US2380869A - Loud-speaker - Google Patents

Description

J. P. QUAM July 31, 1945.

LOUD SPEAKER Filed March 10, 1941 0%206/2/07 c//zzei @zzaza .a m netic-type Speaker- Patented July 31, 1945 MUD-SPEAKER James P. Qusm, Chicago, 11]., assignor to Quain- Nichols Company, Chicago, lll., a corporation Missouri Application-March 10, 1941, Serial No. 382,598

13 Claims.

This invention relates in general to loud speakers, and in particular toa magnetic-lune such as is disclomd in my Patent No. 2,124,338, issued July 19, 1938. Although the magnetic-type speaker of my Patent No. 2,124,338 operated satisfactorily, it had certain limitations peculiar to it, and included certain limitations peculiar to prior art speakers in general, which have allbeen overcome in the present improved construction.

In composition paper diaphragm for magnetic-type loud speakers of the prior art, there has been a noticeable lack of uniformity in composition over the entire body of the diaphragm which has resulted in surface and body variations so that there is not a perfectly uniform movement of all parts of the diaphragm in a normal vibratory operation. .Diaphragms of the cone type are normally well anchored in a diaphragm frame and of considerable size so that they represent quite a body to be moved by the armature of the vibratory motor for the speaker. The lack of uniformity distorts or twists the dia- Dhragm out of its usual operating path, and in turn may move or force the armature of the vibratory unit out of its normal path oi movement so that the armature contacts one or the other pole face, and creates an undesirable metallic sound. Furthermore, the possible distortion of the cone diaphragm, and the armature, or at least one of the two, introduces the possibility of losses in the diaphragm driving energy over the entire operating system of the speaker.

There has been a further diihculty in the prior devices of the type discussed in providing an armature mounting and assembly which was rugged enough to withstand a large driving force on the armature to be transmitted to the diaphragm so as to produce a sound output comparable to the dynamic-type speaker, which is generally recognized as more powerful. In the dynamic-type speaker, the voice coil or movable element, which, in some respects, is comparable to the armature of the magnetic-type motor, has a substantially unlimited path for movement-in a linear direction as contrasted to the air gap which limits the vibratory path of movement of Furthermore, the mounting for a voice coil in the dynamic-type speaker is of such construction that almost unlimited movement can be applied thereto without weakening such mounting. However, the prior art generally has been unsuccessful in providing an energy output at the armature and a mounting therefor rugged enough to accommodate the maximum possible magnetic forces which might be applied to the magnetic-type of motor for speakers.

Another difllculty in the prior art magnetictype speakers, whose motors, after all, have quite a number of parts, has been to provide a compact, sturdy motor. and yet one in which the several parts are readily accessible for inspection and handling. if required. This iaparticulsrly true of those motors in which an armature oscillates or vibrates about an axis centrally of the armature. In many instances, the frame and magnet structure hasserved practicalbz as a housing for the motor unit, and has substantially covered up the other parts.

In the prior art magnetic-type speakers there has been-a further difliculty m an undesired emphasis on the high frequencies in a particular range of operating freque cies, with actual dis tortion sometimes taking lace at the high frequencles. Furthermore, there are many varied likes and dislikes as to the cut-oi! frequency at the upper end of the frequency range among purchasers of speakers and much expense and effort has been expended in providing a line of speakers to match the particular tone require ments of a purchaser. The usual method for taking care of this situation has been to try one diaphragm after anotherfor' the speaker until a sample is obtained with the required matching characteristics. This has been a "cut and try method requiring a very large supply of composition paper diaphragms of various types and composition. Relying upon this method caused difliculties when the diaphragm composition changed after the speaker left the manufacturer due to the absorption of moisture or .the like.

A still further difliculty has been encountered in magnetic-type speakers where metallic sounds resulted from the usual metallic washer and stylus connection at the apex of the diaphragm:

cone. Dimculties in this regard have oiiten be come apparent after the speaker has in high fidelity in a pleasing frequency range, and without undesirable metallic noises, regardless of structural variations in the composition paper cone diaphragm of the speaker.

Another object of this invention is to provide a vibratory motor comprised of relatively few parts easily assembled into an open assembly readily accessible for inspection and handling, and yet provide a motor and loud speaker comparable in fidelity of reproduction with large expensive mechanisms with precision parts.

