US2013953A - Loud speaker attachment - Google Patents

Description

Sept. 10, 1935. E. GRISSBNGER 2,013,953

I LOUD SPEAKER ATTACHMENT Filed May a, 1931 2 Sheets-Sheet 1 gwumioz p 0, 1935- E GRISSINGER LOUD SPEAKER ATTACHMENT Filed May 8, 1951 Z'Sheets-Sheet 2 F/GJT dwomqa til strictly rectilinear,

Patented Sept. 10, 1935:

Uhill'iil S'ETES PATENT OFFIQE Application May 8, 1931, Serial No. 536,055 Renewed danuary 22, 1935 16 Claims. (Cl. 181-31) This invention relates in gen ral to sound reproducing devices, and more particularly has ref.- erence to an attachment for loud speakers of the cone type for improvin the efiiciency thereof.

The cone diaphragms now generally used in dynamic speakers, consist of a cone made of an especially prepared and impregnated substantially non-hygroscopic fibre paper. The cone diaphragm adapted to set the free air into vibra tion by connection of the smaller end corresponding to the apex, to a moving coil of an electromagnet.

For the proper functioning of the cone, it is highly desirable that the motion of the same be In practice, however, it been found difiicult to obtain this condition no matter how light the movable system is con-- structed.

The cones usually employed are generally constructed with a approximately six inches in with a diame oer of substantially one and one fourth inches at the small end or the apex, and with a perpendicular of approximately three inches from the base to the apex. Since these cones are usually mounted with the perpendicular from the base to the apex, in a horizontal position, it is manifest that the inertia and mass efas a whole are directed downwardly. The resultant push and pull of the cone in operation produces an irregularity in the rectilinearmotion of the same, depending to a considerable degree upon the frequency of the actuating wave of the electro-magnetic force. This physical irregularity in the motion of the cone produces an objectionable distortion in the sound reproduced.

The surfaces presented by cones of this type, further, are both internally and externally quite extensive in area, and the gives rise to a considerable amount of resistance against movement of the same. The effect of the air resistance is, of course, greatly increased with an increase in the frequency of vibration. When the cone is moved in one direction, resistance over the surface of one side introduces an error into the sound reproduced, and the cone in returning to its normal position in the opposite direction encoun ers reverse air resistance exerting a further distorting influence.

One of the purposes of. the present invention is to provide for true rectilinear motion of the cone diaphragm and to thus remove the effect which is introduced by forces and movement oblique to the central axis thereof under the influence of different and differing frequencies. This has in some measure been accomplished in the past by the provision of various types of supports for fixing the position of the free end of the cone diaphragm to provide for a true straight line motion thereof.

The types of supports previously employed, however, although providing for the proper support 5 of the cone diaphragm have been of. a character which has detracted from the efficiency of the speaker in other respects, such as the introduction of a damping factor.

Metallic ring supports engaging around the innor periphery of a cone diaphragm, or fibre supports fitted in the throat of a cone diaphragm at its apex, have been those generally employed. Both of these types of supports, while providing for a straight line movement of the cone to eliml5 inate the distortion which results from oblique movement have tended to dampen the vibrations of the cone, as well as to develop a loss of clarity in the reproduced sound.

An object of this invention is to provide for 20 an attachment for a cone diaphragm for additionally supportmg the same to obtain a true straight line movement to greatly reduce distortion of reproduced sound without damping of the same, and for increasing the free period of vibration of the cone diaphragm.

A further object of this invention is to provide an attachment for a cone diaphragm for additionally supporting the same for straight line movement to eliminate distortion of the reproduced 3 sound, which may be adjusted in such a manner as to increase the free period of vibration of the cone diaphragm, and resulting in an improvement in the definition of the reproduced sound.

With these and other objects in view, which may be incident to my improvements, the invention consists in the parts and combination to be hereinafter set forth and claimed, with the understanding that the several necessary elements comprising my invention may be varied in construction, proportions and arrangement without departing from the spirit and scope of is appended claims.

In order to make my invention more clearly understood, I have shown in the accompanying drawings, means for carrying the same into practical effect without limiting the improvements in their useful applications to the particular constructions which, for the purpose of explanation, have been made the subject of illustration. 5

In the drawings forming a part of the specification:

Figure 1 is a front View of my attachment shown in conjunction with a conventional sound reproducing unit.

Figure 2 is a sectional view of my attachment and the sound device shown in Figure 1.

