WO2009000519A1

WO2009000519A1 - Diaphragm arrangement for an air motion transformer (amt), and sound converter comprising such a diaphragm arrangement

Info

Publication number: WO2009000519A1
Application number: PCT/EP2008/005149
Authority: WO
Inventors: Raimund Mundorf
Original assignee: Mundorf Eb Gmbh
Priority date: 2007-06-26
Filing date: 2008-06-25
Publication date: 2008-12-31
Also published as: EP2158789A1; EP2158789B1; DE102007029560B4; DE502008001544D1; DE102007029560A1; ATE484923T1

Abstract

The invention relates to a diaphragm arrangement (16, 26, 39, 47, 62) for an air motion transformer (AMT). Said diaphragm arrangement (16, 26, 39, 47, 62) comprises at least one substantially meander-shaped diaphragm (16a) as well as air pockets (23, 59, 60) for generating sound as a result of the meander-shaped design of the at least one diaphragm (16a). In order to improve the radiation behavior of the diaphragm arrangement and at least reduce the concentration of sounds, the diaphragm arrangement (16, 26, 39, 47, 62) encompasses several diaphragm segments (A, B, C; a, b, c) which are arranged and/or designed such that the diaphragm arrangement (16, 26, 39, 47, 62) has a substantially common acoustic center.

Description

Membrane arrangement for an air-motion transformer (AMT) and sound transducer with such a membrane arrangement

The invention relates to a membrane assembly for an air-motion transformer (AMT), wherein the membrane assembly has at least one substantially meander-shaped membrane and the membrane assembly by the meandering formation of the at least one membrane air pockets for generating sound. Furthermore, the invention relates to a sound transducer with such a membrane arrangement.

Such membrane arrangements are used in the prior art in sound transducers, in particular in so-called AMT loudspeakers. The Air-Motion-Transformer (abbreviated to AMT) is an original of Dr. med. Oskar Heil developed sound transducer. Such an air-motion transformer has a meandering or accordion-like folded membrane. By this shaping of the membrane air pockets are formed. These air pockets are widened and narrowed for pressing out or for sucking in air and thus for generating sound. For this purpose, the membrane arrangement is vzw. in operative connection with a suitable device. Vzw. are arranged on the flanks of the air pockets tracks. The preferably arranged in a magnetic field membrane or the air pockets are excited to generate sound by an alternating current is passed through the tracks. The flanks of the air pockets are moved against each other, wherein the air is forced out of the air pockets or sucked into these air pockets inside.

Air-motion transformers can be used in particular in hi-fi speakers as a tweeter in the frequency range from about 1 kHz to a maximum of about 25 kHz. Air Motion Transformers are characterized by the small moving mass of the membrane by an excellent impulse response, as an AMT speaker a pulse-shaped signal with very little Einbzw. Can reflect decay processes.

FIG. 1 shows a schematic illustration of a membrane arrangement 1 known from the prior art for a not shown in detail, electrodynamic mix transducers, here a speaker. The here meander-shaped membrane assembly 1, which here has a single membrane Ia, takes this form substantially in its operating condition, said membrane assembly 1 then vzw. is arranged between two plates, not shown here, in an air gap. The membrane assembly 1 is first prepared as a sheet-like element, the illustrated interconnects 2 vzw. be formed by means of appropriate etching on the membrane Ia.

Clearly visible are a plurality of wave crests 3 and troughs 4 and the wave crests 3 and the wave troughs 4 interconnecting and opposite edges 5, on which the conductor tracks 2 are arranged. As can be clearly seen from Fig. 1, a plurality of air pockets 6 are formed by this arrangement. By means of the arrows illustrated on the printed conductors, a current I flowing through the printed conductors 2 is indicated in FIG. Furthermore, a static magnetic field is indicated by the arrows B.

The operation of the known in the prior art membrane assembly 1 will now be explained with reference to FIGS. 2 and 3. The rest position of the membrane assembly 1 shown in FIG. 1 is shown in dashed lines in FIGS. 2 and 3. 2 and 3 show with the solid lines the excited state of the membrane 2 and the air pockets 6 in the open and closed position. In detail:

FIG. 2 shows that the flanks 5 of the membrane arrangement 1 move in the direction of the arrows C 1. The air pockets 6a, 6b, 6c and 6d increase in width, ie these air pockets 6a, 6b, 6c and 6d are opened, so that air is sucked into these air pockets 6a to 6d according to the arrows E. Air pockets 6e, 6f, and 6g are arranged between the air pockets 6a to 6d, open to the other side. These air pockets 6e to 6g adjacent to the air pockets 6a to 6d are correspondingly reduced in width - or are closed - so that, according to the arrows A, the air is forced out of these air pockets 6e to 6g. (Arrows A: air outlet, arrows E: air intake). 3 now shows the membrane assembly 1 in the reverse deflection position of the flanks 5. The flanks 5 move in the opposite direction, this being indicated by the arrows C2. The flanks 5 of the air pockets 6a, 6b, 6c and 6d move towards each other, so that these air pockets 6a to 6d narrow and the air is forced out of these air pockets 6a to 6d (see arrows A). The air pockets 6e, 6f and 6g are widened, so that air is sucked into these air pockets 6e, 6f and 6g (see arrows E).

4 shows an AMT sound transducer 15 with the membrane arrangement 1 shown in FIGS. 1 to 3. The membrane arrangement 1 is arranged between two pole plates 7 and 8 in an air gap 9. The membrane assembly 1 is clamped in a frame, wherein only the two frame parts 10a and 10b can be seen from the frame. The frame with the frame parts 10a and 10b is connected to two side parts IIa and I Ib. The side parts IIa and IIb in turn carry the pole plates 7 and 8.