One of the features of this invention is the provision of an improved powerful magnetic circuit for the vibratory unit of the speaker with a large vibratory energy output, which unit is capable of fully utilizing this output in providing a greater volume and fidelity of reproduction in the speaker.

Another feature of this invention is the provision of means for varying the tone of reproduction, and providing a cut-oi! for frequencies at the high frequency end of the operating range to minimize undesirable distortions in the reproduction.

A further feature is the provision of yieldable. diaphragm driving mechanism in the speaker of my invention which mechanism will take up and absorbany undesirable tenseness in the moving parts of the speaker to thus avoid undesirable distortion. noise, and loss of operating emciency.

Further objects, features, and advantages of this invention will become apparent from the following description when taken in connection with the accompanying drawings,inwhich:

Fig. 1 is a side elevation of the compietely.'assembled loud speaker with the diaphragm and diztphragmi supporting frame assembly shown in se on;

Fig. 2 is an enlarged fragmentary sectional view taken along the line 2-2 mm. 1:

Fig. 2A is a fragmentary sectional view along the line 2A-2A of Fig. 2 to illustrate primarily the air gaps between the armature and active faces of the pole pieces, with a mounting in the background intermediate such faces;

Fig. 3 is an exploded fragmentary view of the armature unit for the speaker motor at a step in the process of assembly of the motor prior to its final assembled form;

Fig. 4 is a circuit diagram of the output circuit of a receiver system utilizing the loud speaker, and the electrical circuit of the loud speaker; and

Figs. 5, 6,- and '1 are diagrams of modifications of theshort-circuited coil portion of the electrical system shown in Fig. 4.

In practicing the invention I provide a magnetic-type speaker having a cone-shaped diaphragm with a wooden plug at the apex thereof driven by a vibratory motor including a pair of frame members supported on the diaphragm supporting frame as well as adJustably serving-as a part of the magnetic circuit of the motor}- and clamping means to maintain the separable parts of the motor in assembled condition. The motor unit includes an armature positioned between a pair of pole pieces, and mounted for vibratory movement on mounting blocks at the ends of the armature supported directly upon the active pole faces of'the pole pieces, The blocks also act to space the pole faces apart to form with said armature, air gaps between the armature andpole faces. I The armature is operatively connected with the mounting blocks in a manner to accommodate very heavy operating forces developed in thearmature, and yet provide a comstmction a,sso,aoo A which can beassembled accurateiyandatlow cost. A short-circuited coil is provided around the stationary voice coil of the motor unit to serve optionally, or simultaneously, as a part-of a tone control system for the speaker, and a corrective network for the speaker circuit and output circuit of the radio receiver flierewith to prevent distortion at the high frequency end of the operating range. A driving mechanism yieldahle in substantially all directions radially of the apex of the diaphragm cone. acts to absorb possible distortion in the movement of the diaphragm, and

vibratorymotorl. 'rhevibratornmmormotor.

includes a pair of spaced frame members 8 and ILWiththememberHbeingsuitabIysecuredin arigidfasteningtotheportionlofthediapnrsgm frame. Apermanentmagnetllinbiockshape composedofamaterialhavinghighmagnetiere-v tentivity characteristics, such as variousmatal alloys available commercially,- is positioned with twoopposite facesresflngagainsttheframemsmbersiandllwhich'arepartofthemmdrcult through such permanent magnet is and throughtheremainderofthemagneflcstructure ofthemotor,aswillbeexplained.

'rhearmatureandpolepieceassemblyforthe motor includes a pair of substantially U-sh'aped pole pieces I and I! oppositely disposed, as shown in Fig. 1, both of laminated construction. avoioe coilvsubstantialiyovalinshape fitting snugly withinthe channels of the pole pieces, and

alaminatedarmature II 'withassociatedmountingmcans. 'lhearmature i1,intheillustrated embodiment, includes a pair of relatively heavy laminations ll. outwardly to each side of said heavy laminations are thinner laminations ll of thesamearea. Adiaphragm'drivingarmor portion 2. has a body portion integral therewith ofthesamesizeasthearmaturelaminations. and the body portion is positioned intermediate -.theheavylaminationsllasisshowninl1g.2.

