US3768590A - Molded loudspeaker diaphragm - Google Patents

Molded loudspeaker diaphragm Download PDF

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Publication number
US3768590A
US3768590A US00183135A US3768590DA US3768590A US 3768590 A US3768590 A US 3768590A US 00183135 A US00183135 A US 00183135A US 3768590D A US3768590D A US 3768590DA US 3768590 A US3768590 A US 3768590A
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United States
Prior art keywords
flange
diaphragm
lacquer
mold
rolls
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Expired - Lifetime
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US00183135A
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English (en)
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F Yocum
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Individual
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Individual
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    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K13/00—Cones, diaphragms, or the like, for emitting or receiving sound in general
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R31/00—Apparatus or processes specially adapted for the manufacture of transducers or diaphragms therefor
    • H04R31/003—Apparatus or processes specially adapted for the manufacture of transducers or diaphragms therefor for diaphragms or their outer suspension
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; 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
    • H04R7/122—Non-planar diaphragms or cones comprising a plurality of sections or layers
    • H04R7/125—Non-planar diaphragms or cones comprising a plurality of sections or layers comprising a plurality of superposed layers in contact

Definitions

  • a loudspeaker diaphragm is formed by dipping a suitably-shaped mold into a fibrous slurry. After drying,
  • a diaphragm having a frusto-conical 181/32 R r 4 0 H 0 0 3 l k 0 l G Int.
  • Field of body and a flange arranged to be fixedly mounted. The diaphragm is then laterally compressed.
  • the flange is repetitively flexed. The flange is capable of withstanding substantial and prolonged flexing by virtue of having been compressed during the construction thereof.
  • a diaphragm including a body having a frusto-conical shape, with a flange on the larger end of the body.
  • the flange is secured to a housing, which housing also carries a driver mechanism mechanically coupled to the smaller end of the diaphragm body.
  • the resonant frequency of the diaphragm is the frequency at which the diaphragm vibrations are the greatest. In order to achieve good reproduction of low frequency tones, it is desirable to so construct the diaphragm that the resonant frequency is as low as possible.
  • the thinner diaphragm facilitates the bending action of that flange.
  • the entire diaphram is not made thinner initially, since that would cause the body to have insufficient rigidity to be self-supporting.
  • the shaving of the flange had the desired effect of reducing the resonant frequency, it also undesirably lessened the useful life of the diaphragm. In installations where the diaphram would be subjected to extensive use, or in an environment in which it was subjected to extensive jostling or the like, the shaved flange would tear, crack, or otherwise become damaged.
  • Another object is to apply a lacquer or other hardening agent to a molded loudspeaker diaphragm which has been compressed, thereby retaining the diaphram in its compressed state.
  • a loudspeaker diaphram of a compressible material comprising a body having a frusto-conical shape with a larger end and a smaller end coupled in use to a driver, a flange on the larger end and adapted to be fixedly mounted in use, the flange having been laterally compressed under a pressure of at least about lbs. per square inch, whereby said flange is capable of withstanding extensive and prolonged flexing thereof when the body is vibrated by the driver.
  • an improved method of making a loudspeaker diaphragm comprises the steps of providing a slurry including fibers in a liquid carrier, depositing the slurry on a diaphragm mold, drying the slurry to provide a member generally conforming to the shape of the mold, removing the member from the mold and compressing the member under a pressure of at least about 10 lbs. per square inch.
  • FIG. 1 is a cross-sectional view of a loudspeaker incorporating therein a loudspeaker diaphragm constructed in accordance with the features of the present invention
  • FIG. 2 is a top plan view of the diaphragm
  • FIG. 3 is a bottom plan view of the diaphragm
  • FIG. 4 is a view in vertical section on an enlarged scale taken along the line 44 of FIG. 2;
  • FIG. 5 is a view in vertical section of a mold used in making the diaphragm shown in FIGS. 1-4 and a slurry deposited on such mold;
  • FIG. 6 is a fragmentary view on an enlarged scale of the mold and slurry shown in FIG. 5, with portions broken away to expose the various layers;
  • FIG. 7 is an enlarged view in vertical section showing the diaphragm member being blown from the mold
  • FIG. 8 is a view of the diaphragm with a lacquer coating applied thereto.
  • FIG. 9 is a view of a press consisting of two die members to compress the diaphragm.
  • a loudspeaker 20 including a housing 21 which is round in outline, the housing 21 having a central portion 22 which is generally frusto-conically shaped, and a rear wall 23 disposed in a plane generally perpendicular to the axis of the central portion 22.
  • Toward the front of the central portion 22 is a front wall 24 also located in a plane normal to the axis of the central portion 22.