Figure 3 is a perspective view of a modified form of diaphragm.

Figure 4 is a sectional view of a modified form of attachment.

Figure 5 is a sectional view of a modified form of mounting for the attachment shown in Figure 4.

Figure 6 is a front view partly broken away, showing still another modified form of mounting for the attachment.

Figure '7 is a sectional view of the structure shown in Figure 6.

This invention consists in general of a supplemental diaphragm seated by a force fit around the inner periphery of a cone diaphragm, in coaxial alignment therewith, and statlonarily mounted on the pole piece of the electromag netic reproducing unit, in longitudinal adjustable relation thereto, for additionally supporting the normally free end of the cone diaphragm to provide for a true straight line movement thereof with the elimination of distortion, resulting from Oblique movement, and without damping the reproduced sound; and to provide a means for increasing the free period of vibration of the cone diaphragm to markedly improve the definition of the reproduced sound.

Referring more particularly by numerals to the drawings and especially to Figure 2, there is shown in section a housing I, enclosing a conventional electromagnetic unit for actuating a cone speaker, provided with a cover 2. The electromagnetic unit comprises the usual field coil 3, seated in the closed end of the housing, and a pole piece 4 extending through the coil 3 in central relation thereto, and fixed to the closed end of the housing by a bolt 5. The other end of the pole piece 4 is adapted to extend through a central aperture provided in the housing cover 2, terminating flush with the outer face thereof.

The pole piece is adapted to carry a neutralizing coil 6, positioned against a spacing ring I, secured on the underside of the housing cover 2 by bolts 8. Contact of the neutralizing coil with the field coil is prevented by an annular projection 9, formed on the pole piece therebetween.

The spacing ring 1 is formed with a dishshaped bottom as at ll], adapted to form an air gap for receiving a moving coil ll, positioned on a sleeve l2, telescoped over the end of the pole piece, and adapted for free longitudinal movement with respect thereto.

A conventional transformer Lmit consisting of primary and secondary coils i3 and i3, and a core M, are held on a frame l5 fixed to the housing I by the screw 5, which also fixes the inner end of the pole piece in the housing I. The transformer unit is fixed to the frame l5 through a member l6, connected thereto in any suitable manner (not shown). The member It is fixed to a casing ll, enclosing the core, and having fianges l8 for fixing on the member I6 by a bolt IS.

The operation of this unit, which has been perfunctorily described as illustrative of a conventional structure, will be apparent. The sleeve l2 mounted on the apex of the cone 2!), and free to move longitudinally with respect to the pole piece 4, is under the influence of the actuating coil ll. Standard one hundred and ten volt alternating current is transformed to provide a secondary voltage of twelve volts in the transformer, which is rectified to seven and one half volts, and applied to the terminals of the field coil 3.

Energization of the field coil by the rectified current results in a variation of the magnetic flux, caused by the fluctuation of the rectified current. The movable coil is connected to an audio frequency circuit in which are produced modulations of current corresponding to sound waves. These currents are passed through the movable coil, creating a magnetic field which reacts with the field in the air gap with a force in exact proportion to the current in the movable coil. The coil II is thus moved, causing a corresponding movement of the sleeve i2, according to the variations in the current from the audio frequency circuit. There is a variation of the magnetic flux when the field coil is energized by the rectified alternating current, producing an induced voltage in the movable coil, which is practically short-circuited. The secondary winding of the transformer is thus caused to normally produce an undesirable hum. This hum is much reduced by the neutralizing coil wound directly on the core and connected in series with the movable coil, so that any fluctuations of the current produced by a varying field are impresses equally on both the moving coil and the neutralizing coil. These two coils are so connected that the disturbing currents oppose and neutralize each other thereby reducing the intensity of the undesirable hum.

A cone diaphragm 20 is adapted to be connected to the sleeve ii, for translating the forces set up therein by the coil I i into air vibrations to reproduce the original sound waves. The smaller end or apex of the cone 20 is mounted over the end of the sleeve i2, which is composed of insulating material, and centered thereon by a ring 2!. The base of the cone is connected to a flexible ring 22, secured on a cup-shaped frame 23, provided with apertures 24 to reduce the weight, and to reduce the effect of an air cushion, which would otherwise be present. The ring 22 is connected to an annular flange formed on the frame by screws 25 and held thereon by an outer flanged frame ring 26. Washers 121i, composed of any suitable insulating material, are interposed between the flange '24 and the outer frame member 26.

