US1715705A - Loud-speaker - Google Patents

Description

Jung 4, 1929. J. 5. HIGH 1,715,705

LOUD SPEAKER Filed March 2, 1926 WITNESSES: INVENTOR WW M ATTORNEY Patented June 4, 1929.

UNITED STATES PATENT OFFICE.

J'URJEN S. HIGH, OF WILKINSBURG, PENNSYLVANIA, ASSIGNOR T WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

LOUD-SPEAKER.

Application filed March 2, 1926. Serial No. 91,738.

My invention relates to the art of sound production and more particularly to devices employing a positively actuated surface as the source of sound.

Numerous forms of this general type of device have been constructed in the past, the majority of which have employed a rigid connection, such as a soldered connector rod, between the actuating member and the actu ated member, or sopnd-radiating means.

Such devices have not proved entirely satisfactory, since, in addition to the desired sound frequencies, numerous other frequencies are usually present, due to detrimental inertia reactions in the connecting means.

These reactions result from the rotative oscillations of the actuating member causing angle displacements which are transmitted through the rigid joint to the connecting means, causing the diaphragm per se to be set into vibration at a plurality of double frequency components and harmonics thereof. These foreign frequencies will be superimposed on, and reproduced together with, the

desired frequencies.

Parasitic vibrations of the diaphragm substance may appear either as ripples running radially thereof, or as movements of the entire diaphragm transverse to the direction in which it is desired that such diaphragm move as a whole.

Although there may be some question as to the actual manner in which all of the undesirable vibrations are set up in the diaphragm material, it is very generally admitted that relatively large diaphragms do not give ideal sound reproduction when actuated by the usual means.

It is, accordingly, an object of my invention to provide a vibratory system that shall be free from undesired frequencies.

- Another object is to provide a connection to be used between the electromagnetic or other actuating means and the diaphragm of a loud speaker that will not cause the latter to vibrate other than in an axially translatory manner.

A further object of my invention is to provide a damping means between the actuat- 60 ing means and the diaphragm of a sound reproducer which will absorb residual parasitic vibrations and which will not permit such vibrations to reach the diaphragm.

Another and more specific object of my invention 1s to so improve loud speakers of the type employing a relatively large diaphragm for setting the surrounding air in motion that such diaphragm will have but one mode of vibration and will not vibrate locally in harmonic frequencies such as are set up in a bell.

I attain these objects by using as a diaphragm a relatively large cone freely supported at its base by a flexible medium, and by applying to the apex of this cone a period- 85 1c driving force parallel to its axis. To make certain that the apex of the cone will not be subjected to forces transverse to its axis,

I inter-pose between the driving means and the cone a connector so designed as to pre vent the effective transmission of vibrations other than those desired.

One way of securing this result is to connect the cone to the driving means or armature, by a flexible cord or Wire. This, how ever, would have the disadvantage of only transmitting approximately one half of each cycle of a sound wave. The cone, being so supported as to have little or no restoring force, by reason of its flexible mounting, so would respond satisfactorily only to the periodic pulls of such connection, and would reproduce signals very'imperfectly.

Another Way of securing the above result would be to stretch the wire by moving the actuating means away from the cone until the wire is tensioned by the pull of such driving means at one end and the reactive pull of the cone at its other end. The pull which is exerted on the cone by the wire could then be modulated in accordance with the modulation in tension effected by the oscillations of the driving means at the other end. A considerable increase of sound output may be obtained in this way. However, if the cone is pulled away from its position of rest, its delicate flexible mounting is endangered and the quality of the sound reproduction is impaired. In order, therefore, to relieve the cone from this initial stress, it is necessary to simulate the forces maintaining the tension i on the wire by means which are attached to or are a part of the vibrating system per se. In the preferredform of my invention, the

means for keeping the wire under tension comprises a sleeve of soft rubber, or analogous material, surrounding the wire and abutting against two retaining flanges or cups to which the wire is atfixed.

I may also use, instead of a wire, a thin metal strip or a plurality of strips.

A connector of this type is an element which is statically balanced per se, and though extremely eflicient in transmitting vibrations along its axis, will merely flex to a greater or less degree when subjected to transverse vibration by the actuating means and will nottransmit the such vibrations to the diaphragm.

The diaphragm, which I have shown as a cone by way ofexample, but which may be made in any desirable form, is so mounted as to have minimum restoring force.

Referring now to the drawing and the following description from which a more complete understanding of my invention may be had.

Figure 1 is a View, and partially in section, of my invention,

Fig. 2 is an enlarged cross-sectional view of the connector taken along the line II-I I of Fig. 1,

Fig. 3 is a cross-sectional view of the connector taken along the line Ill-Ill of Fig. 1,

Fig. 4 is a cross-sectional view of a modified form of connector.

Referring specifically to Fig. 1, a diaphragm 1, which for purposes of illustration is shown as a cone, is suspended from an an-' nular member 2 by means of an annulus 3 of thin leather, soft rubber, or material having like characteristics. This element 2 maybe made of wood, metal, or other appropriate material, and preferably comprises two parts between which the annulus 3 may be clamped by means of bolts 4. The annulus 3 is glued or otherwise affixed to the edge of the cone 1, around its periphery.

