US2657758A - Loud-speaker - Google Patents

Loud-speaker Download PDF

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Publication number
US2657758A
US2657758A US151724A US15172450A US2657758A US 2657758 A US2657758 A US 2657758A US 151724 A US151724 A US 151724A US 15172450 A US15172450 A US 15172450A US 2657758 A US2657758 A US 2657758A
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United States
Prior art keywords
diaphragm
coil
loud
winding
speaker
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Expired - Lifetime
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US151724A
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English (en)
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Varnet Pierre
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Individual
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Individual
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R9/00—Transducers of moving-coil, moving-strip, or moving-wire type
    • H04R9/02—Details
    • H04R9/04—Construction, mounting, or centering of coil
    • H04R9/045—Mounting

Definitions

  • the chief obstacle lies in the plurality of resonance conditions possessed by the diaphragm owing to the fact that, while this element operates as a piston that moves bodily at low frequencies, it becomes the locus of radial wave propagation at intermediate frequencies and especially in the upper frequency ranges of the audible spectrum. Reflection of such waves on their reaching the corrugated outer margin by which the diaphragm is suspended creates standing waves and disturbing resonance conditions. It has been attempted in the past to overcome this objectionable effect by endeavouring to absorb in a gradual manner the propagated energy so that only a very small residual fraction thereof will remain as the Wave of energy reaches the peripheral area of reflection.
  • the procedures used heretofore for this purpose may be considered as falling into one or more of the following classes:
  • diaphragms that are not surfaces of revolution (e. g. elliptic surfaces) in order to obtain varying vibratory conditions in the different azimuths.
  • An object-of the invention is to provide :a loudspeaker of high power efficiency, having a response characteristic free of any sensitive resonance peaks and satisfactorily reproducing the higher audible frequencies.
  • a more specific object is to provide a method of movable coil construction whereby the dimensiohs of the coil are markedly reduced without substantially affecting its efficiency and imparting to it increased strength and longer life.
  • a further object is to create on a loud-speaker diaphragm such conditions of wave propagation that reflection is rendered gradual both in time and space, and that resonance peaks are practically eliminated.
  • a further object is to increase in a loud-speaker the solid angle of acceptable reproduction for-the higher audible frequency ranges.
  • One characteristic feature of the invention is concerned with the moving coil: over the external layer of the winding of this coil th wire is stripped of insulation and is cut into or flatted, so as to present a substantially smooth outer cylindrical surface.
  • the invention provides a method of producing uch a type of coil, termed herein a scraped coil, which comprises, immediately after impregnation or after having wound the coil in the presence of an adhesive composition, and while the adhesive is still somewhat plastic, subjecting the coil to a scraping operation by means of an appropriately formed tool on a lathe, this scraping step on the lathe being controlled with the naked eye or preferably with a gauge in such a way as to remove an annular layer comprisiny the full external layer of insulation as well as a small depth of the outer metal of the outer turns of wire throughout the projecting areas thereof.
  • Another feature of the invention lies in the fact that a number of radial areas of heterogeneity are created over the loud-speaker diaphragm, giving rise to propagatory conditions differing from those prevailing throughout the remainder of the diaphragm surface.
  • the diaphragm retains a general form of a surface of revolution, but according to the invention azimuthal heterogeneity is created resulting in variations in the velocity of propagation along the azimuth or azimuths under consideration. Under these circumstances, instead of there being as in known diaphragms a sharp and total reflection of the wave at the periphery of the diaphragm, the energy in motion from the centre towards the periphery of the diaphragm is gradually reflected.
  • Tests performed with the loud-speaker to be described by way of example hereinafter have corroborated the above theoretical forecasts in that they showed a marked flattening out of the response characteristic and total disappearance of disturbance noises due to the resonance occurring in a smooth conical diaphragm, without any detriment to the width of the range of reproduced frequencies.
  • Azimuthal heterogeneity according to the invention may for instance be obtained by differential im regnation of the areas that are to have differential velocities of wave pro agation, or alternatively by the use of corrugations of appropriate contours, or both.
  • the wave front assumes an increasingly great inclination relatively to the axis of the diaphragm. Consequently, radiation at high audible frequencies is not only effected in the direction of said axis, but also along directions forming with said axis an angle that is the greater as the heterogeneity in wave velocity is more marked, and therefore also, as the wave front is more inclined as the wave moves away from the centre of the diaphragm. In other words, the solid angle of radiation of the higher audible frequencies is increased.
  • Figure 1 is a front view of a loud-speaker according to the invention.
  • Figure 2 is a corresponding axial cross-section
  • Figures 3 and 4 are detail views in cross-section of a moving coil according to the inven tion, respectively before and after the scraping step;
  • Figure 5 is an explanatory diagram illustrating one way of performing the scraping operation according to the invention.
  • a loud-speaker according to the invention comprises a diaphragm H mounted on a frame 12 and carrying centrally thereof a movable coil of the above-defined scraped type, produced as more specifically described hereinafter.
  • This coil is arranged in a manner known per se in the magnetic gap of an electro-magnet it the field winding of which is visible at I5.
  • a permanent magnet could of course be used.
  • the central part of the diaphragm is suspended from the core (5 of the magnet in known manner through a suspension member or spider I1.
  • the diaphragm is in the general form of a circular cone and is secured at its radially outer periphery in the conventional way through a flexible part I 8, and is formed with a set of undulations such as i9, 213, 2! each of which, as shown, has a maximum width and depth at its intersection with one radius A of the diaphragm, gradually fading away on each side of this radius so as to be practically nonexistent on reaching the radius 13 diametrically opposed to A. It is quite simple in practice to provide undulations of such form. It is merely necessary for this purpose when machining the undulations, to place the mould out-of-centre with respect to the mandrel of the lathe.
  • the velocity of propagation is a minimum along the radius A and a maximum over the radius B, and there is a gradual and smooth progression from one to the other of these conditions.
  • the velocity of propagation over the radius A is equal to three fourths the velocity over the radius B. Consequently the wave front propagated from the centre to the periphery of the diaphragm will assume an increasing inclination with respect to the axis of the loud-speaker and the inclination of the undulations is so selected as to match this progression, so that the wave front will attain all the points of a given undulation at the same instant. This will prevent mutual interference between the velocities of propagation.
