coaxial speaker system with indoor compression chamber

专利摘要:
COAXIAL SPEAKER SYSTEM WITH COMPRESSION CHAMBER WITH PAVILION. Coaxial loudspeaker system (1) with at least two tracks comprising an electrodynamic transducer (2) for bass, and a treble transducer (3) with a compression chamber comprising a complete pavilion, assembled coaxially and frontally in relation to the bass transducer (2).
公开号:BR112012017572B1
申请号:R112012017572-6
申请日:2011-01-14
公开日:2020-12-08
发明作者:Yoann Flavignard；Philippe Lesage；Arthur Leroux；Nicolas Clevy；Jean-Louis Tebec；Bénédicte Hayne
申请人:Phl Audio；
IPC主号:

专利说明:

The invention refers to the domain of sound reproduction, through loudspeakers, also called electrodynamic and electroacoustic transducers.
Sound reproduction consists of converting an electrical energy (or power) into energy (or acoustic power).
Electricity is most often released by an amplifier, whose power characteristics can vary from a few Watts for low-power home audio installations, to several hundred - or thousands - Watts for certain professional sound installations (recording studios, scenes musicals, public spaces, etc.).
The acoustic energy is irradiated by a membrane, whose displacements cause variations in the pressure of the ambient air, which propagate in space in the form of an acoustic wave.
Although relatively recent, the technology of sound reproduction gave rise to a considerable number of different conceptions from the 1920s and the first tests made by Chester W. RICE and Edward W. Kellog, of the American company GENERAL ELECTRIC, and whose association of the names it currently designates the most common type of electroacoustic transducer: the electrodynamic speaker "Tkeg-Mgnnqi".
In this type of transducer, the membrane is moved by a moving coil, comprising a solenoid immersed in a magnetic field and traveled by a current (from the amplifier). The interaction between the electric current and the magnetic field generates a force known as "hqt> c fg NCRNCEG", swg rtqfwz wo fgunqecogpVq fc dqdkpc mobile, which activates the membrane with it, whose vibrations are the source of the acoustic radiation.
Although each individual has their own auditory characteristics, the human ear is considered to be sensitive to sounds in a frequency range (called the audible range) between 20 Hz and 20,000 Hz (20 kHz). The kpfgrkorgu c 42 Jz u «q fgpqokpcfqu" iphtc-sops "sounds; cswgngu greater than 20 kHz are "ultrasonic" fgnooincfos. Infrasons and ultrasounds perceived by certain animals, but are considered to be imperceptible by the human ear (in this respect, it may be referred to general works, such as the Book of Sound Techniques, Volume 1, fundamental notions, 3 edition , chapter 4, Auditory perception, pp. 191 - 192).
That is why, in the construction of the speakers, it is generally linked to the reproduction of the signals delimited in the audible range. By convention, it is called "itaxg" and hckzc of frequencies between 20 Hz and 200 Hz; "ofifkc". c hckzc fcu htesüêpekcu eqorteepfkfcu entte 422 Jz and 4222 Jz * 4 mJz + = e "agwda", c hckzc fcu htesüêpekcu between 2000 Hz and 20000 Hz (20 kHz).
Many attempts have been made to design a unique electrodynamic speaker, allowing the complete audible range to be reproduced satisfactorily. These attempts were endless.
Indeed, the reproduction of low frequencies requires a large transducer and, therefore, a membrane of considerable size capable of a great amplitude. On the contrary, the reproduction of the high frequencies can only be satisfactory with a small font, therefore, a small membrane. In addition, the bounces of this small membrane will be of low amplitude. These characteristics being contradictory, it is easily understood that the manufacture of a single transducer covering the entire audible range in a satisfactory manner, is truly very difficult to accomplish.
That is why the electrodynamic speaker is generally designed to reproduce a reduced range of frequencies, in the middle of which the transducer response can be optimized.
The frequency acoustic response of this transducer, measured by means of a measurement microphone associated with a spectrum analyzer, is usually represented in the form of a curve, illustrating the variations in the signal's sound pressure level (expressed in dB, in a linear scale generally between 60 dB and 110 dB) as a function of the signal frequency (expressed in Hz, usually according to a logarithmic scale between 20 Hz and 20 kHz).
If, in theory, three families of transducers are considered: low, medium and high, in practice, however, the classification is finer, since the response of a transducer is a continuous function that can overlap several frequency ranges. Thus, for example, a transducer designed to reproduce the bass may offer a convenient response in the low part of the medium (low medium); similarly, a treble transducer may offer a convenient response in the high part of the medium (high medium), so that due to language abuse it is customary to designate: - "VtcPufwVqt fg itcxg" wo VtcPufwVqt crVq c reproduce the bass and at least the medium low; - "VtcPufwVqt fg ofifkq" wo VtcPufwVqt crVq c reproduce the medium and at least one upper part of the bass and / or at least one lower part of the high; - "VtcPufwVqt fg ciwfq" wo VtcPufwVqt crVq c reproduce the high and at least the high mid.
In addition to the differences in dimensions, the design of a transducer varies depending on whether it is a low or medium transducer, or a high-end transducer. Thus, although there are numerous forms of membranes, the conical (or pseudo-conical, depending on the generatrix profile) is currently the most used in the low and medium transducers, while the dome membranes are the most used in the transducers. treble.
In order to obtain a reproduction of the entire audible range, it is therefore customary to combine several transducers to create a sound reproduction system. A widespread solution consists of combining three specialized transducers: one for low, one for medium and one for high. However, for mainly economic reasons, it is common to limit yourself to two transducers, namely: a bass transducer capable of reproducing the bass and at least the low bass, and a treble transducer, capable of reproducing the high and at least the high -medium. The acoustic compartment, most often on the same face (called the front face of the compartment). In the Vgtokponoikc of eqorctVkogpVqu. pg fg "xkcu" fi kiwcn to the number of segmentations performed on the audible range. In practice, the number of tracks in a compartment corresponds to the number of transducers it comprises. Thus, a compartment comprising a bass transducer and a treble transducer is a two-way compartment.
The specialization of transducers, however, presents a difficulty, linked to the electrical distribution of the signal, commonly called filtering. It can be easily understood that, each transducer being optimized over only a part of the spectrum, one must filter the signal to direct to each transducer only the part of the spectrum that can be conveniently reproduced. Poor filtration can have different consequences depending on the frequency. Without going into detail, it will be noted that a signal directed at a bass transducer is not simply reproduced, while a bass signal directed at a high transducer can easily destroy the transducer.
For simplicity, the two-way compartment filter comprises a low-pass filter section, connected to the system's low-level transducer and which mostly allows only frequencies below a predetermined cut-off frequency to pass, and a section of high-pass filtering, connected to the system's treble transducer and which allows frequencies above the chosen cutoff frequency to pass predominantly.
The question of the choice of technology used for filtering has no impact on the design of the transducers, since the filtering is carried out upstream. On the contrary, the very principle of sound reproduction through a multipath compartment presents a fundamental physical problem regarding the spatial arrangement of the loudspeaker systems, due to the necessary recombination of the individual sound signals from the different paths. This recombination takes place in the air, and the smallest difference in the path of the waves from the different transducers in the system generates temporal distortions and creates interference that alters the recombined signal.
To get rid of these distortions and interference, numerous manufacturers try to mount the different transducers of a composite system as close to each other. Experience shows, in fact, that two transducers juxtaposed and radiating in phase, whose inter-axis is less than a quarter of the considered wavelength, behave almost like a single acoustic source. If this dimensional criterion appears to be acceptable at low frequencies (the calculation recommends a maximum inter-axis of the order of 350 mm for a maximum frequency of use below 250 Hz, which is easily accomplished). It can no longer be satisfied at high frequencies: for example, at a frequency of 2 kHz the spacing between transducers in practice (cf. Jacques Foret. The acoustic compartments in The Sound Techniques Book. Volume 2. Technology, 3a edition, ch. 3, p.149).
That is why certain manufacturers have proposed systems, whose transducers are coaxially mounted, in order to make the transducers' radiation axes coincide, in order to reduce distortions and interference when the audio signal is recombined.
However, the coaxial assembly of the transducers does not solve the problem of directivity control. In effect, the acoustic radiation from a transducer is not generally spatially homogeneous. In the grave (that is, in the long wavelengths), the membrane, of small dimension before the wavelength, can be considered as a point source that radiates a spherical wave small wavelengths), the membrane, of great dimension in front of the wavelength, it can no longer be considered as an irradiating sound source in an omnidirectional way, but it tends to become directive.
The directivity of the transducers varying according to the reproduced frequencies, the recombined signal coming from this loudspeaker system can comprise, at the same time, a component of irradiated signal, in a directive way coming from one of the transducers of severe radiator at the top of its spectrum) and a signal component radiated, omnidirectionally, from the other transducer (for example, from the acute radiator transducer at the bottom of its spectrum).
It is easily understood that the recombined signal is not homogeneous in space, and that the perception by the human ear may be altered. In effect, the acoustic signal coming from the compartment is not the same in all directions, the different signals reaching the ears of the listener (direct signal and signals reflected on the walls of the piece) will not be coherent, this defect of coherence being harmful to the sound reproduction quality.
In addition, the directivity of any transducer increases with frequency. Sound professionals know that the audience of an auditorium placed outside the loudspeaker axis does not perceive the treble.
