EP0749265B1 - High frequency loudspeaker - Google Patents

Abstract

The loudspeaker includes the membrane (4) which is made of a flexible elastic material, and the free ends (13,14) are connected to the fixed structure of the loudspeaker to form layers (13A,13B,14A,14B) of air of decreasing thickness towards the fixing point on one or both sides of the membrane. At least one of the annular sections has regularly spaced radial lines around the outside to increase flexibility or has radial slots around the outside, closed off by a flexible elastic resin. The membrane is manufactured in a composite material or high Young modulus polymer. The waveguide (12) is a horn and the membrane and electromagnetic coil (3) form a compression driver chamber.

Description

The present invention relates to a speaker for frequencies high.

We know that a speaker has a vibrating membrane sound generator, said membrane being connected to this effect to a moving electromagnetic coil suspended in the air gap created by the pole pieces of a permanent magnet and powered by a representative electric current sounds to reproduce.

Although not exclusively, the present invention relates to more particularly a speaker with compression chamber. We know that, unlike radiation speakers direct, compression chamber loudspeakers do not radiate directly into the air, but through through an acoustic pavilion. Such speakers therefore generally have an acoustic horn removable and a compression chamber motor.

As regards said compression chamber motor, it basically there are two different embodiments which are known and marketed.

In a first embodiment which is already very old, the speaker membrane is made in the form of a rigid spherical cap, often metallic and fixed on the chassis of said speaker by means of a flexible suspension peripheral. The moving electromagnetic coil is connected at the periphery of said membrane, between said membrane and said suspension, and, during a movement, it displaces said entire cap like a piston infinitely rigid. It will be noted that, by its flexibility, said suspension has for the function of ensuring the movement and guiding of the moving part of the loudspeaker.

• la bobine mobile doit déplacer la totalité de la masse de la partie mobile du haut-parleur, ce qui limite l'émission des sons en hautes fréquences et suppose notamment l'utilisation d'aimants lourds et coûteux pour compenser ce défaut ;
• pour des raisons de performance des haut-parleurs, les matériaux utilisés doivent être le plus léger possible tout en restant extrêmement rigides. Le béryllium est par exemple utilisé pour réaliser ladite membrane, ce qui augmente bien entendu le coût de ces haut-parleurs ; et
• il est nécessaire de prévoir une pièce de mise en phase extrêmement complexe en conception et en réalisation, puisqu'il est nécessaire de faire converger en phase à l'embouchure du pavillon le rayonnement élémentaire de chaque partie de la surface de la membrane.

This embodiment has many drawbacks, in particular:

• the voice coil must move the entire mass of the mobile part of the loudspeaker, which limits the emission of sounds at high frequencies and in particular requires the use of heavy and expensive magnets to compensate for this defect;
• for reasons of speaker performance, the materials used must be as light as possible while remaining extremely rigid. Beryllium is for example used to produce said membrane, which of course increases the cost of these speakers; and
• it is necessary to provide an extremely complex phasing part in design and construction, since it is necessary to make the elemental radiation of each part of the surface of the membrane converge in phase at the mouth of the pavilion.

In a second embodiment, corresponding to a diaphragm tweeter, diaphragm includes a rigid central annular part and a part also rigid peripheral ring, connected together the along an annular junction opposite the pavilion of said speaker. Said annular parts are further connected to the chassis of said speaker via elastic suspensions, said elastic suspensions being formed by concentric softening lines to said annular parts, and generally practiced in these last. In this embodiment, the membrane is also moves like a piston extremely rigid.

• d'émettre des sons à des fréquences élevées ;
• d'utiliser une pièce de mise en phase simple et peu coûteuse ; et
• d'engendrer la variation de pression génératrice de son, en regard de la bobine électromagnétique, ce qui est favorable pour la production de fréquences élevées.

The speaker thus produced allows in particular:

• make sounds at high frequencies;
• to use a simple and inexpensive phasing part; and
• generate the sound-generating pressure variation, opposite the electromagnetic coil, which is favorable for the production of high frequencies.

However, this embodiment has the disadvantage larger than the membrane, too small in area, and whose suspension is too rigid, does not allow this speaker to operate from 500 Hz.

The object of the present invention is to remedy these drawbacks. It concerns a loudspeaker for frequencies high, lighter at equivalent performance than prior art speakers and susceptible to be carried out easily and at reduced cost, while allowing to emit sound waves according to a bandwidth very wide, especially towards high frequencies, with a Improved efficiency.