The rear of the frame 23 is provided with a I central aperture and connected to a central ring 28 for centering the cone with respect to the pole piece. Adjustment of the centering ring ?8 and the spacing ring I is adapted to be accomplished by fixing of the bolts ii to coaxially align the pole piece and the cone.

My novel attachment forming the subject matter of this invention, is adapted to be mounted on any conventional type of speaker such as the one which has been described. In the pr form of my invention, the device is mounted on the pole piece of the electro magnetic unit adjacent the smaller end or apex of the cone diaphragm.

As will hereinafter be seen, however, if this mounting is undesirable in a particular structure, the attachment may be similarly positioned by mounting on an element other than a pole piece, and positioned on the outside of the periphery of the cone diaphragm rather than on the inner periphery, as preferred.

My attachment comprises an anchorage, as shown in Figure 2, consisting of a threaded shaft 29, formed with a shoulder portion 29 adjacent one end. The other end of the threaded shaft 29, carrying the shoulder portion is adapted to be screwed in a central aperture provided in the pole piece 4, the face of the shoulder 23' adjacent the end of the shaft being adapted to abut the face of the pole piece. A diaphragm 3D, composed of mica, spring brass, phosphor bronze or any suitable material, preferably of a resilient nature, is mounted over the shaft 29. The diaphragm at in its preferred form is circular and adapted to engage the cone diaphragm 25 around its inner periphery, with a changeable force fit. The diaphragm is provided with an enlarged central aperture 3i as shown in the modified form of diaphragm to be later described, illustrated in Figure 3, for allowing the diaphragm to be loosely fitted over the neck 32 of the collar 33.

The diaphragm is adapted to be positioned on the shaft by fitting over a neck 32, formed on a collar 33, screwed on the shaft. The diaphragm is held against the face of the collar 33 by a washer E i, and fixed in place by a lock nut 35. The collar, washer, and lock nut, 83, 34, and 35, as well as the shaft 23 are preferably composed of brass or other material possessing a considerable mass, so that these elements will not introduce any vibration into the system.

In the mounting of the diaphragm, the enlarged central aperture permits centering thereof with respect to the inner periphery of the cone, compensating for any inaccuracies in the structure of the complete assembly. The diaphragm is adapted to be securely clamped between the abutting faces of the washer and the collar by the lock nut. It will be appreciated that movement of the diaphragm is limited to the portions projecting radially from the rims of the washer and collar.

The operation of the diaphragm thus clamped is distinctly different from that of the diaphragm clamped at either its center only or at its periphery, in which cases, nodes are formed. In my device, the small portion of the diaphragm 3t lying between the edges of the parts 33 and 34 and the inner surface of the cone 28, will break up such nodal tendencies as will form in diaphrag'ms free to move across their faces, or up to a small central support. Such free period as the exposed portion of the diaphragm 38 will have, will be sufficiently high, when coupled with the damping factor introduced by its contact with the inner faces of the cone 26 as to make its resonance imperceptible to the ear. The mass of the anchorage and the parts 33, 1%, and 35 is made sufficiently great, that no vibration from those sources can be perceptibly introduced. Although the diaphragm engages the inner periphery of the cone diaphragm with a changeable force fit, the insertion of this element in no way mitigates against the vibration of the cone diaphragm. On the contrary, instead of damping or retarding the vibration of the cone diaphragm to reduce the volume, there is a marked improvement in the definition of the sound produced.

The diaphragm 3B, engaging the periphery of the cone diaphragm 2c, appreciably raises the free period of the vibrating system, and tends to reduce the hum normally present in speakers of this character to the practical elimination of the same.

The increase of the free period of vibration of the cone diaphragm is effected by the stiffness which is added thereto by the diaphragm 30,

which is, however, resilient so that the vibrations are not damped.

The supplemental diaphragm 355, while placing a tension on the cone diaphragm to increase the free period of vibration of the same, additionally supports the end of the cone to allow for a true straight line movement thereof to eliminate the distortion due to oblique movement, heretofore present in diaphragms of this character. The diaphragm also makes the cone less sensitive and thus decreases the objectionable hum heretofore generally present.

