US1855836A - Sound producing device - Google Patents

Description

April 26, 1932. l.. A. KING 1,855,836

SOUND PRODUGING DEVICE Filed Nov. l, 1929 2 Sheets-Sheet 1 im mw i j! i unnmmlnm \.-1t14HNMM Niillhlllllll um v f \\f llllllllllllllillllllll April 26, 1932. L. A. KlNG SOUND PRODUCING DEVICE 2 Sheets-Sheet 2 Filed Nov @WMM Patented Apr. 26, 1932 UNITED STATES PATENT OFFICE A LAURENCE A. KING, 0F ST. CHARLES, ILLINGIS, ASSIG-NOR TO OPERADIO MANUFACTUR- ING CO., F ST. CHARLES, ILLINOIS, .A CORPORATION OF ILLINOIS Application filed November The invention relates to sound producing devices, and more particularly to loud speakers adapted to be employed in connection with sound amplifying devices.

VA loudspeaker embodying one form of the invention combines the desirable feature of a speaker of the air-column type and an electrodynamic speaker.

Air-column speakers of the usual design comprise reproducing units having metal dia phragms and the air-column is generally of such length that it will reproduce fundamental frequencies between 50 and 70 cycles. Because of the tremendous power required to i5 drive the higher frequencies through this aircolumn, the sound issuing from the mouth of the horn is distorted as the lower frequencies are predominant. Of course, the advantages of an air-column horn are the fact that first the sound is concentrated and directed in a specific direction, and because of this the carrying power of the various frequencies which are reproduced are more or less equal; secondly, all of the energy comes out of the T95 mouth of the horn and is directed in the dif so frequencies are between that and 100%. The

result is that at a distance feet away from the speaker, the reproduction begins to thin out and only certain frequencies reach one under normal intensity. Another disadvan- 5 tage of this type of speaker is the fact that there is just as much energy projected from the back of the speaker as from the front thereof, and this energy often tends to create very disagreeable acoustical effects. This is particularly noticeable in theatre work 1, 1929. Serial No. 404,090.

where disagreeable acoustical effects are produced back-stage.

The improved loud speaker illustrated in the accompanying drawings preferably employs an electro-dynamic cone type speaker in connection with an air-column horn, the diaphragm of the speaker being arranged in the horn in such manner that the energy issuing from both the back and front of the diaphragm is all projected from the mouth of the horn. The arrangement is such that the walls of the horn function as a baiile, as well as means for amplifying sound.

Many other objects and advantages wil-l appear as this description progresses, reference being had to the accompanying draw-k ings, wherein Figure 1 is a side elevation of a loudspeaker embodying the invention;

Fig. 2 is a front elevation of the improved speaker;

Fig. 3 is a plan elevation of the improved speaker;

Fig. 4 is a section taken on line 4--4 of Fig. 2;

F 5 is an enlarged section taken on line 5 5 of Fig. 2;

Fig. 6 is a rear elevation of a housing member forming part of the improved speaker;

Fig. 7 is a side elevation of the housing member, shown in Fig. 6, and

Fig. 8 is a side elevation of one of a plurality of lbrackets attached to the housing member, sho-wn in Figs. 6 and 7.

Referring to the drawings wherein I have llustrated an improved. form of the invenion embodied in aspeaker particularly adapted for theatre-work, the reference character 10 designates, generally, a horn which is preferably molded from plastic material. The horn preferably comprises a substantially eX- potential sound passage 11 which has its inner end 12 arranged in the mouth 13 of the horn, the inlet end 12 being preferably frusto-conical in shape to accommodate a frusto-conical housing member 15.

The horn 10 is preferably molded in one piece by employing a flexible core during the molding operation, but it is to be understood that my invention is limited to such construction only to the extent indicated in the appended claims. The housing member is preferably embedded in the horn during the molding operation and preferably comprises a plurality of outwardly extending flanges 17 arranged to project into the walls of the horn to rigidly secure the housing member to the horn. In addition to the out- Wardly extending flanges 17, I preferably provide a plurality of bracket members 18 around the outerV surface of the housing member 15, the bracket members 18 being designed to embed themselves in the Wall of the horn during the molding operation.

At its larger end, the housing member 15 is preferably provided with an outwardly extending flange 20 to which are secured a plurality of bracket members 21 comprising plates 23 and block-s 24. Each plate 23 is spotwelded to the flange 20 or secured thereto in any suitable manner. Secured to each plate 23 is one of the blocks 24, screws 26 and knurled nuts 27 being provided for this purpose (see Fig. 8). The knurled nuts 27 are also embedded in the Walls of the horn during the molding operation and serve to secure the housing member 15 to the horn. Each block 24 is preferably provided with a screw-threaded hole 28 adapted to receive one of a plurality of screws 29, whereby a loudspeaker 30 is secured to the housing member 15 and thus to the horn 10.

The loudspeaker 3() is preferably of the electro-dynamic type, and preferably comprises a diaphragm 32 having a conical portion 33 which has its smaller end apertured to receive a sleeve 34, the sleeve 34 being arranged to carry a Winding 35 which is generally referred to as the voice coil winding and is adapted to be connected to the output circuit of a radio-receiving set, or the like.