FIG. 5 shows that the pole plate 8 has a plurality of sound openings 12. The sound holes 12 are formed in the form of slits 12a extending in the horizontal direction. Through the slots 12 a, the sound generated by the membrane arrangement 1 can escape from the sound transducer 15.

By periodically narrowing and widening the air pockets 6 are emitted from the membrane assembly 1 sound waves. The sound waves are - like all waveforms - broken and bent. The strength of the diffraction of the sound waves depends on their wavelength. Long waves, ie low notes, become less than short waves, high notes, bent and broken. This frequency-dependent behavior is summarized under the term radiation behavior. Loudspeakers and therefore also air-motion transformers have a different radiation behavior at different frequencies. The low frequencies are rather spherical radiated and tend to spread equally in all directions. With increasing frequency, the sound waves show an ever stronger concentration. High frequencies are almost only radiated in a certain direction. In Fig. 4, the horizontal bundling and in Fig. 6, the vertical bundling of the sound waves 13 and 14 is shown once for sound waves 13 at low frequency and once for sound waves 14 at a high frequency. The sound waves 13 with a low frequency are radiated in an emission cone with an opening angle relative to the ideal emission axis S. The emission axis S extends perpendicularly and centrally to the membrane arrangement 1. The sound waves 14 having a high frequency are radiated essentially only in the direction of the emission axis S as plane and parallel wavefronts.

In many cases, this bundling of the sound at high frequencies is undesirable. Among other things, it is crucial for the listening impression how the sound is emitted away from the ideal radiating axis (Hörachse), because not all listeners are always in the direction of the horn axis. Ideally, a loudspeaker should reproduce all frequencies identically loud in every direction. In practice, however, a bundling of the sound occurs, in particular in the mid / treble range, and is dependent on the frequency. The all-round radiation capability can therefore be limited, in particular in the case of membrane loudspeakers. With increasing frequency, a bundling of the radiated sound occurs, for example, in the horizontal and vertical directions, as shown in FIGS. 4 and 5.

The invention is therefore based on the object to design and further develop a membrane arrangement such that the radiation behavior of the membrane arrangement is improved and the sound bundling is at least reduced, in particular for the high frequencies.

The previously indicated object is now achieved in that the membrane arrangement has a plurality of membrane segments and that the membrane segments are arranged and / or configured such that the membrane arrangement has a substantially common acoustic center. In this case, the membrane segments are arranged or formed in such a way that the sound waves emitted by the membrane segments are superimposed in such a way that the overall sound-for the listener-appears to come from an acoustic center. This allows a precise picture of the sound to reach. If two speakers are used, it can also achieve a precise stereo location. The acoustic center preferably lies on the emission axis or in the corresponding emission plane of the membrane arrangement. As the following statements will show, there are now different possibilities to realize the "membrane segments." On the one hand, the corresponding "membrane segments" may be formed as subregions of a single membrane, but on the other hand it is also possible that several individual vzw. Meander-shaped membranes are summarized to form a membrane assembly accordingly. The decisive factor is that the membrane segments thus formed are arranged and / or configured in this way - or which will also show the following statements - then be controlled so that the membrane arrangement itself has a common acoustic center.

The individual membrane segments are in turn preferably arranged symmetrically with respect to the emission axis or emission plane of the membrane arrangement. For example. For example, a middle membrane segment and at least one outer membrane segment can be arranged on both sides of the middle membrane segment. The middle membrane segment is preferably designed for reproducing a high-frequency range and the outer membrane segments are then designed for reproducing a low-frequency range.

The subdivision of the membrane assembly into a plurality of membrane segments also has the advantage that the omnidirectional behavior is improved since the limit for an acceptable omnidirectional behavior is given when the extent of a membrane segment in one direction is less than half the wavelength of the frequency to be generated. As the frequency to be radiated increases, therefore, small membrane expansions are advantageous. The division of the membrane arrangement into membrane segments can take place in vertical and / or horizontal extension of the membrane arrangement (in the case of a towering membrane arrangement). For reproducing low frequencies, the membrane arrangement preferably has a correspondingly large area. The deeper the frequency to be transmitted is selected, the larger is preferably the total membrane area for reproducing the lowest frequency. Details may be described below with reference to the embodiments. As a result, however, the aforementioned disadvantages are avoided and achieved corresponding advantages.

There are now a variety of ways to design the membrane assembly according to the invention or a sound transducer in an advantageous manner and further. For this purpose, reference may firstly be made to the patent claims 1 or claim 20 subordinate claims. In the following, several embodiments of the invention with reference to the following drawings and the associated description are explained in detail.

In the drawing shows:

1 shows a schematic representation of the structure of a membrane arrangement known in the prior art,

2 shows the membrane arrangement from FIG. 1 in a schematic representation from the side with the movements of the flanks in a first direction, FIG.

1 shows a schematic representation of the membrane arrangement from FIG. 1 with movements of the flanks in a second, opposite direction, FIG.

4 is a schematic representation of a sound transducer with the assembled known membrane assembly of FIG. 1 in plan view,

5 shows the sound transducer from FIG. 4 in a schematic front view, FIG.

6 shows the sound transducer from FIG. 5 in a schematically greatly simplified side view, FIG.

7 is a schematic representation of a first embodiment of a sound transducer according to the invention in plan view,

8 shows the sound transducer from FIG. 7 in a schematic front view, FIG. 9 shows the sound transducer from FIG. 7 in a schematically greatly simplified side view, FIG.

10 is a schematic representation of a second embodiment of a transducer according to the invention in front view,

11 shows the sound transducer from FIG. 10 in a schematic plan view,

11 shows the sound transducer of FIG. 10 in a schematically greatly simplified side view, FIG.