The laminations II and the intermediate member 20 haveacentralapertureineachofsubstantiallythesamesizeasanarmaturemolmting or torsion spring 2| rectangular in crom-section and extending through the apertures in a press lit. The laminations ll have a larger central aperture which together form a bore 22 oneach side of the laminations It. To rigidly secure the central portion of the spring 2| within the laminated armature II, the spring is driven into the apertures in the laminations II and the member 2| with a drivingv or press fit. This is accomplished with a press. Punches driven in from each side of the armature through the bores 22 then stake the spring and these members together to make the connection even more rigid and secure. Rivets ll extend lengthwise through Bolderwilladheretothelamina'tions "and springil attheirconnectiombutwillbelhaken.

freeofthelaminationssndspringinthsbmu 22 so that the spring will be free of the armature over the length outwardly from laminations l8 to the stationary ends, as will be described. In the illustrated embodiment the free portions of the spring are each inch in length. This length must be great enough to provide a wide amplitude of vibration for the armature, but short enough so that the armature will be snubbed or stopped quickly and decisively for the reverse movement in a complete cycle. At ordinary operating frequencies the armature vibrates at great speeds, and with great power, as can be readily understood. with the present magnetic circuit,

The torsion spring 2| has an extension at eac end beyond the outer armature ends as shown in Figs. 2 and 3 which is yieldable over at least a portion thereof in accordance with the vibratory movement of the armature 11 as has been explained. The outer ends of the extensions, however, are rigidly supported, as will be described. The spring must be of such material as to provide the necessary flexibility and yet not permit the armature to vibrate through so great an amplitude of vibration that it will strike the adjacent pole faces of the pole pieces i l and It. The entire driving force of the armature is applied to the torsion spring between the laminations l8 and the stationary ends, and concentrated at its maximum at the axial center line of the spring. With the strong magnetic field developed in the magnetic circuit of the present invention and the high eiiiciency in the utilization of the magnetic forces in the motor, a considerable twisting or torsional deflection is applied at the axial center of the stationary ends.

The armature 'I1 is supported through the extending ends of the torsion spring 2i in mounting or torsion blocks 24 of a non-magnetic metal, with one of each of said blocks at each spring extension. Slight projections 26 on each of the two opposite sides of the mounting blocks fit between the corresponding legs of the oppositely disposed pole pieces l4 and It to center the blocks with reference to the active pole faces A of the pole pieces, and theadjacent edges 25 of each block rest directly against such active pole faces, as shown in Fig. 1. Thus, the mounting blocks support the armature and at the same time determine the spacing between the active pole faces A of the pole pieces I4 and IS. The faces A with the adjacent faces of the armature, form an air gap, or air gaps between the armature and pole pieces, as shown in Fig. 2A. The width of such air gap or gaps, determines the limits of the amplitude of vibration of the armature about its axial center without it actually striking the pole faces so as to cause an undesirable metallic sound in the speaker.

To accommodate the considerable forces developed upon movement of the armature and transmitted through the torsion spring to the mounting blocks without any danger of loosening betweenthe spring 2| and its entire support, this force is dissipated substantiallyjthrough a relatively integral metal portion at each stationary end of the spring, and is materially lessened sembly of the armature II, a paper disc or element 28 with a central aperture is placed over each spring extension with the edge of the aperture hugging the spring so that no solder will subsequently flow from the outer end of the spring onto the movable portion outside the end of the armature and extending into the bore 22 of the armature. This assembly is then placed in a fixture and the discs 21 are driven or pressed thereon, as previously described, being spaced 9. distance of inch away from the corresponding end face of the armature. In the embodiment of the invention illustrated herein, the armature from end face to end face is inch wide, and with the spacing of 3; inch between each disc 21 and the corresponding armature end, the inside faces of the discs themselves are spaced /2 inch apart. After this operation, the armature and assembled elements are mounted on the blocks 24 with the discs 21 fitting loosely within the aperture 29 in each mounting block. The aperture 29 has an inside diameter greater than the outside diameter of the discs so that there will be relative play therebetween in the original assembly. These parts are then properly positioned in two pole pieces in the manner shown in Fig. 1, and with these parts assembled in a jig, the armature is shimmed on each side to provide the desired airgap intermediate the armature and active pole faces A, the discs 21 meanwhile moving within the aperture 29 of each stationary block 24 until the armature is centered as desired.