The winding 35 is disposed concentrically in an annular magnetic field 37 provided in an electro-magnet 38 which preferably comprises a central pole piece 39 and an annular pole piece 40. The annular pole piece 40 is rigidly secured to a cup-shaped magnet member 42 having an aperture 43 which accommodates one end of the pole piece 39. Preferably formed integral with the cup-shaped magnet-member 42 are a plurality of radially extending arms 46 which carry a ring 48 preferably formed integral with the arms. It will be noted that the ring 48 is provided with apertures 50 through which the screws 29 are passed when the speaker 30 is secured to the blocks 24. Clamped between the ring 48 and the blocks 24 is an annulus 52 which is offset, as at 53, to provide an annular groove 54. The annular groove 54 accommodates a pair of felt rings 55 and 56, between which an annular flange 58, preferably formed integral with the conical portion 33, projects.

In the preferred form of the invention, the front end of the dynamic speaker is prefer-V ably covered by a screen carried by an annular member G1 secured to the ring 4S by the screws 29.

The terminals of the winding 35 are preferably connected by suitable conductors 63 to binding posts 64 carried by a bar G5 of insulation which is preferably rigidly secured to one of the arms 46. Suitable conductors 66 connect the binding posts 64 with the output circuit of a radio-receiving set, 0r the equivalent. The field winding 70 of the electro-magnet 38 is connected by electrical conductors 81 to any suitable source of direct current.

It will be noted that an annular passage.

73 is provided between the outer surface of the conical portion 33 and the inner surface of the housing member 15, and that this passage communicates at its inner end With the inlet end of the sound passage 11, the outer end of the passage 73 being closed. Obviously, sound waves projected from the outer or rear surface of the conical portion 33 will traverse the sound passage 11 and will issue therefrom in substantially the same direction as the sound waves originating from the inner surface of the conical portion 33.

A feature of the invention is the employment of a dynamic speaker in which the electro-magnet or magnetizing structure is disposed in front of the diaphragm 32 so that it is a relatively simple matter to have the space around the outer or rear surface of the conical portion 33 communicate with the inlet end of the sound passage.

The inner or front surface of the diaphragm 32 functions substantially the same way as the usual conical diaphragm provided in the ordinary electro-dynamic speaker, and, of course, the tones of higher frequencies are projected directly from the mouth of the sound passage 11 in such manner that the carrying power of the dynamic speaker is fully utilized as far as these higher tones are concerned. In addition, the sounds projected from the back of the diaphragm 32 are unhindered and undistorted and are utilized to actuate and develop tones starting from the inlet end of the passage 11 to the mouth thereof. By this combination, all of the frequencies of the electro-dynamic cone speaker are projected from the mouth of the sound passage and the carrying power of the electro-dynamic speaker is fully utilized. Of course, there may be an out of phase condition existing to a certain extent, but due to the use of the Walls of the horn as a baille, the out of phase condition cannot be detected by the human ear.

Any suitable means may be provided for supporting the speaker horn 10, such, as for instance, a platform 75. In the preferred form of the invention the horn 10 is provided with lugs 77 and 78 formed integral with the Walls thereof and these lugs are adapted to rest upon the supporting platform 7 5. A reinforcing rod 79 projects through the walls of the horn, as best shown in Fig. 4.

If the field winding of the magnetizing structure is to be operated from a source of alternating current, I preferably provide suitable rectifying apparatus, as indicated at 80.

The speaker 30 is of such size that it has substantially the same volume as loudspeakers of that type usually provided in radioreceiving sets, and the like. In other words, the speaker 3() is of such size so that its volume is sufficient for a relatively large size room. Obviously, when the speaker 30 is combined with the horn 10 and the sound waves coming from both sides of the diaphragm 32 are utilized, the volume of sound issuing from the mouth 13 will be sufficient for theatre or outdoor Work.

While I have illustrated and described a particular construction embodying my invention, I do not wish to be understood as intending to limit it thereto as the same may be variously modified and altered Without departing from the spirit of my invention.

W'hat I claim as new, and desire to secure by Letters Patent, is:

l. A device of the kind described comprising a horn having a sound passage, a loudspeaker disposed at the mouth of said sound passage and provided with a conical diaphragm, the outer side of said conical diaphragm being arranged to project sound into the inlet end of said sound passage and the inner side of said diaphragm being arranged to project sound away from said passage, said horn forming a baffle between the two sides of said diaphragm.

2. A device of the kind described comprising a horn formed from plastic material and provided with a sound passage, a housing member embedded in the inlet end of said passage, a loud speaker secured to said housing member and provided with a conical diaphragm, the outer side of said conical diaphragm being arranged to project sound into the inlet end of said sound passage and the inner side of said diaphragm being arranged to project sound directly away from said sound passage.

3. A device of the kind described comprising a horn having a curved sound passage, the inlet end of said sound passage being disposed in the mouth thereof, a loud speaker embedded in said inlet end and provided with a conical diaphragm, one side of said conical diaphragm adapted to project sound into the inlet end of said sound passage and the inner side of said conical diaphragm being arranged to project sound directly out of said mouth.

4. A device of the kind described comprising a horn having a sound passage, the inlet end of the sound passage being disposed in the mouth thereof, and a loud speaker mount-

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