Internally variable aperture vented loudspeaker.

Abstract

The present invention relates to an acoustic loading device for an electrodynamic loudspeaker, enabling the control of unwanted displacements of the sound cone, resulting in low distortion for good acoustic efficiency. According to the device, the loudspeaker (0) is mounted in a sealed enclosure (10), the assembly forming the acoustic enclosure. The loudspeaker (0) is provided with an internal flat ring (CP), positioned approximately at mid-height of the sound cone (1), forming a small variable active loading volume (CA) in the upper, unperforated portion of the basket (2F). The lower portion of the basket (2A) is perforated, allowing the passage of sound waves to the acoustic suspension volume (VA) formed by the sealed enclosure (10). The flat ring (CP) is characterized by its central opening (D), the diameter of which allows the passage and linear displacement, forward (AV) or backward (AR), of the sound cone (1), forming an internal variable-opening vent (OV).Figure for the abridged version: Fig. 1.

Description

Title of the invention: Internal variable aperture vented loudspeaker.

[0001] The present invention relates to an acoustic loading device for an electrodynamic loudspeaker (sound emitter).

[0002] In prior art, the most efficient acoustic enclosures are most often of the Bass-Reflex type, with external and internal vents, multiple volumes, external or internal horn, compression chamber... Apart from a few sealed volume electrodynamic midrange and treble speakers with horn and external compression chamber, the results obtained are mediocre, mainly concerning acoustic efficiency. The parasitic movements of the sound cone, generated by the main resonant frequency of the loudspeaker, "controlled" by a passive Bass-Reflex acoustic load, produce strong distortions on high amplitude signals, in total inconsistency with low frequencies.

[0003] The present invention provides the answer to these problems. The device according to the invention comprises an electrodynamic loudspeaker (sound emitter), mounted and fixed in a close manner to a closed box, the whole forming the acoustic enclosure. According to a primary and main characteristic, the electrodynamic loudspeaker is provided with a flat-shaped ring located inside its basket, positioned perpendicularly and symmetrically at more or less half the height of the sound cone, according to and following the optimization agreement between the central opening diameter of said flat ring, in relation to the acoustic suspension volume formed by the closed cabinet. The central opening diameter of the flat crown allows the passage of the sound cone, but above all, allows linear movements, forward or backward, of said sound cone. The linear displacements of the sound cone, forward or backward, produced by the electrical energy of the loudspeaker's motor magnet, relative to the central opening of the flat ring, form a variable opening, characteristic of a vent with an internal variable opening, with a variable active load and with an acoustic suspension volume formed by the closed cabinet, whose operation is based on a mechanical, or more precisely electromechanical, process. The centrally opening crown forms two distinct parts in the speaker basket: an upper part without perforations, and a lower part with perforations. The upper part of the non-perforated bowl forms a small volume of variable active load on the upper part of the sound cone, and on part of the external peripheral suspension of said sound cone, these parts being the most sensitive to the formation of resonances. The lower part of the perforated bowl allows the passage of sound waves from the internal variable opening vent and the lower part of the sound cone, towards the closed cabinet whose volume forms an acoustic suspension, very favorable to the control of linear movements, forward or backward, of the sound cone. The flat crown is an integral part of the speaker basket, being molded (aluminum alloy basket) or stamped (steel basket) during the manufacture of the speaker. ([Fig.1]). According to a different embodiment, the flat central opening crown is of a different shape; the crown is conical in shape, forming a truncated cone, giving its shape and structure to the internal variable opening vent, replacing the unperforated upper part of the speaker basket. The large diameter of the conical ring is identical to that of the speaker basket's ring, this ring supporting the external peripheral suspension of the sound cone on its front face. The internal junction between the two forms the upper, unperforated part of the basket, creating the small variable active chamber. The small diameter of the conical crown forms the central opening diameter of the internal variable opening vent, positioned perpendicularly and symmetrically at more or less half the height of the sound cone, allowing the passage and linear forward or backward movements of the sound cone. The perforated part of the bowl allows sound waves to pass into the acoustic suspension volume formed by the closed box. The conical ring is an integral part of the speaker basket ([Fig. 2]). The internal variable-opening vent forms, according to the linear forward or backward movements of the sound cone: - Forward displacement: A large internal variable vent opening area and a "large" variable active charge volume. - Rear displacement: A small internal variable vent opening area, and a small variable active charge volume. - The equilibrium position (the one in which the sound cone is maintained by its external and internal suspensions without electrical signals) determines the average opening area of ​​the internal variable opening vent, and the average volume of the variable active load. ([Fig.3]). The diameter of the central opening of the flat or conical crown, forming the internal variable opening vent, is determined in relation to the theoretical calculation basis for a Bass-Reflex vented enclosure. This theory indicates a diameter equal to: 2 / 3 maximum to 1 / 7 minimum of the active area (Sd) of the sound cone, according to and following the optimization agreement with the load volume of the open box with external vent. The values ​​retained, with reference to this theoretical basis, are according to and following the optimization agreement with the acoustic suspension volume of the enclosed box: The central opening diameter of the flat or conical crown is between 1 / 2 and 1 / 3 of the active area (Sd) of the sound cone, regardless of the diameter of the loudspeaker used, and regardless of the loudspeaker register: Bass, Low-Midrange, Midrange, Midrange-High. - Aperture (D) = 2 / 3 of Sd = The upper part of the sound cone, the source of resonances, is not entirely loaded by the variable active load volume. (Insufficient load). - Opening (D) = 1 / 2 to 1 / 3 of Sd = Reference diameter. Perfect match according to and following the optimization match with the acoustic suspension volume of the closed cabinet. - Aperture (D) = 1 / 4 of Sd = Limit diameter, minimum acceptable. - Opening (D) = 1 / 5 to 1 / 7 of Sd = The upper and lower parts of the sound cone are almost loaded by the variable active load volume, greatly reducing the ratio with the acoustic suspension volume of the closed cabinet, causing a significant loss of sound power, and therefore of acoustic efficiency. The volume of the sealed enclosure forming the acoustic chamber is defined using the theoretical calculation basis for a bass-reflex ported enclosure, and not that for a sealed enclosure. This theory predetermines the low-pass cutoff frequency at -3 dB, according to the characteristics of the loudspeaker used, with respect to a Q factor (S) very well suited to the device of the invention presented. The flat or conical ring is an integral part of the speaker basket, but it can also be made of a different material. This material must be solid and rigid, of sufficient thickness, and must not generate unwanted resonances: rigid plastic, compressed cardboard, fiberglass, carbon fiber, etc. The resulting ring is attached and fixed tightly to the aforementioned location on the speaker basket, forming the solid and vented sections of the internally vented speaker with variable aperture. Depending on the compliance of the loudspeaker used, the optimization of the variable active load volume is determined by using a flat ring with a larger volume. or a conical ring with a smaller volume, the latter producing a larger variable active charge.