In order to prevent these difficulties, certain manufacturers have the will not to make the transducers omnidirectional, regardless of the radiated frequency (which seems impossible at the present stage of the technology), but to control the directivity of the transducers, keeping it relatively constant on the spectrum spectrum emitted.
A well-known technique for controlling the directivity of a loudspeaker system is to use a treble transducer with a compression chamber and pavilion, mounted coaxially at the rear of a bass transducer, then called the main transducer, with a conical membrane.
This technique, known for a long time, has given rise to numerous architectural variants, such as that proposed by Whiteley since 1952 (British Patent GB 701,395), in which the treble transducer pavement bounces in the center of the bass transducer cone. Other variants propose to use the bass transducer cone to form the treble transducer flag, cf. notably the architecture proposed by Tannoy in the 40s and 72s * oqfgnqu "Fwcn EqpegpVtke". "Vygnxg" +. crgthgk> qcfc cVfi the end of the 1970s (US Patents US 4,164,631 1978, and US 4,256,930 1979). This technique allows to achieve a good coherence of the acoustic field with a relatively constant conical directivity over the set of the emitted spectrum, of which certain authors claim that it can reach 90 ° (cf. L. Haidant, Practical Guide to Sound, chapter 6, pp. 64-67).
The use of a transducer with a pavilion and a compression chamber has other advantages. In this transducer, the membrane does not radiate directly into the air space, the irradiation being led to pass in a restricted space (called a gutter) with a section inferior to that of the membrane, hence the "eortoc« eortoc «o".
The performance of a transmission with a compression chamber, with indirect irradiation, is much higher than that of transducers with direct irradiation.
The performance of a transducer is defined as the quotient between the acoustic energy radiated throughout the air space by the transducer, and the electrical energy absorbed (or consumed) by it. In general, the performance of electrodynamic transducers with direct irradiation and current design of the Rice-Kellog type is particularly small, on the order of some to a thousand to some percent (without exceeding, or rarely, 5%).
The performance cannot be directly measured, the IEC 60268-5 standard recommends a measure of acoustic source power. Disregarding the transducer directivity, its level of effectiveness, also called sensitivity level, that is, the sound pressure (in dB) generated by it in a free field in semi-eura> o * "jcnh-space free Hkgnf" + c 3 oetro, rctc wo c 1 W absorbed electrical power, allows a good approximation of its performance. The level of effectiveness is expressed in dB / W at 1 meter. This measurement is made in the useful range of the transducer and in the axis, and can constitute the frequency response curve of this.
If numerous efforts currently refer to the quality of sound reproduction (there is also talk of fidelity), it seems, however, that the time is not looking for the best performance, many manufacturers estimating that a low energy performance can be compensated by the use of amplifiers high power. It is true that domestic installations can be satisfied with a low performance transducer, considering the small sound range required (a few meters at most). On the contrary, for professional sound systems (notably in the case of concerts determined in large rooms or in mid-air) that require a long sound range, experience shows that it is preferable to use high-performance transducers powered under an average electrical power, more than low-performance transducers powered under high electrical power. On the one hand, most of the sense electrical power dissipated in the form of heat at the level of the magnetic circuit, in the second case there are very high thermal levels, with temperatures of several hundred degrees that can affect the acoustic performance of the transducer and require provide for complex cooling devices. On the other hand, the compensation of a low performance by increasing the electrical power is restricted by a phenomenon of limitation of acoustic level, called thermal compression.
We indicate that transducers with pavilion and compression chamber offer much higher yields than classic transducers with direct irradiation. These performances were seen very early, since the 1920s and the first developments in compression chambers. The sensitivity level of the famous model WE 555 W (Commercialized by the American firm WESTERN ELECTRIC from 1928 for the sound of the show rooms and the first talking films), only partially described in the patent of its manufacturer Edward C. Wente in the US 1 ; 707,545, reaches 118 dB / W / m (measurement made on model with pavilion). In order to achieve this level with equal frequency by means of a modern ordinary transducer of sensitivity judged (currently) first of all good in the field of high fidelity (88 dB / W / m), it would be necessary to feed it under an electrical power of 1000 W (remember that, the measure being logarithmic, with a deviation of 10 dB corresponds to a factor 10 in sensitivity, so that to a deviation of 30 dB corresponds to a factor 103 = 1000).
It is understood, therefore, that, in addition to its interesting performances in terms of directivity and spatial coherence, the coaxial speaker system with treble transducer with pavilion and compression chamber is considered by sound professionals for its high performance. This is the type of system that the invention aims to improve. Despite its qualities, it does, in fact, have a number of defects, among which we can mention: - a time delay of the radiation of the acute transducer over that of the main transducer; - the limits imposed to the opening of the radiation coverage angle (in other words, the directivity characteristic) by the main transducer dimensional architecture, since directivity characteristics imposed by the main transducer geometry are inherited; - the volume of the system, mainly axial, as well as its increase in mass; - the difficulties in creating a powerful magnetic circuit for the main transducer, due to the need to have a passage in the center of its core that acts as the beginning of the flag for the high-pressure transducer with a compression chamber. It is possible, in fact, to observe, on certain achievements, a defect in the concentration of the magnetic field of the main transducer circuit (this loss is due to the weakness of the magnetic flow passage section in the middle of the core thus opened, which is saturated magnetically).
In high-end professional sound systems, the delay of the treble path over the bass path can be compensated for by an active numerical type filtering (known under the English acronym DSP, Digital Signal Processing). But this compensation can only be partial, usually on the axis. On the other hand, the more conventional (and less expensive) passive filtering technologies with inductances and capacitors cannot compensate for the important delay that is measured on known coaxial systems, which can reach 250 μs. This delay, although small in appearance, has a non-negligible psycho-acoustic effect and degrades the quality of sound restitution.
It contributes, among other reasons, to the reputation of "ocw tgcnkuoq uqpoto" ow fg "bad swcnkfcfg uopota" swg sound engineers have the habit of associating with professional sound.
The invention aims to provide a contribution to the resolution of the problems mentioned above, providing improvements to the coaxial speaker systems with a compression chamber.
For this purpose, the invention proposes, according to a first embodiment, a coaxial system and speaker with at least two routes, comprising a main electrodynamic transducer for the reproduction of low and / or medium frequencies, which comprises: - a main magnetic circuit that defines a main air gap; - a mobile device comprising a membrane attached to a mobile coil immersed in the main air gap, this system also comprising a secondary electrodynamic transducer for the reproduction of high frequencies, coaxially and frontally mounted in relation to the main electrodynamic transducer and comprising: - a secondary magnetic circuit distinct from the main magnetic circuit and defining a secondary air gap; - mobile equipment comprising a diaphragm attached to a mobile coil immersed in the secondary air gap; - "wo" iwkc "fg" qpfc "mounted in the vicinity of the diaphragm and with a face located in front of and in the vicinity of it and delimiting a compression chamber, this waveguide defining a pavilion attraction in the extension of which the membrane extends of the main transducer, conically.
This system offers the following advantages, thanks to the frontal coaxial assembly of the treble transducer in relation to the bass transducer: - the temporal delay of the first in relation to the second can be minimized, in benefit of the acoustic homogeneity; - likewise, it is possible to push the limits imposed on the directivity of traditional systems characterized by the assembly that crosses from the pavilion to the center of the magnetic circuit of the bass transducer; - the axial volume of the system is equal to that of the bass transducer, and the increase in mass becomes negligible; - the passage section of the magnetic flux is less limited and it is possible to maximize the value and concentration of the magnetic field of the main transducer, as it is no longer necessary to drill the magnetic circuit of the main transducer to open a passage that constitutes a pavilion start for the transducer acute.
The secondary transducer can be mounted on a front face of a polar part of the main magnetic circuit. More precisely, the main magnetic circuit includes, for example, a rear polar part, which comprises a central core that has a front face on which the secondary transducer is mounted.
According to one embodiment, the moving coil of the main transducer comprises a support and a solenoid coiled on that support, the secondary transducer can be received in a space of the main transducer, delimited towards the rear by the front face of the polar part of the main magnetic circuit, and laterally through the cylindrical wall of the coil holder „xgn. uglc go rquk> «q eqczkcn" htoPVal ".
The assembly of the transducers is preferably carried out in such a way that the acoustic centers of the transducers are coincident or almost coincident.
According to an embodiment, the tangent to the beginning of the pavilion, at the level of the junction with the membrane, forms an angle between 30 ° and 70 ° with a plane perpendicular to the transducer axis.
On the other hand, the architecture of the secondary transducer can be vantalqucogpVg fg Vkrq "and the gpfq-guswgngVq" g has a fixed internal frame called an endo-skeleton on which the mobile equipment of the secondary transducer is mounted by means of an internal suspension to the diaphragm, the mobile equipment of the secondary transducer, preferably without external suspension to the diaphragm.
The secondary transducer can be attached to the main transducer via its endo-skeleton. This endo-skeleton comprises, for example, a platinum, fixed in the secondary magnetic circuit, and a rod solidary of the platinum and by which the transducer is fixed over the main magnetic circuit.
