FR2609853A1 - POWERFUL ELECTROACOUSTIC POWER TRANSDUCER WITH FLOOR DIFFUSION SYSTEM - Google Patents

Abstract

THE FIELD OF THE INVENTION IS THAT OF ELECTROACOUSTIC TRANSDUCERS ENSURING HIGH FIDELITY SOUND RESTITUTION, AND LIKELY TO OPERATE AT HIGH TRANSMISSION POWERS. THE OBJECTIVE IS TO REALIZE AN ELECTROACOUSTIC TRANSDUCER OF SIMPLE CONSTRUCTION, WITH MAXIMUM EFFICIENCY, ALLOWING TO WORK AT HIGH POWER WITH OPTIMAL REPRODUCTION FIDELITY. THIS OBJECTIVE IS ACHIEVED USING A TRANSDUCER CHARACTERIZED IN THAT IT CONSISTS OF AT LEAST THREE SEPARATE GAMES 11, 12, 13 OF LOUDSPEAKERS 21, 22, 23 FORMING A DIFFUSION SYSTEM, AT LEAST A FIRST 11 OF THE SAID SPEAKER SETS BEING CENTERED IN FRONT OF THE BROADCAST SYSTEM, AND OPERATING IN DOUBLET, AND AT LEAST TWO OTHER SETS 12, 13 OF SPEAKERS BEING REMOVED FROM THE SAID FIRST SET (S) 11.

Description

i "Electroacoustic power transducer,

  high fidelity, tiered diffusion system ".

  The field of the invention is that of electroacoustic transducers ensuring high fidelity sound reproduction, and likely to function

  at high transmission powers.

  In the field of high fidelity high power reproduction, and particularly for medium and high frequencies, the market has been dominated for many years by horn diffusers, also known as horns. Some embodiments of diffusers of this type have the advantage of a relatively homogeneous directivity over the entire range of available frequencies above 800 Hertz approximately. On the other hand, the technology of the horn diffusers has disadvantages which are manifested in particular by the

  large volumes needed to reproduce the bas-

  medium, by the appearance of distortions

  high sound, and the fragility of the material.

  In fact, so far, no technical solution can satisfactorily solve the equation fidelity / power. At high powers, because of the importance of the solicitations imposed on the diaphragms, it is indeed necessary to reduce the working frequency band of the speakers, so

  to specialize them to limit distortions.

  However, this specialization, often obtained at the cost of complex and expensive filtering, results in uneven sound reproduction levels on each frequency band. The correction of this inequality is generally achieved by increasing the power

  of the source, and the addition of corrective charges.

  In total, these systems are relatively complex, expensive, subject to breakdowns, and

poor performance.

  Accordingly, a first object of the invention is to provide an electroacoustic transducer of simple construction, with maximum efficiency, to work at high sound reproduction power with optimal reproduction fidelity. Another fundamental object of the invention is to provide an electroacoustic transducer having an exceptional ability to fine-tune the sound reproduction conditions (either during assembly or use) of the transducer. This adjustment capacity results mainly from the physical layout configuration (staged diffusion system comprising a doublet whose two opposite emission planes are combined), the electrical filtering means being reduced to a minimum (a few elements) to avoid the

  degradation of the overall efficiency of the transducer.

  Another object of the invention is to provide such a transducer, the operation of which is particularly suitable for the reproduction of frequencies extending from low to medium to high mid-range (approximately 150 Hz

at 5000 Hz, for example).

  An additional object of the invention is to provide the transducer by means of a multiplicity of small speakers, in order to contribute

  both in yield and reproducibility.

  The specific implantation configuration of the transducer according to the invention makes it possible to exploit each loudspeaker in its optimum operating range, by using a reduced electrical filtering for

  minimize deterioration of yield.

  These objectives and others that will appear later are achieved using an electroacoustic transducer, particularly for the sound reproduction of an electrical signal in the low-mid and high-mid frequencies, of the type consisting of several sets of loudspeakers, each game comprising at least one loudspeaker, a transducer characterized in that it is

  consisting of at least three distinct games of

  speakers forming a diffusion system, at least a first one of said sets of loudspeakers being centered in front of the broadcasting system, and functioning as a doublet, and at least two other sets of loudspeakers being set back from said one or more games , and in that electrical filtering means are interposed between the source of the electrical signal and at least the at least one front set of the broadcasting system so as to obtain the preferential reproduction of the high-medium frequencies by said

front games of speakers.

