US1905704A - Acoustic device - Google Patents

Acoustic device Download PDF

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Publication number
US1905704A
US1905704A US452154A US45215430A US1905704A US 1905704 A US1905704 A US 1905704A US 452154 A US452154 A US 452154A US 45215430 A US45215430 A US 45215430A US 1905704 A US1905704 A US 1905704A
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United States
Prior art keywords
diaphragm
secured
magnetic
elements
gap
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US452154A
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English (en)
Inventor
Henry C Harrison
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AT&T Corp
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Bell Telephone Laboratories Inc
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Filing date
Publication date
Priority to BE379817D priority Critical patent/BE379817A/xx
Application filed by Bell Telephone Laboratories Inc filed Critical Bell Telephone Laboratories Inc
Priority to US452154A priority patent/US1905704A/en
Priority to FR716994D priority patent/FR716994A/fr
Application granted granted Critical
Publication of US1905704A publication Critical patent/US1905704A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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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
    • H04R9/06—Loudspeakers
    • 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
    • H04R9/025—Magnetic circuit

Definitions

  • This invention relates to acoustic devices and particularly to sound'reproducers of the direct acting ty e. i
  • the vobject 0 this invention is to radiate sound energy with substantially uniform efficiency over at least a large portion of the entire frequency range of speech and music.
  • One feature of this invention resides in the sound radiator employed to translate the vibrations impressed thereon into sound disturbances.
  • Another feature of this invention' resides in the driving means employed to impart acoustic vibrations to said sound radiator.
  • Still another feature resides in the magnetic structure forming a part of said driving means.
  • a direct acting sound radiator com prising a plurality of tensioned members to which is secured some thin material to prevent acoustic short circuit between 0 posite surfaces thereof and drivin means t erefor comprising a current carrying member of a material having a high ratio of conductivity to mass, said stri being secured to and across one face thereo and intermediate its ends.
  • This current carrying member is disposed in an elongated magnetic air-gap formed by a pair of'parallel pole pieces which are ele-v ments in a magnetic structure which allows a maximum and uniform distribution of magnetic flux with the use of a comparatively small amount of copper in the energizing coils of the magnet.
  • ig. 1 shows fragmentarily an embodiment of this invention incorporating the feaacousrrc DEVICE 1930. serial No. 452,154.
  • Fig. 5-A shows a variation in the .tensioned member securing means shown in views of a portion of the magnet structures shown in Figs. land 2; and i Fig. 10 is a section of the magnetic structure shown in Fig. 1 along the line 10-10.
  • Figs. 1 and 2 show a sound reproducer incorporating the features of this invention.
  • This frame comprises vertical supports 1 which may be of iron pipe or other suitable material and horizontal'channel members 11 which extend between the extremities of the vertical supports and may be secured thereto in any desired manner preferably by welding.
  • the frame. is strengthened by angle irons 3 extendin between'the vertical supportsand by ang e irons 4 which extend angularly between said members 3 and supports 1.
  • bracing members 2 which may be of iron pipe, are secured at their extremities to the vertical supports 1, preferably, by welding, and are maintained spaced therefrom by spacer members 7 and 8.
  • spacer members 8 comprise studs secured *to the bracing member 2 and the support 1 and are coupled together by a turn buckle element 9.
  • This sound reproducer may be placed on any fiat surface resting on either its lon er or shorter dimension, or ma be supporte from a ceiling, wall or frame y means of the eye bolts 10 which are secured to channel members 20, in turn secured to the supports 1 by pat bolts 44 and nuts 45.
  • the magnet structure 16 which is secured at its opposite ends to the supports 1 preferably by welding and supported by the members 5 and 6 which extend angularly between the lower portion thereof and the supports 1. The magnet structure will be more fully described hereinafter with reference to Figs. 6, 8, 9 and 10. Figs.
  • FIG. 1 and 2 show, further, the energizing coils 17 therefor and the terminals 19 for the strip member 40 (Fig. 3) whose movements are communicated to the diaphragm and cause it to vibrate and radiate sound.