The waveguide of the secondary transducer comprises, for example, an outer side wall and fins that form radial inward projection from that side wall.
In addition, this side wall can be provided with external alveoli in which fins extend radially.
The invention proposes, secondly, an acoustic compartment comprising a coaxial speaker system, as described above.
Other objects and advantages of the invention will appear based on the description made below, with reference to the attached drawings, in which: - figure 1 represents a sectional view, showing a coaxial speaker system, comprising a main bass transducer, and a treble transducer with a compression chamber; figure 2 represents a sectional view of the treble transducer; figure 3 represents a top view of the treble transducer; figure 4 represents a detail view of figure 2; figure 5 represents a sectional view, showing a detail of the treble transducer; figure 6 represents a view similar to figure 5, showing a variant of realization of the acute transducer; figure 7 represents a perspective view, showing a variant of making a waveguide for a transducer, as shown in figures 2 to 5; figure 8 represents a view similar to figure 1, illustrating an embodiment variant; - figure 9 represents a perspective view showing a compartment, including a coaxial speaker system, as shown in figure 1.
Figure 1 shows a multipath coaxial speaker system 1. In the example shown, system 1 comprises two ways, but one could imagine a system with three or more ways.
System 1 is designed to cover an extended acoustic spectrum, ideally the entire audible range. It comprises a bass transducer 2, designed to reproduce a lower part of the spectrum and which fgpqokpctá "VtcPufwVqt rtkpekrcn" g wo VtcPufwVqt fg ciwfq 3, designed to reproduce an upper part of the spectrum g swg ug fgpqokpctá "Vt.
In practice, the main transducer 2 can be designed to reproduce the low and / or medium, and possibly a part of the high. For this, its diameter will preferably be between 10 and 38 cm. Although the main object of the present invention is not to define recommendations regarding the spectrum covered by the different transducers of system 1, we nevertheless need that the spectrum covered by main transducer 2 can cover the bass, that is, the range from 20 Hz to 200 Hz, or the medium, that is, the range from 200 Hz to 2 kHz, or at least a part of the low and medium (and, for example, the whole of the low and medium), and eventually a part of the high . For example, the main transducer can be designed to cover a range from 20 Hz to 1 kHz or from 20 Hz to 2 kHz, or from 20 Hz to 5 kHz.
The secondary transducer 3 is preferably designed so that its passband is at least complementary in the high end of that of the main transducer 2. Thus, it will be possible to control so that that of the secondary transducer 3 covers, in part, the middle and totality of the high , up to 20 kHz.
It is preferable that the frequency ranges in which the amplitude response of transducers 2, 3 is of constant level, overlap in part and that the sensitivity level of the treble transducer is at least equal to that of the bass transducer, in order to avoid a fall in the overall response of system 1 to certain frequencies corresponding to the high part of the spectrum of the main transducer 2 and the low part of the spectrum of the secondary transducer 3.
Highly visible in figure 1, the main transducer 2 comprises a main magnetic circuit 4 that includes an annular magnet 5, sandwiched between two polar pieces in mild steel, forming field plates, namely: a rear polar piece 6 and a piece front pole 7, fixed on two opposite faces of the magnet 5 by gluing.
The magnet 5 and the polar parts 6, 7 are symmetrical of revolution around a common axis A1, forming the general axis of the main transducer 2 and which is then called "gkzq rtkpekrd".
In the illustrated embodiment, the rear pole part 6 is monoblock. It comprises an annular bottom 8 fixed on a rear face 9 of the magnet 5, and a cylindrical central core 10, which has, in opposition to the bottom 8, a front face 11 and has a central perforation 12 that empties on both sides of the housing 6.
The polar part or faceplate 7 has an annular washer shape. It has a rear face 13, whereby it is fixed on a front face 14 of the magnet 5, and an opposite front face 15, which extends in the same plane as the front face 11 of the core 10, so that, between this perforation 16 and the core 10 that is housed there is defined an air gap 17, said main, in which a part of the magnetic field generated by the magnet 5 reigns.
The main transducer 2 comprises, on the other hand, a chassis 18 called a container, which includes a base 19 by which the container 18 is fixed on the main magnetic circuit 4 - and more precisely on the front face 15 of the front plate 7-, a crown 20 by which transducer 2 is attached to a supporting structure, and a plurality of branches 21, connecting base 19 to crown 20.
The main transducer 2 further comprises mobile equipment 22, including a membrane 23 and a mobile coil 24, comprising a solenoid 25 wound on a cylindrical support 26 integral with the membrane 23.
The membrane 23 is made of a rigid and light material, such as impregnated cellulose pulp, and has a conical or pseudo-conical shape of revolution around the main A1 axis, with curvilinear generatrix (for example, according to a circular law, exponential, or hyperbolic).
The membrane 23 is fixed on the contour of the crown 20 by means of a peripheral suspension 27 (still called edge) that can be constituted by a complementary toric piece and glued on the membrane 23. The suspension 27 can be made of elastomer (for example, rubber, natural or synthetic), polymer (honeycomb or not) or an impregnated and coated fabric or nonwoven.
At its center, the membrane 23 defines an opening 28 on the inner edge of which the support 26 is fixed by a front end by gluing. The geometric center of the opening 28 is considered, at first approximately, to be the acoustic center C1 of the main transducer 2, that is, the equivalent point source, from which the acoustic radiation of the main transducer 2 is emitted.
A hemispherical concealer 29, made of a non-acoustically emitting material, can be attached to the membrane 23 in the vicinity of the opening 28 to protect it from dust intrusion.
Solenoid 25, made of a conductive metallic wire (for example, copper or aluminum) is wound on the support 26, at a rear end of it that penetrates the main air gap 17. According to the diameter of the main transducer 2, the diameter of the solenoid 25 can be between 25 mm and more than 100 mm.
The centering, elastic control and axial orientation of the mobile equipment 22 are ensured jointly by the peripheral suspension 27 and by a central suspension 30, still called spider, generally annular, with concentric corrugations, presenting a peripheral edge 31 by which the spider 30 is fixed (by gluing) to a flange 32 of the container 18 adjacent to the base 19 and an internal shaft 33 by which the spider 30 is fixed (also by gluing) to the cylindrical support 26.
The electrical signal is supplied to solenoid 25 in a classical manner by means of two electrical conductors (not shown), connecting each of the two ends of solenoid 25 to a terminal of transducer 2, where the connection is made with a power amplifier .
As shown in figure 1, the secondary transducer 3 is housed in the main transducer 2 and is received in a central front space (that is, on the front side of the magnetic circuit 4) delimited to the rear by the front face 11 of the core 10, and laterally by the internal wall of the support 26.
The secondary transducer 3 comprises a secondary magnetic circuit 34, distinct from the main magnetic circuit 4, which includes a central annular permanent magnet 35, sandwiched between two polar pieces that form field plates, namely: a rear polar piece 36 and a front polar piece 37, fixed on two opposite faces of the magnet 35 by gluing.
The magnet 35 and the polar parts 36, 37 are symmetrical of revolution around a common axis A2 that forms the general axis of the secondary transducer 3 and which is then dominated by "gkzq ugewpfátko" o
Magnet 35 is preferably made of a rare earth-neodymium-ferro-boron alloy, which has the advantage of offering a high energy density (up to 12 times more important than that of a barium ferrite permanent magnet of equivalent size ).
As shown in figure 2, the rear polar piece 36, called the housing, is, in this case, monobloc and made of mild steel. It has a cut-out shape with a U-shaped diametrical section, and comprises a bottom 38 attached to a rear face 39 of the magnet 35, and a peripheral side wall 40 that extends axially from bottom 38. The side wall 40 ends, in a front end opposite the bottom 38, by an annular front face 41. The bottom 38 has a rear face 42 applied against the front face 11 of the core 10, in a coaxial manner, that is, in such a way that the secondary axis A2 is substantially confused with the main axis A1.
The front polar piece 37, called the core, is also made of mild steel. It is annular in shape and has a rear face 44, whereby it is fixed to a front face 45 of the magnet 35 and an opposite front face 46 that extends in the same plane as the front face 41 of the side wall 40 of the housing 36.
As shown in figure 2, the magnetic circuit 34 is extra-flat, that is, its thickness is narrow compared to its maximum diameter. On the other hand, the magnetic circuit 34 extends to the outer diameter of the transducer 3. In other words, the size of the magnetic circuit 34 is maximized in relation to the maximum diameter of the transducer 3, which increases its maintenance in power, as well as the magnetic field value, and therefore the sensitivity of the transducer 3.
The core 37 has a maximum diameter smaller than the inner diameter of the side wall 40 of the housing 36, so that between the core 37 and the side wall 40 of the housing 36 a secondary air gap 47 is defined, in which most of the field is concentrated. magnetic generated by magnet 35.
At the air gap 47, the edges of the core 37 and the housing 36 can be chamfered or, preferably, and as shown in Figure 2, rounded, in order to avoid harmful burrs.
Secondary transducer 3 further comprises mobile equipment 48, including a dome-shaped diaphragm 49 and a movable dome 50 attached to diaphragm 49.
Diaphragm 49 is manufactured in a rigid and light material, for example, in thermoplastic polymer or in a light alloy based on aluminum in magnesium or titanium. It is positioned so as to cover the magnetic circuit 34 on the side of the core 37, and in such a way that its axis of symmetry of revolution is confused with the secondary axis A2. In these conditions, the top of the diaphragm 49, located on the secondary axis A2, can be considered as the acoustic center C2 of it, that is, the equivalent point source, from which the acoustic radiation of the secondary transducer 3 is emitted.
The diaphragm 49 has a circular peripheral edge 51 slightly detached to facilitate the attachment of the moving coil 50.
