Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; ELECTRIC HEARING AIDS; PUBLIC ADDRESS SYSTEMS
  • H04R1/00—Details of transducers, loudspeakers or microphones
  • H04R1/10—Earpieces; Attachments therefor ; Earphones; Monophonic headphones
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; ELECTRIC HEARING AIDS; PUBLIC ADDRESS SYSTEMS
  • H04R7/00—Diaphragms for electromechanical transducers; Cones
  • H04R7/02—Diaphragms for electromechanical transducers; Cones characterised by the construction
  • H04R7/12—Non-planar diaphragms or cones
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; ELECTRIC HEARING AIDS; PUBLIC ADDRESS SYSTEMS
  • H04R9/00—Transducers of moving-coil, moving-strip, or moving-wire type
  • H04R9/02—Details
  • H04R9/04—Construction, mounting, or centering of coil
  • H04R9/045—Mounting
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; ELECTRIC HEARING AIDS; PUBLIC ADDRESS SYSTEMS
  • H04R2307/00—Details of diaphragms or cones for electromechanical transducers, their suspension or their manufacture covered by H04R7/00 or H04R31/003, not provided for in any of its subgroups
  • H04R2307/027—Diaphragms comprising metallic materials
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; ELECTRIC HEARING AIDS; PUBLIC ADDRESS SYSTEMS
  • H04R5/00—Stereophonic arrangements
  • H04R5/033—Headphones for stereophonic communication
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; ELECTRIC HEARING AIDS; PUBLIC ADDRESS SYSTEMS
  • H04R7/00—Diaphragms for electromechanical transducers; Cones
  • H04R7/16—Mounting or tensioning of diaphragms or cones
  • H04R7/18—Mounting or tensioning of diaphragms or cones at the periphery
  • H04R7/20—Securing diaphragm or cone resiliently to support by flexible material, springs, cords, or strands

