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
  • H04R1/20—Arrangements for obtaining desired frequency or directional characteristics
  • H04R1/22—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired frequency characteristic only 
  • H04R1/28—Transducer mountings or enclosures modified by provision of mechanical or acoustic impedances, e.g. resonator, damping means
  • H04R1/2807—Enclosures comprising vibrating or resonating arrangements
  • H04R1/2811—Enclosures comprising vibrating or resonating arrangements for loudspeaker transducers
• • 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
  • H04R1/02—Casings; Cabinets ; Supports therefor; Mountings therein
• • 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
  • H04R1/42—Combinations of transducers with fluid-pressure or other non-electrical amplifying means
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; ELECTRIC HEARING AIDS; PUBLIC ADDRESS SYSTEMS
  • H04R11/00—Transducers of moving-armature or moving-core type
  • H04R11/02—Loudspeakers
• • 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
• • 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
  • H04R7/26—Damping by means acting directly on free portion of diaphragm or cone
• • 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
  • H04R9/06—Loudspeakers
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; ELECTRIC HEARING AIDS; PUBLIC ADDRESS SYSTEMS
  • H04R2400/00—Loudspeakers
  • H04R2400/11—Aspects regarding the frame of loudspeaker transducers

Definitions

• the present invention comprises an enclosed acoustic enclosure of the type comprising a box and a loudspeaker comprising a membrane movable relative to the box, the box and the membrane delimiting an essentially closed chamber; the loudspeaker comprising an electrically controlled motor for actuating the diaphragm movable relative to the box, the enclosure further comprising an axial biasing mechanism for the diaphragm away from its median position of rest against of the pressure force exerted by the gas contained in the box on the membrane.
• the sound produced by a loudspeaker is obtained by the displacement of a mobile membrane.
• This membrane has its own resonant frequency linked to its mass and the stiffness of its suspensions which give it mobility.
• the force necessary for the displacement of the oscillatory acceleration membrane of constant amplitude is almost constant.
• the force necessary for the displacement of the membrane with oscillatory acceleration of constant amplitude increases strongly as the frequency of the oscillatory movements decreases due to the preponderant part of the stiffness of the suspensions. relative to mass.
• the speakers' designers sought to obtain a frequency of mechanical resonance of the membrane of the loudspeaker, with its suspensions, the smallest possible because this resonant frequency fixes the frequency of low use of the loudspeaker.
• the acoustic performance of a loudspeaker in the open air is reduced due to the acoustic short circuit linked to the reciprocal cancellation of the "front" and "rear” waves produced by the diaphragm of the speaker.
• the speakers are most often placed in boxes so that only a single wave produced by the membrane, for example the front wave produced by the front of the membrane, is diffused.
• the opposite wave is confined within the enclosure.
• the frequency of mechanical resonance of the membrane increases as the internal volume of the box decreases. This is due to the compression / decompression of the air inside the box during the oscillatory movements of the membrane. Indeed, the compression / decompression of the air behaves like a non-linear spring whose stiffness depends on the volume of the box and the amplitude of the displacement of the membrane. Due to this increase in the resonant frequency of the speaker due to the decrease in volume of the box in which it is placed, speaker manufacturers are forced to use large speakers in order to obtain sound reproduction at low frequencies at high sound volumes because the displacement of the membrane will be as high as the frequency of the sound to be reproduced will be low.
• document US 2,810,021 describes a loudspeaker in which the membrane is linked to a rod axially stressed by helical springs arranged radially and connected to the axial rod by an elastically deformable blade in the form of a cup.
• the object of the invention is to provide an acoustic enclosure the production of the anti-spring mechanism of which is facilitated, and the value of the force applied by this mechanism being well controlled regardless of the position of the membrane.
