Patent Publication Number: US-10313783-B2

Title: Loudspeaker enclosure with at least one loudspeaker with a convex mobile membrane exhibiting continuity of shape with an adjacent member

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a U.S. National Phase application of PCT/EP2014/071842, filed on Oct. 13, 2014, claiming the benefit of FR Application No. 13 60616, filed Oct. 30, 2013, both of which are incorporated herein by reference in their entireties. 
     The present invention relates to a loudspeaker enclosure, of the type including:
         at least one loudspeaker having a convex mobile membrane, the convex side being turned toward the outside of the enclosure, and   a member surrounding the mobile membrane and including an outer surface bounded by an inner edge situated facing the mobile membrane,       

     the mobile membrane including a peripheral edge situated opposite the inner edge of the member and forming a closed loop. 
     In order to preserve a good tone quality and spatial coherence favoring the obtainment of a wide and deep stereophonic image, a loudspeaker enclosure must have an amplitude and phase response that are as linear as possible for the span of audible frequencies, favoring the direction of the listening zone over its entire span in terms of width and height. 
     Traditional loudspeaker enclosures have a noticeable limitation in obtaining a spatially coherent sound, namely the interference phenomena between the acoustic radiation of loudspeakers making up primary acoustic sources, and the acoustic radiation of secondary acoustic sources created by diffraction phenomena. 
     The invention aims to propose a loudspeaker enclosure better limiting diffraction phenomena. 
     To that end, the invention relates to a loudspeaker enclosure of the aforementioned type, wherein the mobile membrane and the member have a shape adapted so that, over a continuous portion of the peripheral edge representing at least 25%, preferably at least 50%, still more preferably at least 90%, of the length of the peripheral edge, for any first point of the continuous portion and any second point situated on the inner edge in a location such that the distance between the first point and the second point is minimal, the mobile membrane has, at the first point, a first tangent plane, and the outer surface of the member has, at the second point, a second tangent plane, the first tangent plane and the second tangent plane being substantially coincident with one another. 
     According to specific embodiments, the acoustic enclosure includes one or more of the following features:
         the outer surface of the member is configured such that, for any third point situated on the outer surface of the member at a distance from the continuous portion of less than or equal to 1/100 th  of the perimeter of the mobile membrane, preferably less than or equal to 1/30 th , and still more preferably less than or equal to 1/10 th  of the perimeter of the mobile membrane, any planar arc belonging to the outer surface and passing through the third point has, at the third point, a curve radius greater than or equal to 1/100 th  of the perimeter of the mobile membrane, preferably greater than or equal to 1/30 th  of the perimeter of the mobile membrane, and still more preferably greater than or equal to 1/10 th  of the perimeter of the mobile membrane;   the loudspeaker enclosure is intended to be pressed against a planar surface, and the member defines a peripheral edge and has a shape adapted so that, over a continuous portion of the peripheral edge representing at least 25%, preferably at least 50%, still more preferably at least 90%, of the length of the peripheral edge, for any point of the continuous portion, the outer surface of the member has, at said point, a third tangent plane, and so that the third tangent plane and the planar surface are substantially coincident with one another;   the member is an at least partially spherical box in a spherical zone; the loudspeaker enclosure includes a plurality of loudspeakers having mobile membranes, the loudspeakers being substantially identical and installed in a wall of the box; and the mobile membranes are in the form of a solid spherical cap with the same curvature as the curvature of the spherical zone of the box, the mobile membranes substantially extending the spherical zone of the box to form, in the idle position of the mobile membranes, a substantially continuous spherical surface;   the loudspeakers have stationary parts secured together rigidly, the loudspeakers being distributed angularly around a distribution axis so as to successively form angles between them substantially equal to 360° divided by N, N being the number of loudspeakers;   the spherical zone of the box and the surface of the mobile membranes define a spherical surface with an expanse greater than the surface of revolution created by rotation of a mobile membrane of a loudspeaker over at least 180° around an axis substantially perpendicular to the distribution axis;   an annular interval separates the periphery of the mobile membrane of each loudspeaker and the box, and the width of this interval measured radially is less than 1/100 th  of the circumference of the mobile membranes;   the diameter of the circle defined by each mobile membrane is greater than half the diameter of the spherical zone of the box;   the maximum axial travel of the mobile membrane of each loudspeaker of said plurality is greater than 1/50 th  of the diameter of the spherical zone of the box;   the stationary parts of the loudspeakers of said plurality are rigidly connected to the box;   the spherical zone, in which the loudspeakers of said plurality are found, is extended by a protuberance outwardly giving the box a generally oblong shape;   said plurality of loudspeakers comprises two loudspeakers;   the loudspeaker enclosure further comprises at least one first other loudspeaker positioned through the box and oriented along an axis substantially perpendicular to the distribution axis, the first other loudspeaker including a convex membrane fitted into a sphere with the same curvature as the curvature of the spherical zone of the box and substantially extending the spherical zone of the box to form, in the idle position of the convex membrane, a substantially continuous spherical surface;   the loudspeaker enclosure further comprises a second other loudspeaker positioned at the center of the first other loudspeaker and coaxial with the first other loudspeaker;   the mobile membranes are made from metal.       

