transducer according to the invention.

It is to be understood that embodiments for use as microphone, the same principal shapes of diaphragm and various electrical conductor configurations may be used, as already described fot the pure loudspeaker embodiments.

Fig. 13 shows a simple electric diagram of a preferred way of using the transducer as a microphone. A large impedance RL, e.g. a resistor of such as more than 10 kQ, e.g. more than 20 kQ, is connected across the electrical conductor terminals CDM disposed on the part of the diaphragm which is to serve as a microphone. In the embodiment shown in Fig. 13, a quarter of the semisphere is to serve as a microphone. Hereby, the electric current in the electrical conductor CDM will result in a voltage E which can be applied to a buffer. The output of the buffer can be sourced to an amplifier and interpreted as an acoustic signal, much like the principle known from a condenser microphone.

To sum up, the invention provides an audio transducer with a diaphragm having a curved shape and with an electrical conductor disposed on a surface on or integrated with the diagphragm, e.g. a diaphragm made of a thin and self- supporting foil, e.g. being dome shaped. The electrical conductor extends in first and second zones at different locations of the diaphragm, wherein outer surfaces of the first and second zones face in different directions. A magnet system below the outer surface of the diaphragm provides a magnetic field in said first and second zones, so as to move said first and second zones of the diaphragm in directions perpendicular to an extension of the diaphragm in the first and second zones in response to an electric input signal being applied to the electrical conductor. Hereby, it is possible to allow a significant portion of the diaphragm, e.g. the entire diaphragm area, to generate an acoustic output even at high audio frequencies, thus providing a wide sound dispersion in a pulsating sphere like manner. In a stereo version, separate diaphragm parts are dedicated to generate respective stereo channel acoustic outputs. Further, a part of the transducer diaphragm or the whole transducer diaphragm may serve as microphone.

Although the present invention has been described in connection with the specified embodiments, it should not be construed as being in any way limited to the presented examples. The scope of the present invention is set out by the accompanying claim set. In the context of the claims, the terms "comprising" or "comprises" do not exclude other possible elements or steps. Also, the mentioning of references such as "a" or "an" etc. should not be construed as excluding a plurality. The use of reference signs in the claims with respect to elements indicated in the figures shall also not be construed as limiting the scope of the invention. Furthermore, individual features mentioned in different claims, may possibly be advantageously combined, and the mentioning of these features in different claims does not exclude that a combination of features is not possible and advantageous.