  Advantageously, said rear games are positioned symmetrically with respect to the central transmission axis of the broadcasting system, to obtain a homogeneity of the sound reproduction in the listening space. However, it is clear that any equivalent means preserving this homogeneity is covered by

this patent.

  Where appropriate, said filtering means comprise means for balancing the sound reproduction levels of the different loudspeaker sets, by adjusting the power supply of each of said sets according to the characteristics of the loudspeaker sets.

matching speakers.

  The physical layout configuration

  characteristic of the transducer, as mentioned above.

  above, makes it possible, after adjusting the electrical and acoustic phase shift of the loudspeaker sets, to obtain a completely surprising and effective synergy between the specialization of the front and rear games and the effect

space of the front doublet.

  The clarity and realism of the sound reproduction obtained by this configuration are all the more unexpected that the skilled person would have spontaneously thought that the addition of a doublet system ahead of a set of speakers unidirectional emission born

  could only confuse the resulting sound emission.

  In addition, the layout configuration allows multiple fine adjustment possibilities ensuring optimal use of each speaker in its

  privileged range of operation.

  Preferably, all of the

  system speakers is divided into three columns, each composed of the same number of loudspeakers arranged in rectilinear vertical parallel alignment with a combined emission plane, said three columns of loudspeakers being located in such a way that one of them constitutes the front part of the transducer diffusion system, the two other columns constituting the rearwardly displaced part, in such a way that the rear columns emit in a plane parallel to the transmission plane of the front column, symmetrically to this last. Advantageously, the number and the characteristics of the loudspeakers constituting each game on the one hand, and their connection on the other hand, are chosen so as to give even greater advantage to the reproduction of the low-medium frequencies by the games. backwards, and those of high-medium frequencies by

front games.

  According to another preferred feature of the invention, the front central column is formed of a simple support-plan for receiving the corresponding loudspeakers, without enclosure wall of the rear face of said loudspeakers, so that the forward emission and rear emission of the diaphragm form doublet; in addition, the loudspeakers of the rear columns are advantageously coupled to a

Resonant cavity of Helmholtz.

  Finally, in an advantageous embodiment of the invention, the columns of loudspeakers mounted behind the transducer form a twin subassembly with adjustable common wall, according to the type described in the patent application No. 8617423 filed on the 12th December 1986 in the names of the same inventors as those of the

this request.

  According to other complementary features which will be detailed later, the transducer on the invention offers multiple adjustment possibilities

  for its development, assembly or use.

  These characteristics will appear on reading

  of the following description of some modes of

  preferred embodiment of the transducers according to the invention, given by way of illustration, and the appended drawings in which: FIG. 1 represents a front view of an embodiment of the three-column transducer according to the invention, each column being constituted four vertically aligned speakers; FIG. 2 represents a horizontal sectional view of the transducer of FIG. 1; FIG. 3 represents an advantageous electric diagram, with filtering means, for feeding the transducer of FIGS. 1 and 2; FIG. 4 represents an embodiment of a portable sound enclosure comprising, on the one hand, a subset of a known type for the reproduction of low frequencies, and, on the other hand, a subset of configurations according to the invention for the restitution of the medium frequencies; FIG. 5 illustrates the effect of equalization and response curve correction achieved by the pairing of two semi-walled Helmholtz cavities.

adjustable.

  As can be seen in FIGS. 1 and 2, the transducer 10 represented consists of a front central column 11, flanked by a pair of columns

rear 12, 13.

  Each of the columns 11, 12, 13 have a

  vertical alignment of 4 loudspeakers.

  As will be seen below, the speakers of the rear columns 12, 13 are identical. In

  However, in certain configurations, the

  speakers in the front column 11 may have characteristics distinct from those of the loudspeakers

rear columns.

  As shown in Figure 2, the

  speakers 22, 23 of the rear columns 12, 13 are mounted in cavities Helmoltz type 32, 33. These cavities consist of a common rear vertical wall, a portion of the two side panels 42, 43 of the speaker , and a front panel 41 of

  receiving the loudspeakers 22, 23.

