Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; 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
  • H04R1/2815—Enclosures comprising vibrating or resonating arrangements of the bass reflex type
  • H04R1/2823—Vents, i.e. ports, e.g. shape thereof or tuning thereof with damping material
  • H04R1/2826—Vents, i.e. ports, e.g. shape thereof or tuning thereof with damping material for loudspeaker transducers

Definitions

• the present invention relates to an acoustic enclosure, and more particularly such an enclosure of the so-called “bass-reflex” type, in which a vent makes the interior and exterior of the enclosure communicate.
• Current "bass-reflex" enclosures are tuned by vents made in the form of cylindrical or parallelepipedal conduits, or more simply by slots made in the front wall of the enclosure.
• vents have a cylindrical or parallelepiped shape, that is to say a constant cross section, causes numerous disturbances in the flow of the aerodynamic flow in the vicinity of the inlet and the outlet of the vent.
• the subject of the invention is an acoustic enclosure of the type in which a duct communicates the interior and the exterior of the enclosure, characterized in that said duct forms an adapter having a longitudinal section in the form of convergent-divergent, connection surfaces being provided between the outer end of the convergent-divergent and the outer surface of the front wall of the enclosure on the one hand, and between the inner end of the convergent-divergent and the inner surface of this front face.
• the cross section of the adapter can in particular be circular.
• the opening section of the convergent-divergent adapter on the inside of the enclosure should preferably have a characteristic dimension R whose measurement, expressed in millimeters, is of the order of measurement in cubic decimetres of the interior volume of the enclosure.
• characteristic dimension is meant, in the case of an adapter with circular cross section, the radius of the opening section. In the case of a non-circular cross section, the characteristic dimension is that which gives the opening section the same surface as the equivalent circular section.
• the length of the convergent-divergent adapter that is to say the distance between the interior and exterior opening sections, it is preferably substantially equal to:
• the profile of the convergent-divergent adapter can be conical, exponential, hyperbolic etc., but it has been found that the best results are obtained when the longitudinal section of the adapter has, at least in its median zone, a substantially hyperbolic shape. .
• the asymptote of the convergent-divergent adapter advantageously makes with the longitudinal direction an angle between 30 ° and 50 °, and preferably of the order of 40 °.
• the acoustic enclosure according to the invention comprises, mounted on its inner wall opposite said adapter, a flow regulator having a longitudinal section converging from said wall to the adapter.
• This flow regulator can, like the adapter, have a circular cross section.
• the base of the flow regulator has a characteristic dimension substantially equal to or slightly greater than the characteristic dimension of the opening section of the convergent-divergent adapter on the interior side of the enclosure. It has been found that the opening angle of the flow regulator should preferably be between 30 ° and 40 °.
• the top of the flow regulator is at a distance from the opening of the convergent-divergent adapter between once and twice, and preferably of the order of one and a half times, the dimension characteristic of this opening.
• means may be provided for regulating the distance from the flow regulator to the opening of the convergent-divergent adapter.
• the role of the flow regulator is essentially to facilitate the flow of air from the enclosure to the convergent-divergent adapter.
• the invention makes it possible, while retaining the advantages of the conventional vent of the "bass-reflex" enclosure, to largely eliminate or attenuate its drawbacks.
• the air flow channeled by the profile of the convergent-divergent adapter and the presence of the regulator, takes place under conditions close to that of laminar flow, with a minimum of vortex effects.
• the profile of the convergent-divergent adapter allows a much more gradual adaptation of the air flow to the pressure, and limits to a large extent the formation of standing waves inside the adapter itself. As a result, the sounds in the high-mid frequency range are much clearer when listening.
• the response curve of a conventional vent reveals, in the mid and high-mid frequency ranges, resonances with a sound level sometimes close to, or even higher than that emitted by the loudspeaker, and even in the most extreme cases. favorable, this level is only 7 to 8 decibels below that of the speaker. On the contrary, the equivalent resonances for the convergent-divergent adapter are 17 or 18 decibels below the reference level. It should also be noted that the convergent-divergent adapter does not generate its own resonance.
• FIG. 1 is a schematic view in vertical section of an acoustic enclosure according to the invention
• FIG. 2 is a detailed view on a larger scale, also in vertical section, of a convergent-divergent adapter and of a flow regulator according to the invention.
• the acoustic enclosure shown in FIG. 1 is constituted in a known manner by a substantially closed volume 1 comprising a front wall 2 in which a loudspeaker is mounted 3.
• Reinforcements 4 make it possible to limit vibrations and the formation of waves stationary, and favor the flow of air flows.
• An adapter 5 is also mounted according to the invention in the front wall of the enclosure, so as to form a convergent-divergent passage 6 bringing the interior volume of the enclosure into communication with the outside.
• a flow regulator 7 is mounted on the rear wall 8 of the enclosure opposite the adapter 5.
• Means 9 are provided for adjusting the distance between the flow regulator 7 and the adapter 5. We will now describe in more detail, with reference to FIG. 2, the adapter 5 and the flow regulator 7.
• the adapter is in this case constituted by a part having a symmetry of revolution about an axis 10, made for example of molded resin and embedded in an orifice Ll formed in the front wall 2 of the enclosure.
• the profile in axial section of the adapter 5 successively comprises a flat connection surface 12 lying in the same plane as the external face 2a of the wall 2, a hyperbolic surface of revolution 13 forming a convergent-divergent whose neck is in a plane 14 parallel to the wall 2, and a conical surface 15 (or rounded as in Figure 1) whose base is located in the plane of the inner face 2b of the wall 2 and whose apex is directed inward of the enclosure.
• Connection surfaces, for example toric, 16 and 17 are provided between the surfaces 12 and 13 on the one hand, and 13 and 15 on the other hand.
• the hyperbolic surface 13 has two axes of symmetry, namely the axis Oy coincident with the axis 10 above, and the axis Ox located in the plane 14 of the neck.
• the trace of the hyperboloid of revolution 13 in the xOy plane is defined by the equation: 2 _
• the value of the angle ⁇ therefore represents the more or less rapid expansion of the convergent-divergent.
• equation (2) gives the value of b from which we deduce L by the relation (3).
• the flow regulator 7 is also of revolution around the same axis 10 as the adapter 5.
• the distance 1 between the top of the spherical cap 19 and the inlet of the convergent-divergent adapter is greater than a, the optimum for an average listening room being approximately 1.5a.
• this length 1. could possibly be provided adjustable.

Landscapes

• Health & Medical Sciences (AREA)
• Otolaryngology (AREA)
• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Acoustics & Sound (AREA)
• Signal Processing (AREA)
• Details Of Audible-Bandwidth Transducers (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=9356907

Family Applications (1)

Country Status (2)

Cited By (5)

Families Citing this family (4)

Citations (6)

Family Cites Families (1)

• 1987
  • 1987-11-18 FR FR8715935A patent/FR2623337B1/fr not_active Expired - Fee Related
• 1989
  • 1989-03-21 WO PCT/FR1989/000130 patent/WO1990011668A1/fr unknown

Patent Citations (6)

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