EP1336322B1 - Electromagnetic driver for a planar diaphragm loudspeaker - Google Patents

Description

The invention relates to an electromagnetic driver for a panel loudspeaker.

Electromagnetic transducers in general, for example, from the WO 95/14363 or in particular with linearization of the characteristic by inserting a permanent magnet, for example, from the EP 0 774 880 or the US 4,680,492 known. Such converters are mainly used as a signal generator or door buzzer. It is characteristic of these applications that the non-linearity of the force-current characteristic curve either does not interfere further (for example, because of high harmonic attenuation) or because of non-linearity due to premagnetization and low modulation.

Plate loudspeakers are in a Planar design as a piston emitter, for example, from US 5,539,835 or the US 4,928,312 or in the multi-resonant design as a bending wave emitter, for example, from WO 97/09842 or the DE 197 57 097 In addition to the sturdy, rigid plate (diaphragm) with a holder, it consists of a drive system (eg one or more drivers) which in one or more points brings the excitation force to the plate.

In addition, for example, in the WO 97/17818 or the US 5,638,456 proposed piezoelectric driver, which are indeed very robust, but in practice for large plates are consistently too weak.

Although electrodynamic drives develop a sufficient force and a sufficient deflection, but have in connection with the plate coupling a settlement problem. The usual sandwich panels of glued together, different materials are very light and rigid, but not very stable in the long term. In particular, adhesive layers used in the manufacture of the sandwich panels change their consistency. For example, the constantly effective gravity gives a certain creeping and flow direction. In addition, thermal stresses during operation lead to local softening with irreversible changes in shape. This in turn results in an offset of the coil mounted on the plate from its original position.

Any relative displacement between the coil mounted directly on the plate and the remotely mounted magnet system will create displacement components that tilt the coil axis out of its normal position or move the coil to an eccentric position. This can cause the voice coil to wipe the walls of the annular gap in the magnet system, rendering the drive unusable.

Furthermore, in the operation of bending wave emitters there is the problem that the usual drivers perform an undesired pumping movement, because unlike piston emitters bending in the case of flexible shaft emitters is desirable without "pumping".

In addition, the previously mentioned drivers do not allow edge excitation when operating bending waves. However, this excitation position is required when using transparent plates or dual use plates as the image surface. The example of the US 4,392,027 or the DE 198 21 860 Although known electrodynamic driver with power normal to the plate surface can be produced inexpensively, but have the disadvantage of a relatively large depth and a relatively large space requirement for support by an outside bead. In addition, a long-term stable adjustment of the position of the voice coil relative to the outer bead is problematic especially in the edge zone of the plate.

The object of the invention is to provide a driver for a panel loudspeaker, which is less sensitive to subsidence.

The object is achieved by an electromagnetic driver according to claims 1, 8, 9 and 10. Embodiments and developments of the inventive concept are the subject of dependent claims.

Advantage of the invention is, inter alia, that the coil height (axial) can be kept very low, whereby a minimum thickness of the panel loudspeaker can be achieved.

This is achieved in detail by an electromagnetic driver for a plate speaker having a soft magnetic core in a three-leg and a back E-shape and a magnetically coupled to the soft magnetic core (in particular fixed) alternating field exciter for generating a dependent of a sound signal magnetic alternating flux in the magnetic core. Furthermore, a DC field magnet magnetically coupled to the soft magnetic core for generating a magnetic DC flux in the soft magnetic core and a soft magnetic element magnetically terminating the limbs via at least one small induction gap and facing the back (eg platelets, magnetic membrane, yoke, etc.). ), wherein the alternating flux and the direct current are superimposed asymmetrically on one another such that, depending on the shape, a resultant force or a resulting torque on the soft magnetic element behaves substantially linearly relative to the sound signal.

A measure essential to the invention therefore consists in the application of the known electromagnetic transducer principle, in which the drive coil is immovable. However, here the magnetic force is proportional to the square of the magnetic Induction and thus to the square of a drive coil flowing through the audio signal stream. On the other hand, without a voice coil and without a tightly-tolerated vibration gap, the inevitable settlements can be tolerated much better.

Another measure provides a bias (for example, by additional direct current or by permanent magnets), which is not used as usual for linearization of the characteristic. "Linearization" means the displacement of the operating point from the zero point to a parabola branch in order to allow the parabola to approximate as a tangent at low modulation.

A third measure consists in the formation of a preferably symmetrically shaped magnetic circuit with asymmetrical field distribution. Thus, for example, a magnetic field vector generated by a drive coil in the soft magnetic outer circle is superimposed by the constant field vector generated by a permanent magnet from the center leg, for example, such that addition takes place in one outer leg and subtraction in the other outer leg. Despite the quadratic force-current characteristic of a single magnetized leg, the force or the torque behaves strictly linearly with the audio-frequency induction and thus with the audio signal itself, depending on the shape.