  The front panel 41 is provided with side vents

46, with laminar effect or not.

  The separation of the cavities 32, 33 is provided by a dividing wall 44, at least one portion of which is adjustable in displacement. The means 45 for adjusting the displacement of the partition 44 consist for example of a threaded rod - threaded nut system,

maneuvered by outside ruffles.

  The operating principle of this type of dual cavity with adjustable common partition is described in the patent application 8617423 already mentioned. The objective is to provide a method of equalization, and correction, of the restored signal, without affecting the performance of the transducers, by adjusting the resonance frequencies of the twin cavities 32, 33. The adjustment operation consists in shifting the amplitude / frequency response curves of each column 12, 13 relative to each other so as to achieve a compensation effect of the irregularities of the response curve, and addition, a modification effect of the

  tone of the resulting sound signal.

  As illustrated in FIG. 5, this phenomenon is explained by the typical shape of the response curve of the Helmholtz cavity transducers, formed by a succession of alternating variations of the power level.

around a mean value Lm.

  The response curve A corresponds to the column

  12, and the response curve C corresponds to column 13.

  These curves similarly show a succession of alternans beyond the slope at 18dB, but have been shifted by the value of a half-life by adjusting the resonance frequencies of the Helmholtz cavities. The curve df supports the displacement of the point P 'of the response curve C of the column 13 when the internal volume of the cavity 33 of the column 13 is varied. As a result, the displacement of the mobile partition 44, or of a portion thereof, causes a relative displacement of the response curves A, C of the two twinned columns 12, 13. The relative position of the response curves A, C at a given moment ensures a more or less complete compensation of

  alternating irregularities of the curves.

  In addition, over the compensation range, it has been found that a fine adjustment of the position of the partition wall makes it possible to produce sound effects likely in particular to correct the timbre of the restored signal. The correction may for example aim to compensate for electrical recording defects of the sound signal, or defects

acoustics of the listening room.

  The central front column 11 is constituted

  a simple panel 31 supporting the line of high-

  21. This panel 31 is anchored, after adjustment, by its upper and lower ends to the horizontal panels 14 and 15 of the enclosure, and can be

  rigidified by connecting struts, between the

speakers, at the back panel.

  In this way, the back side of the

  speakers 21 is perfectly clear and the noise emissions of opposite phases, generated at the front and

  the back, constitute an acoustic doublet.

  This advantageous configuration of the front column enhances the specialization of the speakers 21 for the return of high frequencies. Indeed, only high frequencies can be transmitted without

  weakening in column 11, because of short-term

  acoustic circuit due, from a certain wavelength, to the absence of a screen between the two faces of the

diaphragm of loudspeakers 21.

  Staged implementation of columns 11, 12, 13

  provides a particularly advantageous spatial effect.

  The spatial effect is all the more reinforced

  the paired rear columns 12, 13 produce

  even an equalization effect of the restored signal.

  To this spatial effect is added a "colornne" effect, which increases the effectiveness of the radiation due to the existence of three vertical speaker alignments. In fact, the inventors have been able to note a surprising synergistic effect by its efficiency, after adjusting the phase shift of the noise emissions of the front column relative to the rear columns, between the doublet effect of the front column and the specialization in

frequency of the columns.

  As already mentioned, the doublet of the front column produces in a known manner a spatial effect due to the delocalization of the sources of sound emission. However, it will be noted that, in an original way, the transducer according to the invention produces a doublet whose two emission phases with opposite directions and phases emit substantially from the same plane (the plane of the diaphragm of each of the loudspeakers). 21). However, the doublet effect combined with the emission of the rear columns causes a surprising increase in sharpness and precision, probably by a favorable action on the resulting directivity lobes

different columns.

  This effect of sharpness is obtained all the more efficiently that the transducer according to the invention makes it possible to finely adjust, over a wide range of values, the acoustic and electrical phase shift between the front column and the rear columns: the phase shift acoustic, resulting from the shift "d" between the two emission planes columns 11-, 12-13, is effective particularly in the vicinity of the recovery frequency (that is to say, the frequency of entry into action front speakers); the electrical phase shift, produced by filtering as described below, acts more particularly on

  higher frequencies of the high-medium.