With the inside dimension of the aperture 29 being greater than the perimeter of the disc 21, any misalignment between the discs and the spring 2| which might have occurred from shearing one side or the other in the pressing operation, is accommodated and the axial center of the armature can be centered in the air gap. Furthermore, inequalities in the disc and mounting blocks can be accommodated, and rather wide manufacturing tolerances permitted for the discs 21, and the apertures 29 in the mounting blocks. This makes possible a fast and inexpensive assembly, and also p rmits greater tolerances in the parts themselves which speeds up manufacturing and reduces costs without in any way sacrificing precision of operation in the finally assembled unit. When the armature is properly positioned with reference to the pole faces A, solder is flowed onto the mounting blocks to completely solder the gap between the edge of the discs and the inside edge of the apertures 29. At the same time the ends of the spring extensions in the apertures 21' of the discs are soldered to the discs. As mentioned, the paper blocks 28 prevent any of this solder from flowing on to the free portion of the spring where it might change the twisting action of the spring. The papers can be quickly torn from the armature assembly after the soldering operation.

After this assembly operation, a voice coil V including a wire coil 3| is inserted in the oppositely disposed channels of the pole pieces, the corresponding armature assembly is inserted into the center opening in the voice coil, and the active pole faces of the pole pieces l4 and iii are pressed against the edges 25 of the mounting blocks, as previously described. The armature will take the same position with reference to the pole faces as it did in the original assemblv which included the soldering of the discs 21 and mounting blocks 2i.

The pole-piece-armature assembly is positioned intermediate the frame members 8 and H at the end of the frame opposite that in which the magnet I2 is supported. The attraction between the frame members, in the magnetic circuit of the permanent magnet is such that the pole piece and armature assembly is maintained stationary, but in addition a pair of bolts or screws 32 extend through the two frame members to maintain a clamping tension on the motor to supplement the normal magnetic holding force, as described. The difference in length between the magnet l2 and the pole-piece-armature assembly is accommodated by bending the frame member ll inwardly toward the diaphragm frame at the outer end of the motor as shown in Fig. 1.

The diaphragm driving portion 20 extending from the armature is flat in form and provided in a relatively rigid material. The member 20 is operatively connected with the diaphragm by means of driving mechanism including elements constituting a step-up transformer for the vibratory motion of the armature. The mechanism is yieldable in at least four directions extending radially outwardly from the apex of the diaphragm cone 5. The yieldability of the driving mechanism absorbs strains and stresses which might develop in the cone in its normal vibratory motion as a result of a lack of uniformity in composition over its entire body and surface. It has been substantially impossible to provide entirely uniform cone diaphragms of composition paper material so that each part of the diaphragm will move uniformly in a straight-line direction axially of the axis of the cone. In magnetic-type speakers of the prior art this condition of the cone diaphragms resulted many times in distorting the armature out of its normal path of movement so that it was forced into contact with one or the other, or both, of the, pole faces A causing undesirable noises to be reproduced in the speaker. This difliculty has been overcome, however, by the driving mechanism including a stylus member 34 rigidly secured at one end in a wooden plug 36, which in turn is cemented to a flange F at the apex of the diaphragmu Abore, or recess R, is provided centrally of the plug at the rear face thereof, and a hooked end 35 of the stylus member 34 is secured in the recess R by a suitable cementious material.

The stylus 34 is preferably provided in a phosphor-bronze alloy material, of flat form, and about .007 of an inch in thickness. This thickness provides suflicient rigidity so as to faithfully transmit the movement of the driving mechanism to the diaphragm in a direction substantially longitudinally of the stylus, and yet the thickness and fiat form permits the stylus to yield or bend slightly when necessary in two opposite lateral directions extending from the opposite flat faces of the stylus. The projecting end 31 of the stylus is rigidly secured to the outer end of a step-up arm 38, which is yieldably supported at its inner end on a rubber mounting or grommet 39. The mounting 38, in turn, is supported on the frame member II, by a screw or similar supporting means 4|. The step-up arm 38 likewise is preferably provided in a phosphor-bronze alloy material, flat in form, and approximately .020 of an inch in thickness. Although the step-up arm 38 is thicker in cross-section than stylus 34, it is still yieldable in two opposite lateral directions which are at right angles to the direction of lateral movement of the stylus 34 as can be understood from the consideration of Fig. 1. However, the step-up arm 38 is sufliciently rigid so that it accurately transmits the movement of the driving arm 20in the desired step-up ratio. The step-up arm 38 is connected to the driving arm 20 by a connecting member 42 of substantially the same thickness as the stylus 34 and of the same material. Connecting member 42 is rectangular in cross-section and yieldable in the same lateral directions as the stylus 34 if strains are applied to the driving mechanism to move it slightly out of a normal substantially straightline movement for its individual parts.

