FR2474800A1 - MEMBRANE ELECTRO-ACOUSTIC TRANSDUCER IN THE FORM OF A SPHERICAL RING - Google Patents

Abstract

ELECTRO-ACOUSTIC TRANSDUCER INCLUDING, IN THE NEARBY OF A DIFFUSER BODY, A MEMBRANE ASSOCIATED WITH AN EQUALIZING ELEMENT AND A COIL INSTALLED NEAR A MAGNET. THIS TRANSDUCER IS CHARACTERIZED BY THE FACT THAT THE SAID MEMBRANE 4 IS CONSTITUTED BY AN ANNULAR-SHAPED PART OF A HEMISPHERIC CAP CONNECTED, BY ITS EXTERIOR PERIOD, TO AN ELASTIC HOLDING STRUCTURE 5 AND TO THE INTERNAL COIL 3 AND RETURNED BY ITS PERIOD. , BETWEEN TWO CONTIGUOUS SHOCK ABSORBERS 7, THE LATTER BEING COUPLED TO THE AUDIT EQUALIZING ELEMENT 9 BY MEANS OF A COMPRESSION WASHER 14 AND A LOCKING DEVICE 12. APPLICATION TO HAUTE-FIDELITE INSTALLATIONS.

Description

The present invention relates to an electro-acoustic transducer,

  particularly well suited to

  high fidelity installations of the industrial type, for example

  all cinemas, radio stations, stadiums, public places, and the like, in the form of compression devices for acoustic loudspeakers and analogue equipment. .oguies. It is known that, in the case of compression devices for loudspeakers and the like, the pressure exerted on the air by the convex part or by

  the concave part of a hemisphere-shaped limb

  to strengthen sound signals in acoustic signals. Naked hemispherical cap-like membranes are also known. the pressure exerted on the air by their convex part have the disadvantage of giving, especially in the upper middle range of their

  sound spectrum, a response curve that is only mediocre-

  linear. This is because the acoustic signals generated by the diaphragm, coupled with an equalizer

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  at the exit of a device of any type under compres-

  They are not phase matched, ie they have staggered delays between them, depending on the distance between the emission point of each signal on the membrane and the output of this device under compression. This phenomenon occurs despite the presence

  of the saddler who, as we know, has the role of uni-

  make the output as good as possible, especially at high frequencies. The differences in length, indicated above, between the paths of the various signals provoke, in the

  response curves, large deformations and rup-

  tures. This disadvantage has been overcome by using the said hemispherical cap-shaped membrane in such a way that the electrical signals are transformed into acoustic signals by the pressure exerted on the non-aerosolized air.

  not by the convex part of the membrane but by its

  cellar. In this way, all the signals have the same length and move towards the same point, represented by the fictitious center of the hemispherical cap-shaped membrane.

  point corresponding to the output of the device under compression.

  But for that, we must provide equalizers

  in addition to the fact that they constitute the

  under pressure having the desired volumetric characteristics, shall be provided with a series of radial slots

  concentric for the output of said signals.

  The making of these equalizers is, in fact, very expensive because of the fact that these slots must be

  carried out by special methods and by means of instru-

particular circumstances.

  The aim of the invention is an electro-acoustic transducer making it possible to remedy the disadvantages mentioned above,

  that is to say, to obtain net response curves

  linearly although it involves the process of forming acoustic signals for the convex part of the membrane and, consequently, of producing a device under compression

High quality.

  The invention also relates to an electronic transducer

  acoustically constructed, easy to use, having excellent characteristics and a significantly lower price than transducers using the method of forming acoustic signals by the concave portion of the membrane,

  while being like these high quality.

  More specifically, the subject of the invention is an electroacoustic transducer consisting essentially of

  by a membrane represented by a hemispherical cap ring

  phérique retained by its outer periphery, supporting a coil and enclosed, on its inner periphery, between two contiguous damping disks, these disks being coupled

  to an equalizing element by means of a compression washer

  and a locking device the effect of which is regulated by

a spacer.

  Other features and advantages of the invention

  will be apparent from the following description, made in

  Regarding the accompanying drawings and giving, by way of explanation but not limited to, an embodiment, with a variant. In these drawings: Figure 1 shows, in cross section, an electroacoustic transducer applied to a device under compression; - Figure 2 is a partial cross section

  another embodiment of the membrane in the form of

  hemispherical cape; and FIG. 3 represents two comparative frequency response curves along the emission axis, one of these curves corresponding to a conventional type of transducer and the other to a transducer according to the invention, having the same characteristics; in abscissa are worn

  in hertz, and, on the ordinate, the frequency responses

quence in decibels.

  It can be seen from FIG. 1 that the device under compression 1 is constituted by a magnetic assembly,

  or permanent magnet 2 of conventional type.

  In the air gap between the poles of the magnet 2 there is a voice coil 3, connected at one end to the outer peripheral part of the membrane 4.

  In practice, the membrane consists of a

  hemispherical celtic surface connected by its outer circumference.

  inner, to an elastic structure 5 and to the said circular voice coil 3. Cuant to the inner periphery 6 of the membrane 4, it is interposed between two damping disks

  7 that not only locally enclose it in a particular way

  made but, in addition, closes its central hole S. The upper damping disk, as seen in Figure 1, is contiguous to the equalizer 9 and the latter in turn, is connected to the diffuser body 1 which delimits, with

  the membrane 4, the compression chamber 11.

