US1943499A

US1943499A - Sound amplifier

Info

Publication number: US1943499A
Application number: US267968A
Authority: US
Inventors: Selden T Williams
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1928-04-06
Filing date: 1928-04-06
Publication date: 1934-01-16
Anticipated expiration: 1951-01-16
Also published as: FR673498A; GB309162A

Description

Jan. 16, 1934.

s. T. WILLIAMS sotmn AMPLIFIER Filed April 6. 1928 5 Sheets-Sheet l nvcntor Solder; 73W u Gttorncgs 16, 1934 5:. T. WILLIAMS sovnb mmnsn' Filed April 6. 1928 5 Sheets-Sheet 2 Gttomegs Jan. 16, 1934.

s. T. WILLIAMS 1,943,499

SOUND AIPLIFI BR Filed April 6. 1928 5 Sheets-Sheet 3 attorneys s. T. WILLIAMS SOUND AMPLIFIER Filed April 1928 v 5 sheets-Sheet 4 Gnom s-'- Jan. 16, 1934- Y s. T. WILLIAMS SOUND AMPLIFIER Filed April 6. 1928 5 Shets-Sheet 5 lhwcntor Gttorncgs Patented Jan. 16, 1934 UNITED STATES PATENT OFFICE SOUND AMPLIFIER Selden T. William, Woodbury, N. J., assignor, by mesne assignments, to Radio Corporation of America, New York, N. Y., a corporation of Delaware Application April 6, 1928. Serial No 267,968

39 Claims.

This invention relates to sound radiators, and more particularly to apparatus combined with a diaphragm or like sound radiating means for controlling and directing the sound emitted therefrom.

'It is a well known fact that the effectiveness of any vibrating diaphragm may be increased by loading the diaphragm with an air column formed by a suitable tone chamber such as a horn. creases its ability to radiate bass notes in proportion to the degree of loading, and in general the radiating characteristics of any diaphragm 'may be said to be controllable by the design of the loading chamber. It is therefore highly desirable to load a vibrating diaphragm with means such as a horn to control the operation and increase the effectiveness thereof. Heretofore, however, the loading of the diaphragm as by horns and the like has been largely restricted to one side thereof, for reasons. discussed hereinafter.

It is an equally well known fact that a vibrating diaphragm or like sound radiating means transmits energy in the form of sound waves equally from both surfaces thereof, and it is desirable in order to utilize the complete available energy to combine the energy outputs of both surfaces of the diaphragm to increase the volume of sound produced. Such a result may be accomplished, for example, by so conducting the sound waves from the two surfaces as to com--.

bine them in a single output.

Certain problems are involved, however, in combining the energy output from the two sides of a diaphragm. One factor is the tendency for a wave from one side of a diaphragm to surge to the other side so as to interfere with the diaphragm action. If, for example, the wave path from one side of the diaphragm to the other side thereof is of the order of one-half of a useful wave length, a wave produced by movement of the diaphragm in one direction will reach the other side of the diaphragm on the reverse movement thereof and will oppose the same. There- ,fore the useful tone range of the diaphragm is reduced by low frequency cut-offs due to the surge.

Surge may be avoided by providing a relatively long wave path from one surface of the diaphragm to the other, by any suitable means such as horns, baffles, and the like. In'apparatus of this character heretofore proposed, however, surge has been avoided at the expense of loss of the energy output from one side of the diaphragm,

Loading the diaphragm, for example, in-' as. for example, by the useof large bailles or of a single horn loading one side of the diaphragm only. On the other hand, where the sound waves have been conducted from one side of the diaphragm to the other by a relatively long wave path, it has been found that the direct superposition of waves from the two surfaces results in interaction therebetween of first order importance. This is due to the fact that the distances traveled by the waves from the two sides of the diaphragm are unequal so that the superposed waves vary in phase, resulting in interference and causing distortion and weakening of the resulting sound waves. Furthermore, such apparatus has generally imparted definite directional characteristics to the waves so that what may be termed the directional output of the device is restricted to a relatively narrow range.

One of the objects of the present invention is to provide a diaphragm with a sound radiator capable of employing the output from both surfaces of the diaphragm without distortion or interference between the waves.