In increasing the free period of vibration of the cone diaphragm to markedly improve the definition and quality thereof, there is an apparent impression of raising the pitch of the reproduced wave. If too great a tension is placed upon the periphery of the cone diaphragm by the supplemental diaphragm with the attempt to raise the free period of the system to too great a degree, there is an apparent reduction in the volume of the reproduced sound thereof, although the definition thereof is improved. Manifestly this reduction. in volume may be compensated for by adjustment of the volume control as respecting the input energy into the actuating coil I I.

While it is preferred to employ a mica diaphragm, as has been previously stated, suitable metallic diaphragms may be substituted therefor U and portions of the periphery of the diaphragm may be cut away, for example, as is shown in Figure 3, wherein a diaphragm having portions cut away around the periphery is illustrated.

Three spiders 35 having their ends turned over as at 3'1 for providing smooth bearing surfaces for engaging the inner periphery of the cone diaphragm are shown. Manifestly, while only three projections are illustrated, any other number may be substituted therefor, engaging a corresponding number of points around the periphery of the cone diaphragm. With a lesser portion of the periphery of the supplemental diaphragm engaging with the periphery of the cone diaphragm, the centering of the supplemental diaphragm is simplified to a corresponding degree.

Any physically vibrating system possesses, somewhere in the scale of frequencies, a region of resonance. The location of this region of resonance in the frequency band, in the absence :1

it is highly desirable that the said vibrating sysl tem shall possess, as near as possible, but one degree of freedom. The introduction of the device herein referred to, as one of the elements of a physically vibrating system, will not change the fundamental requirement of a single degree of freedom in a physically vibrating system, for reasons to be pointed out when referring to the sp cific details of the element as shown in Figures 1 and 2.

The mica, or other type of diaphragm, serves as a restoring force to the vibratory element. Such resonance as it may have will be in the region of the higher frequencies, practically imperceptible and, moreover, it will be damped out by the action of the cone itself.

The addition of my device, properly assembled and adjusted with respect to the type of movable system described, gives a positive restoring force to the vibratory elements.

In Figures 4 through 7 are illustrated modified forms of supplemental diaphragins and mountings therefor, capable of being substituted for the preferred forms described.

In Figure 4 is shown a diaphragm 38 provided with an enlarged central aperture for engaging the outer periphery of a cone diaphragm 2t adjacent its smaller end or apex. lhe diaphragm 3B is adapted to similarly support the free end of the cone diaphragm and increase the free period of vibration thereof, as has already been escribed with reference to my preferred form of diaphragm. The diaphragm 38 is clamped around its outer periphery between the iiange 39 former on an internally and externally threaded sleeve 4G and a ring 4| screwed therein. The ring 48 is screwed in a sleeve 42 provided with an angularly formed peripheral portion 43 for being secured to the inner surface of the cup-shaped member 23. Adjustment of the fit between the supplemental diaphragm and the outer periphery of the cone diaphragm is adapted to be accomplished by screwing the sleeve 40 relative to the sleeve 42.. Fixing of the diaphragm is effected through the agency of a locking ring as, secured on the sleeve M] for engaging the outer face the fixed sleeve 42.

In Figure 5 is shown a similar type of mount ing, except that the assembly for screv g th supplemental diaphragm is hired on the housing cover 2, in place of the frame member In this construction the centering ring is formed with an outer externally threaded tubular flange 45 for receiving a threaded sleeve having an integrally projecting flange 4! formed on the outer end. A diaphragm 38 with an enlarged central aperture for engaging the outer periphery of the cone diaphragm, is adapted to be secured between the flange 4? and an integrally projecting flange :18, formed on a sleeve l screwed on the sleeve 46. Positioning of the diaphragm 2-3 with respect to the cone diaphragm adapted to be ac complished by screwing the sleeve relative to the tubular flange 45. The position of the diaphragm fixed by a locking ring 50 screwed on the tubular 45 for the inner face of the sleeve 46.

In Figures 6 and '7 is shown a modified form of attachment for mounting on loud. speakers having the sound reproducing on is mounted in the base portion of the cone diaphra m, rather than ou side of the small end or A cone diaphragm 5|, having a flanged base portion is mounted between supplemental i'raine members and 53. The frame member 52 is formed with cross bars 54, terminating in a central disk to which is fixed a sound reproducing unit The moving coil of the sound reproducing unit (not shown), is connected to the apex of the diaphragm 5! by a rod 5'! engaging an aperture in a cup member 53, on the apex of the cone diaphragm. Relative movement between the cup member and diaphragm is prevented by a lock nut 59.