    
    
     
       The invention will be better understood upon reading the following description, provided solely as an example and done in reference to the drawings, in which: 
         FIG. 1  is an elevation side view of a loudspeaker enclosure according to the invention; 
         FIG. 2  is a front view of the enclosure shown in  FIG. 1 ; 
         FIG. 3  is a diagrammatic sectional top view of the enclosure shown in  FIGS. 1 and 2 ; 
         FIG. 4  is a detailed view of the interval separating the mobile membrane of the loudspeaker and the member surrounding the loudspeaker from the enclosure shown in  FIGS. 1 to 3 , the view being done in a direction substantially perpendicular to the mobile membrane; 
         FIG. 5  is a detailed view of the interval shown in  FIG. 4 , the view being done in a direction substantially parallel to the interval; 
         FIG. 6  is a profile view of an enclosure according to one particular embodiment of the invention; and 
         FIG. 7  is a front view of the enclosure shown in  FIG. 6 . 
     
    
    
     A loudspeaker enclosure  10  according to the invention is described in reference to  FIGS. 1 to 5 . 
     The enclosure  10  comprises at least one first loudspeaker  30 A having a first convex mobile membrane  32 A, the convex side being turned toward the outside of the enclosure, and a member  12  surrounding the first mobile membrane  32 A and including an outer surface  12 A bounded by an inner edge Γ′ situated across from the mobile membrane  32 A. 
     The member  12  is advantageously a box, as in the illustrated example, or a second loudspeaker (not shown) surrounding the first loudspeaker  30 A, or a grate (not shown) covering this second adjacent loudspeaker. 
     The first mobile membrane  32 A includes a peripheral edge Γ situated across from the member  12  and forming a closed loop. 
     As shown in  FIGS. 4 and 5 , the first mobile membrane  32 A and the member  12  have a shape adapted so that, over a continuous portion Γ″ of the peripheral edge Γ representing at least 25%, preferably at least 50%, still more preferably at least 90%, of the length of the peripheral edge Γ, for any first point M of the continuous portion Γ″ and any second point M′ situated on the inner edge Γ′ at a location such that the distance between the first point M and the second point M′ is minimal, the first mobile membrane  32 A has, at the first point M, a first tangent plane P M , and the outer surface  12 A of the member  12  has, at the second point M′, a second tangent plane P′ M . 
     The first tangent plane P M  and the second tangent plane P′ M  are substantially coincident with one another. 
     “Substantially coincident” means that the first tangent plane P M  and the second tangent plane P′ M  do not substantially differ from one another to the human eye. For example:
         on the one hand, the first point M is situated at a distance D M  from the second tangent plane P′ M , smaller than 1/100 th  of the perimeter of the first mobile membrane  32 A, preferably than 1/200 th  of the perimeter of the mobile membrane  32 A, and still more preferably than 1/400 th  of the perimeter of the mobile membrane  32 A. For example, for a mobile membrane whereof the perimeter forms a circle of 160 mm in diameter and 500 mm in perimeter, the first point M is situated at a distance P M  from the second tangent plane P′ M , smaller than 5 mm, preferably smaller than 2.5 mm, still more preferably smaller than 1.25 mm, and   on the other hand, the first tangent plane P M  and the second tangent plane P′ M  form an angle α m  between them smaller than 10°, preferably smaller than 5°.       