• the subject of the invention is an acoustic enclosure of the aforementioned type, characterized in that the mechanism comprises a cam movable relative to the box along an axis of displacement of the cam under the action of displacement of the membrane and to at least one cam follower biased transversely to the cam by at least one spring and bearing on the cam, the cam having at least one cam surface capable of converting the transverse force of the or each spring into an axial force on the cam whose the intensity varies according to the position of the cam relative to the box.
• the acoustic enclosure includes one or more of the following characteristics: -
• the cam is linked to the speaker membrane by a rod extending along the axis of movement of the membrane;
• the cam is connected to a movable wall relative to the box, the movable wall defining with the box a substantially closed rear chamber and a substantially closed front chamber partially delimited by the diaphragm of the loudspeaker;
• the cam comprises at least two cam surfaces distributed angularly around the axis (of displacement of the cam and the axial biasing mechanism of the membrane comprises for each cam surface a cam followers biased towards the axis of displacement of the cam and the cam being sandwiched between the cam followers;
• the or each cam follower comprises a rotary element suitable for rolling on the cam
• each cam follower is carried by a pre-stressed elastic arm extending in a plane transverse to the axis;
• the cam has a range whose distance to the axis of movement of the cam 54 is locally constant along the axis of movement of the cam, this range being in contact with the or each cam follower when the membrane is in position rest so that no force is applied by the cam to the diaphragm by the cam in this diaphragm rest position;
• the cam has on an inclined range relative to the axis of movement of the cam.
• the inclination of the cam surface along the inclined range is gradually increasing along the axis of movement of the cam away from the zone of contact with the cam follower when the diaphragm is in the rest position so that the cam imposes an increasing intensity force on the membrane as the membrane moves away from its rest position.
• Figure 1 is a longitudinal section view of an enclosure according to a first embodiment of the invention
• Figure 2 is a partial sectional view of the cam and the roller of the anti-spring mechanism of the enclosure of Figure 1;
• Figure 3 is a view identical to that of Figure 1 of an alternative embodiment of an enclosure according to the invention.
• FIG. 1 is a closed enclosure. It comprises a box 12 delimiting a chamber 14 essentially closed separated from the external environment.
• the box 12 comprises rigid and impermeable walls connected to each other.
• a calibrated decompression vent 16 is provided through a wall to allow a pressure balance between the interior and the exterior of the enclosure during slow variations in atmospheric pressure. This decompression vent 16 is small enough to avoid the circulation of air from and to the chamber 14 during operation of the enclosure and in particular during movements of the speaker membrane.
• the enclosure comprises a loudspeaker 20 comprising a membrane 22 movable through a hole in the box.
• the membrane 22 locally delimits the chamber 14 and seals it.
• the membrane 12 is connected to the side walls of the box by a deformable waterproof seal 24.
• the loudspeaker comprises a motor 30 with electric actuation for actuating the membrane 22 for its displacement along an axis X-X.
• the motor essentially comprises an electromagnet, having a carcass 32 secured to the casing 12 by link arms 34 and a coil 36 carried by a movable assembly 38 at the end of which the membrane 22 is carried.
• the coil 36 is connected, as known per se to terminals 39 for connecting the acoustic enclosure to an amplifier.
• the moving element 38 is guided relative to the box 12 for movement along the axis X-X by an elastic joint formed by an elastic and breathable corrugated textile plate 41 known as a spider.
• This textile structure delimits air circulation passages making it possible to balance the pressures on both sides of the spider.
• the enclosure 10 includes an anti-spring mechanism 50 acting on the membrane 22 and capable of compensating for the effect of the variations in air pressure in the chamber 14 during movements of the membrane 22.
• the anti-spring mechanism 50 is an elastic mechanism for axially biasing the membrane 22 away from its median position of rest against the pressure force exerted by the air contained in the box on the membrane, that is to say in the direction of movement of the membrane.
• the mechanism 50 comprises a rod 52, extending along the axis XX, connected, at one end, to the mobile assembly 38 carrying the membrane 22 and, at its other end, to a cam 54 movable relative to the box 12.
• the rod 52 is thus driven by the movable assembly 38.