Another object is to provide a sound radiating diaphragm with horns or tone chambers for both so surfaces thereof having the same or different loading and radiating characteristics.

Another object is to load both surfaces of a diaphragm with horns each having suitable loading and radiating characteristics and to combine the output from the two surfaces without distortion or interference.

A further object is to combine the energy output from both surfaces of a diaphragm without.

imparting to the resultant waves restricted di-v rectional characteristics.

A still further object is to provide a sound radiator combining the sound energy from both surfaces of the diaphragm and radiating the same substantially in a hemisphere.

Another object is to provide a sound radiating diaphragm with horns or tone chambers for bofh surfaces thereof combined with an intermediate equalizing chamber whereby mutual interaction between waves from the tone chambers will be substantially eliminated.

Another object is to provide a sound radiating diaphragm with tone chambers for both surfaces thereof radiating energy substantially in a hemisphere and having therebetween an equalizing chamber whereby a hemispherical wave front will be produced of varying phase relation but substantially without interference between waves.

A further object is to provide a novel combined sound radiator and diaphragm mounting operative either singly or in multiple to produce a complete or partially spherical sound radiation.

A further object is to provide an efficient and economical sound radiator and diaphragm mounting which requires no cabinet and may be supp rted or suspended either singly or in multiple in any desired position.

Other objects will appear hereinafter as the description of the invention proceeds.

With the above objects in view, the invention, broadly stated, consists in a sound radiating means, which may be molded from a suitable plastic or made of other suitable material, and

is preferably in such form as to be assembled with a diaphragm or the like into a unitary, readily transportable structure, said radiating means being provided with walls forming horns or tone chambers adapted for the accomplishment of the above objects. To these ends the radiator includes a plurality of true horns or tone chambers adapted to suitably load both surfaces of the diaphragm, and having any suitable loading and radiating characteristics which may be the same or different as desired; The separation of the energy output of the two diaphragm surfaces effectively prevents surge and its attendant disad vantages, and the use of separate horns or tone chambers loading the opposite sides of the diaphragm not only insures the utilization of all of the useful energy but provides for a plurality of separate ouiputs of individually controlled varying characteristics which may be combined to form composite waves in the manner hereinafter described with material advantages.

Said horns may be adapted to radiate sound waves in different directions, whereby a resultant wave front of generally sphericalor other form may be produced of approximately equal intensity throughout, thus eliminating the usual directional limitations introduced by horns. Furthermore, due to the separation of the horn mouths and the different direction of emission of waves therefrom, the individual horn outputs conduit or chamber which flares radially out-.

ward from the axis of the diaphragm and terminates in a substantially annular mouth which emits sound waves radially of the diaphragm in planes generally at large angles to its axis. The term "annular as employed herein to designate the mouth of a horn, is intended to include any horn mouth such as would be defined by two circles or like curves, whether said circles are concentric and coplanar, or coaxial and in different planes. Thus the sound waves emitted from the axial tone chamber and spreading therefrom in all directions, and the sound waves emitted from the annular mouth of the second tone chamber and spreading therefrom in all directions, tend to meet across the intervening zones to form a substantially hemispherical wave front. Preferably the external surface of the sound radiator is cut out or concaved throughout or partially throughout the said intervening zone, to constitute an annular depression or chamber. This chamber is reentrant with respect to the direction of the waves emitted from the respective tone chambers, and serves to aid in preventing undesirable interaction between the wave fronts, in a manner described hereinafter.

While the invention is readily adaptable to vibrating diaphragms or the like of any size or type, it is particularly well fitted for use in connection with the loud speakers of electrically reproducing phonographs, radio receiving sets, etc., where a large volume of sound is desired. In the several embodiments of the invention illustrated in the accompanying drawings, therefore, the diaphragm has been illustrated for purposes of exemplification as a. cone diaphragm combined with electromagnetic operating means therefor; but it is to be expressly understood that the invention is susceptible of a variety of expressions and applications, and that said drawings are for purposes of illustration only and are not to be construed as defining the limits of the invention, reference being bad to the appended claims for this purpose.