  • the outer end of the front wall 24 carries a forwardly-directed lip 25.
  • Mounted on the rear wall 23 is a driver mechanism 26 including a field coil case 26a, which carries therein a field coil 27 wrapped about a" pole piece 28. Associated with the pole piece 28 is the usual voice coil 29.
  • driver mechanism 26 is well-known in the art, whereby further details will not be given herein.
  • a diaphragm 40 Also carried in the housing 21 is a diaphragm 40, the details of which will be described presently.
  • the smaller end of the diaphragm 40 is attached to the voice coil 29, and the flange on the larger end of the diaphragm 40 abuts against the front wall 24.
  • a ringshaped baffle gasket 30 fits inside the lip 25 and holds the outermost portion of the flange of the diaphragm 40 against the front wall 24 of the housing 21.
  • the diaphragm 40 is constructed of a molded fibrous material, which fibers may be sulfites, sulfates, cotton, wool, kapok, combinations thereof, or other fibrous materials capable of being compressed.
  • the diaphragm 40 includes a body 41 in the shape of the frustum of'a cone. In the particular form shown, the cone is one of revolution. However, it is to be understood that other conical shapes are contemplated, such as one in which the directrix is an ellipse.
  • the smaller end of the body 41 terminates in a circular neck or apex 42 which has its axis common with the axis of the body 41.
  • a plurality of laterally spaced apart, circular ridges or ribs 43 (FIG. 3) which serve to rigidify the body 41.
  • a flange 44 which is ring-like in form and isdefined by a plane that is normal to the axis of the body 41.
  • a plurality of annular undulations or rolls 45 On the innermost portion of the flange 44 is a plurality of annular undulations or rolls 45, the innermost one of which is a continuation of the body 41.
  • the outermost portion 46 of the flange 44 is flat and is arranged to be disposed between the front wall 24 of the housing 21 and the gasket 30.
  • the voice coil 29 is mechanically coupled to the apex 42 of the diaphragm 40.
  • the voice coil 29 When the driver mechanism 26 is energized by virtue of an AC signal applied to the input conductors (now shown) of the field coil 27, the voice coil 29 will reciprocate at a frequency dependent upon the frequency of the signal.
  • The'diaphragm 40, being connected to the voice coil 29, will be moved thereby in a piston-like motion, with the rolls 45 serving as a hinge or pivot to enable the body 41 to reciprocate with respect to the outermost portion 46 of the flange 44.
  • the resonant frequency of the diaphragm 40 be low.
  • the resonant frequency of the diaphragm 40 can be reduced. In the past, such reduction in thickness was accomplished by shaving material from the flange, or in the case of a molded diaphragm depositing less material in the flange region.
  • the flexing of the rolls formed in such a flange would, after a certain periodof time, crack, tear or otherwise become damaged. 7 I I
  • the material making up the rolls 45 is compressed, as will be explained, so as greatly to lengthen the life of the dia-' phragm.
  • the diaphragm 40 has a'coating oflacquer 47 or other hardening agent applied thereto. If desired, the hardening agent may be mixed in with the slurry.
  • the lacquer 47 serves to retain the diaphragm 40 in its compressed state, to repel water and to affect the over-all frequency response, characteristic of the diaphragm 40.
  • a lacquer of one concentration was applied over the body 41 and a lacquer of another concentration was applied to the flange '44. Pres-' sure was applied to the flange 44 and to the portion of all frequency response of the diaphragm 40 can be ad- -justed.
  • FIGS. 5-9 the method of making the diaphragm 40 will be described.
  • a mold 50 which is round in outline and has a base 51 with an inlet opening 52.
  • the mold also includes a body 54 in the shape of a frustrum of a cone. At the smaller.
  • the body 54 is a head; 55, and at the larger end of the body 54 is a ring-like flange 56 which is arranged to be substantially normal to the axis of the body 54.
  • the screen 60 has the overall shape of the mold 50, that is, it has a body 61 which is in the shape of the frustrum of a cone, a head 62 at the smaller end of the body 61, and a flange 63 on the larger end of the body 61, the flange 63 having centric undulations or rolls 64 therein.
  • the mold 50 is dipped into a tank containing a slurry made up of a water carrier and fibrous materials, such as sulfites, sulfates, cotton, wool, kapok, or the like. Any wood or vegetable fibers may be used, the requisite characteristic being that the fibers be capable of compression.
  • the slurry solution is prepared by stirring and agitating a pulp and water solution to separate the fibers, one from the other. A dye is added to provide the solution with the proper color.
  • the basic'characteristics of the fibers will have an effect on the frequency response of the diaphragm. Softer fibers, such as wool, would result in a lower resonant frequency thanwould harder fibers, such as wood.
  • a vacuum pump (not shown) is connected to the opening 52, which vacuum pump is operated to create a partial vacuum within the mold 50, drawing onto the mold a-uniform thickness of the slurry.
  • the mold 50 and the slurry thereon are then withdrawnfrom the tank, with the vacuum pump continuing to operate to dry the slurry.
  • Hot air in'the immediate vicinity of the mold 50 is sucked through the opening 52 to complete the drying'of the slurry and thereby provide a partiallyformed member 70.