• the rod 52 passes axially through the actuator motor 30 of the loudspeaker.
• the cam 54 is generally of X-X axis revolution. It has a continuous cam surface of revolution forming in a plane passing through the axis X-X two diametrically opposed cam surfaces 56A, 56B. These cam surfaces are axisymmetric with respect to the X-X axis.
• the cam 54 is clamped between two cam followers 58A, 58B biased transversely to the axis X-X by springs 60A, 60B holding the cam followers in contact with the cam surfaces 56A, 56B.
• the cam followers 58A, 58B each advantageously comprise a rotary element 62A, 62B such as a roller suitable for rolling along the length of the cam surfaces 56A, 56B.
• the axis of rotation of the rollers extends perpendicular to the axis X-X.
• the rollers 62A, 62B have a diabolo shape, with a concave surface complementary to the cylindrical surface of the cam 54.
• the springs 60A, 60B extend transversely to the cam surfaces. They are coaxial from axis Y-Y intersecting to axis X-X. These springs, kept constantly compressed and bear at one end on the box 12 and at their other end on the axis of the rotary rollers 62A, 62B forming the cam followers.
• An additional spider 70, formed between the cam 54 and the actuation motor 32 ensures the axial guidance of the rod 52 and of the cam 54 to ensure a displacement of the latter along the axis X.X.
• the spider 70 is permeable to gas.
• the cam surfaces 56A, 56B have in the middle part, along the length of the axis XX and in section along the path of travel of the rollers, a range 72 whose distance from the axis XX of movement of the cam is locally constant along the axis X- X of displacement of the cam.
• This range 72 extends over a few tenths of a millimeter along the X-X axis.
• This median range 72 is positioned on the cam so that each roller presses on this median range when the membrane 22 is in the rest position, that is to say in a median position between the two extreme positions which can be occupied under the motor action 30.
• the cam surfaces 56A, 56B have areas 74 inclined relative to the axis XX.
• the inclination of these ranges increases by deviating along the axis XX on either side of this median range so that when the cam followers deviate from the median zone, the angle between the axis XX and the normal at the point of contact of the roller on the cam surface increases so that the force applied to the diaphragm increases.
• the distance between the axis X-X and a point on the cam surface decreases while deviating from the median range 72.
• the cam surfaces converge away from the median zone.
• the speaker illustrated in Figure 1 operates as follows.
• the membrane 22 moves as known per se.
• the cam 54 driven by the diaphragm, moves axially relative to the cam followers 58A, 58B.
• the cam followers then exert a force directed along the Y-Y axis toward the X-X axis on the cam surfaces 56A, 56B.
• These cam surfaces being inclined and maintained along the axis Y-Y between the two rollers, the cam surface is subjected to an axial force, which is applied to the membrane 22 through the rod 52.
• the cam 54 is moved away from the membrane 22. Under the action of the springs 60A, 60B acting at the through cam followers 62A, 62B, the cam 54 is biased in its direction of movement.
• the overpressure in the enclosure 14 acts on the membrane 22 to take the membrane 22 out of the box 12.
• the cam 54 produces a return force of the membrane 22 inside the box.
• the shape of the cam 54 is adapted so that the sum of the two forces produced by the cam and that resulting from the overpressure in the chamber 14 vanishes practically at any point of the cam or is equal to a desired value in all point of the cam.
• the shape of the cam surface makes it possible to transform part of a force F Rz exerted by the springs 60A and 60B along the axis YY into a force F Rx along the axis XX.
• the membrane 22 undergoes, during its displacement, a force F Rx , by means of the rod 52, along the axis XX in the same direction as that of the displacement .
• the amplitude of this force depends on the angle formed by the surface of the cam 54 with the axis XX at the point of contact of the rollers 62A, 62B.
• This force is of the form:
• the stiffness K R (x) is negative because it produces a force in the same direction as the displacement of the membrane.
• the shape of the cam 52 is chosen so that whatever the position x of the membrane, the sum of the stiffnesses K m (x) + K air (x) + K R (x) is close to the desired value K min .
• F AR the resonant frequency of the moving mechanical system
• M is the mass of the moving element 38, the winding 36, the membrane 22 and in part the seals 24 and 41;
• M AR is the moving mass of the rod 52, the cam 54 is partly the seal 70.