12 is a detail view of a portion of a first membrane segment in plan view in a schematic representation,

13 is a detailed view of a portion of a second membrane segment in maximum compressed state in a schematic representation,

14 shows a further detailed view of the subregion of the second membrane segment in a state following that of FIG. 13 in a schematic representation,

FIG. 15 is a schematic plan view of a third embodiment of a sound transducer according to the invention;

16 shows a first electrical circuit diagram for the sound transducer from FIG. 15, FIG.

17 is a second, electrical circuit diagram for the transducer of FIG. 15,

18a shows a fourth embodiment of a sound transducer according to the invention in a schematic plan view, 18b shows an electrical circuit diagram for the sound transducer from FIG. 18a, FIG.

19 shows a fifth embodiment of a sound transducer according to the invention in a schematic plan view,

FIG. 20 shows an electrical circuit diagram for the sound transducer from FIG. 19

21 shows a further electrical circuit diagram for the sound transducer from FIG. 19, FIG.

Fig. 22a shows a sixth embodiment of a sound transducer according to the invention in a schematic plan view, and

Fig. 22b is an electrical circuit diagram for the transducer of Fig. 22a.

FIG. 7 shows a sound transducer 15 with a membrane arrangement 16, namely here with a single membrane 16a. The sound transducer 15 is a so-called air-motion transformer (AMT), namely designed here as a speaker.

The membrane 16a is meander-shaped and arranged between two pole plates 17 and 18 in an air gap 19. The membrane 16 a is vzw. initially produced as a sheet-like element, wherein the conductor tracks, not shown here vzw. be formed by means of appropriate etching on the membrane 16a and the membrane 16a vzw. lying in a plane between the pole plates is arranged.

Clearly visible are a plurality of wave crests 20 and troughs 21 and the wave crests 20 and wave troughs 21 interconnecting and opposing flanks 22, on which the conductor tracks, not shown here are arranged. In this case, there is a corrugation valley 21 between two wave crests 20 and a corrugation peak 20 between two adjacent corrugation troughs 21, so that a corresponding "accordion shape" is created as indicated in the respective figures. is recognizable, a plurality of air pockets 23 are formed for generating sound by this arrangement.

Further, by the pole plates 17 and 18, a vzw. static, not shown magnetic field or an electrostatic magnetic field generated. Sideways forces act on the printed conductors (not shown) when the printed conductors are traversed by a current. In particular, the current may be an alternating current, which may in particular be proportional to an audio signal. By the lateral forces in the operating state the Luftta- see 23 of the membrane assembly 16 shown here or the membrane 16 a compressed and widened - depending on the direction of current in the tracks - whereby 16 sound waves 24 are generated by the diaphragm assembly. Adjacent flanks 22 of the membrane 16a move either towards or away from each other.

The disadvantages described above are now avoided in that the membrane assembly 16 has a plurality of membrane segments - here in Fig. 7, the three membrane segments - A, B and C, wherein the membrane segments A, B and C are arranged and / or configured so the membrane arrangement 16 has a substantially common acoustic center. The division of the membrane assembly 16 into three membrane segments A, B and C is indicated by the two dashed lines in Figs. 7 and 8. The design of the individual membrane segments A, B and C or their exact training / arrangement with the illustrated wave crests, Wellentä- lers and flanks, but without illustrated interconnects and on their "control" may be discussed in more detail below, in advance may the following to be executed:

The membrane segments A, B and C are arranged such that the emitted from the membrane segments A, B and C sound waves 24 are superimposed so that the total sound 24, as coming from an acoustic center appears. The acoustic center corresponds to a - indicated in Fig. 7, vzw. punctiform - sound source, being emitted from this sound source, indicated by circular arcs sound waves. A common acoustic center here means that the respective circular arc centers of the sound waves lie on the emission axis S and not laterally offset from the emission axis. As long as the circular arc centers are close enough to each other on the emission axis S, the sound appears as coming from a common acoustic center. This makes it possible to achieve a precise image of the sound image. In other words, it is possible for the circular arcs 24a to associate a geometrical first point-shaped sound source and the circular arcs 24b with a second geometrical point-shaped sound source, which on the one hand lie on the emission axis S and on the other hand are so close to each other that a common acoustic center is realized for the listener ,

The membrane segments A, B and C are arranged symmetrically to the emission axis S or to the radiation plane of the membrane arrangement 16. The membrane segment B is arranged in the middle between the preferably identically designed outer membrane segments A and B. The middle diaphragm segment B is designed to reproduce in particular a high-frequency range and the two outer diaphragm segments A and C only to reproduce a low-frequency range. The membrane segment B generates the wavefronts 24a of the high-frequency range and the two membrane segments A and C together generate the wavefronts 24b of the low-frequency range. In another embodiment, the low frequency range can also be represented by all membrane segments together and the high frequency range, for example, only by the middle membrane segment B.

The frequency spectrum to be reproduced by the membrane arrangement 16 can be, for example, from 700 Hz or from 1 kHz to, for example, 20 kHz, vzw. even up to 30KHz. If a membrane arrangement with a correspondingly large total membrane area is used, the frequency range to be transmitted can also extend to less than 1 kHz, or even less than 700 Hz. The frequency spectrum can be in a high frequency range, vzw. from 3000 Hz to over 20,000 Hz, and a low-frequency range, vzw. from below 1000 Hz to 3000 Hz or above. In another embodiment of the invention, the frequency spectrum can also be divided into more than two frequency ranges, with at least one membrane segment being provided for each frequency range can.