The movable coil 50 comprises a metallic, circular (rectangular or rectangular) wire conductive solenoid (for example, copper or aluminum), of a preferred width of 0.3 mm, wound in a spiral to form a cylinder, which an upper end is fixed by gluing to the detached peripheral edge 51 of the diaphragm 49. The coil 50 is, in this case, without support (but could contain one).
The moving coil 50 is introduced into the secondary air gap 47. The inner diameter of the moving coil 50 is much slightly larger than the outer diameter of the core 37, so that the internal functional clearance between the moving coil 50 and the core 37 is small in front of the air gap width 47. As a variant, the functional clearances could be dimensioned in a conventional manner.
According to a preferred embodiment, the contour of at least core 37 is preferably coated with a thin layer of polymer with a low coefficient of friction, such as polytetrafluoro ethylene (PTFE or teflon) of a thickness close to the hundredth millimeter (or less) and preferably a few tens of μm (for example, approximately 20 μm).
It follows that, despite the small gap between the core 37 and the moving coil 50, on the one hand, the placement of the moving coil 50 in the air gap 47 is relatively easier and, on the other hand, that the axial movement of the moving coil is in operation 50 is not contradicted by the proximity of the nucleus 37, even in the hypothesis that these two elements would accidentally and temporarily come in contact with each other.
In practice, the moving coil 50 and the air gap 47 are preferably dimensioned so that: - the clearance between the moving coil 50 and the core 37 (covering included) is less than tenth of a millimeter, and, for example, between 0.05 and 0.1 mm. In accordance with a preferred embodiment, the internal clearance is 0.08 mm (without excluding the classic clearance dimension); - the external clearance between the moving coil 50 and the side wall 40 of the housing 36 is less than 0.2 mm, and, for example, between 0.1 mm and 0.2 mm. According to a preferred embodiment, the external clearance is 0.17 mm.
Thus, the maximum air gap width 47 for a 0.3 mm wide moving coil 50 is 0.6 mm (with an internal clearance of 0.1 mm and an external clearance of 0.2 mm). In this configuration, the occupancy rate of the moving coil 50 in the air gap 47, equal to the ratio of the sections of the moving coil 50 and the air gap 47, is close to 50%. In the preferred configuration, for an air gap width of 0.55 mm, an internal clearance of 0.08 mm and an external clearance of 0.17 mm, the occupancy rate of the moving coil 50 in air gap 47 is on the order of 55% .
These values must be compared with the occupancy rates of the prior art transducers, less than approximately 35%.
The reduced air gap width 47 results in an increase in the magnetic flux density in the air gap 47, and a subsequent increase in the sensitivity level of the transducer 3, the sensitivity varying as the square of the magnetic flux density in the air gap 47.
One can have the advantage of filling the air gap 47 of a mineral oil loaded with magnetic particles, for example, of the type sold by the company FERROTEC under the trade name Ferrofluid (deposited brand). This seal has the following advantages: - it favors the centering of the moving coil 50 in the air gap 47; - it has a dynamic lubrication function, to the benefit of the silent operation of the transducer 3; - thanks to its thermal conductivity much higher than that of R, it favors the evacuation to the magnetic circuit 34, and, in particular, to the housing 36, of the heat produced by the moving coil 50.
The secondary transducer 3 further comprises a support 52 fixed on the secondary magnetic circuit 34, and on which the mobile equipment 48 is suspended. Support 52, made of a diamagnetic and electrically insulating material, for example, a thermoplastic material, such as as polyamide or polyoxymethylene (glass loaded or not), it presents a general synthetic form of revolution around an axis confused with the secondary axis A2, with a T-shaped section.
The monobloc support 52 forms an endo-skeleton for the transducer 3, comprising an annular plate 53 applied against the front face 46 of the core 37, and a cylindrical stem 54 that extends to the rear, from the center of the platinum 53, which is housed in a complementary cylindrical location 55 opened in the magnetic circuit 34 and formed by a succession of open coaxial perforations in the housing 36, the magnet 35 and the core 37.
As shown in figure 2, the endo-skeleton 52 is rigidly fixed in the magnetic circuit 34, by means of a nut 56 screwed on a threaded part of the rod 54 and pressed against the housing 36, inside a practical lamination 57 on the face rear 42 in its center. In this way, the plate 53 is firmly placed against the front face 46 of the core 37, with no possibility of rotation. This fixation can possibly be completed by the application of a glue film between the plate 53 and the core 37.
Considering its frontal location in relation to the magnetic circuit 34, the stage 53 extends in the internal lenticular volume delimited by diagram 49. The stage 53 comprises a peripheral ring ring 58 and a central disc 59 to which the stem 54 is connected. disk 59 may have holes 60, the function of which is to maximize the volume of air under the diaphragm 49, in order to decrease the resonance frequency of the mobile equipment 48.
The rim 58 has a profile similar to a pulley and comprises a peripheral annular track 61 that flows radially towards the outside, facing a peripheral annular part 62 of the internal surface of the diaphragm 49, located near the edge 51.
The rail 61 separates the rim 58 into two front plates, forming the side walls of the rail 61, namely a rear plate 63, in support against the front face 46 of the core 37, and a front plate 64. The plates 63, 64 are connected by a cylindrical core 65 that forms the bottom of the rail 61.
The mobile equipment 48 is mounted on the endo-skeleton 52 by means of an internal suspension 66 that ensures the connection between the diaphragm 49 and the platinum 53. This suspension 66 is presented in the form of a piece of revolution made in a light material , elastic and non-acoustic emissive (you can choose a porous material for this). This material is preferably resistant to the heat prevailing in the transducer, and its elasticity is chosen so that the resonance frequency of the mobile equipment 48 is lower than the lowest frequency reproduced by transducer 3 (in the 500 Hz to 2 kHz species).
Due to the non-acoustic emissivity of the suspension 66, only the domed diaphragm 49 emits an acoustic radiation. In this way, proper modes, resonances, and more generally the parasitic acoustic irradiation of the suspension 66, which would interfere with that of the diaphragm 49 and alter the performance of the transducer 3, are avoided.
According to a preferred embodiment, fgnomknafo pq eauo "monVaigm hnwVwcpVg" g knwuVtcfq notably in figures 2, 4 and 5, the suspension 66 has a section of substantially polygonal shape and comprises an inner edge 67, that is, cylindrical of cladding around the secondary axis A2, and a substantially tapered peripheral outer edge 68.
The suspension can be carried out on a fabric made of natural fibers (for example, cotton) or synthetic (for example, polyester, polyacrylic, nylon, and, more particularly, aramids, of which Kevlar, deposited brand) or in a mixture of natural and synthetic fibers (for example, cotton-polyester), these fibers being impregnated with a thermosetting or thermoplastic resin, which gives maintenance and rigidity and elasticity to the suspension 66. But the suspension will preferably be carried out in a foam of cross-linked polymer (for example, polyester or melamine), particularly well adapted, as it has a high porosity.
By its tapered outer edge 68, the suspension 66 is fixed, by gluing, on the peripheral part 62 of the internal surface of the diaphragm 49. As a variant, in the hypothesis that the moving coil 50 would comprise a cylindrical support solidary to the diaphragm 49 and on the on which the solenoid would be mounted, the suspension 66 could be fixed, by its outer peripheral edge (which would then be cylindrical), on the internal surface of this support.
As shown in figure 2, the thickness of the suspension 66 (measured according to the secondary axis A2), although less than its free length (measured radially between the plates 63, 64 and the internal surface 62 of the diaphragm 49) is not negligible in relation to this, but it is of the same order of magnitude. More precisely, the ratio between the free length a and the thickness of the suspension 66 is preferably less than 5 (in this case, this ratio is less than 3). By minimizing the free length of the suspension 66, it is possible to stabilize the mobile equipment 48 and prevent it from oscillating (anti-sway effect).
On the side of its inner edge 67, the suspension 68 is housed in the rail 61 and is slightly compressed between the plates 63, 64, in order to avoid parallel noises, but without, however, being fixed on them. In addition, the internal diameter of the suspension 66 is greater than the internal diameter of the rail 61 (i.e., the outer diameter of the core 65 of the rim), so that an annular space 69 is opened between the suspension 66 and the core 65.
Thus, the suspension 66 is floating in relation to the rim 58 of the platinum 53, with a possibility of radial folding, the suspension 66 being able to slide in relation to the plates 63, 64. In order to favor this slip, it can be applied on the plates 63, 64 a layer of pasty lubricant, such as grease. The radial clearance defined by the annular space 69 between the suspension 66 and the core 65 (i.e., the bottom of the track 61) is preferably less than 1 mm. According to a preferred embodiment, this gap is approximately 0.5 mm. In the figures, this slack has been exaggerated for the sake of clarity.
Fg aeotfo eoo woc xctkcpVg fg oqpVcieo fkVc "p« q hnwVwcpVg ". c uwurepuão 88 run uet eoncdc po kpVetkot dcu plates 63, 64 instead of simply being lubricated. In this case, the dimensioning of the radial clearances will be of the conventional type and not reduced according to the floating assembly described above. In non-floating assembly, the mobile equipment 48 will be centered in relation to the air gap by means of a centering instrument (still called "hcnuc eateaçc" +, oaneita deuetkta hereinafter regarding xatianVe de uwupenuão 88 de Viro "uridet", terteuenVada in figure 6.
In addition, it is preferable that the part of the suspension 66 housed in the rail 61 is of a width (measured radially) greater than or equal to its thickness, in order to guarantee a mechanical support-plane connection and to minimize any harmful effect of oscillation of the suspension 66 in relation to platinum 53.
The suspension 66 thus extends internally to the diaphragm 49. The suppression of an external peripheral suspension allows to suppress the acoustic interference existing in the known transducers between the irradiation of the diaphragm and that of its suspension.
In addition, the suspension 66 does not exert any radial effort on the diaphragm 49, it does not impose its centering function in relation to the secondary magnetic circuit 34, in benefit of the simple connection of the secondary transducer 3 or the replacement of the diaphragm 49 in case of failure.