• the force F T is opposed to the movement of the Force moving part to the right with positive movement of the moving part to the left.
• Profile 4 of the cam is given by the function expressing y BC as a function of x BC .
• K min ⁇ K m (x) + K air (x) makes it possible to choose the value of the mechanical resonance frequency F AR of the loudspeaker placed in a closed box.
• F AR the mechanical resonance frequency
• the value of F AR will be between 30 Hz and 50 Hz.
• the additional mass M AR provided by the anti-spring mechanism is reduced to the maximum in order to minimize the force, and therefore the current, necessary for the displacement of the membrane beyond the resonant frequency.
• FIG. 3 illustrates another embodiment of a closed acoustic enclosure according to the invention.
• the cam 54 is not connected to the movable assembly by a rod 52.
• the cam 54 is connected to a movable wall 102, separating in the box 12, the closed chamber 14 in a front chamber 104 partially delimited by the membrane 22 and the movable wall 102 and a rear chamber 106 delimited by the walls of the box 12 and by the movable wall 102.
• the movable wall 102 is a rigid and impermeable wall connected to the walls of the box 12 by a flexible gas-tight joint 108.
• the wall 102 extends perpendicular to the axis XX of movement of the cam 54.
• the same rear chamber 106 is provided for two or more of two speakers whose membranes define the same front chamber 104 separated from the rear chamber in a single wall 102.
• a calibrated decompression vent 1 14, 1 16 connects the front chamber 104 and the rear chamber 106 to the outside environment. These vents are small enough to avoid the circulation of air during the movement of the membrane 22, but are capable of ensuring pressure balancing between the exterior and the interior of the box during variations in atmospheric pressure.
• the wall 102 moves due to the vacuum or compression in the front chamber 104.
• the cam 54 is moved and produced, under the action of the cam followers 58A, 58B, a force applied to the wall 102.
• This force is contrary to the effect of the pressure acting on the same wall 102 and therefore oriented in the direction of movement of the wall 102.
• This force is transmitted to the membrane 22 via the gas trapped in the front chamber 104.
• the stiffness of the compression of the gas in the front chamber 104 is compensated by the force applied by the cam 56 of the axial biasing mechanism 50.
• the profile of the cam 54 is identical to the profile described with regard to the preceding figures.
• the cam 54 is enclosed between rollers 202A, 202B, 202C, regularly angularly distributed around the axis XX. These rollers are carried at the free end of elastic arms 204A, 204B, 204C. These elastic arms are each fixed at their other end on a rigid structure 206, itself integral with the box 14.
• the arms 204A, 204B, 204C extend perpendicular to the axis X-X in the same plane. They are offset transversely to the X-X axis.
• the rollers 202A, 202B, 202C are mounted to rotate in the extension of the axis of the arms 204A, 204B, 204C respectively, and along the axis of the arms. They are suitable for rolling along the surface of the cam 54 along the axis X-X.
• the arms 204A, 204B, 204C are prestressed so as to ensure permanent contact between the rollers 202A, 202B, 202C and the cam 54, regardless of the position of the rollers along the length of the cam 54 considered along the axis X-X.
• the presence of three rotary elements angularly distributed around the axis XX ensures satisfactory guiding of the cam 54 along the axis X- X.
• the presence of elastic pre-stressed arms deformable in bending ensures a relatively constant force rollers 202A, 202B, 202C on the cam, whatever their position and avoids blocking of the rollers.

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• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Acoustics & Sound (AREA)
• Signal Processing (AREA)
• Multimedia (AREA)
• Health & Medical Sciences (AREA)
• Otolaryngology (AREA)
• Electromagnetism (AREA)
• Audible-Bandwidth Dynamoelectric Transducers Other Than Pickups (AREA)
• Reciprocating Pumps (AREA)
• Details Of Audible-Bandwidth Transducers (AREA)

Applications Claiming Priority (2)

Publications (2)

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Family Applications (1)

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Family Cites Families (15)

• 2018
  • 2018-12-03 FR FR1872229A patent/FR3089381B1/fr not_active Expired - Fee Related
• 2019
  • 2019-12-03 WO PCT/EP2019/083498 patent/WO2020115044A1/fr not_active Ceased
  • 2019-12-03 US US17/298,795 patent/US11770648B2/en active Active
  • 2019-12-03 CN CN201980081370.3A patent/CN113196799B/zh active Active
  • 2019-12-03 EP EP19809862.6A patent/EP3892011B1/de active Active

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