At its apex, the cone 1 is also glued or otherwise afiixed to a cup-shaped element 5 of aluminum, celluloid, hard rubber, or analogous light material, which has anopening 6 through the bottom thereof. Extending through this opening 6 is a threaded boss or stud 7 that is integral with a cup 8, and which is firmly held in place by a nut 9. Hold tightly against the cup 8 is a rubber sleeve 10, against the other end of which bears a cup 11, similar to the cup 8, and also provided with a threaded stud 12.- The stud 12 passes through an opening in a driving member 13, and is held in place by a nut 14. The driving member 13 may be an extension of the usual balanced armature, or it may be connected to some other form of actuating means.

The construction of the connector comprising the elements 7, 8, 10, 11 and 12 is more clearly shown in Figure 2. Each of the studs 7 and 12 is provided with an opening axially therethrough, these openings being slightly partially in elevation of a preferred form countersunk. Passing through the studs 7 and 12, and secured therein by solder, is a wire 16, which is surrounded by the rubber sleeve 10. The wire 16 is kept tensioned by the reaction of the sleeve 10 against the cups 8 and 11.

It is assumed, for purposes of explanation, that the upper end of the member 13 has pendulum-like motionindicated by the arrows E-F. The amplitude of this motion is shown as greatly exaggerated. It is apparent that if the connection between the driving means 13 and the cone 1 is a rigid one, there Wlll be a very pronounced tendency to move the apex of the cone transverse to the axis II-II. Such transverse movement would, in the usual device, cause the cone to be set into local or parasitic oscillation and give rise to undesirable noise in the sound output.

If, instead of the type of connector which Ihave illustrated, the connection between the driving member 13 and the cone 1 has a certain amount of rigidity, the rotative or pendulum motion of the driving member will also, because of the inertia reaction of the cone, tend to flex the connector to a certain extent. The inertia of the connector will cause its flexure to be carried beyond the amount caused by the movement of the driving member, exerting in this way an additional pull upon the apex of the cone at such times as the driving member reaches its extreme position. The result will be that a superimposed vibrational force will be exerted on the cone, having twice the frequency of any component of the vibration of the driving member, and undesired harmonic vibrations will, accordingly, be initiated in the cone.

By employing as a connecting means a wire, for example 8 mils in diameter and one-fourth to one-half inch long, held under tension by means of a surrounding sleeve of soft rubber, substantially no force transverse to the axis II-II can be exerted on the apex of the cone. Vibratory forces along the axis IIII are transmitted by changes in the tension of the wire which is prevented from buckling by the surrounding rubber sleeve which stresses it. Bending moments, however, flex the rubber and wire assembly and are, consequently, either damped out or transmitted with very diminished intensity to the cone. As a result, the cone or diaphragm is constrained to move as a whole along a line substanitally parallel to the axis of the connecting wire 16 and it will not vibrate transversely thereto to any marked degree.

The rubber sleeve may be split as shown in Fig. 4 and, after having been placed upon the connecting wire or cord, the opening 18 may be filled with rubber cement, or an analogous substance.

It is also feasible to imbed a coiled spring in the rubber sleeve, through the axis of which the wire passes, in order to exert additional tension thereon.

I prefer, however, to either mold this rubber sleeve on the wire or provide it simply with a hole of the same diameter as the wire, through which the wire may be threaded. This form is illustrated in Fig. 3. In either event the result is essentially the same, as the wire or cord will transmit longitudinal vibrations and will be restrained from buckling by the surrounding sleeve and the tension thereon. It is also feasible to re lace the wire by one, or a plurality of, thin at strips, so arranged as to have a minimum of resistance to bending moments having a vector that is perpendicular to the vibratory system.

A loud speaker in accordance with my invention is characterized by an extreme purity of tone and lack of the fuzziness which is so apparent in many reproducers having a rigid connection between the actuating means and the diaphragm.

There is a noticeable lack of distortion, even when the power input to the speaker is increased beyond the value which causes the usual type to blast, and it is also noted that the lower notes of music stand out with their true proportion of volume.

It also appears that the ratio of sound volume to power input is increased, which is a very valuable feature, particularly when the reproducer is to be used in auditoriums, churches, etc.

Although I have illustrated and described herein certain specific embodiments of myinvention, I am fully aware that many other modifications are possible and my invention is not to be limited except in so far as is necesmeans, connecting means there sitated by the prior art and as indicated by the following claims.

I claim as my invention:

1. In a sound reproducer, a diaphragm, flexible supporting means therefor, anactuatin device, connecting means between said diap ragm and said device, and means whereby undesired motion of said device is prevented from affecting said diaphragm.

2. In combination, a diaphragm, actuating means, connecting means therebetween adapted to transmit energy along an axis, and means for preventing transverse vibrations of the actuatlng means from being transmitted to the diaphragm.

3. In combination a diaphra m, actuating tween, and a tension device r preventing buckling of said connecting means.

4. In combination, a diaphragm adapted to vibrate in any direction, actuatin means therefor, connecting means there etween adapted to transmit vibrations in two opposite directions, and' means to prevent the generation of undesired vibrations.

5. In combination, a diaphragm, an actuating device, a wire connection therebetween, and resilient means surrounding said wire for maintaining it under tension and preventing buckling thereof.

6. The method of transmitting motion from one'object to another, which comprises establishing therebetween a state of balanced tension, and modulating the tension in accordance with the motion to be transmitted.

In testimony whereof, I have hereunto subscribed my name this first day of March, 1926.

JURJEN S. HIGH.

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