The centering of the diaphragm 49 is carried out at the level of the moving coil 50, which is adjusted with a small gap on the core 37 and is automatically centered in relation to this, since the moving coil 50, introduced in the magnetic field of the air gap 47, is placed in motion by a modulating electric current.
On the contrary, the suspension 66 ensures a command function of the mobile equipment 48 for a median resting position, adopted in the absence of axial effort exerted on the mobile coil 50 (that is, in practice, in the absence of current that runs through this ). It is in this median position that secondary transducer 3 is represented in the figures.
The suspension 66 also ensures a function of maintaining the balance of the diaphragm 49, that is, of maintaining the peripheral edge 51 of the diaphragm 49 in a plane perpendicular to the secondary axis A2, in order to avoid any oscillation or balance of the diaphragm 49 that would burden its operation.
In figure 6, a variant of embodiment fq VtcPufwVqt ugewpfátkq 5. fkVc "p« q hnwVwcpVg "swg ug is distinguished from the preferred embodiment that has just been described by the design of the suspension 66 and the shape of the skeleton endo-skeleton 52.
The suspension 66 is, in effect, of the spider type and made of a fabric made of natural fibers (for example, cotton) or synthetic (for example, polyester, polyacrylic, nylon, and, more particularly, aramids, of which Kevlar, brand deposited) or in a mixture of natural and synthetic fibers (for example, cotton-polyester), these fibers being impregnated with a thermosetting or thermoplastic resin, which, after forming by thermoforming, provides maintenance, rigidity and elasticity to the suspension 66.
The suspension comprises an annular, flat inner part 98, fixed by gluing to an upper face 99 of the platinum 53, and a peripheral part 100 that extends around the inner part 98. The peripheral part 100 extends radially freely beyond the platinum 53 and comprises ripples 101 obtainable by thermoforming.
By an outer edge 102, the suspension 66 is fixed, by gluing, on the inner surface of the diaphragm 49, in the vicinity of the peripheral edge 51 thereof. As a variant, in the event that the moving coil 50 would comprise a cylindrical support attached to the diaphragm 49 and on which the solenoid would be mounted, the suspension 66 could be fixed, by its outer edge, on the internal surface of this support.
It should be noted that the mobile equipment 48 must be perfectly centered in relation to the magnetic circuit 34, and more precisely in relation to the air gap 47, in which the mobile coil 50 is housed. For this, a centering assembly (still called a false housing) is used, in which the endo-skeleton 52 is positioned. The centering assembly comprises a perforation (with a diameter equal to that of the housing (55), in which it is inserted the stem 54 of the endo-skeleton 52. The suspension 66 is then glued to the platinum 53. Before the glue has caught, the centering assembly is secured, which ensures the centering of the mobile equipment 48 in in relation to the endo-skeleton 52. After drying the glue, the assembly comprising the mobile equipment 48 and the endo-skeleton 52 can then be assembled being perfectly centered on the magnetic circuit 34, in manufacture as in case of repair by replacement of the mobile equipment 48.
The electric current is carried to the moving coil 50 by two electrical circuits 70 that connect the ends of the moving coil 50 to two electrical terminals (not shown) for supplying the transducer 3.
As shown in figure 2, each electrical circuit 70 comprises: - a high section conductor 71, comprising an insulated copper wire processing a plastic wrap, which passes through the magnetic circuit 34, being housed in a longitudinally open groove in the endo stem 54 - skeleton 52, from which an uncovered front end 72 flows into the internal volume to the diaphragm 49, forming a protrusion of the magnetic circuit 34 at the level of one of the holes 60 of the disk; - an electrical junction element in the form, for example, of a metal eye 73 (in copper or brass) embedded in that hole 60 to which the bare end 72 of conductor 71 is electrically connected (for example, via a point welding, not shown); - a conductor 74 of smaller section, in the form of a very flexible and conveniently shaped metal braid, which extends in the internal volume of the diaphragm 49, surrounding the rim 58 and the suspension 66, in the case of the mode fg tgcnkzc> «q rtghgtkfq fkVq "monVcigm hnwVwcpVg". g fc to which an inner end 75 is electrically connected to the eye 73 (for example, by means of welding, not shown) and from which an opposite outer end is electrically connected to one end of the moving coil 50.
A single conductor 74 of smaller section is visible in figure 2, the second conductor of smaller section, diametrically opposite the first, being located in front of the cutting plane of the figure.
The arcuate shape (in U), added to the great flexibility of these conductors 74, allows it to deform without difficulty and follow the bending movements of the diaphragm 49, following the vibrations of the moving coil 50, without applying radial or axial mechanical effort, which can compromise the freedom to position the mobile equipment 48.
The secondary transducer 3 finally comprises an acoustic wave guide 76, integral with the magnetic circuit 34.
The waveguide 76 is in the form of a monoblock piece made of a material that has a high thermal conductivity, greater than 50 W.m-1.K-1, for example, in aluminum (or in an aluminum alloy).
The revolutionary waveguide 76 is fixed on the housing 36 and comprises a substantially cylindrical outer side wall 77 that extends in the extension of the side wall 40 of the housing 36. The fixation is preferably made by screwing, by means of a number of screws equal to or greater than 3. In order to maximize the thermal contact between the two parts, it is advantageous to complete this screwing with a coating of thermal conductive paste.
As shown in figures 2 and 5, the waveguide 76 has, on a peripheral rear edge, a flap 78 that comes to fit over a socket 79 in the housing 36, with a complementary profile. This results in a precise centering of the waveguide 76 in relation to the housing 36 and, more generally, in relation to the magnetic circuit 34 and the diaphragm 49. In addition, the thermal conduction between the two parts 36, 76 is improved there.
The waveguide 76 has a rear face 80 which has a substantially spherical disc shape, which extends concentric to the diaphragm 49, in front of and in the vicinity of an external face of which it partially covers.
According to a preferred embodiment illustrated in figures 1 to 5, the rear face 80 is perforated and comprises a continuous peripheral part 81 which extends in the vicinity of the rear edge of the waveguide 76, and a discontinuous central part 82 carried by a series of fins 83, forming a radial projection, from the side wall 77 inwards (i.e., it stops the A2 axis of the transducer 3). The rear face 80 is bounded internally - that is, on the diaphragm side 49 - by a petaloid edge 84.
As shown in figure 3, the fins 83 do not join on the A2 axis, but are interrupted at an internal end located at a distance from the A2 axis. At the top, the fins 83 each have a curved edge 85.
The side wall 77 of the waveguide 76 is internally bounded by a discontinuous tapered front face 86 divided over a plurality of angular sectors 87 that extend between the fins 83. This front face 86 forms a pavilion beginning, extending from the inside to the outside and from a rear edge, formed by the petaloid edge 84, constituting a track from the beginning of pavilion 86, to a front edge 88 that constitutes a circuit from the beginning of pavilion 86. The angular sectors 87 of the beginning of pavilion 86 they are parts of a cone of revolution, whose axis of symmetry is confused with the secondary axis A2, and whose generatrix is curvilinear (for example, according to a circular, exponential or hyperbolic law). The beginning of pavilion 86 ensures a continuous adaptation of acoustic impedance between the air environment delimited by channel 84 and the air environment delimited by edge 88.
According to an embodiment, the tangent to the beginning of pavilion 88 over edge 88 forms an angle between 30 and 70 ° with a plane perpendicular to the A2 axis of the secondary transducer 3. In the example illustrated in the drawings, this angle is approximately 50 °.
The fins 83, the function of which will be described later, each have two sides 89 which are externally connected to the angular sectors 87 of the beginning of pavilion 86 by means of frames 90.
In the variant shown in Figure 7, the waveguide 78 forms not a flag start, but a complete flag (for example, symmetrical of revolution around the secondary axis A2), whose track 84 is circular in contour and whose length it is such that, when the secondary transducer 3 is mounted on the main transducer 2, the edge 88 can extend as shown in figure 8, beyond the level of the peripheral suspension 27 of the membrane 23.
The waveguide 76 delimits on the diaphragm 49 two distinct and complementary zones, namely- an internal zone 91 discovered, in a petaloid form, delimited externally by the channel 84; - an outer area 92 covered, complementary to the covered area 91, delimited internally by the rail 84.
The rear face 80 of the waveguide 76 and the corresponding outer area 92 of the diaphragm 49 define between them a volume of air 93 called a compression chamber, in which the acoustic radiation of the vibrant diaphragm 49 driven by the moving coil 50, moving air gap 47 is not free, but compressed. The uncovered internal zoin 91 communicates directly with the channel 84 in front, which concentrates the acoustic radiation of the entire diaphragm 49.
The compression rate of transducer 3 is defined by the ratio of its emissive surface, corresponding to the flat surface bounded by the maximum diameter of the membrane 49 (measured on edge 51) by the surface bounded by the projection, in a plane perpendicular to the A2 axis, of the rail 84. This compression ratio is preferably greater than 1.2: 1 and, for example, approximately 1.4: 1. Higher compression ratios, for example, up to 4: 1 are considerable.
As shown in figure 1, the secondary transducer 3 is mounted on the main transducer 2, at the same time: - coaxially, that is, the main axis A1 e3 and the secondary pebble A2 are confused; - frontally, that is, the secondary transducer 3 is placed in front of the main magnetic circuit 4 (in other words, on the side of the magnetic circuit 4 where the membrane 23 extends). In practice, the secondary transducer 3 is fixed on the main magnetic circuit 4 in front of it, being received, as we have seen, in the space delimited towards the rear by the front face 11 of the core 10, and laterally by the inner wall of the cylindrical support 26 , the housing 36 of the secondary magnetic circuit 34 being placed directly or through a crosspiece against the front face 11 of the core 10. For this, the secondary transducer 3 has a maximum diameter smaller than the inner diameter of the cylindrical support 26. However, it is It is preferable to minimize the gap between the secondary transducer 3 and the support 26, in order to reduce the harmful acoustic effect produced by the open annular cavity between them. This clearance must, however, be sufficient to avoid supporting friction 26 on the secondary transducer 3. A small clearance, of a few tenths of a millimeter (for example, between 0.2 mm and 0.6 mm) is a good compromise (in figures 1 and 7, this gap was exaggerated, for the sake of clarity of the drawings).