  • the number of axes of heterogeneity such as AB may be varied in accordance with the specific characteristics desired in each instance, and the nature and dimensions of the diaphragm, but will generally lie between 1 and 8.
  • the various areas of heterogeneity need not be identical; the greater their number, the more difficult will it of course be to achieve substantially different speeds of propagation.
  • the plane of the undulations will also be gradually made steeper as the radius of the undulation under consideration increases so that in this case also the wave front will reach all the points of any given undulation simultaneously or substantially so.
  • the undulations are so formed that their general shape in cross-section on a radial plane will be similar to the general form of the wave front as it passes through the undulation under consideration.
  • the first step may be to subject the diaphragm as a whole to 'a moderate impregnation with a varnish the chief function of which is to render the diaphragm impervious to moisture and then additional impregnation is made using an appropriate varnish applied to the radial zones of the diaphragm in which it is desired to create an increased propagational velocity.
  • a mask may be used for protecting from the varnish all but the radial Zones selected; a similar result may alternatively be achieved by using a set of suitably-arranged spray-guns.
  • This method involving heterogeneous impregnation may be used alone or in combination with the dissymmetrical undulations described above.
  • rib or corrugation is used to designate a fold or flute formed in a radial direction, in contradi'stinction to what herein is termed an undulation i. e. a corrugation defined by the intersection with the diaphragm of planes variably inclined with respect to the axis of the diaphragm.
  • Figures 3 and 4 relate to the movable coil 'ac cording to the invention.
  • a movable coil with two layers of wire such as it may appear while still on its winding mandrel and in its heated and as yet non-set condition from the impregnation step, or after having been wound in the presence of adhesive, some of the various defects such a coil may offer being purposely exaggerated in the drawing; thus represents a foreign body and 26 an aggregate of adhesive, both acting to produce surface irregularities or bulges over the theoretically cylindrical surface of the mandrel or core 21 and a corresponding displacement of the turns 28 and 29 of the first course of the winding.
  • 30 represents another aggregate of adhesive which raises the turns 31 and 32 of the second layer or course.
  • the turn 33 is shown as possessing increased thickness due to a defect in the coating operation; and 34 is the last turn of the coil and accordingly tends to spring out or escape due to its resiliency.
  • the over-all thickness dimension of the movable coil is that indicated by the dimension H.
  • the coil is subjected, in its heated condition as it is withdrawn from its impregnating bath or alternatively in its as yet non-set condition if it has been wound in the presence of adhesive, to a turning operation on a lathe with an appropriate tool to remove the entire external depth of insulation, plus .a certain depth of the outer metal.
  • This scraping action should be effected in the direction of winding, so as to terminate at the outlet of the coil. Owing to the radial pressure of the tool, the turns of the Winding are tightly packed against one another. The more outer turns will then assume a'circular shape without any elastic tension and will no longer tend to escape on the coil being stripped from its mold. Any defects or irregularities that may have occurred in the manufacture of the wire or in the winding operation are removed or considerably reduced,the compression of the turns being facilitatedbecause the impregnating composition and the insulating coating of the coil are both still hot and plastic during this operation.
  • the thickness dimension of the coil is now that indicated at h; the saving in space thus accomplished is self-evident and chiefly corresponds to the elimination of the dimensional tolerance or clearance required, prior to or in the absence of, the scraping step according to the invention, by the irregularities mentioned above.
  • the scraping operation is extremely easy to carry out and does not require complicated equipment for its performance. It may indeed be effected by hand, the movable coil being retained on the core which served for the winding operation.
  • the procedure illustrated in the diagram of Figure may be used, the movable coil on its winding core being shown at 35, and the tool used being shown as simply comprising a shank into one end of which is inserted a wedge-shaped tool El blocked with a setscrew the tool being held in the operators hand.
  • the coil is set into rotation in the direction of the arrow, and the tool is then simply moved into engagement with the surface of the coil and held against it with a slight degree of manual pressure until the coil surface assumes a typical glossy watered or moire aspect denoting that the outer layer of enamel and adhesive have been removed to a suflicient depth.
  • This operation only requires a few seconds.
  • the base of the shank 36 may first be rested as at 33 onto any convenient support, so that the tool will initially be presented in a position such as 317, then the shank may be gradually shifted to the position shown in chain lines with the tool at 31:! so that the cutting angle assumes a favorable value, and the desired result is instantaneously obtained.
  • a coil scraped as described acquires a highly compact and strong structure owing to the packing of the turns of winding, which from place to place has the effect of filling up any voids by adhesive composition squeezed out from areas where the adhesive was in excess.
  • the method of imparting heterogeneity to the loud-speaker diaphragm according to the invention is applicable concurrently with one or more procedures known in the art, in the case of diaphragms of any special contour, and of elliptical diaphragms.
  • the heterogeneous structure involving one radial zone of heterogeneity may be applied to an elliptical diaphragm with the direction of maximum velocity extending along one of the minor axes of the ellipse, in such a way as to obtain wave fronts approaching circumferential shape and thus improving the operation of the elliptic diaphragm, especially from the standpoint of reproduction of the higher audible frequencies and of transient vibratory conditions.
  • An acoustical diaphragm in the general form of a conical surface of revolution formed of material of substantially uniform thickness, said conical diaphragm being provided with means driving it at the center thereof, said conical diaphragm having a plurality of arcuate undulations extending substantially circumferentially about at least a portion of the circumference thereof and varying progressively in width and depth circumferentially of the conical diaphragm from a maximum along one radius to a minimum along a radius spaced 180 from the first mentioned radius, said undulations lying in planes with the planes of the undulations being substantially perpendicular to the axis of the conical diaphragm for the undulations nearest the center of the conical diaphragm and being inclined more and more to said axis as the distance between the undulations and the center of the conical diaphragm increases.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Diaphragms For Electromechanical Transducers (AREA)
US151724A 1949-03-31 1950-03-24 Loud-speaker Expired - Lifetime US2657758A (en)