Definitions

• the invention relates to the field of broadband electrodynamic transducers for headphones.
• a broadband transducer corresponds to a transducer configured to ensure, alone, the reproduction of sounds for the human ear, unlike architectures integrating several transducers, for example with a first speaker configured to generate the low frequencies and a second loudspeaker. speaker configured to generate the high frequencies.
• the invention more particularly relates to the field of high-performance sound reproduction, that is to say by limiting the degradation of the signal.
• the invention relates, more generally, to an audio headset incorporating an electrodynamic transducer.
• An electrodynamic transducer is a device converting an electrical signal into an acoustic wave.
• an electrodynamic transducer generally consists of a magnetic motor, a coil, a membrane and a suspension.
• the motor has a groove, called gap, into which penetrates the coil configured to capture the magnetic field so as to move in translation under the effect of Laplace force.
• the coil is fixed with the membrane having a shape of revolution adapted to transform the translational movement of the coil acoustic wave.
• the moving part of an electrodynamic transducer is thus composed of the coil and the membrane. This moving part is guided in displacement by a suspension arranged around the membrane.
• the moving part is characterized by at least three mechanical parameters that affect the performance of the electrodynamic transducer.
• a first parameter relates to the rigidity of the membrane.
• the more a membrane is rigid the less it is deformable, and therefore the more it ensures a role of piston for generating movements of the surrounding air masses with a kinematic faithful to the control signal.
• the more rigid a membrane is the more it allows piston operation, limiting or even eliminating the distortion phenomena.
• a moving part is its mass. Indeed, the more mobile part is light, the more it can be moved at high frequency with a satisfactory amplitude, at a constant activation energy level. In other words, the more mobile a part is light, the more it allows a significant acceleration, allowing it to faithfully reproduce the high frequencies, without generating dragging phenomenon.
• a third critical parameter of a broadband electrodynamic transducer is its resonant frequency which must be as low as possible in order to reproduce the low frequencies without attenuation.
• an electrodynamic transducer has a resonant frequency corresponding to a local maximum of impedance as a function of frequency.
• the electrodynamic transducer operates at a frequency below this resonant frequency, the transducer displacements become limited and can be saturated regardless of the frequency used.
• the electrodynamic transducer operates at a frequency above this resonance frequency, the transducer displacements decrease as the frequency increases. It is therefore sought an electrodynamic transducer whose resonant frequency is as low as possible to avoid displacement saturation of the electrodynamic transducer.
• the ideal moving part is one that has both a very high rigidity, while being extremely light and with a low resonant frequency.
• other critical parameters are also to be taken into account, such as the emitting surface, the decompression volumes and the volume of the vents.
• a headphone is subject to strong design constraints, and it is sought to use a wider membrane possible to improve the volume of air displaced by the membrane.
• the movement of air at the membrane causes a depression or compression of air under the membrane.
• the air decompression volumes of the membrane must therefore be sufficient not to slow the movement of the membrane.
• a conventional solution consists in making the diaphragm and the suspension in the same layer of polyester, for example of Mylar ®.
• the realization of the suspension and the membrane in one piece makes it possible to increase the emitting surface by using part of the suspension to generate the acoustic waves.
• the displacement of the membrane is provided by a self-supporting mounted coil or on a support fixed on the lower face of the membrane.
• the material constituting the membrane is light, the weight of the moving part is negatively impacted by the weight of the coil and the coil support, thus limiting the dynamics of the electrodynamic transducer.
• a polyester membrane also has the disadvantage of being deformed in high frequencies, that is to say above 4kHz. As a result, unwanted harmonics appear in the acoustic wave due to uncontrolled deformations of the membrane or suspension.
• a suspension polyester membrane also creates amplitude modulation during large excursions, thereby generating distortion.
• another solution proposes to use an aluminum or cellulose membrane in order to improve the rigidity of the membrane. This solution makes it possible to generate high frequency acoustic waves by limiting the distortions.
• the weight of the membrane negatively impacts the weight of the moving part and limits the dynamics of the electrodynamic transducer.
• an electrodynamic transducer for audio headphones generally has a first resonance of its impedance between 2 and 4.5 kHz. This first resonance is defined by the characteristics of the moving part and the set of decompression volumes. Without action on the architecture of the headphones, the frequencies generated by the electrodynamic transducer below this first resonance are attenuated. To remedy this problem and generate a clear signal over the entire audible frequency band, between 20 Hz and 20 kHz, it is customary to provide vents in the transducer and in the structure of the headphones. These vents form a frequency resonance lower than that of the first resonance so as to compensate the attenuation of frequencies lower than the frequency of the first resonance.