The yieldability of the driving mechanism in at least four directions in addition to absorbing unequal stresses and strains in the diaphragm 5 also prevents undesirable strains which have heretofore been applied to the diaphragm by the driving mechanism of the magnetic-type speakers of the prior art. As will be noted from Fig. 1, the upper end 33 of the driving arm 20, by virtue of the length of such driving arm, moves through an arcuate path of appreciable length. The movement of the end 33 is stepped-up in the driving mechanism, and there is appreciable movement of the members 38 and 34, with the end of the member 38 moving in the same general arcuate path. With the normally rigid parts of the prior art driving mechanism it is readily understood that an element comparable to the stylus member 34 would act to pull the diaphragm out of a straightline movement axially of the axis of the cone. The members of the present driving mechanism yield so that the diaphragm moves in the desired straight-line path, rather than beingfor'ced, due to a rigid stylus and associated elements, to follow the stylus.

As previously mentioned, if the diaphragm, on the other hand, would tend to move irregularly due to any inequalities in its composition this is absorbed in the driving mechanism and the armature is not disturbed in its normal-vibratory path. The yieldability of the entire driving mechanism connected to the arm 20 is improved by virtue of the rubber mounting 38 for the step-up arm, and the entire mechanism has a desired degree of flexibility without in any way impairing an efficient transmission of force from the arm 20 to the diaphragm 5.

The accepted method of connecting a stylus and paper cone diaphragm in the prior art ma netic-type speakers has been a metal washer assembly at the apex of the cone to which the stylus is soldered or otherwise secured. This has resulted in undesirable metallic sound being reproduced in such speakers, and at times difliculties have arisen as a result of the metal washer unit becoming loose on the cone. These difficulties have beenovercome, and a more mellow,

pleasing tone obtained from the speaker by use of the wooden plug 36 cemented to the cone 5 at its apex and carrying the stylus 34, as previously described. In the preferred embodiment of the invention a plug of white birch has been employed. There is a desired porosity in this wood, although somewhat limited, and a hardness such that sound is faithfully reproduced by the speaker. A soft wood is undesirable because it will not faithfully reproduce sounds, and yet the plug material must not be so hard that a. shrillness results.

In loud speakers of the prior art, particularly of the magnetic type there have been at least two problems of a serious nature with reference to the frequency of reproduction in the speaker system. The normal extremes of frequencies in the operating range are cycles and 5000 cycles.

Various radio receiver manufacturers desire different cut-oi! frequencies in' the loud speakers for their receivers, so that the final result seems to be an emphasis on one range of frequencies or another rather than the maximum fidelity over the entire range. The accepted method in the prior art of satisfying these requirements has been to shift from one paper composition cone diaphragm to another until the desired reproduction is obtained. This has necessitated carrying a large number of cone diaphragms in stock. light, heavy, and intermediate, in composition. Merely by "cut and try" the desired result was finally obtained. Such efforts in this respect were sometimes wasted, however, when diaphragm characteristics changed as a result of absorbing moisture or the like after the speaker was manufactured.

The second difliculty considered above has been that of providing a corrective network for magnetic-type speakers, in particular, to compensate for a normal impedance increase with an increase in frequency in the output tube and speaker circuit. Normally, as the impedance rises in the vibratory motor circuit beyond an optimum resistance, or load, to be applied to the output tube in the circuit of the receiver, harmonics are generated and they introduce distortion in the speaker system.

Both of these difficulties have been overcome by the use of a supplementary short-circuited coil 43 wound around the insulation on the wire 3| of the voice coil and inductively coupled to such voice coil. The voice coil has a certain self-induction, and with the coil 43 wound upon the voice coil so that the coupling, or mutual inductance between the coils is not zero, the effective inductance of the voice coil 3| is reduced. The

voice coil becomes, in one sense, a primary and the coil 43, a short-circuited secondary thereon. The amount of reduction in the effective inductance of the voice coil depends upon the degree of coupling between the two coils, upon the frequency in the voice coil, and upon the resistance of the circuit of the supplementary coil 43. Furthermore, the coil 43 not only produces a re duction in the effective inductance of the voice coil, as the frequency increases in the coil circuit, but the coil 43 also increases the resistive component of the voice coil. Therefore, as the frequency in the circuit of the output tube 44, and hence in the voice coil, increases, the amount of current induced in the coil 43 is increased and a greater proportion of the energy available from the tube 44 is consumed by the coil 43. This tends to maintain the optimum resistance or load on the tube 44 constant throughout the frequency range to be produced, and to prevent generation of harmonics at the high frequencies which would result in undesirable distortion in the sound reproduced in the speaker.