  • a blast of air delivered through the opening 52 and oneof the openings 57 blows the mem ber off themold 50 (see FIG. 7).
  • the mold 50- is then used to mold the next member 70. It is to be' understood that a number of techniques may be utilized in mass-producing the member 70 on'such a moldor molds. I
  • the Iower'surface (as viewed in FIG. 5) of the member 70 conforms precisely to the screen 60.
  • the flange 63 inthe screen 60 causes a similarlyshaped flange 72 to be formed in the member 70.
  • the portion of the flange 63 having the rolls 64 therein forms similarly-shaped rolls 72a in the flange 72; and the flat portion of the flange 63 causes the flange 72 also to have a flat portion.
  • the conically-shaped body 61 of the screen 60' causes the body 71 of the member 70'to have a similar shape,'and the head 62 forms a head 73 in the member 70.
  • the surface of the member 70 in contact with the screen 60 has the precisely desired final shape, the upper surface is not so well defined, as most clearly seen in FIG. 7. Particularly, it should be noted that the valleys of the rolls on the member 70 are thicker than the peaks.
  • the next step in making the diaphragm is to apply laquer 75 or other hardening agent to the member 70, preferably to both sides of the member 70. Good results have been attained by dipping the member 70 into the lacquer so as to impregnate the lacquer in the member. Alternatively, the lacquer may be applied in a variety of other ways, such as brushing or spraying. The lacquer 75 will cause the member 70 to retain the compressive forces which are applied in the following step.
  • lacquer of one concentration was applied to the body 71 of the member 70 and lacquer of a different concentration was applied to the flange 72 of the member 70.
  • the frequency response of the completed diaphragm may be selected.
  • using a low concentration lacquer on the flange 72 will not significantly increase the resonant frequency.
  • the compression applied to the flange 72 serves to reduce the resonant frequency, and any lacquer applied to the flange 72 would serve to increase the resonant frequency.
  • the amount of increase may be minimized by selecting a lower concentration lacquer, yet achieving water repellancy and the ability to retain the compressive forces.
  • the frequency response in the higher range of frequencies may be controlled. It is to be understood that the invention contemplates a single lacquer or hardening agent, on the one hand, or any number of different hardening agents, on the other, depending upon the exact type of frequency response sought.
  • the member 70 is subjected to pressure by two dies 80 and 90, which dies have mating surfaces that conform precisely to the shape of the final product.
  • the dies 80 and 90 respectively have mating undulations 81 and 91 therein conforming precisely to the undulations or rolls that are to be present in the finished product.
  • the lower die 90 in addition to the undulations 91, has a frusto-conical surface 92 and a vertical surface 93, the upper die 80 also having a vertical surface 83.
  • the portion of the member between the surfaces 83 and 93 will become the apex of the member 70.
  • the undulations 81 and 91 compress the rolls 72a in the flange 72 of the member 70, to give better definition to the valleys and also to decrease the over-all thickness of the rolls, in accordance with the objectives previously explained.
  • the die 80 also includes a relief portion 82, that is, a portion which does not contact, and hence does not compress the member 70.
  • a relief portion 82 that is, a portion which does not contact, and hence does not compress the member 70.
  • the lower die 90 is also provided with a plurality of stops 94 and 95 which serve to limit the extent to which the upper die 80 can compress the member 70.
  • the force applied to the upper die 80 was about 2,400 lbs., whereby on a member 70 having 10 square inches of area, the pressure exerted on the member would be about 240 lbs. per square inch.
  • the area of the member 70 where, say, [00 square inches, the pressure would be 24 lbs. per square inch.
  • the pressure should be at least 10 lbs.
  • the member 70 is moistened prior to being compressed, and the dies 80 and 90 are heated so as to steam-press the member 70.
  • the finished member is then trimmed, both at the flange and at the neck 73 to provide the diaphragm 40 shown in FIGS. 1-4.
  • the resonant frequency was about 100 Hz.
  • the application of lacquer or other hardening agent to the flange had the effect of slightly increasing the resonant frequency to about 1 10 Hz.
  • a molded loudspeaker diaphragm comprising a body having a frusto-conical shape with a larger end and a smaller end coupled in use to a driver means, and a flange on said larger end, said flange having a flat portion and a roll portion, said flat portion adapted to be I fixedly mounted in use, said flange portion further comprising a lacquer of a first concentration, said body comprising said lacquer of a second concentration, said flange and at least a portion of said body having been laterally compressed under a pressure of at least about 10 pounds per square inch, whereby said roller portion is capable of withstanding extensive flexing thereof as the result of said body being vibrated by the driver means and whereby the response of said diaphragm is improved.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Multimedia (AREA)
  • Manufacturing & Machinery (AREA)
  • Diaphragms For Electromechanical Transducers (AREA)
US00183135A 1971-09-23 1971-09-23 Molded loudspeaker diaphragm Expired - Lifetime US3768590A (en)

