US2478642A - Combined moving coil loudspeaker and transformer - Google Patents

Description

Aug. 9,1949. J. JLYROOT 2,478,642 I COMBINED MOVING con. LOUDSPEAKER AND TRANSFORMER Filed 001:. 9, 1946 F1. E- J J 43 /J 53 34 I 1 3 3 I AZYURIYEY Patented Aug. 9, 1949 John-J: Root, NewYorli NLY'. Apiii'itatitn downer-'9, 194%? serisr'rte 'mz-izta partofmfy 9310a; fired June 25 ii I anciesea loud 1p design as to be of a d What ii tne' oi eraii I g e s aner was subsan any deterfaiged tithe erect its a instantinvent'idri mearp es oi't'lie advantages prior application; an further princi s to entering coil type-or ti re i s lecti od spalfi. x g p r T prior t pes; of iiioviiigf coi driving" spe wit; the was" gneiau mspcsea at the so orafii bhi'fid the'cone. Bent arcane the g fu ther rarwa Iy'was either using orapo fizng neat 'ifia gnt arrangement. An ofitut t n's former was generally mounted on the framewof'li iii order to match the impedance of the voice coil to theoutput circuit to which the speaker was contacted. h h

The preseat intentiii turmerares possible the mounting of the matchiag'transrormerso that the overallspaeerequirements of the loud speaker are minimized. A

tfii-objects of my invention will be, anagram thei'jllowing descriptionit being" un er- Etiiod that the above general statements of the objects of myinvention are intended to describe and not limit it any manner.

' :;l e cross sectional new iii 'a lodd speaker "'c'b stfiicteii 'inaccordanee tvith 'tlie principles of the invention, and taken across line 22 of Fig. 1.

Fig. 2 is a top view thereof.

The speaker assembly comprises a cone diaphragm II) which may be fabricated of stiff paper or any other non-magnetic material having Suite able acoustical properties. Diagram H] is formed with conventional corrugations H and is secured around its periphery l2 to an annular bracket member l3.

Bracket member I3 is connected at spaced points thereof as by screws l4 to an annular casing wall l5 having an integral depending flange l6. Casing wall l5 as well as flange l6 function as a portion of the ferromagnetic circuit and are therefore made of steel or equivalent ferromagnetic substance. The casing further comprises the annular floor I1 formed with an integral reene e i the deter or t-h seniors:- (01. mow-1:15am

trant columrrl a'f whiclig, co operation with flange l 6, provides-amelectromagnetic: aireap? asrwilUiQ herernaftadescribedr Mm "tamed: betweenlwall t5 fltiol fl boltsgnotshown, is; anon? ntiiar peflnarient mag-iiet B9 for supplying a poijarizing nelatotneunit, v

we phragmiltkis connected as by a; suitable adhesive an annular, hl zeeiitensioni 20 whieliramay: be offinsulatin m Ma l. sucneoane tio is: fliected: substmr t y mater-it to the peripheral portion. of: the cortical area; rror the -diaphragm Wort. as Othell-v wise stated; massacre-the periphery or brim. of the diaphragm as represented by the edgepob tioii more the corrugations Secured in a coir analliner toftne extension 20 is; the moving or voice coil 22' so that it is: concentric ivi the aitis of the diaphragm and disposed within the-electromagnetic air gap produced by the'fiahge Tia-rid ieiitrant column IE.

' asiiig wan lie-rid new IT; as spaced-by the permanent magnet t9, define an annular chamher in which is disposed the annular output transformer Tra'nSformer "23 comprises a primary winding having leads 25 and 26 and a secondary winding 21 having leads 2! and 2!.

is conventional, leads 2'8 and 29 of the secondary winding are. connected to the voice coil 22 which isthereupoh'provi'ded with audio currents so as to produce a magnetic field. In the instant 'erribodiinent'such connection is effected through the rivet 3'0 and lug 3| to which both one voice eouiead and secondary winding lead '29 are adhered, similar connection for the other voice coil lead is effected through the rivet 32 and soldering lug 33; It will beirecognized that the "construction "of "transformer 23 is Sikh as vto produce a stepped down secondary windingfl to match the impedance of the voice coil 22. Transformer leads 25, 26, 28 and 29 may emerge from suitable openings 34 and 35 formed in the floor H.