The amount of decrease of the impedance of the voice coil depends upon various factors in the supplementary coil 43, and in the relation between the two coils. The action of the coil 43 depends upon the degree of coupling between it and the voice coil, upon the number of turns of wire in the supplementary coil, and upon the resistance in the supplementary coil circuit. These factors can be changed in a single coil by varying the spacing between the coils 3| and 43, by varying the number of turns in the coil 43, and changing the resistance in the coil 43 circuit, by the means, for instance, of changing the wire to one of a different resistance. Some one or all of these factors can be changed to affect the optimum load resistance on the output tube 44, as well as change the frequency cut-off point to obtain the tone desired by a particular purchaser. After the particular result is obtained the coil 43 can be duplicated for all future speakers to provide the same coil factors, and consequently the same speaker characteristics.

However, since the coupling, and the number of turns in the coil 43 can be designed to be constant for a rather wide variety of conditions, control over the operating range of the speaker can be obtained by inserting variable means in the supplementary coil circuit. In Fig. 5 the coil 43 is illustrated in a circuit with a variable resistor 46 which can be installed so that it is available at the front of the radio receiver cabinet in which the speaker is installed, and hence serve as a tone control for the speaker. Likewise, as can be understood, such a circuit can be used to advantage by a manufacturer in determining the speaker characteristics he desires. The resistor can be varied until the desired frequency cut-off is obtained and the circuit of coil 43 can then be duplicated in a coil to be wound upon the voice coil 3|, as previously described.

Another variable circuit is illustrated in Fig. 6 with the short-circuited coil circuit including a fixed resistor 41, and a switch in which an arm 48 can be moved to various terminals to vary the resistance in the complete circuit.

Fig. 7 illustrates a coil 43' normally of a number of turns to take care of the maximum conditions, and a switch with terminals 49 connected to various parts of the coil 43'. A switch arm 5! is movable over the terminals to vary the effective coil portion in the circuit. The circuits and structures of Fig. 6 and Fig. 7 can be employed as tone controls in the same manner as described for the circuit of Fig. 5.

The invention thus provides a magnetic-type loud speaker with a powerful magnetic circuit, and a ruggedness of mechanical design to accommodate the large power output of the vibratory motor. The vibratory motor and associated elements are simple in design, and readily adapted for inexpensive and yet accurate manufacture, and with all of the parts easily accessible in the motor frame both during manufacturing assembly, and service work. The entire unit is provided in a construction and with an electrical circuit (including the magnetic circuit), such that a pleasing reproduction is obtained with remarkably high fidelity. The same vibratory unit embodying the present invention has been used in a single size, except possibly a slight change in the size of the permanent magnet, to drive cone diaphragms ranging all the way from three to eight inches in diameter, and provide the same desirable operating characteristics for the speakers in all of these sizes.

It is to be understood that only the preferred embodiment of the present invention has been illustrated and described herein, and that alteration thereof can be made which are within the scope of the invention as defined by the appended tween the pole faces and axially of the correspending end of the armature, with each mounting block having an aperture centrally thereof, means for operatively connecting each mounting portion and its corresponding mounting block including a disc with an outside perimeter smaller than the inside dimensions of the mounting block aperture, whereby the armature may be centered with reference to the pole faces during the assembly of the parts, and means rigidly mounting each of said discs in its corresponding aperture against relative movement after the final positioning thereof.

'2. In a vibratory unit for a loud speaker having a diaphragm, an armature unit including an armature member having an axially extending supporting spring, a disc element rigidly mounted at each end of said spring, a pair of spaced nonmagnetic supporting members for said spring, each of said non-magnetic members having an opening therein adapted to loosely receive a corresponding one of said disc elements, and a pair of oppositely arranged magnetic pole faces operatively associated with said armature member, said two disc elements being of lesser dimensions than the openings in said non-magnetic members to provide for a predetermined spaced relation of said armature member with said pole faces, and means rigidly securing said disc elements to said non-magnetic members to retain said predetermined spaced relation.