In a further development of the invention, a yoke is provided as a soft magnetic element, which is tiltably mounted on the free end of the middle leg of the soft magnetic core and at least relative to the other two legs induction column has such that the means of the alternating field driven yoke generates a corresponding torque. By forming moments in the yoke acting as a two-sided lever, the nonlinear components of the outer leg forces compensate each other so that, in a symmetrical design, the resulting torque is strictly proportional to the sound-frequency induction and thus the electric sound signal itself. The yoke closes the open ends of the E-core via small induction gaps (eg air gaps or resilient non-magnetic material). The yoke supported supported on the central leg of the E-shaped core is tilted so that the sound frequency excited by the coil system on the tiltable yoke emits an audio-frequency torque whose counter-moment is formed by the rotational moment of inertia of the E-shaped core (inertial moments -Driver).

Furthermore, it can be provided that the alternating field exciter is a coil arranged on one of the two outer limbs and controlled by the sound signal, and a permanent magnet, which is arranged in the central limb of the soft magnetic core, being provided as DC field generator. Thus, an asymmetrical superposition of AC and DC flow can be achieved without much effort.

Instead of a permanent magnet, a coil through which a direct current flows can also be used as DC field generator, wherein the coil can be arranged according to the arrangement of the permanent magnet on the middle leg of the soft magnetic core. The advantage of a DC-current coil is that by changing the magnitude of the DC current, the volume of the sound emitted by the panel loudspeaker can be varied.

Preferably, the yoke is held by two arranged in the induction gaps between the outer legs and yoke non-magnetic spring elements in a rest position. Thus, a rotational movement is possible, wherein the spring elements fill the induction gap or the induction gaps instead of air with another non-magnetic material. Thus, the driver can be mounted on the plate without external support only by means of the soft magnetic element (eg, the yoke). Instead of or in addition to the spring elements, the back of the soft magnetic core in E-shape via a bridge (beams, traverse, etc.) are also attached to a frame of the disk speaker, thereby improving the sensitivity of the disk speaker at low frequencies.

Furthermore, a non-magnetic bearing can be provided for supporting the yoke on the middle leg of the soft magnetic core, so that effectively also results in an induction gap between the soft magnetic element and the middle leg. With regard to the mechanical properties, a defined bearing on the middle leg is advantageous over a solution without such a bearing, since shearing movements or pumping movements are definitely prevented from being carried out with respect to a holder with only the aforementioned resilient elements.

Instead of an inertial-moment loudspeaker can be realized in the same way with the invention, a monopoly plate speaker such that two soft magnetic cores in each case a three legs and a back having E-shape, which are firmly connected back to back, and two with one of the soft magnetic cores magnetically coupled alternating field exciter to produce a dependent of a sound signal alternating magnetic flux in the respective soft magnetic core are provided. In addition, such a driver comprises two DC field exciters magnetically coupled to one of the soft magnetic cores for generating a magnetic DC flux in the respective soft magnetic core and two soft magnetic elements magnetically terminating the respective limbs via at least one small induction gap for coupling to the plates of the respective back Plate loudspeaker, wherein the alternating flux and direct current are in turn superposed asymmetrically on each other such that a resulting torque at the respective soft magnetic element behaves substantially linearly to the audio signal. The polarity of the alternating field exciters is chosen so that the alternating currents to the back of the E-cores are not directed in the opposite direction, but the same. In this case, the moments to be output to the outside receive their counter-momentum from the other E-core, so that the entire driver arrangement undergoes no rotational acceleration with similar external loading (preferably by lining up the identical front and rear plates) and thus forms a torque driver for monopole plate loudspeakers ,

Alternatively, instead of two back-to-back arranged soft magnetic cores in E-shape and a one-piece soft magnetic core can be used with six legs together, which has two back-to-back mutually firmly connected E-part shapes. Both the one-piece core of two E-part shapes and the driver constructed of two individual cores of E-shape can be designed and refined in the same way as the single core in E-shape.

In another embodiment of the invention, a soft magnetic core is arranged in a three legs and a back having E-shape on the edge of the plate of the plate speaker, with its outer legs are tongs like bent towards the plate and wherein on the opposite side of the back plate located. Furthermore, a magnetically coupled to the soft magnetic core alternating field exciter for generating a dependent on a sound signal alternating magnetic flux in the soft magnetic core and magnetically coupled to the soft magnetic core, arranged in the plate in the region of the open ends of the legs direct field exciter to generate a magnetic DC flux is provided , Wherein alternating flux and direct current are superimposed asymmetrically on each other such that a resultant force on the constant field exciter is proportional to the sound signal. This makes it possible to excite the plate from the edge, so as plates either transparent panels or plates which can be used from both sides can be used.