     The outer surface  12 A of the member  12  is configured so that, for any third point M″′ ( FIGS. 4 and 5 ) situated on the outer surface  12 A of the member  12  at a distance D M″′  from the continuous portion Γ″ smaller than or equal to 1/100 th  of the perimeter of the mobile membrane, preferably than 1/30 th  of the perimeter of the mobile membrane, and still more preferably than 1/10 th  of the perimeter of the mobile membrane, any planar arc Γ″′ belonging to the outer surface  12 A and passing through the third point M″′ has, at the third point a curve radius R M″′  greater than or equal to 1/100 th  of the perimeter of the mobile membrane, preferably greater than or equal to 1/30 th  of the perimeter of the mobile membrane, and still more preferably greater than or equal to 1/10 th  of the perimeter of the mobile membrane. 
     In the example illustrated in  FIGS. 1 to 3 , the enclosure  10  is an active loudspeaker enclosure, i.e., including a set of loudspeakers positioned in the box  12 . The enclosure  10  also includes, inside the box  12 , an amplifier  14  specific to each loudspeaker. This amplifier is connected to an excitation source, such as an audio reader. 
     The enclosure  10  outwardly has a generally oblong shape with axis X-X, more specifically with a lancet shape with a front end  16  having a spherical shape. The front end  16  outwardly forms a spherical zone  17  whereof the center O is positioned on the axis X-X. 
     The spherical zone  17  is extended toward the rear by a protuberance  18  in which the amplifier  14  is housed. 
     Over its length, the body  12  has a planar shape in the lower part to form a foot  20  making it possible to set the enclosure in a stable position on a horizontal surface. The enclosure  10  symmetrical around a plane perpendicular to the surface of the foot  20  and passing through the axis X-X. 
     In the plane of  FIG. 1 , i.e., seen from the side, the spherical zone  17  extends over an angular expanse β substantially equal to 180°, and more generally advantageously greater than 150°. 
     In the plane of  FIG. 2 , i.e., seen from the end, the spherical zone  17  extends angularly over an angle α of 270°, and more generally preferably greater than 225°. 
     The enclosure  10  includes a plurality of loudspeakers  30 A,  30 B, which are for example woofers. Each loudspeaker of said plurality respectively comprises a mobile membrane  32 A,  32 B. 
     Woofers refer to loudspeakers suitable for diffusing acoustic waves with frequencies lower than 1000 Hz, preferably lower than 500 Hz, still more preferably lower than 150 Hz. 
     The enclosure  10  for example includes two first woofers  30 A,  30 B positioned symmetrically relative to the axis X-X and emerging in the spherical space  17 . The two loudspeakers are positioned along the same axis Y-Y extending perpendicular to the axis X-X of the enclosure. The axis Y-Y is parallel to the bearing surface  20 . The axes X-X and Y-Y are secant to the point O forming the center of the spherical region  17 . 
     The loudspeakers  30 A,  30 B form an angle equal to 360° divided by two, therefore 180°, between them around a distribution axis Z-Z substantially perpendicular to the axis X-X and substantially perpendicular to the axis Y-Y. 
     These two loudspeakers have a membrane  32 A,  32 B in the form of a solid spherical cap with the same curvature as the spherical zone  17 . The spherical membrane extends the spherical zone  17  substantially continuously, when the membrane  32 A,  32 B is idle. 
     Thus, preferably, the spherical zone  17  of the box and the surface of the spherical membranes  32 A,  32 B of the two woofers  30 A,  30 B define a spherical surface with an expanse at least equal to the surface of revolution created by rotation of a spherical membrane  32 A,  32 B of a woofer  30 A,  30 B over at least 180° around an axis X-X perpendicular to the axis Y-Y of the two spherical membranes  32 A,  32 B. 
     An annular peripheral interval  34 A,  34 B separates the membrane  32 A,  32 B of the speakers from the spherical zone  17 . Preferably, the width i of this annular interval between the membrane of each woofer and the box, measured radially in the plane of the circumference of the membrane of the loudspeakers, is smaller than 1/100 th  of the perimeter of the membrane of the loudspeaker. Preferably, it is smaller than 1/200 th , and still more preferably smaller than 1/400 th . Thus, for example for a loudspeaker with a circumference of 500 mm, this width is smaller than 5 mm, preferably smaller than 2.5 mm, and still more preferably smaller than 1.25 mm. 
     Advantageously, the diameter d of the circle defined by the spherical cap forming the membrane  32 A,  32 B of each woofer is larger than half of the diameter denoted D of the spherical zone  17  of the box. Preferably, it is greater than ⅔ of this diameter D, and still more preferably greater than ¾ of this diameter ¾. 
     For example, for a diameter d of the woofer of 160 mm, the diameter D of the spherical zone is then comprised between 320 mm and 220 mm. 
     The two loudspeakers  30 A and  30 B are identical and are mounted back-to-back. Thus, the stationary parts of the two loudspeakers form chassis  42 A,  42 B that are rigidly connected to one another. Furthermore, these chassis are secured using any appropriate means to the box  12 . 
     Said plurality of loudspeakers  30 A,  30 B is advantageously positioned such that the reaction forces of the mobile membrane  32 A,  32 B on the chassis  42 A,  42 B have a zero sum. 