3. In a motor for a magnetic type loud speaker having spaced pole means defining a gap therebetween, the combination of an armature positioned in said gap adapted to oscillate about an axial center therein and apertured mounting means on each of two sides of the armature for mounting the armature in said gap, with said armature and the two mounting means being operatively connected at one portion on each mounting means in a fused metal connection, said armature having an extension to each side thereof including the axial center for the armature, and means for displacing said fused metal connection radially from the axial center of the extension at each mounting means including a disc on each extension and rigidlysecured thereon and fitting within the aperture in the corresponding mounting means, with the perimeter of each disc displaced radially from said axial center, and said fused metal connection being between said disc and said mounting means at said perimeter and said aperture.

4. In a motor of the magnetic type having spaced pole faces with a gap therebetween, the combination of a vibratory armature positioned in the gap between said pole faces having an axial portion extending to each of two opposite sides beyond the corresponding side faces of the armature, said axial portion being stationary at its outer ends outside of the corresponding sides of said armature and being movable with said armature inwardly of said ends, an apertured stationary mounting block for each stationary end, and means for anchoring the outer ends of said axial portion within the apertures of said mounting blocks, said anchoring mean comprising flat metal parts rigidly mounted upon the ends of said axial portion and having edges which loosely fit within said apertures, and a fused metal connection between the outer edge surface of each of said metal parts and the adjacent inner edge surface of its associated mounting block.

5. A motor for driving a loud speaker diaphragm including a frame member, a permanent magnet in block shape resting on said frame member at one end thereof, a pair of pole pieces having an armature and a voice coil therebetween supported as an assembly on said frame member at the other end thereof with the outside of said assembly exposed and readily accessible at the end of the frame member, said armature having a driving portion thereon extending toward said one end, a second frame member ubstantially parallel to said first frame member engaging said magnet on a side thereof opposite said first frame member and engaging the pole piece assembly on a side thereof opposite the first frame member, with said frame members being maintained in position generally by the magnetic attraction in the magnet block and pole pieces, means operatively connected to said driving portion and extending therefrom for connection with a loud speaker diaphragm, and supplementary frame assemblylng means consisting of a pair of bolts extending between said frame members, with said driving portion and said operatively connecting means being exposed and readily accessible at the ends of the frame members adjacent the permanent magnet.

6. A motor for driving a loud speaker diaphragm including frame means, an armature unit having a diaphragm driving portion, and means operatively connected with said driving portion for connection to a diaphragm including a stylus member having a projecting end, with said stylus member being rectangular in cross-section and yieldable laterally in only two opposite directions, a step-up arm rigidly secured at one end to the projecting end of said stylus member, being rectangular in cross-section and yieldable only in two opposite directions, said directions being substantially at right angles to the direction of lateral movement of the stylus member, said step-up arm being supported at its other end on said frame. means, and means connecting said step-up arm with said diaphragm driving portion being rectangular in cross-section and yieldable laterally in the same directions as the stylus member, said yieldability of the stylus member, said stepup arm, and said connecting means being such as to accurately transmit the driving motion of said driving portion to a diaphragm while permitting a substantially free movement of such diaphragm in a direction other than a straight-line direction longitudinally of the stylus member.

7. A vibratory unit for a loud speaker diaphragm including frame means, an armature unit having a diaphragm driving portion, a step-up arm of fiat form laterally flexible in two directions, means supporting one end of said step-up arm on said frame means, with its other end being rigidly secured to the projecting end of a stylus element for a diaphragm, a stylus element of flat form laterally flexible in two directions which are substantially at right angles to the directions of lateral movement of said step-up arm, and a connecting portion rigidly secured at one end to said step-up arm at a point intermediate said supported end and stylus element and rigidly secured at its opposite end to said diaphragm driving portion, said connecting portion being of fiat form and laterally flexible in the two lateral directions of said stylus member, with the flexibility and relative arrangement of said stylus member, step-up arm, and connecting portion providing for a free vibrational movement of a diaphragm in response to the movement of said armature and diaphragm driving portion.