  In any case, the combination of the phase shift of the emissions with the doublet effect, far from producing a confusion of the sound, improves very clearly its "definition". It is also noted that, for the different phase shift adjustment positions (adjustment of the offset "d", and of the characteristics of the filter), one obtains timbre variations of the sound reproduced. Advantageously, these variations of timbre can be exploited to produce specific sound effects, or else to make corrections of the sound signal, as a function, for example, of recording defects, or

  characteristics of the listening room.

  The fidelity of reproduction is obtained in particular by the specialization of the front column 11 on the one hand, and twin rear columns 12, 13

on the other hand.

  Advantageously, a passive filter defines a feed path of the central front column 11

  favoring higher frequencies.

  It is understood that the extreme frequencies, low and low, are removed from the source signal to be reproduced by foreign transducers to the broadcast system described in this patent application. The selectivity effect is further accentuated by the connection mode of the loudspeakers of each column. As represented in FIG. 3, the source electric signal introduced at the input of the passive filter 50 is delivered before filtering towards the loudspeakers 22, 23 of the columns 12, 13. The four loudspeakers 22 and 23 of the columns 12, 13 respectively are mounted in series, the columns 12, 13 being fed in parallel. In contrast, the speakers 21 of the column 11 are connected in series-parallel, so that the column 11 has a lower impedance in

  comparison of that of each of columns 12, 13.

  This arrangement thus makes it possible to accentuate the

  selectivity of column 11 for high frequencies.

  According to one embodiment of the invention in which the four loudspeakers of the column 11 are PR17 HR 37 TSM 2 CN7, and the eight loudspeakers of the twinned columns 12, 13 are PR17HR 37 TSM 2CN7 (manufactured by Audax), the values of the passive components of the filter 50 may be the following: l Cl 0.1 microfarad; C2 = 1.5 microfarad; C3 = 1 microfarad; C4 = 3.3 microfarads;

L = 0.22 millihenrys.

  Note that, in this embodiment, the speakers of the front column 11 on the one hand, and rear columns 12-13 on the other hand, have a

  slight difference in structure: indeed, the

  Front speakers include a macromolecular plastic coil holder, while the rear speaker coil stand is made of aluminum. In a known manner, the use of a conductive material for the coil support increases the permissible power of the speaker, because it increases its heat dissipation capacity; on the other hand, a non-conductive coil support is preferable to the high frequencies, for which the restored power, and therefore the dissipation requirements are lower, but where the risks of harmful coupling coil / support-coil are

more important.

  The choice of separate speakers enhances the specialization of the front columns compared to the rear columns, and optimizes the use of the transducer. Thanks to these characteristics of connections and acoustic and electrical filtering, the columns are specialized in the following way: the columns 12, 13 rear reproduce preferentially lower frequencies, especially when taking care to tune the corresponding Helmhotz cavities at these frequencies; - the high frequencies are

  preferentially restored by the column before 11.

  In addition, the rear columns 12, 13 are particularly adapted to provide the largest requested transmit power in the lower frequency register. The column before 11 favors in

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  however the fidelity of reproduction of the high frequencies. In summary, it may be noted that the transducer according to the invention offers the following adjustment possibilities: 1 'Adjustment of the balance of frequencies and the power distribution in the two groups (column 11, and columns 12-13) speakers; Adjustment of the two resonant cavities 32, 33, in particular by adjusting the mobile partition 44; 3 'Setting the spacing distance d of the two transmission planes of the groups of loudspeakers; 4 'Adjustment of the electrical phase shift of the two groups, in particular by passive filter 50; of course, the feed path of the twinned columns 12, 13 can

  also be provided with a complementary filter.

  Adjusting the impedance presented by each group according to the frequency, in particular through the connection configuration in each column, and

  the impedance of the filtering means of each channel.

  The invention has been implemented in a

  prototype of the type shown in Figure 1 and 2.

  For this prototype the dimensions are those shown in the figures. Of course, these

  dimensions are given for illustrative purposes only.