In such a driver, a permanent magnet arranged on the middle limb and controlled by the sound signal is preferably provided as a direct field exciter, the outer limbs detecting a magnetic direct flux of the permanent magnet directed parallel to the plate normal, and an alternating flow emerging from the middle limb. that the alternating flux and the direct current add on one of the outer legs and subtract on the other outer leg.

Preferably, in each case non-magnetic spring elements are inserted for holding between the outer legs and the plate, with which then grab the tong-like legs of the plate and store hingedly at the edge. Thus, in addition storage of the plate is achieved with minimal effort.

Likewise, with all drivers, the DC flux of the DC field exciter (s) can be changed, so that the volume of the panel loudspeaker is changeable.

Finally, an inventive electromagnetic driver is arranged, for example, such that the forces generated by it attack within an edge region of the plate, wherein the edge region has a width which is approximately equal to the thickness of the plate.

Figur 1

eine erste Ausführungsform eines erfindungsgemäßen Treibers zur Anwendung bei einem Plattenlautspre- cher,

Figur 2

eine zweite Ausführungsform eines erfindungsgemäßen Treibers zur Anwendung bei einem Monopolplatten- lautsprecher und

Figur 3

eine dritte Ausführungsform eines erfindungsgemäßen Treibers zur Montage am Rand des Plattenlautspre- chers,

Figur 4

eine vierte Ausführungsform eines erfindungsgemäßen Treibers zur Montage am Rand des Plattenlautspre- chers und

Figur 5

eine fünfte Ausführungsform eines erfindungsgemäßen Treibers zur Montage am Rand des Plattenlautspre- chers.

The invention will be explained in more detail with reference to the embodiments illustrated in the figures of the drawing, wherein the same effect elements are provided with the same reference numerals. It shows:

FIG. 1

A first embodiment of a driver according to the invention for use in a disk loudspeaker,

FIG. 2

A second embodiment of a driver according to the invention for use in a Monopolplatten- speaker and

FIG. 3

A third embodiment of a driver according to the invention for mounting on the edge of the disk loudspeaker,

FIG. 4

A fourth embodiment of a driver according to the invention for mounting on the edge of the Plattenlautspre- chers and

FIG. 5

A fifth embodiment of a driver according to the invention for mounting on the edge of the Plattenlautspre- chers.

FIG. 1 shows an electromagnetic intertial torque driver according to the invention, which is coupled to a sandwich membrane 1 resulting in a multi-resonant plate speaker. A soft magnetic pole core 2 in E-shape (for example made of ferrite material) with two outer legs and a center leg is equipped with a stationary drive coil 4 as an alternating field exciter on one of the outer leg. The assembly of both outer legs with one of the same power duchflossenen driver coil is possible. In the embodiment according to FIG. 1 the bias takes place in the center leg by means of a Gleichfelderregers such as a DC-current coil or by a permanent magnet 3. The direction of the associated DC field vector 10 is oriented in the direction of the middle leg, wherein the polarity (NS or SN) is arbitrary. A pitch-frequency alternating current I flows through the drive coil 4 and thereby generates an alternating field vector 9. This sound frequency fluctuating alternating field vector 9 adds in an outer leg to the DC field vector 10 and in the other outer leg, however, he subtracted from the DC field vector 10th

A soft magnetic yoke 5 closes a magnetic circuit which continues over the soft magnetic pole core 2. The yoke 5 is tiltably mounted on the middle leg. The tilting bearing 6 can as in FIG. 1 can be shown as a sharp cutting edge, but can also be realized in any other suitable manner. It is important that the existing rectified forces from both outer legs in the bearing 6 find a quasi incompressible support, but that tilting movements are exposed to the bearing 6 as a pivot point a comparatively low resistance.