To this end, according to the invention, the loudspeaker for frequencies high with a vibrating membrane comprising a central annular part and an annular part peripheral connected together along an annular junction located opposite the waveguide of said loudspeaker, said membrane being connected at said junction annular to a suspended electromagnetic coil in the air gap of the pole pieces of a permanent magnet and powered by an electric current representative of the sounds to reproduce, is remarkable in that said membrane is made of a flexible and elastic material so as to present a defined deformation during the movement of said electromagnetic coil, and in that said annular parts are curved and are directly connected by their free end to a fixed structure of said loudspeaker, the convex side of said annular parts being arranged opposite said waveguide.

Thus, thanks to the invention, only part of the mass of the membrane is to be driven by the voice coil, since a displacement thereof causes progressive deformation said flexible and elastic annular parts, from of said annular junction. Therefore, performance in terms of efficiency and bandwidth are greatly improved. In addition, the present invention does not require not the implementation of specific suspensions, since they are an integral and indivisible part of the membrane.

In the context of the present invention, the term “ flexible and elastic membrane, a membrane capable of distort and able to return to its original position after termination of the constraint applied to him.

• il peut émettre des sons à des fréquences élevées, au moins jusqu'à 16 kHz pour certains modes de réalisation ;
• il peut être réalisé, de même que la pièce de mise en phase associée, de façon simple et à coût réduit, puisque sa structure est du type annulaire ;
• il présente une surface émissive importante pour un diamètre déterminé de la bobine ; et
• la membrane peut être réalisée en un matériau, par exemple un matériau composite ou un polymère à haut module de Young, moins coûteux que celui utilisé dans les modes de réalisation connus précités, puisqu'on ne lui demande plus d'être quasiment infiniment rigide.

The loudspeaker according to the invention also has many other advantages, in particular:

• it can emit sounds at high frequencies, at least up to 16 kHz for certain embodiments;
• it can be produced, as well as the associated phasing part, in a simple manner and at reduced cost, since its structure is of the annular type;
• it has a large emissive surface for a determined diameter of the coil; and
• the membrane can be made of a material, for example a composite material or a polymer with a high Young modulus, less expensive than that used in the aforementioned known embodiments, since it is no longer asked to be almost infinitely rigid.

Note also that we already know a speaker whose membrane is flexible and elastic and is held in its center. Such a membrane is designed in the form of a portion of torus, the peripheral part of which is connected to the voice coil.

• premièrement, si on essayait d'adjoindre à ladite membrane du type "CSD" une partie annulaire externe à la bobine mobile, en vue de rendre la membrane annulaire, le flux sonore engendré par cette partie annulaire externe ne pourrait converger vers l'embouchure du pavillon dans le même temps que le flux sonore engendré par la partie annulaire interne, condamnant dans ce cas ce perfectionnement ;
• deuxièmement, le pavillon ou guide d'ondes est en regard du côté concave de ladite membrane et non du côté convexe comme dans la présente invention ;
• troisièmement, la prise de pression de l'embouchure du pavillon n'est pas située directement en regard de la bobine mobile, comme dans le cas de l'invention.

Although it is flexible and self-hanging, such a membrane has a design quite different from that of the present invention and therefore cannot suggest the production of the latter. Indeed, in this embodiment known under the name "CSD"("Centrally Supported Diaphragm", that is to say membrane supported in the center), which was notably presented in a publication relating to the 98th Convention of the 'AES ("Audio Engineering Society") from February 25 to 28, 1995 in Paris, number 3997 (L3) and entitled "Computer Modeling and Design of Compression Drivers Based on a Centrally Supported Diaphragm":

• firstly, if we tried to add to said "CSD" type membrane an annular part external to the voice coil, in order to make the annular membrane, the sound flux generated by this external annular part could not converge towards the mouth of the flag at the same time as the sound flux generated by the internal annular part, in this case condemning this improvement;
• secondly, the horn or waveguide is opposite the concave side of said membrane and not on the convex side as in the present invention;
• thirdly, the pressure tap at the mouth of the roof is not located directly opposite the voice coil, as in the case of the invention.

It will be noted that, in the context of the present invention, the bulging of said annular parts can take all possible forms, in particular that of an arc of circle or that of a half-torus.

In a particularly advantageous embodiment of the invention, at least one of said annular parts is connected to said fixed structure so as to form blades of air relative to said fixed structure.

These air knives create dynamic rigidity and cause viscous damping proportional to the frequency and allow in particular to dynamically reduce the emissive surface of the membrane as a function of speed vibratory.