8. A vibratory unit for a loud speaker diaphragm including frame means, an armature unit having a diaphragm driving portion, said diaphragm driving portion being of relatively rigid construction and straight over its longitudinal length, a stylus member rigidly secured at one end to said diaphragm and having a portion projecting therefrom, said stylus member being adapted for yielding in a plane which is at substantially right angles to the plane in which said driving portion normally moves, a step-up arm rigidly secured at one end to the projecting portion of said stylus member, means including yieldable means for directly supporting said stepup arm at its opposite end on said fram means, said step-up arm extending longitudinally substantially in the direction of said driving portion but spaced therefrom and being yieldable in lateral directions opposite to the directions of lateral yielding of said stylus'member, and a member connecting said driving portion with said step-up arm and yieldable laterally in the same directions as said stylus member, with said connecting member extending in a plane substantially parallel to the plane of said stylus member, said stylus member, said connecting member, said step-up arm, and said yieldable supporting means cooperating on movement of said driving portion to absorb any strains which might develop in a diaphragm and thereby provide for a substantially fre vibratory movement of such a diaphragm.

' 9. In driving means for a loud speaker diaphragm a vibratory armature with a diaphragm driving portion, the means connected to said diaphr gm driving portion for operatively connecting said portion to a diaphragm and absorbing in said means strains-which might develop in said armature or such a diaphragm to be driven thereby tending to disrupt th free movement of either, said means including a plurality of connected driving members, at least two of which driving members are rectangular in cross-section and substantially non-yieldable in either of two lateral directions ther from, and yieldable in two oppositely disposed la eral directions substantially at right angles to said first two mentioned lateral directions.

10. In a vibratory motor having an air gap and a movable driving member therein having axial extensions extending outwardly in two opposite directions therefrom, apertured mounting means for each axial extension, and means for securing ,each axial extension in a corresponding aperture with said driving member occupying a predetermined position in said air gap, including a. soldered connection displaced from the axial center of the driving member so that the forces generated upon movement of said driving member are transmitted to said mounting means through substantial segments of the soldered connections, and including a disc rigidly secured on each axial extension with the perimeter of the disc smaller than the inside edge of the aperture of the corresponding mounting means into which it is positioned, and with said soldered connection being applied between the disc and the mounting means at such aperture.

11. In a unit for vibrating a loud speaker diaphragm, a pair of spaced-apart metal supporting members each provided with an opening therein, a spring bar having ends positioned within said openings, a mounting element rigidly mounted upon each end of said spring bar within one of said openings, said mounting elements being of lesser dimensions than said openings but of substantially greater dimensions than the cross-sectional dimensions of said spring bar, fused metal connections between the adjacent surfaces of said mounting elements and said supporting members, and an armature rigidly mounted upon said spring bar between said supporting members.

12. in a unit for vibrating a loud speaker diaphragm, a pair of spaced-apart assembly members, a field structure including said members and a pair of magnetic field pieces having oppositely disposed pole faces, spaced-apart nonmagnetic mounting platesv interposed between said neld pieces and having edge portions bearing against said pole faces to maintain said field pieces spaced apart, means extending between said assembly members for clamping the named parts together to Provide a rigid assembly, an elongated armature driving element flexibly anchored at one end on one of said assembly members, a second elongated driving element connected at one of its ends to an intermediate portion of said armature driving element and extending substantially normal thereto, an armature interposed between said pole faces and provided with a driving arm connected to the opposite end of said second driving element, said mounting plates each being, provided with an opening therethrough, an elongated torsion spring rigidly supporting said armature between said pole faces and provided with ends extending within said openings, mounting elements rigidly mounted upon the ends of said torsion spring positely disposed pole faces, spaced-apart nonmagnetic mounting plates interposed between said field pieces and having edge portions bearing against said pole faces to maintain said field pieces spaced apart, means extending between said assembly members for clamping the named parts together to provide a rigid assembly, an elongated armature driving element flexibly anchored at one end on one of said assembly members, a second elongated driving element connected at one of its ends to an intermediate portion of said armature driving element and extending substantially normal thereto, said two driving members being rectangular in cross section and being arranged with their fiat surfaces disposed in planes which are substantially normal to each other, an armature interposed between said pole faces and provided with a driving arm connected to the opposite end of said second driving element, said mounting plates each being provided with an opening therethrough, an elongated torsion spring rigidly supporting said armature between said pole faces and provided with ends extending within said openings, mounting elements rigidly mounted upon the ends of said torsion spring and loosely fitting within said openings, and fused metal connections between the adjacent edge surfaces of said mounting elements and said plates.

JAMES P. QUAM.

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