und die Kraft F_R(t) im anderen Schenkel ist dann gleich $${\mathrm{F}}_{\mathrm{R}}\left(\mathrm{t}\right)\mathrm{=}\mathrm{\beta }\mathrm{\cdot }{{\mathrm{B}}_{\mathrm{R}}}^{\mathrm{2}}\left(\mathrm{t}\right),$$

wobei sich für die Kraftdifferenz ΔF(t)daraus ergibt: $$\mathrm{\Delta F}\left(\mathrm{t}\right)\mathrm{=}\mathrm{\beta }\left({{\mathrm{B}}_{\mathrm{R}}}^{\mathrm{2}}\mathrm{-}{{\mathrm{B}}_{\mathrm{L}}}^{\mathrm{2}}\right)\mathrm{=}\mathrm{4}\mathrm{\beta }{\mathrm{B}}_{\mathrm{T}}{\mathrm{B}}_{\mathrm{O}}\mathrm{.}$$

mit $${\mathrm{B}}_{\mathrm{L}}\mathrm{=}{\mathrm{B}}_{\mathrm{T}}\left(\mathrm{t}\right)\mathrm{+}{\mathrm{B}}_{\mathrm{O}}$$

$${\mathrm{B}}_{\mathrm{R}}\mathrm{=}{\mathrm{B}}_{\mathrm{T}}\left(\mathrm{t}\right)-{\mathrm{B}}_{\mathrm{O}}$$

$${\mathrm{B}}_{\mathrm{T}}\left(\mathrm{t}\right)\mathrm{=}\mathrm{\alpha }\mathrm{\cdot }\mathrm{I}\left(\mathrm{t}\right)$$

ist. Dabei steht B_L für den magnetischen Fluss in dem ersten äußeren Schenkel, B_R für den magnetischen Fluss in dem zweiten äußeren Schenkel, B_T(t) für den durch den Wechselfelderreger erzeugten Wechselfluss, B_o für den durch den Gleichfelderreger erzeugten Gleichfluss, I(t) für den zeitabhängigen tonfrequenten Erregerstrom und α, β für Wandlerkonstanten.The force F _L (t) over time t in a leg is included $${\mathrm{F}}_{\mathrm{L}}\left(\mathrm{t}\right)\mathrm{=}\mathrm{\beta }\mathrm{\cdot }{{\mathrm{B}}_{\mathrm{L}}}^{\mathrm{2}}\left(\mathrm{t}\right)$$

and the force F _R (t) in the other leg is then equal $${\mathrm{F}}_{\mathrm{R}}\left(\mathrm{t}\right)\mathrm{=}\mathrm{\beta }\mathrm{\cdot }{{\mathrm{B}}_{\mathrm{R}}}^{\mathrm{2}}\left(\mathrm{t}\right).$$

whereby for the force difference ΔF (t) results from: $$\mathrm{.DELTA.F}\left(\mathrm{t}\right)\mathrm{=}\mathrm{\beta }\left({{\mathrm{B}}_{\mathrm{R}}}^{\mathrm{2}}\mathrm{-}{{\mathrm{<figure-callout\; id="2"\; label="B\; L"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">B\; </figure-callout>}}_{\mathrm{L}}}^{\mathrm{2}}\right)\mathrm{=}\mathrm{4}\mathrm{\beta }{\mathrm{B}}_{\mathrm{T}}{\mathrm{B}}_{\mathrm{O}}\mathrm{,}$$

With $${\mathrm{B}}_{\mathrm{L}}\mathrm{=}{\mathrm{B}}_{\mathrm{T}}\left(\mathrm{t}\right)\mathrm{+}{\mathrm{B}}_{\mathrm{O}}$$

$${\mathrm{B}}_{\mathrm{R}}\mathrm{=}{\mathrm{B}}_{\mathrm{T}}\left(\mathrm{t}\right)-{\mathrm{B}}_{\mathrm{O}}$$

$${\mathrm{B}}_{\mathrm{T}}\left(\mathrm{t}\right)\mathrm{=}\mathrm{\alpha }\mathrm{\cdot }\mathrm{I}\left(\mathrm{t}\right)$$

is. Here B _L stands for the magnetic flux in the first outer leg, B _R for the magnetic flux in the second outer leg, B _T (t) for through the alternating field exciter generated alternating flux, B _o for the direct current generated by the DC field exciter, I (t) for the time-dependent pitch frequency excitation current and α, β for converter constants.

As can be seen, despite the quadratic force-current characteristic of a single magnetized leg, the force difference at the ends of the yoke 5 acting as a two-sided lever, ie the torque, behaves strictly linearly to the audio-frequency induction and thus to the audio signal itself.

For mechanical stabilization of the driver construction, in particular the definition of a mechanical rest point, non-magnetic spring elements 7 are inserted so that they connect each of the outer legs with the yoke 5. The reaction torque for the pitch-frequency tilting oscillation comes from the in FIG. 1 shown arrangement exclusively from the rotational inertia of the entire arrangement. Alternatively, a bridge gantry could connect the back of the driver to a plate mount.

Starting from the in FIG. 1 The driver shown can be easily realized a monopoly multi-resonant plate speaker with one or more internal electromagnetic monopole torque drivers.