  • Conductors 18 Connected to the terminal blocks 19 are conductors 18 of highl conductive material and of lar e cross section which provide the return Ti to the transformer 14 for the currents passing therefrom to the conducting strip 40.
  • Conductors 18 may be of aluminum or ofcopper or of any other material having preferably a low impedance and ma be securedconveniently to, but conductive y insulatedfrom, a portion of the magnet structure. As shown in Fig.
  • the diaphragm 61 comprises a plurality of parallel tensioned members 13 spaced very short distances apart and extending between the extremities of the frame, and a thin material 12 preferably, imperforate to air, which is secured to said tensioned members to prevent acoustic short circuit between the opdposite surfaces thereof.
  • the length of the iaphragm is preferably greater than twice its width and also greater preferably than onehalf the wave len h of the lowest frequency to be radiated. u'ch a diaphragm has been found highly satisfactory as a sound radiator which ma be tensioned to a desired degree in the direction of its lon dimension only, if desired, and having su stantially no tenssion therein in a direction transverse to its len h.
  • the diaphragm is referably tensione to such a degree that t e sound vibrations are propagated therein at a velocity greater than one-quarter that of sound in 1113 ⁇ It may be desirable to introduce a'slig'ht lateral tension in the diaphragm to maintain the desired velocity of propagation in the diaphragm and to counteract the effect of the mass of air into which it is working which has a tendency to reduce the attenuation.
  • tensioned members 13 may be wires of duralumin and the thin material secured to them may be of paper.
  • FIG. 4 A means for securing these wires in spaced relation and maintaining them in that condition is shown in Figs. 4 and- Secured by bolts 50 to the channel member 11 extending between the supports 1 is a member 49 which is preferably of a material similar to that employed for the tensioned elements 13.
  • This member 49 has parallel saw cuts 52 and at right angles thereto a series of saw cuts in which the extremities of the elements 13 are positioned and clamped against movement by forcing the portions 53 between the vertical saw cuts about the portions of the tensioned elements in each saw cut.
  • Such a flexible strip is employed alon' each lateral edge 'of the diaphragm exten ing in the direction of its longer dimension to, prevent acoustic short circuit between 0 posing surfaces of the sound radiator in t e area between the lateral edges thereof and the vertical supports 1 of the frame.
  • Substantially the result obtained with the tensioned element holding means of Fig. 5 may be secured by the modification thereof shown in Fig. 5-A.
  • Cross cuts 52 are omitted and continuous parallel vertical slots 62 are provided in which the'extremities of the elements 13 .are placed. They are secured therein by causing the material between the slots 62 to overlap the elements 13therein as shown. This may be accomplished by using a punching tool and striking the member 49 at the staggered points 63 with suflicient force to cause the desired displacement of the material between said slots thereby clamping the wires therein.
  • the diaphragm or sound radiator comprising tensioned elements 13 and thin material secured thereto is driven by a current conductin strip which is secured intermediate the en s thereof to and across the face of the diaphragm at substantially right angles thereto.
  • This strip is of a material having a high ratio of conductivity to mass and is disposed in an elongated magnetic airap ormed by the parallel pole pieces of an e eetromagnetically energized magnet structure 7 Referring to Fig. 3, a portion of this contrial havin non-integral feet ortions which ducting strip is shown and is, preferably, of aluminum or copper. As shown it is thin,
  • Terminal block 19 which maybe of a material such as brass is fastened to the support 1 by a screw 57 which is surrounded by a sleeve 58 of insulating material to avoid a metallic circuit between the terminal block and support.
  • the terminal block is electrically insulated therefrom further by a plate 'of insulating material 59, such as hard rubber.
  • Guard member 56 secured'to the terminal in section at'all points therealong or that it] may consist of aribbon-like strip of matearesecured-to. one edge thereo and providing means for positioning the conductor wholly within the field of the'magnet structui'e and.
  • feet portions 54 may be omitted altogether and the conductor secured directly along one edge thereof to and across the face of the diaphragm, substantially at ri ht angles thereto.
  • . ig. 7 is a schematic of the circuit for the electrical impulses which are to be reproduced by the sound reproducer incorporating the features of this invention;