Each membrane segment of a membrane assembly or a membrane therefore forms a separate "oscillatory unit" with several of these membrane segments associated wave crests and wave troughs, each membrane segment vzw. a certain frequency range is assigned. Here, the membrane segments are then arranged and / or formed so that the acoustic center is common for different frequencies or for the different frequency ranges. Vzw. Therefore, the directivity of the membrane assembly and the membrane is independent of the frequency.

Vzw. But now every membrane segment for a particular frequency range is provided, for example. For a high-frequency range or even for a low frequency range.

The subdivision of the membrane assembly 16 into the three membrane segments A,

B and C also has the advantage that the omnidirectional behavior of the membrane assembly 16 is improved. The limit for an acceptable omnidirectional behavior is vzw. characterized in that the extension of the membrane segments A, B and C in one direction is less than half the wavelength of the frequency to be generated. This condition is for the low-frequency reproduction associated membrane segments A and C usually not critical. For the emission characteristics of the high frequencies, only the extent of the central membrane segment B is crucial. Since with increasing frequency to be radiated membrane expansion should be small, is vzw. the extent of the membrane segment B at least in the horizontal direction substantially less than half

Wavelength of the upper limit frequency of the high frequency range. The subdivision of the membrane assembly 16 in its membrane segments A, B and C is here in a horizontal extension of the membrane assembly 16 is carried out (seen from the perspective of the towering erected membrane assembly 16).

To reproduce low frequencies, the membrane arrangement 16 preferably has a correspondingly large area, in particular the total area of the membrane segments A and C has been chosen to be sufficiently large. The deeper the frequency of the diaphragm assembly 16 to be transmitted is selected, the greater preferably to choose the total membrane area for the reproduction of the lowest frequency. With a suitable choice of dimensions results in a horizontal plane bundle-free playback over the entire desired frequency range.

As can be clearly seen from FIG. 9, the bundling of the high-frequency sound 24a remains only in the width (as horizontal) and not in the height (vertically) due to the segmentation of the membrane arrangement 16, while the low-frequency sound waves are radiated cone-shaped.

It should be noted that the considerations made here on three membrane segments A, B and C analogously apply to a larger number of membrane segments, in particular for the following embodiments, which will be described.

There are now several ways to divide a membrane assembly into several membrane segments. For example, as already shown in FIGS. 7 to 9, the membrane segments may be formed as partial regions of a single membrane. In this case, the partial regions, that is to say the corresponding membrane segments, for example the membrane segments A, B and C, can be fixed in their marginal / border regions by separately arranged webs, so that the membrane segments are "decoupled" from one another in terms of oscillation "Buffer zones" are formed, that is, for example, the corresponding air pocket 23, which forms exactly the border region between two membrane segments, just not provided with conductor tracks. It is also conceivable that corresponding "buffer zones" can be realized or fixed by air pockets filled with adhesives, depending on the particular application.

In the preferred embodiments, therefore, the membrane assembly 16 and 26 consists of a single membrane, for example. The membrane 16 a, wherein the single membrane 16 a in corresponding membrane segments, vzw. the membrane segments A, B, C is divided. In this case, a membrane segment A, B or C is essentially defined by a specific number of wave components. gene and troughs, and in particular from Fig. 7 shown. Here, each membrane segment A, B, C forms a substantially separate "oscillatory unit", wherein the membrane segments A, B and C vzw. by elements not shown here in the figures, in particular webs, strips, etc. are limited to the membrane segments A, B, C vzw. to decouple vibration from each other. Thus, for example, in FIG. 7, at the boundary regions between the membrane segments A and B or the membrane segments B and C shown in dashed lines, such webs / strips can be provided in the region of the wave crest shown here in the respective boundary region in order to realize the vibration-related decoupling. This means that each membrane segment is assigned a certain number of wave crests and wave troughs as well as flank sides, wherein the wave troughs, wave crests and flanks of a first membrane segment, for example of the membrane segment A, can oscillate in a different way than the wave crests and wave valleys In the case of the preferred exemplary embodiments illustrated here, the membrane arrangement 16 or the membrane 16a is arranged substantially in one plane between two pole plates 17 and 18.

Furthermore, several individual vzw. Diaphragm-shaped membranes are provided, which then form corresponding respective membrane segments and, for example, are combined in one or more frames into a unit as a "membrane arrangement." This depends on the particular application.

FIGS. 10, IIa and IIb show a second exemplary embodiment of an AMT sound transducer 25. With regard to the construction of the sound transducer 25 - with the exception of the segmentation of the membrane assembly 26 - reference is made to the above description of FIGS. 7 to 9, since the basic structure with the pole plates 27 and 28 and with an air gap 29, the above first embodiment in essentially corresponds.

As can be clearly seen in FIG. 10, in contrast to the sound transducer 15 shown in FIGS. 7 to 9, the membrane arrangement 26 is here in addition also segmented in the vertical direction.

The membrane assembly 26 has a central membrane segment B and laterally of this membrane segment B two outer membrane segments A and C. In addition, two membrane segments E and D are arranged above and below the membrane segment B and preferably also above and below the lateral membrane segments A and C. Both the outer, lateral membrane segments A and C and the outer membrane segments D and E are arranged symmetrically to the middle membrane segment B, so that the entire membrane assembly 26 has a common acoustic center on the emission axis S. This acoustic center is in this embodiment for the listener - as already explained above with reference to FIGS. 7 to 9 - vzw. punctiform. While in FIG. 7 the division of the membrane 16a in the horizontal direction into three membrane segments A, B, C is shown, which are formed in the vertical direction, ie over the entire height, FIG. 10 shows a different division of a single membrane 26, wherein in the middle region, the three membrane segments A, B, C and in each case in the upper and lower region - seen in the vertical direction - further membrane segments D and E are formed. The vibrational decoupling of the membrane segments A, B, C, D and E can be realized here again via corresponding elements, in particular webs / strips and / or separate frame, so the corresponding membrane segments A to D can be limited by means of such elements. This also depends on the particular application.