In addition, these air spaces repel clean modes from the membrane to the high frequencies and avoid the appearance of eigen modes distorting the generation sounds.

To amplify the advantageous effects described above, said air gaps have a decreasing thickness gradually towards the membrane attachment area on the fixed structure.

According to the embodiment envisaged, said air knives can be formed on one side or on both sides of the membrane.

Furthermore, advantageously, at least one of said annular parts is provided with softening lines radially uniformly distributed over the periphery of said annular part, which increases the flexibility of the membrane.

This flexibility can be increased, according to another mode of realization, by practicing at least on one of said annular parts of the radial slots uniformly distributed on the periphery of said annular part and in closing said slots by means of a flexible resin and elastic.

In a preferred embodiment of the invention, said waveguide is a horn and said membrane and said electromagnetic coil constitute a motor with compression chamber.

The single figure in the attached drawing will make it clear how the invention can be realized. In this figure, we has shown schematically, in axial section, a loudspeaker according to the invention.

The loudspeaker for high frequencies 1 conforms to the invention and shown partially and schematically in the single figure usually comprises a coil electromagnetic 3, connected to a one-piece vibrating membrane 4, suspended in the air gap 5 of the pole pieces 6 and 7 a permanent magnet 8 and powered by a current electric representative of the sounds to reproduce.

The above elements are produced symmetrically relative to the X-X axis of said speaker 1.

The membrane 4 is of the type comprising an annular part central 9 and a peripheral annular part 10 connected together along an annular junction 11 which is located next to a waveguide which, in this case, is shown in the form of a flag 12. In addition, the coil 3 is connected to said membrane 4 at this junction annular 11, directly facing the mouth of said pavilion 12.

According to the invention, said membrane 4 is produced in a flexible and elastic material, as light as possible, by example a composite material or a high modulus polymer of Young, so as to present a defined deformation during the movement of said electromagnetic coil 3, and said annular parts 10 and 9 are curved and are directly connected by their free end respectively 13 and 14 to a fixed structure specified below of the said loudspeaker 1, the convex side of said annular parts 9 and 10 being located opposite said pavilion 12.

Note that a displacement of the coil 3 causes a deformation in the membrane 4, which moves from the junction 11 towards the ends 13 and 14 and which causes a variation in the local pressure, generating sound. Thanks to the invention, this variation in pressure is created near the coil 3 and it is oriented in the same direction as the propagation of the deformation in the membrane 4, which allows energy efficiency high with regard to energy transformation mechanical in acoustic energy.

In addition, the volume swept by the deformation of the membrane 4 can be higher than that swept by a rigid membrane of the same size moving like a piston, like this is generally the case for known membranes. Thus, in particular, greater sensitivity is imparted to the speaker 1.

• le haut-parleur 1 peut émettre des sons jusqu'à des fréquences sensiblement plus élevées que les haut-parleurs de l'état de la technique ;
• il peut être réalisé de façon simple et à coût réduit ;
• il présente une surface émissive importante (au niveau des deux parties annulaires souples 9 et 10) pour un diamètre déterminé de la bobine 3 ; et
• il présente un encombrement réduit car il peut notamment être réalisé avec un aimant plus petit que dans les modes de réalisation connus, puisque la masse à déplacer est moins importante.

Furthermore, the following advantages are obtained by virtue of the present invention:

• the loudspeaker 1 can emit sounds up to frequencies substantially higher than the loudspeakers of the prior art;
• it can be carried out in a simple manner and at reduced cost;
• it has a large emissive surface (at the level of the two flexible annular parts 9 and 10) for a determined diameter of the coil 3; and
• it has a reduced size because it can in particular be produced with a smaller magnet than in the known embodiments, since the mass to be moved is less significant.

It should also be noted that, within the framework of the present invention, the bulging of said annular parts 9 and 10 can take all possible axisymmetric forms, in particularly that of an arc of a circle or that of a half-torus.

• soit des lignes d'assouplissement radiales non représentées, uniformément réparties sur la périphérie desdites parties annulaires ;
• soit des fentes radiales non représentées, également réparties uniformément sur la périphérie et fermées au moyen d'une résine élastique et souple, par exemple du latex de butyle.

In addition, to increase the flexibility of said annular parts 9 and 10, it is possible to provide, on said annular parts:

• either radial softening lines, not shown, uniformly distributed over the periphery of said annular parts;
• or radial slots, not shown, also distributed uniformly over the periphery and closed by means of an elastic and flexible resin, for example butyl latex.