  • the conducting strip 40 is shown connected at its extremities to the terminal blocks 19 as are also the return conductors 18 to the secondary of the transformer 14 whose primary is shown connected in the output circuit of the last stage 60 of anamplifier.
  • the return conductors 18 are of 'aymaterial of high conduc-' tivity, forinstance,--.of copper, and are of large cross section'to reduce to a minimum dissipation of energy therein.
  • the impedance of the strip 40 is substantially equal to the combined impedances of the secondary of the transformer 14 and the low impedance return conductors 18 which are shown in Figs. 1, 3 and 7 as connected to the terminal blocks 19. It will be apparent that a ne ligible percentage only of the currents flowing through the strip 40 will pass through the feet portions 54 and that these portions may be connected directly to the tensioned elements 13. In the normal position of the strip 40 in the elongated air-gap of the magnetic structure, these feet portions need not be therewithin. This provides the necessary clearance between the diaphragm and the magnet structure without any appreciable portion of the currents passing through the strip 40 traversing the portion thereof without the magnetic air-gap. If the feet portions 54 were of non-conductive material, the current fiow in the strip or conductor 40 would be whollyin that portion thereof within the magnetic air-gap. The normal position of the conducting portion 40 is shown clearly in Fig. 10.
  • ma net structure 16 extends between the vertica supports 1. It provides an elongated air-gap 64 in which is positioned a con- I uctingstrip 40 secured across the face of the diaphragm 61.
  • An elon ated permanent magnet with oppositely disposed pole portions might be employed to provide the desired uni-directional magnetic field across, said airap but for the purpose ofthis disclosure e ectromagnetic means are preferred.
  • Figs. 6, 8 and 9 are exploded, plan and rear elevation views of slightly more than onehalf of the magnet structure, it being understood that the structure is symmetrical in outline.
  • a metallic plate 24 of a magnetic material, such as soft iron, is secured to an angularly disposed metallic plate 27, which may be of soft iron also, which forms one ole piece of the electromagnet.
  • the memr 27 has a tapered edge portion 65 convergin to form a long narrow ed 66, so that w en magnetic flux is roduce in said pole piece, it is concentrate in an elongated rectangular area.
  • blocks 34 and 28 are fastened, for
  • members 23 of magnetic material and triangular in shape are ositioned on the under surface of the memer 24 and may be secured thereto in any suitable wa fer instance by welding.
  • Supported by t e member 27 are blocks 32 whose upper portions 33 are of a non-magnetic material such as brass and are provided with tapped drillings 68 into which screws 38 may be threaded.
  • Supported by the member 24 are cores 31 of magnetic material which are surrounded by energizing coils 17 which may be connected to a source of current when it is desired to magnetically energize the cores.
  • the core is secured to the triangular mem-' ber 23, preferably by welding it thereto but a screw projecting through said member and into the core would be satisfactory.
  • the other pole of the electromagnet comprises members 22 which are also triangular in shape. Each member 22 has an opening'69' therein into which the core 31 projects and dowel ins 30 with which the openin the V- aped members 21 register. embers 21 and 22 are of magnetic material and may be fastened to one another by any suitable means.
  • the portion of the member 22 projecting out beyond this support by the blocks 32 is so shaped as to concentrate the magnetic flux which may be present therein and terminates in an elongated surface 71 opposite- I disposed with reference to the surface 66 orming the other pole face of the electromagnet.
  • the structure described permits of a uniform distribution for the magnetic flux produced in the core 31 when energizing currents are flowing in coils 17 and rovides a long narrow air-gap within whic a current conducting strip may be placed.
  • the width of the air-gap may be varied by using different thicknesses of washers 36 between the under surface of the member 22 and the upper portion 33 of the block 32.
  • elements 21 and 22 may be formed as an integral unit'as may, also, elements 23 and 24.
  • the moving element comprises a conducting strip disposed in an elongated magnetic airgap and secured to and across the face of an elongated diaphragm which is in a condition of uniform tension and which comprises preferably a plurality of tensioned elements securely held at their extremities.
  • the conducting strip is referably provided with a multiplicity of eet portions, one secured, preferably, to each tensioned element and is adapted for movement in accordance with the sounds to be reproduced, said movement resulting from motor action between the current conducting strip and the uni-directional magnetic field in which it is located; the movements being in the plane of the conductor. These movements are communicated to. the diaphragm and sound energy is radiated therefrom to the atmosphere.