The stem 54 of the endo-skeleton 52 is received in the perforation 12 of the core 10, and the secondary transducer 3 is rigidly fixed in the magnetic circuit 4 of the main transducer 2 by means of a nut 94 screwed on a threaded part of the stem 54 and pressed against frame 6 with eventual interposition of a washer, as shown in figure 1.
Guuc oqpVcigo. swcnkhkecfc fg "htonVal" rot qrquk> «q § rear mounting from which the transducer is mounted on the rear face of the housing (cf. for example, the Tannoy US patent 4,164,631), is made possible thanks to the particular architecture of the acute transducer 3 which is from Vkpo fkVo "eoo epfo-essweleVo".
Firstly, the location of the suspension 66 inside the dome-shaped diaphragm 49 and the realization of the suspension 66 in a non-emissive material acoustically suppresses the acoustic interference between the suspension 66 and the diaphragm 49.
Second, the fact that the suspension 66 extends inside the diaphragm 49 and not outside the diaphragm allows to increase the emissive surface to 100% of the maximum diaphragm diameter 49.
This increase in the emissive surface of the diaphragm 49 allows a substantial gain in sensitivity of the transducer 3, since this gain is proportional to the square of the emissive surface. In practice, the architecture of transducer 3 allows, with the maximum diameter of the transducer, an increase in the emissive surface, which may rise to 17%. It results from this for that value u gain in sensitivity of approximately 1.4 dB
Third, thanks to the absence of external suspension to the diaphragm, the diameter of the moving coil 50 can be increased, being made equal to the diameter of the diaphragm 49. This results in an increase in the permissible power of the moving coil 50, proportional to the increase in its diameter More precisely, a 20% increase in the diameter of the moving coil induces an equivalent gain in maintenance in power.
Four, the fixation of the mobile equipment 48 being carried out inside the diaphragm 49, via the suspension 66 and the endo-skeleton 52, the transducer 3 is released from the radial volume of a support external to the diaphragm 49. Considering the character Emissive to 100% of the diaphragm 49, the emission surface / maximum radial volume ratio is thus significantly increased (equal to the quotient of the squares of the diaphragm and transducer rays), which can rise to approximately 70%.
This reason allows the realization of a pavilion start 86 short axially, which effectively authorizes the assembly of transducer 3, axially and frontally in the low transducer 2, with tangential connection of the beginning of pavilion 86 with the membrane profile 23 of the low transducer two.
In addition, the absence of an exo-skeleton avoids the thermal confinement of the magnetic circuit 34. This aspect, combined with the direct thermal contact between the housing 36 and the waveguide 76, made of a good heat-conducting material, significantly improves the capacity thermal dissipation of transducer 3 and, therefore, its maintenance in power.
As indicated, transducer 3 is released from the radial volume of a support external to the diaphragm 49, as this support is performed by means of an endo-skeleton 52. This aspect ,. Combined with increasing the diameter of the moving coil 50, equal to that of the diaphragm 49, it allows to increase the diameter of the magnetic circuit 34, which can match the maximum diameter of the transducer 3, as shown in figure 2 and figure 6.
This results in a gain in BL product (product of the magnetic circuit in the air gap 47 by the wire length of the solenoid 50, to which the Laplace force is proportional, generating the displacements of the mobile equipment 48), hence a gain in sensitivity of the transducer (proportional squared increase in product BL). In practice, it is possible to obtain with the arqukVgVwtc fg Vkrq "eoo gpfq-guswgngVq" fq transducer 3 an increase in the BL product of approximately 40%, and, therefore, a gain in sensitivity that can rise to approximately 3 dB.
In addition to the frontal coaxial positioning of the secondary transducer 3 in relation to the main transducer 2, their respective geometries, in particular (but not only) the thickness of the magnetic circuits 4,34 and the curvature (and therefore the depth) of the membrane 23 , are preferably adapted to allow at least an approximate coincidence of the acoustic centers C1 and C2 of the transducers 2, 3, just as the time lag between the acoustic irradiations of the transducers 2, 3 is imperceptible (we speak then of temporal alignment transducers 2, 3). The system can then be considered as perfectly coherent, despite the duality of the sound sources.
It can be rationally considered that a lag of approximately Vgorqtcn h ipheriqr c 47 μs is entirely imperceptible. Concretely, this time lag is translated, along the A1 axis, by a physical lag d between the acoustic centers C1, C2 less than approximately 10 mm, due to the following conversion formula: in which Fall is the speed of sound in the air .
The good coherence of system 1 eliminates the need to introduce a time lag compensation, impossible to correct in passive filtering and whose correction in active filtering can introduce defects in temporal coherence outside the acoustic axis.
In addition, in the main embodiment, the axial positioning of the secondary transducer 3 in relation to the main transducer 2, and the geometry of the waveguide 76, are such that the membrane 23 extends in the extension of the beginning of the pavilion 86, as illustrated in figure 1. In other words, the tangent to the beginning of pavilion 86 on edge 88 is confused with the tangent to membrane 23 over its central opening 28. In this configuration, waveguide 76 and membrane 23 of main transducer 2 form together a complete pavilion for the secondary transducer 3, allowing the two transducers 2, 3 to present characteristics of homogeneous directivity.
In the variant of figure 7, the waveguide 76 forming a complete pavilion is independent of the membrane 23 of the main transducer 2. In this configuration, the directivity characteristics of the two transducers 2, 3 are different and can be optimized separately, which it is advantageous in certain applications such as scene feedback speakers.
The waveguide 76 ensures, in addition to adapting the acoustic impedance of the secondary transducer 3 between the rail 84 and edge 88, a function of dissipating the heat produced at the level of the magnetic circuit 34, thanks notably to the presence of the fins 83.
According to an optional embodiment illustrated in figure 8, the waveguide 76 acting as a radiator can comprise, in cells 96 open in the outer contour of the side wall 77 in front of each fin 83, reliefs 97 complementary formed by radial fins external elements that extend radially to the maximum diameter of transducer 3, without exceeding it.
These external fins 97 effectively contribute to the cooling of the transducer and, considering its position in the annular space between it and the internal face of the support 26 of the moving coil 24 of the main transducer 2, a space in which a pulsed air flow produced by the displacements circulates. of mobile equipment 22 of transducer 1.
In the front coaxial architecture described above, a part of the heat radiated by the solenoid 25 inwards is evacuated to the rear of the magnetic circuit 4, but a part of that heat is also communicated to the secondary transducer 3. This heat causes an exogenous heating of the secondary transducer 3, which is added to its endogenous heating produced by the Joule effect by its own moving coil 50. Even if the endogenous heating of the secondary transducer 3 is less important than that of the primary transducer 2, it is nevertheless necessary to ensure the dissipation of the heat produced in the level of the secondary transducer 3: this is the second function of the waveguide 76, thanks to: - firstly, it is made of a material whose thermal conductivity is high (that is, greater than 50 Wm-1.K-1, and even, preferably greater than 100, even 200 Wm-1.K-1); - secondly (for the main embodiment illustrated in figures 1 to 5) the presence of the fins 83 (and possibly that of the external fins 97) that increase the exchange surface with the ambient air; - thirdly, to the internal suspension 66 of the diaphragm 49 and the absence of external suspension, which have the following consequences: - on the one hand, the increase in the diameter of the moving coil 50, a heat source, and, therefore, its deviation towards the periphery of transducer 3; - on the other hand, the direct fixation of the waveguide 76 on the frame 36 (the existence of an external peripheral suspension would have triggered the interposition, between the waveguide 76 and the frame 36, of a piece in thermally insulating material that would have thermal dissipation is blocked); - fourthly, by reducing the operating clearances between the moving coil 50 and the air gap 47 of the magnetic circuit 34, resulting from the preferred mode of oqpVcigo fkVq "hnwVwcpVg" g go rctVkewnct fc hqnic gzVgma, thus reducing the thickness of the air blade annular (by insulating nature) between the moving coil 50 and the housing 36 and therefore favoring the conduction of heat from the moving coil 50 towards the waveguide 76 via housing 36.
In this way, the heat accumulated at the level of the secondary transducer 3 can be at least partially evacuated by irradiation and convexation, from the front of the system. In practice, when the system 1 is fixed by the crown 20 of its container 18 on the vertical wall of an acoustic compartment (the shaft therefore extends horizontally), the heat released from the front by the waveguide 76 heats the ambient air that has tendency to rise, thus creating an appeal for fresh air and an upward convective movement of air circulation, evacuating the calories and ensuring the cooling of the secondary transducer 3.
In the main embodiment, the tapered and rounded embodiment of each fin 83, whose faces 89, on the one hand, are angled from the base of fin 83 located on the diaphragm side (and bearing the central part 82 of the rear face 10 80 ) towards its somital edge 85, located in the front and, on the other hand, they are connected to the beginning of pavilion 86 by frames 90 of circular section, aiming to minimize the influence of fins 83 on the acoustic radiation of the diaphragm 49. The system 1 can be mounted on any type of acoustic compartment, for example, a scene return compartment 95, with an inclined front face, as illustrated by way of example in figure 9.