FIG. 2 shows a section of a monopole multiresonance plate speaker with a front 1 and rear 1 'sandwich panel. The two plates 1,1 'are connected by means of one (or more) monopole moment drivers. A Monopolmomententreiber created by back-to-back arrangement of two identical Intertialmomententreiber according to the in FIG. 1 shown embodiment. In this case, the back-to-back assembly can be formed by a one-piece core with appropriate shape for more efficient production and / or to reduce the depth.

In the case of the exemplary monopole torque driver, this is the case FIG. 2 two intertial torque drivers accordingly FIG. 1 Back-to-back with each other and on the side opposite the back with two sandwich membranes 1, 1 'coupled. Two soft-magnetic pole cores 2, 2 'in E-shape (for example made of ferrite material) with two outer legs and one center leg are accordingly each equipped with an immovable driver coil 4, 4' as an alternating field exciter on one of the outer limbs. The premagnetization takes place in the respective center leg by means of a respective Gleichfeldregers such as a DC-current-carrying coil or by a permanent magnet 3, 3 '. The associated DC field vector 10, 10 'is oriented in the direction of the middle leg, wherein the polarity (NS or SN) is arbitrary. A pitch-frequency alternating current I flows through the driver coil 4, 4 'and generates an alternating field vector 9, 9'. This pitch-fluctuating alternating field vector 9, 9 'is added in an outer leg to the DC field vector 10, 10' and in the other outer leg, however, he subtracted from the DC field vector 10, 10 '.

The advantage of the electromagnetic monopole torque driver is that it does not rely on the intertial force as a moment reaction. As a result, the mass of the fixed drive coils 4, 4 'can be substantially reduced. The two drive coils 4, 4 'must be traversed by the same audio frequency current, the coil circuit is to be chosen so that compensate for the drive torque at the back-to-back connection. Another advantage of a monopole speaker is the reduction of the acoustic dipole short circuit.

FIG. 3 shows in cross section the edge of a plate 1 of a plate speaker and a forceps electromagnetic edge driver in working position. The plate 1 is a sandwich construction, but any other construction is possible. Usually one ensures continuous or piecewise interrupted, circumferential pad for a hinged mounting of the plate 1, in particular in multi-resonance operation. This "articulated" pad is supported by the surrounding frame. At the in FIG. 3 shown driver takes a spring element 7, the role of the articulated bearing. A pincer-shaped, soft magnetic pole core 2 in E-shape is supported on a frame not shown in detail.

Unlike the in FIG. 1 and FIG. 2 shown magnetic systems is the driver after FIG. 3 a derived from a coil 4 driving flux 9 generated in a middle leg 8. A permanent magnet 3 of low weight (for example, a rare earth magnet such as neodymium) is embedded in the plate edge or (not shown in the drawing) glued as two thin plates on each surface of the edge region. It generates the permanent flux (DC field vector 10). The flow between the middle limb and one of the outer limbs in this arrangement results in each case from the sum or difference of the individual flows (9, 10). As a result, the resulting difference in the forces acting on the permanent magnet 3 embedded in the plate 1, from both pincer-shaped bent legs in spite of the square characteristic again proportional to the coil current.

Finally, drivers of the present invention, alone or in addition to other drivers, can drive a single plate or front and back plates, preferably by a single, lightweight, rigid, cantilevered sandwich membrane. In addition, a frame can hold one or both plates.

At the in FIG. 4 shown driver according to the invention, a soft magnetic yoke 5 is embedded in a sound plate 1 near the edge. Furthermore, there are an E-shaped pole core 2, a stationary magnet coil 4 through which the signal flow flows, and an in the center leg of the E-shaped pole core 2 inserted permanent magnet 3 is provided. The E-shaped pole core 2 is supported by a (tip or) cutting bearing 6 on the pole core 2, so that this yoke 5 due to a magnetically induced torque about a fixed pivot point (blade bearing 6) can rock. A moment driver of this kind can be placed anywhere on the surface of the sound plate 1. Preferably, a just described arrangement is duplicated. The duplicated arrangement acts by using a further magnetic coil 4 ', a further pole core 2', another permanent magnet 3 'mirror image of the opposite side of the sound panel 1. In the in FIG. 4 As shown, the rocking movement is not optimal due to the cutting edge bearings 6, 6 '.

In contrast, the improved in FIG. 5 shown embodiment, which differs initially only by the absence of the cutting edge bearings 6, 6 '. The missing supports (blade bearings 6, 6 ') are in the embodiment after FIG. 5 balanced by a backside rigid connection (post 23), which in FIG. 5a not yet recognizable, but on average AB off FIG. 5b is apparent.