[0004] The accompanying drawings illustrate the device according to the invention. ([Fig.l]) represents in cross-section, according to a primary and principal characteristic, the device according to the invention with a flat-shaped internal ring (CP). ([Fig.2]) represents in cross-section, a variant of the device with a crown of different shape; the crown is conical (CC) forming a truncated cone, replacing part (2F) of the loudspeaker bowl (2) (0). (CC = 2F). The closed box (10) is not shown. ([Fig.3]) represents a simplified schematic drawing of the electromechanical operation produced by the linear forward (AV) or backward (AR) displacements of the sound cone (1), with respect to the central opening diameter (D) of the internal flat ring (CP), showing the variations of the internal variable opening (OV), (OV+) and (OV-), and the variations of the volume of the internal variable active load (CA), (CA+) and (CA-). (A) = equilibrium position of the sound cone (1).

[0005] According to one embodiment, the closed box (10) can be of various shapes, such as cubic, parallelepiped, cylindrical, spherical. The structure of the enclosed box (10) can be made of wood, particleboard, glass, or any solid and rigid material of suitable density and thickness, without generating unwanted resonances, assembled in a manner known per se. The interior of the enclosed box (10) is provided with very little (or no) sound-absorbing treatment such as: fiberglass, acoustic foam, felt, etc. The position of the flat (CP) or conical (CC) crown, relative to the half-height of the sound cone (1), is determined by the maximum linear excursion capacity (Xmax) of the voice coil (7), defined by its winding height (h), relative to the air gap height (He) of the motor magnet (6), relative to the central opening diameter (D) of the flat (CP) or conical (CC) crown, including the total overvoltage coefficient (Qts) of the loudspeaker (0), in order to avoid collisions between the sound cone (1) and the central opening (D) forming the internal variable opening vent (OV). According to this embodiment and with reference to [Fig. 1], the device comprises an electrodynamic loudspeaker (0) with a driving magnet (6); the ring (3) of the loudspeaker basket (2) (0) is fixed and closes the front opening (9) provided for this purpose, of the closed enclosure (10) whose acoustic volume (VA) forms an acoustic suspension, very favorable to the control of the linear displacements (AV) or (AR) of the sound cone (D- The moving assembly consists of the external (4) and internal (8) suspensions, an exponential sound cone (1), a dust cap (5), and a voice coil (7). Note: An exponential sound cone (1), due to its flared shape, provides greater variations in surface area and volume, compared to an internal variable aperture vent (OV), than a conical sound cone (1) (better impulse response). A flat ring (CP), (bonded tightly for an applied ring), forms two distinct parts, (2F) and (2A), inside the loudspeaker basket (2) (0), at approximately half the height of the sound cone (1), according to the optimization tuning of the acoustic suspension volume (VA) formed by the sealed enclosure (10). The upper part (2F), which is not perforated, forms a small volume of variable active charge (CA). The lower part (2A), which is openwork, allows the passage of sound waves towards the acoustic suspension volume (VA) formed by the closed box (10). The diameter of the central opening (D) of the flat crown (CP) allows the passage and linear forward (AV) or backward (AR) movements of the sound cone (1), forming the internal variable opening vent (OV). The acoustic operation of the present invention is similar to that of a Bass-Reflex vent speaker, and therefore incorporates some of the basic parameters of the latter, the invention presented being only different and representing only that of an active Bass-Reflex speaker, with internal variable opening vent (OV), variable active load (CA) and acoustic suspension volume (VA) formed by the closed cabinet (10). The variable active load (CA) can be compared to an internal compression chamber, a sound cone depending on the composition of its membrane (cellulose pulp, glass fiber, polypropylene, carbon...) being more or less "acoustically" transparent. Depending on the variations and oppositions of acoustic pressure produced by the loudspeaker (0), in relation to the acoustic suspension (VA) formed by the closed cabinet (10), the variable active load (CA), depending on the power of the impulses of the sound cone (1), produces a variable acoustic damping providing a direct reinforcement of the acoustic power at the very level of the sound cone (1). Controlling the parasitic movements of the sound cone (1) makes it possible to reduce the electric induction current of the loudspeaker (0), this induced electric current opposing the electric current which powers the said loudspeaker (0). It also allows for a very linear response curve, limiting the use of electronic filters (low-pass and high-pass) which are very detrimental to sound reproduction.