权利要求:
Claims (7)
[0001]
1. Coaxial loudspeaker system with at least two routes, comprising a main electrodynamic transducer (2) for the reproduction of low and / or medium frequencies, comprising: - a main magnetic circuit (4) that defines an air gap (17 ) main; - a mobile device (22) comprising a membrane (23) attached to a mobile coil (24) immersed in the main air gap (17); this system being characterized by the fact that it comprises a secondary electromagnetic transducer (3) for the reproduction of high frequencies, coaxially and frontally mounted in relation to the main electrodynamic transducer (2) and which comprises: - a separate secondary magnetic circuit (34) the main magnetic circuit (4) and defining a secondary air gap (47), said secondary magnetic circuit (34) having a symmetry of revolution in relation to the axis (A2); - a mobile device (48) comprising a diaphragm (49) attached to a mobile coil (50) immersed in the secondary air gap (47); - a waveguide (76) that forms a complete pavilion, mounted in the vicinity of the diaphragm (49), a system in which: - the waveguide (76) has a face (80) located in front of and near the diaphragm ( 49) and delimiting a compression chamber (93), said compression chamber having a compression rate defined as the ratio between the planar surface delimited by the general diameter of the diaphragm (49) in relation to the surface delimited by the projection, in a plane perpendicular to the axis (A2), of the face (80) delimiting the compression chamber (93), greater than 1.2: 1; the secondary electrodynamic transducer (3) has a fixed endo-skeleton (52) on which the mobile equipment (48) of the secondary electrodynamic transducer (3) is mounted by means of a suspension (66) internal to the diaphragm (49).
[0002]
2. Coaxial speaker system (1) according to claim 1, characterized by the fact that the moving coil (24) of the main electrodynamic transducer (2) comprises a support (26) and a solenoid (25) attached to this support (26) and the fact that the secondary transducer (3) is received in a space delimited behind by a front face (11) of a polar piece (6) of the main magnetic circuit (4), and laterally by the wall of the support (26) of moving coil (24).
[0003]
3. Coaxial speaker system (1), according to claim 1 or 2, characterized by the fact that electrodynamic transducers (2, 3) have acoustic centers (C1, C2) that are coincident or almost coincident.
[0004]
4. Coaxial speaker system (1) according to any one of claims 1 to 3, characterized by the fact that the mobile equipment (48) of the secondary electrodynamic transducer (3) is devoid of external suspension to the diaphragm (49 ).
[0005]
5. Coaxial loudspeaker system (1), according to claim 5, characterized by the fact that the secondary electrodynamic transducer (3) is fixed on the main electrodynamic transducer (2) by means of its endo-skeleton (52 ).
[0006]
6. Coaxial loudspeaker system (1) according to claim 5, characterized by the fact that the endo-skeleton (52) comprises a plate (53), fixed on the secondary magnetic circuit (34) and a rod ( 54) attached to the plate (53) and by which the secondary transducer (3) is attached to the main magnetic circuit (4).
[0007]
7. Acoustic compartment (95), characterized by the fact that it comprises a coaxial speaker system (1), as defined in any one of claims 1 to 6.