Again, a "pincer-like" construction of the inventive driver is seen. The two pole cores 2 and 2 'are fixedly connected outside the edge zone of the plate by a rigid support 23. The sound plate 1 with the embedded soft magnetic yoke 5 "floats" in the middle of the contactless grip of the slightly open "pliers". The sound plate 1 must be held in this position (for example by the non-magnetic spring element 7), but this can also be done independently of the driver.

In the case of an electromagnetic driver without current-carrying conductors in the pole field, essentially three force effects must be considered. The force on saturation magnetized parts in the homogeneous field, the force on soft magnetic parts in the homogeneous field and the force on soft magnetic parts in the inhomogeneous field. The two first mentioned effects are already mentioned above, while the third effect, where the force is proportional to the field gradient, is completely eliminated in this case. To a good approximation, the field between the upper and lower E-shaped pole core 2, 2 'is homogeneous. Since the yoke 5 is not magnetized, remains in the in FIG. 5 embodiment shown significantly the force on soft magnetic parts in the homogeneous field.

wobei A die Polfläche und s den Spaltabstand bezeichnen. Entsprechend gilt für den rechten Außenschenkel: $${\mathrm{F}}_{\mathrm{R}}\mathrm{=}\mathrm{As}{\left({\mathrm{B}}_{\mathrm{S}}-{\mathrm{B}}_{\mathrm{P}}\right)}^{\mathrm{2}}/\mu ,$$

Looking at first only one half of the mirror image structure of the driver (in FIG. 5 the upper half), the result is the following: The middle leg of the pole core 2 is highly saturated by the insertion of the permanent magnet 3 and practically no longer conductive and therefore practically regarded as a constant flux magnetic source. This permanent flux is distributed symmetrically and rectified on the two outer legs of the E-shaped pole core 2. The originating from the magnetic coil 4 signal flow, however, flows without regard to the no longer conductive center leg to the other outer leg. Thus, an addition takes place on one outer leg and a subtraction of the respective inductions B on the other outer leg. The soft magnetic yoke 5 closes all circles. This results in different attractive forces F _L , F _R in the left and right outer thighs. For the left outer leg results with it. $${\mathrm{F}}_{\mathrm{L}}\mathrm{=}\mathrm{ace}{\left({\mathrm{B}}_{\mathrm{S}}\mathrm{+}{\mathrm{<figure-callout\; id="2"\; label="B\; P"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">B\; </figure-callout>}}_{\mathrm{P}}\right)}^{\mathrm{2}}/\mu .$$

where A is the pole face and s the gap distance. The same applies to the right outer thigh: $${\mathrm{F}}_{\mathrm{R}}\mathrm{=}\mathrm{ace}{\left({\mathrm{B}}_{\mathrm{S}}-{\mathrm{<figure-callout\; id="2"\; label="B\; P"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">B\; </figure-callout>}}_{\mathrm{P}}\right)}^{\mathrm{2}}/\mu .$$

wobei d für die Jochlänge und damit für den "Dipolabstand" steht. Das Drehmoment M ist linear proportional zur Induktion B_s und damit zum Signalstrom I. Voraussetzung dafür ist die Abstützung auf dem Kipplager (Schneidenlager 6) und damit eine daraus resultierende Hebelwirkung. Ohne das Kipplager (Schneidenlager 6) als Stütze wäre auch die Summenkraft wirksam, die sich quadratisch zum Signalstrom verhält.As a result, a torque M arises in the yoke 5, which can be described as follows: $$\mathrm{M}\mathrm{=}\left({\mathrm{F}}_{\mathrm{L}}\mathrm{-}{\mathrm{F}}_{\mathrm{R}}\right)\mathrm{d}\mathrm{/}\mathrm{2}\mathrm{=}\mathrm{2}\mathrm{asd}{\mathrm{B}}_{\mathrm{S}}{\mathrm{B}}_{\mathrm{P}}/\mu .$$

where d stands for the Jochlänge and thus for the "dipole distance". The torque M is linearly proportional to the induction B _s and thus to the signal current I. Prerequisite for this is the support on the tilting bearing (knife edge bearing 6) and thus a resulting leverage. Without the tilting bearing (cutting edge bearing 6) as a support and the sum force would be effective, which behaves quadratically to the signal flow.

As in the FIGS. 4 and 5 shown, a "marginal pliers construction" can replace the support on the pole core by a rear mutual support of the two E-shaped pole cores. When supporting with torque while the polarity of the individual coils and permanent magnets is to be chosen so that the sum force is formed on one outer leg and the other the differential force, the mirror image E-shaped pole core is polarized exactly opposite. That is, the sum force of the outer leg of an E-shaped pole core 2, a differential force on the corresponding outer leg of the other E-shaped pole core 2 'and vice versa is formed. If the polarity is chosen incorrectly, no moment will arise, with the right choice twice the moment.