• vents are provided with paper or acoustically resistive fabrics so as to tune the phenomenon of resonance of the vents. It follows that an audio headset typically has a second resonance of its impedance, located between 50 Hz and 150 Hz, and defined by the characteristics of the moving part and those of the largest and least damped vent.
• vents to generate low frequencies by resonance causes latency in the generation of low frequencies.
• tissue or sheets of paper limits the volume of air decompression of the membrane.
• the technical problem of the invention is to provide an electrodynamic transducer having a low intrinsic resonance frequency so as to limit or eliminate the use of vents to form the low frequencies, while ensuring a good compromise between the other parameters of the transducer electrodynamics.
• the invention proposes to solve this technical problem by coupling a rigid membrane, preferably aluminum or beryllium, with a self-supporting coil on the membrane so as to remove the coil support and limit the weight of the moving part.
• the invention relates to a broadband electrodynamic transducer for a headphone, said transducer comprising:
• a magnetic motor configured to generate a magnetic field
• a membrane connected to said coil so as to convert the translational movement of said coil into an acoustic wave.
• the invention is characterized in that said transducer comprises a self-supporting coil fixed by bonding to said membrane, said membrane having a Young's modulus greater than 40 GPa and in that said suspension has a thickness of between 50 and ⁇ .
• a membrane composed of a material whose Young's modulus is greater than 40 GPa corresponds to a rigid membrane made, for example, of aluminum or beryllium.
• the invention proposes to couple the advantages of this rigid membrane with a self-supported coil by the membrane, that is to say without using a coil support.
• the mechanical strength of the coil is ensured by the single gluing of the turns together.
• the weight of the moving part is greatly diminished by the removal of the coil support.
• the invention makes it possible to obtain a low weight and a great flexibility of the suspension.
• the inventors have found that the combination of a rigid membrane with a self-supporting coil makes it possible to obtain a light mobile part capable of reproducing the high frequencies without distortion.
• the combination of this light moving part with a very flexible suspension makes it possible to obtain an electrodynamic transducer having a single very low resonance frequency, close to 40 Hz.
• a Beryllium membrane operates as a piston over the entire audible frequency band, between 20Hz and 20kHz.
• said membrane is made of a material selected from the group consisting of beryllium, magnesium and aluminum. Unlike other metallic materials with Young's modulus greater than 40 GPa, these materials offer a good compromise between rigidity and lightness so as not to degrade the acceleration factor of the electrodynamic transducer.
• said coil comprises a single conductive wire wound on itself according to the height of said electrodynamic transducer.
• This embodiment makes it possible to limit the weight of the coil, and therefore of the moving mass.
• said coil has a diameter of between 20 and 30mm. Unlike conventional coils, whose diameter is close to 10 mm, the use of a self-winding single winding coil, and therefore very light, increases the diameter of the coil and optimize its location on the membrane. Thus, the guidance of the membrane is improved, and the forces are applied to an optimal location of the membrane to shift the nodal modes to the highest frequency. In addition, this embodiment makes it possible to release a very large volume of air decompression inside the coil. According to one embodiment, said coil has a height of between 4 and 5mm.
• said electrodynamic transducer has an opening area greater than 35%.
• This opening surface corresponds to the ratio between the emitting surface of the membrane and the surface of the rear openings.
• this embodiment improves the dynamics of the electrodynamic transducer because the variations of air volume generated by the movement of the membrane are removed without constraints through the central recess and the recess at the periphery.
• said electrodynamic transducer also comprises a suspension connecting an outer edge of said membrane with a fixed support, said suspension being made of rubber.
• this embodiment allows to separate these two elements. It is therefore possible to use a suspension and a membrane more effective compared to those implemented in the prior art thus allowing the electrodynamic transducer to reach low and high frequencies with very little distortion.
• said electrodynamic transducer has a compliance greater than 40 mm / N.
• the invention relates to an open or semi-open audio headset comprising an electrodynamic transducer according to the first aspect of the invention.
• FIG. 1 is a rear perspective view of an electrodynamic transducer according to one embodiment of the invention
• FIG. 2 is a front perspective view of the transducer of FIG. 1;
• FIG. 3 is a partial sectional view of the transducer of FIG.