This second exemplary embodiment of the sound transducer 25 shown in FIGS. 10 or IIa and IIb can therefore be regarded as a supplement to the first exemplary embodiment (of the sound transducer 15) about the two additional membrane segments D and E.

These two membrane segments D and E give vzw. only the low frequency range again and thus behave in particular as the membrane segments A and C. The middle membrane segment B is vzw. again responsible for the reproduction of the treble range. By segmenting the membrane assembly 26 in the horizontal and now also in the vertical plane becomes one in both planes improved omnidirectional behavior is achieved, as can be seen for the horizontal plane of Fig. IIa and for the vertical plane of Fig IIb.

For the possible lower limit frequency of individual membrane segments the following:

FIG. 12 shows in a detailed view a partial region 30 of a membrane segment once in the initial state 31 and once in the deflected state 32, wherein the direction of movement of the membrane segment 30 in the deflected state 32 is indicated by the outward-pointing arrows. In the deflected state 32, the air pocket 33 is widened by twice the distance a. in the

Initial state 31, the unspecified wave peaks and troughs with the radius R are curved. In the deflected state, the wave troughs with the radius rl and the wave peaks with the radius r2 are curved. In this deflected position 32, the radius rl is smaller than the radius r2. The maximum deflection of a, that is to say "a _m ax", is now chosen such that the spring forces acting in the radii r 1 and r 2 due to the inherent rigidity of the membrane material are approximately proportional to the deflection The lower limit frequency is selected by the proportionality condition of the spring forces occurring in relation to the deflection, and the lower limit frequency is therefore also dependent on the specific material properties of the membrane segment 30.

For the possible upper limit frequency of individual membrane segments the following:

13 and 14 show a detailed view of a membrane segment 34 in maximum compressed state 35 and the initial state 36. The air in the air pocket 37 is compressed in Fig. 13 (compressed air "VK"), which is represented graphically by the black bar is, and is therefore pushed out of the air pocket 37, which is indicated by the lower arrow in Fig. 13. The resulting pressure wave needs in dependence on the travels in the air bag s way a certain time t to cover this path s is by the speed of sound and the Way determinable.

As the membrane movement progresses, which is indicated in FIG. 14 by the outward-pointing arrows, the flanks 38 and 39 generate a negative pressure Vu. With increasing frequency, a portion of the compressed air, ie a part of Vk, the air pocket 37 and the fold not leave before this pressure wave is compensated by the resulting negative pressure Vu again, which is also shown schematically here by means of black bars. The strength of this effect is dependent on the frequency with which the air pocket 37 is expanded and compressed and the ratio of the radius to the edge length of the air pocket 37. The longer the path in the air pocket 33 or 37 - or the depth of the air pocket - in proportion is the radius of the wave crest or the wave trough, the lower is the upper limit frequency of the membrane segment 34. Vzw. Therefore, the depth of the air pockets - especially for the high-frequency range - is adjusted to the radius with regard to the upper frequency limit.

FIG. 15 shows a third exemplary embodiment of a sound transducer 38 with a membrane arrangement 39. The membrane arrangement 39 has three membrane segments a, b and c. The membrane segments a, b and c have substantially the same geometry, i. Size, convolution and expansion, up. The geometry of the membrane segments a, b and c is chosen in accordance with the above considerations so that the membrane segments a, b and c can transmit the entire desired frequency range.

16 shows an electrical circuit diagram (equivalent circuit diagram) for the sound transducer 38. The resistances Ra, Rb and Rc represent the resistances of the conductor tracks on the corresponding membrane segments a, b and c. The resistances Ra, Rb and Rc represent the possibly complex alternating current resistance of the membrane segments a, b and c. The inductive component of the corresponding strip conductors can be small, which is why the complex alternating current resistance here can correspond essentially to ohmic resistances.

It can be clearly seen that the resistors Ra, Rb and Rc are connected in series. At the contact terminals 40 and 41, an AC signal can be applied. To the resistor Ra, a capacitor Ca is connected in parallel, and to the resistor Rc, a capacitor Cc is connected in parallel. Due to the parallel connection of the capacitors Ca and Cc, the high-ton part of the alternating-current signal is conducted past the membrane segments a and c and is therefore reproduced only by the membrane segment b. As a result of this connection, the phase angle between current and voltage at the membrane segments a, b and c is the same in the region of the transition frequency between the high and the low-frequency range. This constant phase angle guarantees no phase jumps between high and low tone segments on the

Transition frequency occur, which could be clearly perceived by the ear.

The bass frequency is vzw from the capacitors. not transmitted and flows through the electrically connected in series segments a, b and c. In this low frequency range is therefore vzw. the whole membrane arrangement is active and contributes to the impedance. The overall impedance of the circuit is frequency dependent. For low frequencies, the total impedance is essentially Ra + Rb + Rc. For equally sized membrane segments a, b and c, Ra = Rb = Rc, i. the total impedance in the low frequency range is equal to 3 * Rb. In the high-frequency range, the resistors Ra and Rc do not contribute, since they are bridged by the capacitors Ca and Cc. The total resistance in the high-frequency range therefore essentially corresponds only to Rb and thus amounts to only one third of the total impedance 3 * Rb in the low-frequency range.