Applications Claiming Priority (1)

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FR987123T 1949-03-31

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FR (1) FR987123A (en(2012))
NL (1) NL73443C (en(2012))

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2732908A (en) * 1951-12-05 1956-01-31 brittain
US2815823A (en) * 1953-03-02 1957-12-10 Rca Corp Loudspeaker structure
US3180945A (en) * 1961-09-22 1965-04-27 Wm H Welsh Co Inc Loudspeaker
US6219433B1 (en) * 1996-09-27 2001-04-17 Matsushita Electric Industrial Co., Ltd. Wax, copper foil flexible wire with wax and speakers using this flexible wire
US20040129492A1 (en) * 2002-10-28 2004-07-08 Alejandro Bertagni Planar diaphragm loudspeaker and related methods
US20050041830A1 (en) * 2003-08-19 2005-02-24 Hiroyuki Takewa Loudspeaker
US9628917B2 (en) 2014-07-23 2017-04-18 Bose Corporation Sound producing system
US20180338207A1 (en) * 2017-05-17 2018-11-22 Bose Corporation Method of fabricating a miniature device having an acoustic diaphragm
US10321238B2 (en) 2016-06-14 2019-06-11 Bose Corporation Miniature device having an acoustic diaphragm
US10448183B2 (en) * 2017-07-27 2019-10-15 Bose Corporation Method of fabricating a miniature device having an acoustic diaphragm