Claims

Demands

1. 1 - Acoustic loading device for an electrodynamic loudspeaker, mounted and fixed in a close fit to a closed enclosure, the assembly forming the acoustic enclosure, characterized in that the electrodynamic loudspeaker (0) is provided with a centrally opening ring (D), either flat (CP) or conical (CC), positioned inside the basket (2) of the loudspeaker (0). The diameter of the central opening (D), the flat ring (CP), or the conical ring (CC) allows the passage of the sound cone (1) of the loudspeaker (0), but above all allows the linear forward (AV) or backward (AR) movement of said sound cone (1). The linear displacements of the sound cone (1), forward (AV) or backward (AR), produced by the electrical energy of the motor magnet (6) of the loudspeaker (0), relative to the central opening (D) of the flat ring (CP) or the conical ring (CC), form a variable opening characteristic of a vent with internal variable opening (OV), variable active load (CA) and acoustic suspension volume (VA) formed by the closed cabinet (10), whose operation is based on a mechanical, or more precisely electromechanical, process. The internal variable opening vent (OV) shapes the sound cone (D) according to linear displacements, forward (AV) or backward (AR): Forward displacement (AV): a large internal variable vent opening area (OV+) and a "large" variable active charge volume (CA+). Rear displacement (AR): A small internal variable vent opening area (OV-) and a small variable active charge volume (CA-). The equilibrium position (A), in which the sound cone (1) is maintained by its external (4) and internal (8) suspensions without electrical signals, determines the average opening area of ​​the internal variable opening vent (OV), and the average volume of the variable active load (CA). Flat crown (CP): The flat-shaped crown (CP) with a central opening (D) forms two distinct parts in the bowl (2) of the loudspeaker (0): A non-perforated upper part (2F), and a perforated lower part (2A). The upper, unperforated section (2F) forms a small variable active load (CA) volume on the upper part of the sound cone (1) and on part of the external peripheral suspension (4) of said sound cone (1), these parts being the most sensitive to resonance formation. The lower, perforated section (2A) allows the passage of sound waves from the internal variable aperture vent (OV) and the lower part of the sound cone (1) to the cabinet. closed (10) whose volume forms an acoustic suspension (VA), very favorable to the control of linear displacements, forward (AV) or backward (AR), of the sound cone (1). Conical crown (CC): The conical crown (CC) with central opening (D) forms a truncated cone, giving its shape and structure to the internal variable opening vent (OV), replacing the unperforated upper part (2F) of the speaker basket (2) (0). (CC = 2F). The large diameter of the conical ring (CC) is identical to that of the ring (3) of the loudspeaker bowl (2) (0), the said ring (3) supporting on its front face the external peripheral suspension (4) of the sound cone (1). The internal junction between the two forms the upper part of the non-perforated bowl (2F) forming the small volume of variable active charge (CA). The small diameter of the conical crown (CC) forms the central opening diameter (D) of the internal variable opening vent (OV), allowing the passage and linear movements, forward (AV) or backward (AR), of the sound cone (1). The openwork part of the bowl (2A) allows the passage of sound waves to the acoustic suspension volume (VA) formed by the closed box (10). Depending on the compliance of the loudspeaker (0) used, the optimization of the volume of the variable active load (CA) is determined by the use of a center opening (D) ring of flat shape (CP) with a higher volume, or a conical shape (CC) ring with a lower volume, the latter producing a larger variable active load (CA).