The signal component, which is reproduced only via the membrane segment b, or the resistor Rb, therefore generates at the same amplitude voltage a threefold higher current through Rb and thus exerts a threefold higher force on the membrane segment b. As a result, a threefold higher diaphragm deflection is brought about in the linear region of the reproduction. This compensates for the fact that only the membrane segment b is provided for the high-frequency range, ie only one third of the total diaphragm area is used for high-frequency reproduction. For other ratios of the membrane segments a and b to c analogous considerations apply, as by the reciprocal ratio of membrane area F to impedance

(Ra + Rb + Rc) / Rb = Fb / (Fa + Fb + Fc) a linear frequency response can be generated.

Preferably, these transducers are operated with amplifiers, the amplifiers vzw. at the occurring, different impedances depending on the frequency spectrum to be transmitted work stable.

FIG. 17 shows an alternative circuit for the sound transducer 38 shown in FIG. 15. The membrane segments a and c represented by the resistors Ra and Rc are in this case connected in series to a woofer unit which is not described in greater detail. At this woofer unit can be fed to the contact terminals 42 and 43, a low-frequency signal. The membrane segment b, or the resistor Rb, is formed separately from the woofer unit and can be contacted at separate terminals 44 and 45 with a further signal. This signal can either contain only high-frequency components or, in addition to high-frequency components, also low-frequency components. The different control of the woofer unit and Rb can eg. Via an active or a passive

Crossover made. In this case, the ratio of membrane areas and ohmic resistance vzw. also inversely proportional:

(Ra + Rc) / Rb = Fc / (Fa + Fb), so that a linear frequency response can be generated.

FIG. 18 a shows a fourth exemplary embodiment of a sound transducer 46 with a membrane arrangement 47, wherein the membrane arrangement 47 is divided into three membrane segments a, b and c. The membrane segments a and c are in turn vzw. constructed identical and in particular arranged symmetrically to the central membrane segment b. In this case, the middle diaphragm segment b only reproduces the high-frequency range and is adapted accordingly. The membrane segments a and c are adapted to reproduce only the low frequency range. The membrane segment b has a fold with a lower air pocket depth, so that this membrane segment b has a very high, upper limit frequency may have (see Figures 13 and 14 and the accompanying description). The air pockets of the membrane segments a and c thus have a greater depth than the air pockets of the membrane segment b.

Furthermore, vzw. the height Hb of the air gap 48 in the region of the tweeter membrane segment b is smaller than the height Ha / c of the air gaps 49 in the region of the woofer membrane segments a and c. The air gap 49 is bounded by two pole plates 50 and 51. The air gap 48 is limited here, for example, on the one hand by the pole plate 51 and on the other hand by an additional pole plate element 52. Due to the smaller extent of the folding of the membrane segment b in

Direction Hb, can here with a relation to the height Ha / c reduced air gap 48 are worked. Preferably, the magnetic field Bb acting in the air gap 48 of the high-tone membrane segment b is stronger than the magnetic field Ba / c acting in the air gap 49 of the low-frequency membrane segments a and c. Due to the stronger magnetic field, higher edge deflections can be generated. As a result, a compact design of the central membrane segment b can be achieved while at the same time having sufficient sound pressure through the membrane segment b. The magnetic fields Bb and Ba / c oriented perpendicular to the membrane arrangement 47 are indicated by arrows in FIG. 18a.

FIG. 18b shows a circuit for the sound transducer 46 shown in FIG. 18a. The membrane segments a and c represented by the resistors Ra and Rc are in this case connected in series to a woofer unit which is not described in greater detail. At this woofer unit can be fed to the contact terminals 53 and 54, a low-frequency signal. The membrane segment b or the resistor Rb is formed separately from the woofer unit and can be supplied at separate terminals 55 and 56 with a high frequency signal. The different activation of the woofer unit and of the membrane segment b or of the resistor Rb can, for example, take place via an active or a passive frequency sweep.

FIG. 19 shows a fifth exemplary embodiment of a sound transducer 57 with a membrane arrangement 58. The membrane arrangement 58 is in turn corresponding to the preceding embodiments in three membrane segments a, divided b and c. The diaphragm segments a and c provided for low-frequency transmission are designed such that they have an upper cutoff frequency, this upper cutoff frequency simultaneously corresponding substantially to the lower cutoff frequency of the high tone range, wherein the high frequency range of the membrane segment b is transferable. Vzw. For this purpose, the membrane segments a and c have a corresponding depth T of the air pockets 59 and a corresponding radius R of the curvature of the undefined peaks and troughs of the air pockets 59. The high-tone membrane segment b has air pockets 60 with a smaller depth T 'and peaks and valleys with a smaller radius R'. Therefore, the air pockets of each membrane segment a, b, c depending on which frequency range is assigned to the respective membrane segment a, b, c different depths, vzw. have the depth T or T '. Vzw. is then the high-tone membrane segment b and the depth T 'of the air pockets 60 is less than the depth T of the air pockets 59. The respective membrane segments a, b and c are therefore in the preferred case with different depths vzw. T / T 'of the air pockets 59 and 60, respectively. Here, the membrane segments a, b, c are formed and / or arranged so that the acoustic center is common for different frequencies or for the different frequency ranges. The geometry of the membrane segments a, b and c, in particular the respective air pockets 59 and 60, is selected so that on the one hand the desired cutoff frequency is transferable and on the other hand, the frequency range of the membrane segments a and c is trimmed so that no further filtering measures are required ,

The membrane geometry is selected by the membrane arrangement 58 so that the membrane segment b can only reproduce the high-frequency range which lies beyond the upper limit frequency of the membrane segments a and c.