In the case of the drivers according to the invention, it is useful to fill the oscillation gaps in the pole region of the permanent magnets of the drivers with flexible pads which have little effect on the vibrations but can absorb the static weight of the sound plate. The more drivers are arranged on the edge, the softer the pads can be designed. For better clarity, however, these pads were omitted in the figures.

A general problem with multi-resonant plate loudspeakers is the tuning of the sound plate, so that the frequency response of the acoustic radiation shows the desired broadband linear course. This vote can usually with some success done by skillful placement and sensitivity adjustment of distributed on the sound board driver. The more drivers are used, the harder the vote. The mass burden creates new serious moods. In the drivers according to the invention, however, opens up the possibility of sound plate tuning without mass load.

Three significant adjustable parameters of additional signal carrying current drivers according to the invention can be used for active plate tuning: the dipole distance d, the sensitivity and the position along the edge. The dipole spacing can be used to target vibration modes of the appropriate bending wave length. By choosing the placement along the edge, the accuracy increases. Adjusting the sensitivity properly doses the effect of this electronic active plate tuning. In addition, when used for display purposes sound panels with only marginally arranged drivers by appropriate adjustment of the parameters just mentioned a vote can be brought about.

LIST OF REFERENCE NUMBERS

1, 1 '

plate

2, 2 '

pole core

3, 3 '

permanent magnet

4, 4 '

Kitchen sink

5, 5 '

soft magnetic yoke

6, 6 '

cutting camp

7, 7 '

non-magnetic suspension element

8, 8 '

Middle leg of the pole core

9.9 '

magnetic alternating field vector

10, 10 '

magnetic dc field vector

17, 17 '

solenoid

18, 18 '

pole core

19, 19 '

permanent magnet

20

cutting camp

21

plate

22

yoke

23

support

I

Tonfrequenter alternating current

N

North Pole

S

South Pole

d

yoke length

Claims (14)