Citations (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US804903A (en) * 1905-05-25 1905-11-21 John H Van Mater Acoustic diaphragm.
US1040294A (en) * 1911-10-11 1912-10-08 James H Ellis Diaphragm.
US1624357A (en) * 1923-06-15 1927-04-12 Western Electric Co Phonic diaphragm
US1722805A (en) * 1926-07-31 1929-07-30 Bell Telephone Labor Inc Sound radiator
US1825833A (en) * 1929-06-21 1931-10-06 Tennesse Hans Acoustic diaphragm
US1846937A (en) * 1930-05-09 1932-02-23 Gen Electric Diaphragm for loud speakers
FR738415A (fr) * 1931-10-02 1932-12-26 Diaphragme vibrant pour appareils sonores
US1941476A (en) * 1930-06-27 1934-01-02 Jensen Radio Mfg Company Method of making sound reproducers
US1956826A (en) * 1932-06-16 1934-05-01 Rola Company Method of making alpha voice coil
US2030501A (en) * 1934-01-31 1936-02-11 Rca Corp Loudspeaker cone diaphragm and method of producing same
US2288832A (en) * 1937-08-31 1942-07-07 Rca Corp Fibrous acoustic diaphragm
US2512323A (en) * 1946-09-09 1950-06-20 Radio Frequency Lab Inc Reentrant diaphragm with central closure member
US2531634A (en) * 1945-01-11 1950-11-28 Athol E N Lawrance Acoustical diaphragm with stiffening means

Patent Citations (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US804903A (en) * 1905-05-25 1905-11-21 John H Van Mater Acoustic diaphragm.
US1040294A (en) * 1911-10-11 1912-10-08 James H Ellis Diaphragm.
US1624357A (en) * 1923-06-15 1927-04-12 Western Electric Co Phonic diaphragm
US1722805A (en) * 1926-07-31 1929-07-30 Bell Telephone Labor Inc Sound radiator
US1825833A (en) * 1929-06-21 1931-10-06 Tennesse Hans Acoustic diaphragm
US1846937A (en) * 1930-05-09 1932-02-23 Gen Electric Diaphragm for loud speakers
US1941476A (en) * 1930-06-27 1934-01-02 Jensen Radio Mfg Company Method of making sound reproducers
FR738415A (fr) * 1931-10-02 1932-12-26 Diaphragme vibrant pour appareils sonores
US1956826A (en) * 1932-06-16 1934-05-01 Rola Company Method of making alpha voice coil
US2030501A (en) * 1934-01-31 1936-02-11 Rca Corp Loudspeaker cone diaphragm and method of producing same
US2288832A (en) * 1937-08-31 1942-07-07 Rca Corp Fibrous acoustic diaphragm
US2531634A (en) * 1945-01-11 1950-11-28 Athol E N Lawrance Acoustical diaphragm with stiffening means
US2512323A (en) * 1946-09-09 1950-06-20 Radio Frequency Lab Inc Reentrant diaphragm with central closure member

Cited By (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2732908A (en) * 1951-12-05 1956-01-31 brittain
US2815823A (en) * 1953-03-02 1957-12-10 Rca Corp Loudspeaker structure
US3180945A (en) * 1961-09-22 1965-04-27 Wm H Welsh Co Inc Loudspeaker
US6219433B1 (en) * 1996-09-27 2001-04-17 Matsushita Electric Industrial Co., Ltd. Wax, copper foil flexible wire with wax and speakers using this flexible wire
US20040129492A1 (en) * 2002-10-28 2004-07-08 Alejandro Bertagni Planar diaphragm loudspeaker and related methods
US6929091B2 (en) * 2002-10-28 2005-08-16 Sound Advance Systems, Inc. Planar diaphragm loudspeaker and related methods
US20050041830A1 (en) * 2003-08-19 2005-02-24 Hiroyuki Takewa Loudspeaker
US7447328B2 (en) * 2003-08-19 2008-11-04 Matsushita Electric Industrial Co., Ltd. Loudspeaker
US9628917B2 (en) 2014-07-23 2017-04-18 Bose Corporation Sound producing system
US10321238B2 (en) 2016-06-14 2019-06-11 Bose Corporation Miniature device having an acoustic diaphragm
US11546696B2 (en) 2016-06-14 2023-01-03 Bose Corporation Miniature device having an acoustic diaphragm
US20180338207A1 (en) * 2017-05-17 2018-11-22 Bose Corporation Method of fabricating a miniature device having an acoustic diaphragm
US10499159B2 (en) * 2017-05-17 2019-12-03 Bose Corporation Method of fabricating a miniature device having an acoustic diaphragm
US11095987B2 (en) * 2017-05-17 2021-08-17 Bose Corporation Method of fabricating a miniature device having an acoustic diaphragm
US10448183B2 (en) * 2017-07-27 2019-10-15 Bose Corporation Method of fabricating a miniature device having an acoustic diaphragm
US11019444B2 (en) 2017-07-27 2021-05-25 Bose Corporation Method of fabricating a miniature device having an acoustic diaphragm

Also Published As

Publication number Publication date
NL73443C (en(2012))
FR987123A (fr) 1951-08-09

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