       FIG. 3  diagrammatically illustrates the stationary magnets  44 A,  44 B of the two woofers  30 A,  30 B. In each loudspeaker, a piston  46 A,  46 B on which a coil is arranged is mounted translatably relative to each magnet  44 A,  44 B. At its end, this piston bears the spherical membrane  32 A,  32 B. 
     Advantageously, the membrane is made from metal, in particular aluminum, magnesium, titanium. Thus, the membrane is not very deformable. It is connected to the chassis of the loudspeaker by a sealing device, for example a bellows  48 A,  48 B. According to alternatives, the membrane is made from plastic, composite material, paper, etc. 
     The two woofers  30 A,  30 B are designed such that the maximum angular travel along the axis Y-Y of the membrane of each woofer is greater than 1/50 th  of the diameter D of the spherical zone  17  of the box. Advantageously, this travel is greater than 1/20 th  of the diameter D of the spherical zone  17 , and still more preferably greater than ⅕ th  of the diameter D of the spherical zone  17 . 
     The enclosure  10  further includes a loudspeaker  50 , for example a mid-range loudspeaker, positioned along the axis X-X and emerging in the spherical zone  17 . The loudspeaker  50  has a membrane  52  forming an incomplete spherical cap open-worked at its apex. This spherical membrane  52  has a radius equal to the curve radius of the spherical zone  17  and extends in the extension of that spherical region to form a substantially continuous spherical surface when the membrane  52  is idle. 
     A mid-range loudspeaker refers to loudspeaker suitable for diffusing acoustic waves at frequencies from 300 Hz to 3 kHz, or from 150 Hz to 6 kHz. 
     Preferably, a tweeter  60  is positioned axially at the center of the loudspeaker  50 . 
     A tweeter refers to a loudspeaker suitable for diffusing acoustic waves with frequencies from 3 kHz to 20 kHz, or from 1 kHz to 40 kHz. 
     The tweeter also has a spherical membrane with a radius equal to the radius of the spherical zone  17  and fits in the enclosure of the spherical zone  17 . 
     Owing to the features of the enclosure  10  described above, the convex mobile membranes of the loudspeakers marry the shape of the box on either side of the intervals separating the mobile membranes and the box. Thus, the diffraction phenomena are greatly reduced. 
     Furthermore, one can see that with such an enclosure, the woofers placed back-to-back have identical movements of their membrane, the chassis of the two loudspeakers remaining immobile relative to the box, the reaction forces applied by the membranes on the chassis canceling each other out. 
     In reference to  FIG. 6 , a loudspeaker enclosure  110  is described representing one particular embodiment of the invention. The enclosure  100  is similar to the enclosure  10  shown in  FIGS. 1 to 5 . As with the enclosure  10 , the enclosure  100  comprises a loudspeaker  30 A having a first convex mobile membrane  32 A, the convex side being turned toward the outside of the enclosure, and a member  12  surrounding the first mobile membrane  32 A and including an outer surface  12 A. The member  12  is for example a box. 
     Only the differences with respect to the enclosure  10  shown in  FIGS. 1 to 5  will be described in detail below. 
     The enclosure  100  is pressed against a wall  110  defining a planar surface  110 A. 
     The wall  110  is for example a vertical wall, or the top of a table (not shown). 
     The member  12  comprises a radially distal peripheral portion  112  relative to the mobile membrane  32 A, and a radially proximal inner portion  114  relative to the mobile membrane  32 A. 
     The peripheral portion  112  is for example convex. The peripheral portion  112  defines a closed peripheral edge B. The peripheral portion  112  surrounds the inner portion  114 . 
     The inner portion  114  is for example concave. 
     Between the inner portion  114  and the peripheral portion  112  is an inflection zone S, which is a closed line in the illustrated example. 
     The member  12  has a shape adapted so that, over a continuous portion B′ of the peripheral edge B representing at least 25%, preferably at least 50%, still more preferably with 90%, of the length of the peripheral edge B, for any point N of the continuous portion B′, the outer surface  12 A of the member  12  has, at the point N, a third tangent plane P N . 
     The third tangent plane P N  and the planar surface  110 A are substantially coincident. 
     “Substantially coincident” means that the third tangent plane P N  and the planar surface  110 A do not substantially differ from one another to the human eye. For example:
         on the one hand, the point N is situated at a distance D N  from the third tangent plane P N  smaller than 1/100 th  of the perimeter of the first mobile membrane  32 A, preferably than 1/200 th  of the perimeter of the mobile membrane  32 A, and still more preferably than 1/400 th . For example, the point N is situated at a distance D N  from the planar surface  110 A smaller than 5 mm, preferably smaller than 3 mm, still more preferably smaller than 1 mm, and   on the other hand, the third tangent plane P N  and the planar surface  110 A form an angle α N  between them smaller than 10°, preferably smaller than 5°.       

     The enclosure  100  makes it possible to minimize the diffraction and reflection related to the presence of the wall  110  in the immediate vicinity of the enclosure.