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US18313571A 1971-09-23 1971-09-23

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0185833A1 (en) * 1984-12-27 1986-07-02 Audiotecnica Italina srl Membrane in plastic materials for loudspeakers
US4803242A (en) * 1986-08-04 1989-02-07 Matsushita Electric Inductrial Co., Ltd. Diaphragm for loudspeakers
US6644182B1 (en) * 2002-09-23 2003-11-11 Chui-Che Chen Method of producing cone diaphragm having color patterns
US20110155502A1 (en) * 2007-07-25 2011-06-30 C.V. Sinar Baja Electric Ring shaped membrane for an electro-acoustical loudspeaker
US20190055969A1 (en) * 2017-08-21 2019-02-21 Out of the Box Audio, LLC Methods and Apparatus for Improving Sound Within an Acoustical Boundary Laer

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1984019A (en) * 1932-05-25 1934-12-11 Jesse B Hawley Fibrous sound reproducing diaphragmatic members and means for and method of making the same
US2006830A (en) * 1930-12-24 1935-07-02 Jesse B Hawley Sound reproducing diaphragm
US2017496A (en) * 1930-12-24 1935-10-15 Jesse B Hawley Method of making sound reproducing diaphragms
US2605855A (en) * 1948-12-22 1952-08-05 Hawley Products Co Method of making acoustic diaphragms
US2619012A (en) * 1947-08-05 1952-11-25 Joseph B Brennan Method of making loud-speaker diaphragms
US3253970A (en) * 1962-01-31 1966-05-31 Hawley Products Co Molding, decorating and finishing die dried fibrous articles

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2006830A (en) * 1930-12-24 1935-07-02 Jesse B Hawley Sound reproducing diaphragm
US2017496A (en) * 1930-12-24 1935-10-15 Jesse B Hawley Method of making sound reproducing diaphragms
US1984019A (en) * 1932-05-25 1934-12-11 Jesse B Hawley Fibrous sound reproducing diaphragmatic members and means for and method of making the same
US2619012A (en) * 1947-08-05 1952-11-25 Joseph B Brennan Method of making loud-speaker diaphragms
US2605855A (en) * 1948-12-22 1952-08-05 Hawley Products Co Method of making acoustic diaphragms
US3253970A (en) * 1962-01-31 1966-05-31 Hawley Products Co Molding, decorating and finishing die dried fibrous articles

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0185833A1 (en) * 1984-12-27 1986-07-02 Audiotecnica Italina srl Membrane in plastic materials for loudspeakers
US4803242A (en) * 1986-08-04 1989-02-07 Matsushita Electric Inductrial Co., Ltd. Diaphragm for loudspeakers
US6644182B1 (en) * 2002-09-23 2003-11-11 Chui-Che Chen Method of producing cone diaphragm having color patterns
US20110155502A1 (en) * 2007-07-25 2011-06-30 C.V. Sinar Baja Electric Ring shaped membrane for an electro-acoustical loudspeaker
US8141677B2 (en) * 2007-07-25 2012-03-27 C.V. Sinar Baja Electric Ring shaped membrane for an electro-acoustical loudspeaker
US20190055969A1 (en) * 2017-08-21 2019-02-21 Out of the Box Audio, LLC Methods and Apparatus for Improving Sound Within an Acoustical Boundary Laer
US20190055968A1 (en) * 2017-08-21 2019-02-21 Out of the Box Audio, LLC Methods and apparatus for improving sound within an acoustical boundary layer
US10393155B2 (en) * 2017-08-21 2019-08-27 Out of the Box Audio, LLC Methods and apparatus for improving sound within an acoustical boundary layer

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JPS4841729A (OSRAM) 1973-06-18

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