2. - Acoustic loading device for electrodynamic loudspeaker according to claim 1, characterized in that the central opening diameter (D) forming the internal variable opening vent (OV) of the flat-shaped ring (CP) or the conical-shaped ring (CC), as well as the acoustic suspension volume (VA) of the closed cabinet (10), are determined with respect to the theoretical acoustic loading basis for a Bass-Reflex vented speaker. This theory indicates a diameter equal to: 2 / 3 maximum to 1 / 7 minimum of the active surface Sd of the sound cone, according to and following the optimization agreement with the load volume of the open box with external vent. With reference to this theoretical basis, the central opening diameter (D) of the flat (CP) or conical (CC) shaped crown is between 1 / 2 and 1 / 3 of the active surface Sd of the sound cone (1), positioned perpendicularly and symmetrically at more or less the mid-height of the sound cone (1), according to and following the optimization agreement with the acoustic suspension volume (VA) of the closed cabinet (10), the acoustic suspension volume (VA) of the closed cabinet (10) being defined using the theoretical basis for calculating acoustic load for a Bass-Reflex vented speaker, and not that for a Closed speaker. This theoretical basis predetermines the low cutoff frequency at -3 DB according to the characteristics of the loudspeaker (0) used, relative to a Q factor S. Parameters defined regardless of the diameter, or the register of the speaker (0): Bass, Low-Mid, Mid, Mid-High. Aperture (D) = 2 / 3 of Sd = The upper part of the sound cone (1), the source of resonances, is not fully loaded by the variable active load volume (CA). Insufficient load. Opening (D) = 1 / 2 to 1 / 3 of Sd = Reference diameter (D). Perfect match according to and following the optimization match with the acoustic suspension volume (VA) of the closed box (10). Aperture (D) = 1 / 4 of Sd = Limit diameter (D), minimum acceptable. Aperture (D) = 1 / 5 to 1 / 7 of Sd = The upper and lower parts of the sound cone (1) are almost entirely filled by the variable active load volume (CA), significantly attenuating the ratio with the acoustic suspension volume (VA) of the closed enclosure (10), causing

3. a significant loss of sound power, and therefore of acoustic efficiency. - Acoustic loading device for electrodynamic loudspeaker according to claim 1, characterized in that the centrally opening ring (D), of flat shape (CP) or of conical shape (CC), is an integral part of the basket (2) of the loudspeaker (0), being molded, basket in aluminium alloy, or stamped, basket in steel, during the manufacture of the loudspeaker (0), but can also be made of a different material than that of the basket (2) of the loudspeaker (0). This material must be solid and rigid, of a suitable thickness that does not generate unwanted resonances: rigid plastic, compressed cardboard, fiberglass, carbon fiber... The centrally opening ring (D), of flat shape (CP) or of conical shape (CC), thus formed, is attached and fixed in a contiguous manner at the aforementioned location, forming the non-perforated (2F) and perforated (2A) parts of the bowl (2) of the loudspeaker (0) with internal variable opening vent (OV).

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