• FIGS. 1 to 3 are described with reference to an electrodynamic transducer 10 whose front face has a membrane 14 and whose rear face has a motor 11.
• the orientation of the front and rear faces can vary without changing the invention. .
• the engine 11 is a conventional engine and can take all known forms.
• the motor 11 has a shape of revolution extending around a central axis x of the electrodynamic transducer 10. As illustrated in FIG. 1, the motor 11 can be fixed on a fixed support 18 by means of three screw.
• the motor 11 comprises a central recess 15 so as to create an air expansion column extending from the membrane 14 to the rear of the electrodynamic transducer 10.
• this expansion column of air has a zero or almost zero acoustic impedance so as to limit the maximum braking of the membrane 14.
• a zero or almost zero acoustic impedance indicates that the acoustic transducer 10 has no papers disposed behind the membrane 14, in the axis of the motor 11.
• the motor 11 has an air gap 13 for receiving a coil 12.
• the coil 12 is fixed directly by gluing under the membrane 14 without using a coil support 12 so as to limit the weight of the moving part of the electrodynamic transducer 10
• the coil 12 is preferably made with a single conductive wire wound on itself according to the height of the electrodynamic transducer 10.
• the conductive wire may be of circular or square section.
• the conductive wire may be made of copper or type "CAW", that is to say that it is composed of an aluminum core covered with a copper coating and a protective layer.
• the heating of the conductive wire makes it possible to secure the windings of the wire together by bonding the protective layers together, thus ensuring the structure of the coil 12.
• the coil 12 is therefore particularly light.
• this embodiment makes it possible to obtain a coil with a very large diameter and height in the field of audio headsets.
• this embodiment has made it possible to obtain a coil 12 whose diameter d is between 20 and 30 mm for a height h of between 4 and 5 mm.
• the inductance of the coil 12 is between 150 and 250 ⁇ unlike the state of the art in which the inductance of the coil is generally between 400 and 500 ⁇ .
• the coil 12 may have several series of windings without changing the invention.
• the performance of the electrodynamic transducer 10 is also improved by the use of a membrane 14 having a Young's modulus greater than 40 GPa.
• the membrane 14 is made of aluminum with a Young's modulus substantially equal to 69 GPa, or in beryllium with a Young's modulus substantially equal to 240 GPa.
• the thickness of the membrane 14 is preferably between 20 and 30 ⁇ for a diameter of between 30 and 32 mm.
• the membrane 14 is particularly rigid while having a certain lightness compared to titanium or steel.
• the membrane 14 has a slightly domed front face forming a dome at the edges of which the coil 12 is fixed.
• the membrane 14 also extends radially, after the dome, by a substantially straight end portion 17 extending towards the fixed support 18.
• the moving part of the electrodynamic transducer 10 is completed by a dedicated suspension 16, preferably made of rubber.
• the suspension 16 extends in the form of a simple arc between the end portion 17 of the membrane 14 and a radial edge of the fixed support 18.
• the suspension 16 has a thickness of between 50 and 100 ⁇ .
• the suspension 16 is fixed by gluing on the end portion 17 of the membrane 14 and on the radial edge of the fixed support 18. With the aid of this suspension 16, the compliance of the electrodynamic transducer 10 is particularly improved. Indeed, the compliance of the electrodynamic transducer 10 has been measured greater than 40 nm / N.
• a rear portion of the electrodynamic transducer 10 is also open on a portion of the suspension 16 so as to limit the braking of the membrane 14. It follows that the electrodynamic transducer 10 has an opening area greater than 35%. This opening surface corresponds to the ratio between the emitting surface of the membrane 14 and the surface of the rear openings.
• the electrodynamic transducer 10 thus obtained, has spectacular performance. For example, for a membrane 14 made of aluminum, the total weight of the moving part (including the membrane, the suspension, the coil and the glue) does not exceed 160 mg. Similarly, for a membrane 14 made of beryllium, the total weight of the moving part (including the membrane, the suspension, the coil and the glue) does not exceed 125 mg. Mass measurements are performed with a scale accurate to 1/10 milligrams. Finally, two electrodynamic transducers 10 can be used to form a headset, for example an open or semi-open headphone.

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• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Acoustics & Sound (AREA)
• Signal Processing (AREA)
• Multimedia (AREA)
• Audible-Bandwidth Dynamoelectric Transducers Other Than Pickups (AREA)

Applications Claiming Priority (2)

Publications (2)

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Family Applications (1)

Country Status (5)

Families Citing this family (3)

Family Cites Families (10)

• 2016
  • 2016-06-13 FR FR1655416A patent/FR3052624B1/fr active Active
• 2017
  • 2017-06-13 EP EP17729135.8A patent/EP3469812B1/de active Active
  • 2017-06-13 US US16/307,575 patent/US10932026B2/en active Active
  • 2017-06-13 CN CN201780035866.8A patent/CN109314823B/zh active Active
  • 2017-06-13 WO PCT/EP2017/064332 patent/WO2017216126A1/fr not_active Ceased

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