In Fig. 20, a circuit for the diaphragm assembly 58 is shown, wherein the membrane segments a and c, and the corresponding resistors Ra and Rc are connected in series to a woofer unit and the high-tone membrane segment separately, for example, by an active crossover not shown controlled is (see, for example, Fig. 18b). Fig. 21 shows another circuit for the diaphragm assembly 58. Here, the diaphragm segments a, b and c are connected in series, wherein an inductive resistor L bridges the high-tone membrane segment b and the resistor Rb. The inductive resistor L is small for low frequencies and large for high frequencies. Since the resistor Rb is in parallel with the inductive resistor Rb, the same voltage drops at both. For low frequencies, therefore, only a small amount of the signal on the membrane segment Rb drops off. For high frequencies, preferably the voltage drops substantially at the high-tone membrane segment b.

FIG. 22a shows a further sound transducer 61 with a membrane arrangement 62. As in the embodiment shown in FIG. 18a, the height of the air gap in the region of the tweeter membrane segment b is smaller than the height of the air gaps in the region of the woofer membrane segments a and c. The air gap is partially bounded by two pole plates 50 and 51. The air gap is additionally narrowed by an unspecified pole plate in the region of the tweeter membrane segment. As a result, the extent of the folding of the membrane segment b - or the depth of the air pocket - in the region of the high-tone segment drops to allow a high upper cut-off frequency of this membrane segment b. Preferably, the magnetic field acting in the air gap of the tweeter membrane segment b is stronger than the magnetic field acting in the air gap of the woofer membrane segments a and c. Due to the stronger magnetic field, higher edge deflections can be generated.

Furthermore, in this embodiment, the geometry of the membrane segment b is selected so that the membrane segment b can also reproduce the lower limit frequency of the membrane segments a and c. In particular, the radius R of the wave crests and troughs in the membrane segment b is adjusted accordingly. Vzw. The membrane segments a, b and c have a convolution with the same radius R, even if the depth of the unspecified air pockets in the membrane segments a and c deviates from the depth of the air pockets of the membrane segment. As already stated, the lower limit frequency is determined by the radius of the wave crests and wave troughs. This makes it possible to dispense with a crossover completely. The membrane segments a, b and c are, as shown in Fig. 22b, vzw. connected in series without bridging or filter links. In this embodiment, the signal or the current flows completely through all membrane segments a, b and c - or the resistors Ra, Rb and Rc. The bass range is represented by all membrane segments a, b and c. The electrical signal of the high-frequency range also flows through the resistors Ra, Rb and Rc, but is not reproduced due to the above-described relationships of the membrane segments a and c. Vzw. the high-frequency signal component is amplified compared to the low-frequency signal component. This can happen, for example, by electronic means, in particular with an equalizer, in particular before the overall signal is amplified. This amplification of the high-frequency signal component can be boosted / amplified, especially without a significant or audible phase shift between the high-frequency signal component and the low-frequency signal component, in particular in a digital or analog way. On an active or passive crossover, which separates the signal components for the membrane segments a / c and b, can be dispensed with.

The sound transducers shown substantially schematically in FIGS. 7 to 22, which are designed in particular as AMT loudspeakers, have corresponding membrane arrangements 16, 26, 47 or 58 and 62, which are designed in accordance with the above-described explanations , vzw. each having a single membrane. In the event that these membrane assemblies have a single membrane, the corresponding subregions, ie the corresponding membrane segments A, B, C, D, E or a, b and c vzw. according demarcated or divided by that at the edge areas or in the transition areas vzw. web elements not shown here can be arranged to separate the respective membrane segments from each vibration technology. However, it is also conceivable to design "buffer zones" formed in the corresponding transitional areas, for example by virtue of the fact that air pockets provided here have no conductor tracks or if these corresponding air pockets are possibly fastened with adhesive and / or partially filled in. This depends on the particular application. Due to the different control possibilities of the individual membrane segments A, B, C or a, b, c, as described, exists vzw. a tweeter segment and vzw. a plurality of low tone segments arranged corresponding to one another to form a common acoustic center, particularly for the listener. In particular, the individual membrane segments can be correspondingly controlled differently with the aid of an electrical / electronic control unit, vzw. because the respective interconnects of a membrane segment are electrically driven differently than the respective interconnects of another membrane segment. The allocation of the frequency ranges can also be effected or controlled by the different air pocket depth of the air pockets assigned to the respective membrane segments. It is also conceivable that the individual membrane segments are formed by a plurality, that is, by a plurality of individual membranes, which are arranged correspondingly in different frames. This means that the corresponding membrane arrangement does not have to consist of a single membrane, as in the preferred embodiments shown here in the figures, but the membrane arrangement can also be formed by a plurality of individual membranes, each individual membrane then forming a corresponding individual membrane segment, and these membrane segments are in turn designed and / or arranged such that - corresponding to the above statements - the entire membrane arrangement has a substantially common acoustic center. This also depends on the particular application.

Due to the arrangement of the membrane segments to each other and also due to the formation of the different air pockets, the corresponding disadvantages are avoided in the prior art and in particular realized AMT speakers with an optimal omnidirectional behavior. LIST OF REFERENCE NUMBERS