The free ends 13 and 14 of said annular parts 10 and 9 are fixed by being embedded between elements of the fixed structure of the loudspeaker 1, namely between said horn 12 and a fixing piece 15 for the end 13 and between a phasing part 16 and a attachment 17 for end 14.

These elements 12, 15, 16 and 17 are formed at the level of the fixing zone so as to create air gaps 13A, 13B, 14A and 14B respectively on either side of said ends 13 and 14.

In addition, said air knives 13A, 13B, 14A and 14B have thickness gradually decreasing towards the area fixing ends 13 and 14, which allows to spread in the frequency domain the advantageous effects generated by these air knives and specified below.

• elles créent une rigidité dynamique et provoquent un amortissement visqueux ;
• elles permettent de réduire de façon dynamique la surface émissive de la membrane en fonction de la vitesse vibratoire ; et
• elles repoussent les modes propres naturels de la membrane vers les hautes fréquences.

Said air knives indeed have numerous advantages, in particular:

• they create dynamic rigidity and cause viscous damping;
• they make it possible to dynamically reduce the emissive surface of the membrane as a function of the vibrational speed; and
• they push back the natural eigen modes of the membrane towards the high frequencies.

Of course, in the context of the present invention, may provide air gaps only on one side of the ends 13 and 14 of the membrane 4.

In the absence of an air gap, there is a risk that the membrane 4 touches the fixed structure during its vibration, we can advantageously coat the area concerned of said structure of a suitable material damping the shocks in order to avoid the generation of noises likely disturb the sound emission from the speaker.

It will also be noted that, thanks to the invention, the piece of phasing 16, generally conical, can be very simple and inexpensive.

As can be seen in the figure, this fitting piece phase 16, the fixing piece 17 and the pole piece 7 are connected together by means of a screw 18 of axis X-X through an appropriately practiced cylindrical hole in these different rooms. Of course, others fixing methods can be considered. It is the same for unspecified fixing of other parts of the loudspeaker 1.

Claims (10)

1. A loudspeaker for high frequencies (1) including a vibrating diaphragm (4) comprising a central annular part (9) and a peripheral annular part (10) connected together along an annular junction (11) situated opposite the waveguide (12) of said loudspeaker (1), said diaphragm (4) being connected in the vicinity of said annular junction (11) to a moving electromagnetic coil (3) suspended in the air gap (5) of the pole pieces (6, 7) of a permanent magnet (8) and supplied with an electric current representative of the sounds to be reproduced,
   characterized in that said diaphragm (4) is made from a flexible and elastic material so as to exhibit a defined deformation during the motion of said electromagnetic coil (3), and in that said annular parts (9, 10) are domed and are connected directly via their free end (13, 14) to a fixed structure of said loudspeaker (1), the convex side of said annular parts (9, 10) being arranged opposite said waveguide (12).
2. The loudspeaker as claimed in claim 1,
   characterized in that at least one of said annular parts (9, 10) is connected to said fixed structure in such a way as to form air sheets (13A, 13B, 14A, 14B) with respect to said fixed structure.
3. The loudspeaker as claimed in claim 2,
   characterized in that said air sheets (13A, 13B, 14A, 14B) exhibit a thickness decreasing progressively toward the region for fixing the diaphragm (4) to the fixed structure.
4. The loudspeaker as claimed in either of claims 2 and 3,
   characterized in that said air sheets are formed on one side of the diaphragm.
5. The loudspeaker as claimed in either of claims 2 and 3,
   characterized in that said air sheets (13A, 13B, 14A, 14B) are formed on both sides of the diaphragm (4).
6. The loudspeaker as claimed in any one of the preceding claims, characterized in that,
   characterized in that at least one of said annular parts is furnished with radial flexibilizing lines uniformly distributed over the periphery of said annular part.
7. The loudspeaker as claimed in any one of the preceding claims,
   characterized in that at least one of said annular parts is furnished with radial slots uniformly distributed over the periphery of said annular part and closed by means of a flexible and elastic resin.
8. The loudspeaker as claimed in any one of the preceding claims,
   characterized in that said diaphragm (4) is made from a composite material.
9. The loudspeaker as claimed in one of claims 1 to 7,
   characterized in that said diaphragm (4) is made from a polymer with high Young's modulus.
10. The loudspeaker as claimed in any one of the preceding claims,
    characterized in that said waveguide (12) is a horn and wherein said diaphragm (4) and said electromagnetic coil (3) constitute a compression-chamber motor.

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