To operate the loud speaker from a vacuum tube amplifier, leads 25 and 26 are directly connected to the plate of the final power tube of the amplifier and the positive plate voltage terminal, respectively. In the absence of an audio signal from the power tube, the permanent magnet I9 polarizes flange I6 and column l8 north and south, respectively, so as to establish a constant field in the air gap formed between them. Upon the introduction of an audio signal to the amplifier, an alternating current component corresponding to the signal appears in the output of the power tube. The resultant current which flows through the voice coil 22 produces a magnetic field which interacts with the polarizing or constant magnetic field to produce a force which moves the coil parallel to the axis of the diaphragm II]. This produces the required vibration or movement which generates sound waves.

It is to be observed that by driving diaphragm ID at its peripheral area and by disposing the voice coil thereat, a substantial reduction is made possible in the spaceoccupied by the speaker assembly.' This objective is further contributed to by the disposition of the output transformer which, in distinction to conventional dispositions thereof, does not jut out from'the, main body of the speaker. The magnetic structure of the speaker is built away from the central area of the diaphragm so as to permit the formation of a cone thereat. transformer laterally surround the conical area, the depth of the motor assembly being substantially equivalent to the height of the conical central area so that it'is disposed in'a plane defined by the height of the conical area.

Thus, there has been'shown what at present is considered a preferred embodiment of the invention. It will be apparent, however, that many changes and modifications are possible without departing from the spirit thereof. For example, vwherethepower tube-of the amplifier is drawing'a high value of current,- the primary Winding-24 may be relied upon to supply a polarizing'source as described in myprior above mentioned application. In this event, the permanent magnet [9 would. be unnecessary.

-Iclaim:, r 1. An'electroacoustic transducer comprisingin combinationan acoustical diaphragm having a conical central area, a voice'coil mounted adjacent to the periphery of said diaphragm so as to permit said conical central area to vibrate freely, and electromagnetic pole means of annular form disposed in operativerelation to said voice coil adjacent the periphery of said diaphragm whereby the apex of said conical area is unobstructed thereby, said electrical pole means forming a chamber, and an annular transformer for supplying audio signals disposed within said chamber and electrically connected to said voice coil.

2. An article according to claim 1 wherein said chamber is of a depth substantially equal to the height of the conical central area and is substantially disposed in a plane defined by said height.

3. An article according to claiml including a permanent magnet of annular form for supplying a polarizing force tosaid voice coil, said permanent magnet'being disposed adjacent the periphery of said diaphragm, and substantially in the plane of said chamber.

The magnetic structure and 4. An electroacoustic transducer comprising a combination an acoustical diaphragm having a conical central area, a voice coil mounted adjacent to the periphery of said diaphragm so as to permit said conical central area to vibrate freely, electromagnetic pole means of annular form disposed in operative relation to said voice coil adjacent the periphery of said diaphragm whereby the "apex of .saidiconical area is unobstructed thereby, a permanent magnet for supplying a polarizing force to said voice coil,

' said electromagnetic pole means and permanent magnet forming a chamber laterally surrounding said conical central area, said chamber being of a depth substantially equal to the height of the'conical central area so as to be disposed in -a plane substantially defined by the height thereof, and an annular transformer for supplying audio signals disposed within said chamber and electrically connected to said voice coil.

. 5. An electroacoustic transducer comprising in combination an acoustical diaphragm having a central area and a brim integral therewith, an annular extension formed on said diaphragm adjacent said brim, a voice coil wound around said extension so as to be disposed adjacent the periphery of said diaphragm and so as to leave the central area of said diaphragm free to vibrate, electromagnetic pole means of annular form disposed in operative relation to said voice coil-adjacent the periphery of said diaphragm so that the apex of said conical central area is unobstructed thereby, a permanent magnet for sup plying a polarizing force to said voice coil, said electromagnetic pole means being mutually spaced by said permanent magnet so as to form a chamber therewith, said chamber being of a depth substantially equal to the height ofthe conical central area, and annular transformer means for supplying audio signals disposed within said chamber and electrically connected to said voice coil.

JOHN J. ROOT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 306,839 Great Britain Sept. 25, 1930

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