1 membrane arrangement

Ia membrane

2 trace

3 wave mountain

4 wave valley

5 flanks

6 air pocket

6a air pocket

6b air bag

6c air pocket

6d air pocket

6e air bag

6f air pocket

6g air pocket

7 pole plate

8 pole plate

9 air gap

10a frame part

10b frame part

IIa side panel

IIb side panel

12 sound openings

12a slots

13 sound waves 14 sound waves

15 transducers

16 membrane assembly 16a membrane 17 pole plates

18 pole plates

19 air gap

20 wave mountain

21 wave trough 22 flanks

23 air pockets

24 sound waves 24a wavefronts 24b wavefronts 25 sound transducers

26 membrane arrangement

27 pole plates

28 pole plates

29 Air gap 30 subarea

31 initial state

32 deflection state

33 air pocket

34 section 35 maximum compressed state

36 initial state 37 air pocket

38 sound transducers

39 membrane arrangement

40 contact connections 41 contact connections

42 contact connections

43 contact connections

44 contact connections

45 contact connections 46 sound transducers

47 membrane arrangement

48 air gap

49 air gap

50 pole plates 51 pole plates

52 pole plate element

53 contact connections

54 contact connections

55 contact connections 56 contact connections

57 sound transducers

58 membrane arrangement

59 air pockets

60 air pockets 61 sound transducers

62 membrane arrangement I electricity

A, B, C, D, E and a, b, c membrane segments Vu negative pressure Vk compressed air

Claims

claims:

A diaphragm assembly (16, 26, 39, 47, 62) for an air-motion transformer

(AMT), wherein the membrane assembly (16, 26, 39, 47, 62) at least one substantially meander-shaped membrane (16a) and the membrane assembly (16, 26, 39, 47, 62) by the meandering formation of the at least one Membrane (16a) has air pockets (23, 59, 60) for generating sound, characterized in that the membrane arrangement (16, 26, 39, 47, 62) has a plurality of membrane segments (A, B, C; a, b, c) and in that the membrane segments (A, B, C; a, b, c) are arranged and / or configured in such a way that the membrane arrangement (16, 26, 39, 47, 62) has a substantially common acoustic center.

2. Membrane arrangement according to claim 1, characterized in that the membrane arrangement (16, 26, 39, 47, 62) has a radiation axis (S) and the membrane segments (A, B, C, a, b, c) symmetrical to the emission axis ( S) are arranged.

3. Membrane arrangement according to one of the preceding claims, characterized in that a central membrane segment (B) and on both sides of the central membrane segment (B) in each case at least one outer membrane segment (A, C, D, E) is arranged.

4. Membrane arrangement according to one of the preceding claims, characterized in that the middle membrane segment (B) for reproducing a first frequency range and the outer membrane segments (A, C) are formed for reproducing at least a second frequency range.

5. Membrane arrangement according to one of the preceding claims, characterized in that the middle membrane segment (B) are formed for reproducing a high-frequency range and a low-frequency range and the outer membrane segments (A, B) are formed for reproducing a low frequency range.

6. Membrane arrangement according to one of the preceding claims, characterized in that the extension of the membrane segments (A, B, C) is substantially smaller than half the wavelength of the upper limit frequency of the frequency ranges.

7. Membrane arrangement according to one of the preceding claims, characterized in that the surface of the membrane segments (A, B, C) is adapted to the lower limit frequency to be transmitted of the membrane assembly (16, 26, 39, 47, 62).

8. Membrane arrangement according to one of the preceding claims, characterized in that the depth of the air pockets is tuned in particular to the radius of the wave crest or wave trough of the air pocket.

9. Membrane arrangement according to one of the preceding claims, characterized in that the depth (T ') of the air pockets of the membrane provided for Hochtonübertra- tion segment (B) is less than the depth (T) of

Air pockets of the diaphragm segments (A, C) provided for low-frequency transmission.

10. Membrane arrangement according to one of the preceding claims, characterized in that the side of the middle membrane segment (B) outer

Membrane segments (A and C) are arranged.

11. Membrane arrangement according to one of the preceding claims, characterized in that above and below the central membrane segment (B) outer membrane segments (D, E) are arranged.

12. Membrane arrangement according to one of the preceding claims, characterized in that the membrane segments (A, B, C, D, E) are formed substantially rectangular or square.

13. Membrane arrangement according to one of the preceding claims, characterized in that the ratio of the membrane area of a single membrane segment to the total membrane area is reciprocal to the ratio of impedance of the individual membrane segment to the total impedance of all membrane segments.

14. Membrane arrangement according to one of the preceding claims, characterized in that the membrane assembly (16) by a single membrane (16 a) is formed and the membrane segments (A, B, C) through the

Subdivision of the membrane (16 a) is realized in partial areas.

15. Membrane arrangement according to one of the preceding claims, characterized in that a plurality of individual membranes are provided, wherein each individual membrane forms a specific membrane segment.

16. Membrane arrangement according to one of the preceding claims, characterized in that each individual membrane is arranged in a separate frame.

17. Membrane arrangement according to one of the preceding claims, characterized in that the individual membrane segments (A, B, C; a, b, c) are decoupled from each other in terms of vibration technology.

18. Membrane arrangement according to one of the preceding claims, characterized in that the vibration-technical decoupling of the membrane segments (A, B, C) web-shaped elements are arranged at the bottom of the respective air pockets in the transition areas.

19. Membrane arrangement according to one of the preceding claims, characterized in that for the realization of the vibration control decoupling of the membrane segments (A, B, C) in the transition areas "buffer zones" are realized in that here air pockets have no traces.

20. Sound transducer, in particular AMT loudspeaker, characterized by a membrane arrangement according to one of claims 1 to 19.

21. Acoustic transducer according to the preceding claim, characterized in that the membrane segments (A, B, C) are at least partially connected in series and a Hochtonanteil by means of a bridging member at the provided for deep-tone transmission membrane segments (A, C) is vorbeleitbar ,

22. Sound transducer according to one of claims 20 or 21, characterized in that the membrane segments (A, B, C) in an air gap between pole plates (50, 51) are arranged.

23. A sound transducer according to any one of claims 20 to 21, characterized in that the diaphragm segment (B) intended for high-frequency reproduction is arranged in an air gap of lesser height than the diaphragm segments (A, C) the low-tone reproduction.