  • a sound reproducing device comprising an elongated direct actin diaphragm, means defining a magnetic air-gap and a current conducting member disposed in said air-gap and secured to and across the face of said diaphragm along its short dimension, said member having integral flexible portions near its extremities.
  • a direct acting diaphragm comprising a plurality of elongated elements, means defining a magnetic air-gap, and a current conducting member disposed in said air-gap and secured to said diaphragm, said member havin a plurality of projecting portions, each of which engages with at least one of said elongated elements.
  • a direct acting diaphragm comprising a plurality of elongated meta lic elements, air-gap, and a. current conducting member disposed in said air-gap and secured to said diaphragm, said member having a plurality of projecting portions, each of which is attached to at least one of said elements.
  • a diaphragm having a length substantially greater than twice its means defining a magnetic width and more than one half the wavelength of the lowest frequency to be reproduced, eom n'ising a plurality of spaced elements and a thin nmterial secured thereto, said diaphragm being tensioned substantially along its length only, means defining a magnetic air-gap, and a current conducting member attached to said diaphragms spaced elements. said member being disposed in said magnetic air-gap.
  • a diaphragm comprising a plurality of spaced elongated elements, means for securing. said el ments at their extremities.
  • said meiins comprising a memher having depressions into which the extremities of said elements are placed and clamped therein by displacement of the material between said depressions, and means for actuating said diaphragm.
  • a frame In a sound reproducing device, a frame, a diaphragm supported by said frame, and comprising a plurality of metallic elements to which is secured a thin material imperforate to air, thin flexible means intermediate the lateral edges of said diaphragm and frame to minimize acoustic short circuit between the surfaces of said diaphragm, means for actuating said diaphragm comprising a thin flat conductor secured to and across one surface of said diaphragm intermediate its ends, said conductor having flexible portions near its extren'iities, and a magnet structure providing an elongated magnetic air-gap in which a portion of said conductor is disposed. 7.
  • a diaphragm and means for driving said diaphragm said means comprising a conducting member secured to said diaphragm and a magnet structure including pole pieces disposed to form a magnetic airgap, each of said pole pieces being so shaped as to insure a uniform distribution of magnetic flux. at all points along said air-gap one of said pole pieces comprising a triangular shaped portion and a V-shaped portion.
  • a diaphragm comprising a plurality of elongated metallic elemeats. means defining amagnetic air gap, and a current conducting member disposed in. said air gap and secured to said diaphragm, said member comprising a plurality of serratioi'is each of which is attached to at least one of said elements.
  • a diaphragm and means for driving said diaphragm comprising a conducting member secured to said diaphragm and a magnet structure including pole pieces disposed to form a magnetic air gap, one of said pole pieces comprising a triangular shaped portion and a V shaped portion. the apex of said V being farthest removed from the air gap, and the arms of the V extending toward the magnetic air gap.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Audible-Bandwidth Dynamoelectric Transducers Other Than Pickups (AREA)
US452154A 1930-05-14 1930-05-14 Acoustic device Expired - Lifetime US1905704A (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
BE379817D BE379817A (enrdf_load_stackoverflow) 1930-05-14
US452154A US1905704A (en) 1930-05-14 1930-05-14 Acoustic device
FR716994D FR716994A (fr) 1930-05-14 1931-05-13 Perfectionnements aux dispositifs acoustiques

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US452154A US1905704A (en) 1930-05-14 1930-05-14 Acoustic device

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US1905704A true US1905704A (en) 1933-04-25

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US452154A Expired - Lifetime US1905704A (en) 1930-05-14 1930-05-14 Acoustic device

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US (1) US1905704A (enrdf_load_stackoverflow)
BE (1) BE379817A (enrdf_load_stackoverflow)
FR (1) FR716994A (enrdf_load_stackoverflow)

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Publication number Publication date
FR716994A (fr) 1931-12-30
BE379817A (enrdf_load_stackoverflow)

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