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JP2016220007A|2016-12-22|Earphone and speaker

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EP3788795A1|2021-03-10|An electroacoustic earcup for open-back headphones

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WO2017045162A1|2017-03-23|Resonant loudspeaker

同族专利:

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公开号 | 公开日

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EP2524518A1|2012-11-21|

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EP2524518B1|2016-07-13|

---

BR112012017572A2|2018-09-25|

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EP2524519B8|2019-05-22|

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CN102907115B|2015-12-09|

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US20130064414A1|2013-03-14|

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WO2011086299A1|2011-07-21|

---

CN102884809A|2013-01-16|

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FR2955444B1|2012-08-03|

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FR2955444A1|2011-07-22|

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CA2787167A1|2011-07-21|

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EP2524519B1|2019-03-06|

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US9232301B2|2016-01-05|

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WO2011086300A1|2011-07-21|

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CA2787167C|2017-10-31|

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BR112012017575A2|2016-08-16|

---

CN102907115A|2013-01-30|

---

US9084056B2|2015-07-14|

---

CA2787160C|2018-05-22|

---

CA2787160A1|2011-07-21|

---

US20130121522A1|2013-05-16|

---

BR112012017575B1|2021-01-19|

---

EP2524519A1|2012-11-21|

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CN102884809B|2015-07-22|

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法律状态:
2019-01-08| B06F| Objections, documents and/or translations needed after an examination request according art. 34 industrial property law|

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2019-09-17| B06U| Preliminary requirement: requests with searches performed by other patent offices: suspension of the patent application procedure|

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2020-08-18| B09A| Decision: intention to grant|

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2020-12-08| B16A| Patent or certificate of addition of invention granted|Free format text: PRAZO DE VALIDADE: 20 (VINTE) ANOS CONTADOS A PARTIR DE 14/01/2011, OBSERVADAS AS CONDICOES LEGAIS. |

优先权:

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申请号 | 申请日 | 专利标题

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FR1000154A|FR2955444B1|2010-01-15|2010-01-15|COAXIAL SPEAKER SYSTEM WITH COMPRESSION CHAMBER|

---

FR1000154|2010-01-15|

---

PCT/FR2011/000023|WO2011086300A1|2010-01-15|2011-01-14|Coaxial speaker system having a compression chamber with a horn|

---