1. An electromagnetic driver for a planar diaphragm loudspeaker including a soft magnetic core (2) of E shape having three limbs and a spine, and alternating magnetic field exciter (4), which is magnetically coupled with the soft magnetic core (2), for producing an alternating magnetic flux dependent on an audio signal (I) in the soft magnetic core (2), a constant field exciter, which is magnetically coupled with the soft magnetic core (2), for generating a constant magnetic flux in the soft magnetic core (2), a soft magnetic element (5), which is opposed to the spine and magnetically closes the limbs over at least one small induction gap, for coupling with the diaphragm (1) of the planar diaphragm loudspeaker, wherein the alternating flux and constant flux are additive at one of the outer limbs of the soft magnetic core (2) and are subtractive at the other outer limb of the soft magnetic core (2) such that a resulting force or a resulting torque on the soft magnetic element (5) alters substantially linearly with the audio signal (I).
2. An electromagnetic driver as claimed in Claim 1, in which a yoke (5) is provided as the soft magnetic element, which is tiltably mounted on the free end of the central limb of the soft magnetic core (2) and affords induction gaps, at least with respect to the two limbs of the magnetic core (2), such that the yoke (5), which is driven by means of the alternated field exciter (4), produces a corresponding torque.
3. An electromagnetic driver as claimed in Claim 1 or 2, in which a coil (4), which is controlled by the audio signal (I) and is arranged on one or both outer limbs of the soft magnetic core (2), is provided.
4. An electromagnetic driver as claimed in Claims 1 to 3, in which a permanent magnet (3) is provided as the constant field producer, which is arranged in the central limb of the soft magnetic core (2).
5. An electromagnetic driver as claimed in one of Claims 1 to 3, in which a coil is provided, through which direct current flows and which is arranged on the central limb of the soft magnetic core (2).
6. An electromagnetic driver as claimed in one of Claims 1 to 5, in which the yoke (5) is held in a rest position by two non-magnetic spring elements (7), which are arranged in the induction gaps between the outer limbs of the soft magnetic core (2) and the yoke(s).
7. An electromagnetic driver as claimed in one of Claims 1 to 6, in which a non-magnetic support (6) is provided for supporting the yoke (5) on the central limb of the soft magnetic core (2).
8. An electromagnetic driver for a planar diaphragm loudspeaker including two soft magnetic cores (2, 2'), which are each of E shape having three limbs and a spine and are arranged fixedly with respect to one another spine to spine, two alternating field exciters (4, 4'), which are magnetically coupled with a respective one of the soft magnetic cores (2, 2'), for producing an alternating magnetic flux, which is dependent on an audio signal (I), in the respective soft magnetic core (2, 2'), two constant field exciters (3, 3') which are coupled with a respective one of the soft magnetic cores (2, 2'), for producing a constant magnetic flux in the respective soft magnetic core (2, 2'), two soft magnetic elements (5, 5'), which are opposed to respective spines and magnetically close the respective limbs over at least one small induction gap, for coupling with the diaphragms (1, 1') of the planar diaphragm loudspeaker, wherein the alternating flux and constant flux are additive at one of the outer limbs of each soft magnetic core (2, 2') and are subtractive at the other outer limb of the soft magnetic core (2, 2') such that a resulting force or a resulting torque on the respective soft magnetic element (5, 5') alters substantially linearly with the audio signal (I).
9. An electromagnetic driver for a planar diaphragm loudspeaker including a soft magnetic core (2, 2') in the form of two partial E shapes (2, 2'), which are connected together spine to spine and each have three limbs, two alternating field exciters (4, 4'), which are magnetically coupled to a respective one of the partial E shapes (2, 2'), for producing an alternating magnetic flux, which is dependent on an audio signal (I), in the soft magnetic core (2, 2'), two constant field exciters (3, 3'), which are coupled with a respective one of the one of the partial E shapes, for producing a constant magnetic flux in the respective soft magnetic core (2, 2'), two soft magnetic elements (5, 5'), which are opposed to the respective spine and magnetically close the limbs of the respective partial E shapes over at least one induction gap, for coupling with the diaphragms (1, 1') of the planar diaphragm loudspeaker, wherein the alternating flux and constant flux are additive at one of the outer limbs of the respective soft magnetic core (2, 2') and are subtractive at the other outer limb of the soft magnetic core such that a resulting force or a resulting torque on the soft magnetic element(s), (5, 5') alters substantially linearly with the audio signal (I).
10. An electro magnetic driver for a planar diaphragm loudspeaker including a soft magnetic core (2) of E shape having three limbs and a spine and arranged at the edge of the diaphragm (1) such that the diaphragm (1) is situated at its side opposite the spine and its two outer limbs are curved towards the plate (1) in the manner of tongs and an alternating field exciter (4), which is magnetically coupled with the soft magnetic core (2), for producing an alternating magnetic flux, which is dependent on an audio signal (I), in the soft magnetic core (2) and a constant field exciter (3), which is magnetically coupled with the soft magnetic core (2) and is arranged in the diaphragm (1) in the region of the open ends of the limbs, for producing a constant magnetic flux in the soft magnetic core (2), wherein the alternating flux and constant flux are additive at one of the other outer limbs of the soft magnetic core (2) and are subtractive at the outer limb of the soft magnetic core (2) such that a resulting force or a resulting torque on the constant field exciter (3) alters substantially linearly with the audio signal (I).
11. An electromagnetic driver as claimed in Claim 10, in which a fixed coil (4), which is controlled by the audio signal (I) and is arranged on the central limb, is provided as the alternating field exciter and a permanent magnet (3) is provided as the constant field exciter, wherein a constant magnetic flux from the permanent magnet (1), directed parallel to the normal to the diaphragm, acts on the outer limbs of the soft magnetic core (2) and an alternating flux leaving the central limb of the soft magnetic core (2) acts on it.
12. An electromagnetic driver as claimed in Claim 10 or 11, in which respective non-magnetic spring elements (7) are arranged between the outer limbs of the soft magnetic core (2) and the diaphragm (1).
13. An electromagnetic driver as claimed in Claims 1 to 12, which is so arranged that the forces produced by it act within an edge region of the diaphragm (1), wherein the edge region has a breadth which is approximately equal to the thickness of the diaphragm (1).
14. An electromagnetic driver as claimed in one of Claims 1 to 7, including a further soft magnetic core (2') of E shape having three limbs and a spine, a further alternating field exciter (4'), which is magnetically coupled with the further soft magnetic core (2'), for producing an alternating magnetic flux, which is dependent on an audio signal (I), in the further soft magnetic core (2'), a further constant field exciter (3'), which is magnetically coupled with the further soft magnetic core (2'), for producing a constant magnetic flux in the further magnetic core (2') wherein the two soft magnetic cores (2, 2') are arranged with the ends of their limbs directed towards one another on both sides of the diaphragm (1) such that the soft magnetic element (5) for coupling with the diaphragm (1) magnetically closes the limbs of the further magnetic core (2') over at least one small induction gap, and wherein the alternating flux and constant flux are additive on one of the outer limbs of the further magnetic core (2') and are subtractive at the other outer limb of the further soft magnetic core (2') such that a resulting force or a resulting torque on the soft magnetic element (5) alters substantially linearly with the audio signal (I).

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