  In addition, the damping disks 7 and the equalizing

  9 are connected to each other by means of the screw 12, the spacer 13 and the compression washer

  14. Those elements 12, 13 and 14 together constitute the

  adjustment, or calibration, of the pressure exerted by

  the disks 7 on the inner periphery 6 of the membrane 4.

  It can not be excluded that the equalizer 9 and the

  corresponding shock absorbers 7, instead of being connected

  firmly to the diffuser body 10, be connected (as

  interrupted) at the central pole 15 of the magnet

permanent 2 by a pivot 16.

  In addition, the screw 12 can be replaced by a rivet or by any other blocking element, provided that the

  fastening of the compression washer 14 obtained by

  With the aid of the spacer 13, the damping discs 7 are provided with a constant pressure independent of the

  force exerted on said locking element.

  It follows from the foregoing that the active part of the membrane 4 consists exclusively of the annulus zoslise ent ed the edge of the elastic structure 5 and the outer edge of the damping disks 7. In this way, the sound waves produced by the membrane 4 must all travel almost the same path in the compression chamber 11 and reach the output of the device 1 in phase concordance.

  It should be noted, moreover, that the dimensions

  the damping discs 7 and the hole 8 of the diaphragm 4 as a function of the operating frequency register, the diameter of the diaphragm 4 and the coil 3, as well as

of the power of the whole.

  Figure 2 shows a second form of reali-

  of the membrane 4, according to which the inner periphery

  is also equipped with a 5 'elastic structure

  In this case, the active part of the membrane is between the two elastic structures and 5t, so that the sound waves, on their course in the crimp chamber 11, are practically all.

  equal and, consequently, are in phase agreement. The court-

  the response of irrequency, taken along the axis of

  if-ifs under compression provided with an electro-acoustic transducer

  according to the invention, appear much more linear than conventional curves; an example of this fact is given in Figure 3, in which the dashed curve 18 is the response curve of conventional transducers, while the curve 19 in solid line is that of the transducer

  according to the invention, as described above.

  For example, and for devices having the same characteristics, the dashed line curve 18 is linear between the frequencies of 600 Hz and 5 kHz, while the solid line curve 19 is linear between 600 Hz and 10 kHz.

  As can be seen, the electronic transducer

  The acoustics according to the invention have an extremely simple and therefore inexpensive structure, and yet they ensure a good linearity of the frequency response curve, even if the efficiency is slightly decreased due to the use of a membrane constituted only by a

  fraction of the hemisphere of known conventional membranes.

  This yield, in any case, is higher than that of the high

conical shaped speakers.

  The membrane 4 may be made of various materials, for example aluminum, bakelized cloth, plastic film, glass or carbon fiber or the like, while the damping discs 7 may be made of felt, made of polystyrene. expanded or similar product, provided that such materials permit

  to adequately limit the emissive zone of the membrane.

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Claims (10)

  1. An electroacoustic transducer comprising, in the vicinity of a diffuser body, an associated membrane   an equalizing element and a coil installed   simity of a magnet, characterized in that said membrane (4) is constituted by a portion of annular shape of a hemispherical cap connected, by its outer periphery, to a resilient holding structure (5) and to said coil (3) and retained, by its inner periphery between two contiguous damping disks (7), the latter being coupled to said equalizing element (9) by means of a   compression washer (14) and a locking device (12).   2.Electro-acoustic transducer according to the   1, characterized in that said membrane (4) comprises an active part between the edge of said elastic holding structure (5) and the edges, applied against one another, of the two damping disks ( 7).   3. Electro-acoustic transducer according to the   claim 1 or 2, characterized by the fact that   two damping discs (7) are made of felt or equivalent material.   4. Electro-acoustic transducer according to one   any of the preceding claims, characterized   in that said membrane (4) and said equalizing element (9) are coupled by means of these two disks dampers (7).   5. Electro-acoustic transducer according to one   any of the preceding claims, characterized by   the fact that said compression washer (14) is fixed   said equalizing element (9) by means of a   this distance (13), so as to constitute a device which makes known the pressure of said dampers (7) on   the inner edge of said membrane (4).   6. Electro-acoustic transducer according to one   any one of the preceding claims, characterized   2474800a cor does fact that the said recloser element (9) is connected   erffmment aU di + diffuser body (10).   7. Electroacoustic transducer according to one   Either of the preceding claims, characterized   by the fact that it says it! element égalisation (9) is connected   firmly at p the central (15) of said magnet (2).   8. Electro-acoustic transducer according to one   any of the preceding claims characterized by   the fact that said membrane (4) is made of aluminum or canvas   Bakélisée, or constituted, by a film of material ples-   tick, fiberglass and carbon or any suitable material. 9. Electro-acoustic transducer according to one   any of claims i to 8, characterized by the fact   that said membrane (4) is constituted by a portion, of annular shape, of hemispherical cap, delimited by two elective structures (5,5 ') formed along the edge   outside and the edge of the central hole (8).   10. Electro-acoustic transducer according to one   any of claims 1 to 9, characterized by the fact   that the dimensions of the damping disks (7) and the central hole (8) and the membrane (4) are a function of the operating frequency register, the diameter of the membrane, the diameter of said coil (3) and the power of installation.