A supplemental diaphragm lid, having an enlarged central aperture is fitted over a neck 5i formed on a collar 62. The diaphragm fixed on the collar by a ring 63, screwed over the neck 6! thereof. The collar 62 is mounted on arm M secured at the other ends in internally threaded sleeves 65, mounted for rotation in the cross bars 54. It will be seen that adjustment of the diaphragm with respect to the cone diaphragm 5i may be accomplished by rotation of the sleeves B5. Centering of the diaphragm (it! is effected by relative potation of the sleeves 65 to decrease or lengthen the respective arms 64 supporting the diaphragm attachment.

It will be appreciated from the foregoing description of my invention and the modifications thereof, that the same is susceptible of wide variation in construction to additionally support the free end of a cone diaphragm to provide for true straight line movement thereof and eliminate distortion, and to improve the definition of the sound reproduced by increasing the free period of vibration of the cone diaphragm.

There accomplished by this invention an attachment for a sound reproducing device including a cone diaphragm adapted to additionally support the same to provide for a true straight l ne l'novenient thereof, eliminating the distortion heretofore introduced in such cliaphragnis by oblique vibrations, and further adapted to increase the free period of vibration of the cone for diaph improving the definition and at in any wise damping the vibrations of the cone.

While 1. have shown and described the preferred embodiment of my invention, I wish it to be understood that I do not confine myself to the precise details of construction herein set forth way of illustration, as it is apparent that many changes and variations be made therein, by those skilled in the art, without departing from the spirit of the invention, or exceeding the scope of the appended claims.

I cla m:

1. In a sound reproducer including a cone diaphragm, a supplemental diaphragm having its outer peripheral edge adapted to engage the 3. In a sound reproducer including a cone diaphragm, a flexible member connected by a force it at portions around the periphery of the cone diaphragm adapted to increase the free period of vibration thereof.

l. In sound reproducer a cone diaphragm, a I supplemental diaphragm for engaging the cone diaphragm on its peripheral edge, at portions around the periphery of the cone diaphragm.

5. In a sound reproducer a cone diaphragm, a diaphragm for force iit connection to the cone diaphragm on its peripheral edge, at portions around the periphery of the cone diaphragm to additionally support and provide for a true straight line movement of the cone diaphragm and to crease the free period of vibration thereof.

6. In a sound reproducer a cone diaphragm, a member for additionally supporting and providing for a true straight line movement of, and for increasing the free period of vibration of the cone diaphragm, comprising a stationarily mounted disk for force fit connection to a cone diaphragm at portions around its periphery.

7. In a sound reproducer, a cone diaphragm, a member for additionally supporting and increasing the free period of vibration of the cone diaphragm fitted around the periphery thereof but unattached.

8. In a sound reproducer a cone diaphra a all) circular diaphragm having a continuous sLu'face 75 for engaging with its peripheral edge the periphcry of the cone diaphragm to additionally support and increase the free period of vibration thereof.

9. In a sound reproducer, a cone diaphragm, a diaphragm having radial projections for engaging portions of the cone diaphragm around. its periphery to additionally support and increase the free period of vibration thereof.

In a sound reproducer, a cone diaphragm, a diaphragm for engaging portions of the cone diaphragm around its peripheral edge, against the inner periphery of the cone diaphragm to additionally support and increase the free period of vibration thereof.

11. In a sound reproducer, a cone diaphragm, a diaphragm for engaging portions of the cone diaphragm around its outer periphery to additionally support and increase the free period of vibration thereof.

12. In the reproduction of sound, a method of increasing the free period of vibration or" a cone diaphragm comprising distorting a cone diaphragm around its periphery through a force fit with a supplemental diaphragm element.

13. In the reproduction of sound, a method of increasing the free period of vibration of a cone diaphragm, comprising distorting a cone diaphragm around its periphery with a vibrating element having a portion fixed against vibration.

14. In the reproduction or" sound, a method of increasing the free period of vibration or" a cone diaphragm comprising connecting a supplemental diaphragm at portions around the periphery thereof, through a force fit, to vibrate therewith and fixing the central portion of the supplemental diaphragm against vibration.

15. In the reproduction of sounds, a method of changing the free period of vibration of a cone diaphragm comprising distorting a cone diaphragm around its periphery with a vibrating element having a portion fixed against vibration.

16. In a sound reproducer including a cone diaphragm a supplemental diaphragm positively 20 connected thereto under tension adapted to change the free period of vibration of the cone diaphragm with changes in the tension.

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