  FIG. 4 furthermore represents an alternative embodiment of the invention, in which the three-column transducer 60 is mounted in a box 61 also comprising 3 loudspeakers 62, 63 for the bass voices, and 1 loudspeaker extreme acute not figured for

harmonics.

  The broadcasting system implementing the principle of the invention, represented under the reference 60, consists of 3 columns each comprising only two

  speakers aligned vertically.

  26d098 In another embodiment, the "columns" can be arranged horizontally, by 90 'rotation of the diffusion system in a vertical plane, resulting in a modification of the spatial frequency distribution as well as the dimensions of the footprint. The invention is not limited, of course, to the implantation configurations shown in the drawings. By way of example, are also included in the claimed field of protection, the transducers of which

  the game before is formed by a group of several

  speakers arranged in lines, columns, circles, etc., or combinations of these figures. It is the same for the rear games of speakers: indeed, nothing prevents the rear games themselves form, for example, a crown of speakers more or less uniformly distributed with respect to the central axis of the

broadcasting system.

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Claims (7)

  1) Electroacoustic transducer, particularly for the sound reproduction of an electrical signal in the low-mid and high-mid frequencies, of the type consisting of several sets of loudspeakers, each set comprising at least one loudspeaker, characterized in that it consists of at least three distinct sets (11, 12, 13) of loudspeakers (21, 22, 23) forming a broadcasting system, at least one first (11) of said sets of loudspeakers being centered ahead of the broadcast system, and operating in   doublet, and at least two other games (12,13) of   speakers being set back from said one or more sets (11), and in that electrical filtering means (50) are interposed between the source of the electrical signal and at least said front set (s) (11) of the diffusion system, so as to obtain the preferential restitution of the high-medium frequencies by said front games (11) of speakers.   2) Transducer according to claim 1,   characterized in that said rear sets of high-   speakers are positioned symmetrically with respect to   the central axis (34) of emission of the diffusion system.   3) Transducer according to claim 1, characterized in that each of said sets consists of a vertically aligned column of speakers in the same transmission plane, the columns (11, 12, 13)   being parallel and made up of the same number of loudspeakers   speakers (21, 22, 23), and in that a first column (21) constitutes said front clearance of the transducer diffusion system, the two other columns (12, 13) being arranged symmetrically recessed from said column (11) , in a plane parallel to the emission plan of the front column (11).   4) Transducer according to claim 1, characterized in that the number and characteristics of the loudspeakers (21, 22, 23) constituting each set (11, 12, 13) on the one hand, and their connection on the other hand , are chosen so as to favor the restitution of the frequencies of basmédium by the back games (12, 13), and the restitution of the frequencies of high-medium by the front games (11).   ) Transducer according to claim 3, characterized in that said front column (11) consists of a flat panel (41) forming a support speakers (21) of the column, said panel (11) being devoid of wall d enclosing the back side loudspeakers (21).   6) Transducer according to claim 3, characterized in that said rear columns (12, 13) consist of Helmholtz cavities 20. 7) Transducer according to claim 6, characterized in that said rear cavities consisting of Helmholtz cavity are twinned so as to have a partition wall (44) of which at least one portion is mobile and adjustable.   8) Method of sound reproduction by electroacoustic transducer, of a source electrical signal, in particular in the range of low-mid and high-medium, characterized in that it consists in specializing at least a first set (11) of high o0-speakers (21) for the preferential reproduction of the high-mid frequencies, and at least two other sets (12, 13) of loudspeakers (22, 23) for the preferential reproduction of the low-medium frequencies, in this case that the loudspeakers (21) of said first game (11) are doubled, and that said other sets (12, 13) are set back from said front sets (11), the offset ( d) between the front and rear games for adjusting the acoustic phase difference between the high-medium front doublet sound emission and the sound emission back to low-midrange.   9) A method according to claim 8, characterized in that it realizes said specialization of the game before (11) on the one hand and rear games (12, 13) on the other hand, and the equalization of the levels of restitution sound of said games, by the choice of the characteristics of the loudspeakers (21, 22, 23)   corresponding and / or the choice of the connection of   speakers (21, 22, 23) of each of said sets (11, 12, 13)   and / or selective electrical filtering of said sets.