In said drawings,

Fig. 1 is a perspective view of a sound radiator constructed according to the invention;

Fig. 2 is a sectional view of Fig. 1;

Fig. 3 shows a slightly modified form of radiator;

Figs. 4 and 5 show respectively in perspective and in section another form of sound radiator;

Fig. 6 shows a further form of the radiator slightly modified from Fig. 5;

Figs. 7 and 8 show respectively in perspective and in section a further embodiment of the sound radiator;

Fig. 9 shows a form of radiator similar to Fig. 7;

Figs. 10 andgll show respectively in perspective and in section a still further embodiment;

Figs. 12 and 13 show respectively in perspective (with parts broken away) and in section a still further embodiment, to illustrate the applicability of the sound radiator to use with a plurality of diaphragms; and

Figs. 14 and 15 indicate diagrammatically and by way of example two ways in which the sound radiator may be employed.

In the form of the invention to be described, the sound radiator comprises a plurality of suitably shaped and cooperating body parts, which may be formed of any suitable material, such as metal, wood, or preferably a molded plastic. It is to be expressly understood, however, that the particular arrangement and assembly of the body parts, their number, size, and dimensions, etc., may be suitably varied to meet different conditions, provided only that the desired characteristics and arrangement of the sound chambers within the spirit of the invention are maintained.

In the form of the invention shown in Figs. 1 and 2, the body parts include a base member 1, generally circular in shape, which is provided with suitable means for supporting the sound radiator in a desired position. Such means, for example, may take the form of a ring 2, secured to an eye bolt 3 on the periphery of the base member and a similar ring 4 secured to an eye bolt 5 and preferably seated in a recess 6 formed in the center of the base member. The central portion of said base member is formed into an outwardly extending boss '1, from which sloping sides extend to the periphery; Said base member is thus generally conical in outline, but the sloping sides are relatively deeply concaved nearthe center thereof, as shown at 8,1rom whence said sides straighten out and approach parallelism with the bottom of the base member near its periphery.

Cooperating with and, spaced from the base member l is a wall 10, in the form of ,a shallow annular cup, provided, if desired, with strengthening ribs 11, and spaced from the base member in any suitable manner as by means of bolts 12 and spacers 13. Between the base member 1 and the cup member 10 is thus formed a sound passage or tone chamber 14, which at its inner end adjacent the boss 7 is substantially circular in shape, and from said circular end flares outwardly, annular in cross section and following the contour of the base member 1, so as to form therewith a passage radiating concentrically with the axis of said base member and extending in planes generally at right angles thereto, and terminating in a mouth 15.

The circular end of passage 14 is extended axially relative to the base member and to the plane or planes of the concentrically radiating passage 14 by a third body member 16 having outwardly flaring walls and forming an axially directed expanding horn terminating in a mouth 1'7, preferably protected by a grill 18. Sound passages are thus provided having walls which, from an intermediate point of small cross section, which is the plane of the circular and of passage 14, flare radially outward on both sides of said plane and form two expanding horns, I terminating in the mouths 15 and 1'7. Intermediate the mouths of said passages and pref erably in said plane of small cross section is placed a diaphragm of any suitable type. In the form shown, said diaphragm forms part of 'a loud speaker comprising an electromagnet 19 mounted in the body member 16 by. means of suitable supports 20, and provided with a perforated guard 21 having a flange clamped between

body members

10 and 16. The diaphragm 22 is of the cone type, supported by a flexible rim likewise clamped between said body members, and may be provided with a suitable coil which is placed in the field of the magnet 19. The loudspeaker is of the well-known electro-dynamic type as illustrated in Farrow patent, 1,831,235, November 10, 1931.

The operation of the device may be clearly understood from Fig. 2 showing the action of the sound waves emitted by the apparatus. As the diaphragm 22 vibrates, it transmits sound waves in both directions from its opposite surfaces. One surface of the diaphragm is loaded by the horn 16. having loading and radiating characteristics of any desirable kind, and the sound waves from this surface of the diaphragm are emitted from the mouth 17 in a direction which is, generally speaking, axial relative to the diaphragm. Since a sound wave from a source, if unrestricted, tends to expand simultaneously in all directions, waves from the horn 15 will not only travel in the axial direction, but will also travel towards al sides from the mouth of the horn. Similarly, waves from the mouth 15, having traveled through the horn 14 which suitably loads the, diaphragm, are emitted radially from the axis of the dia phragm'and in directions which'are substantially perpendicular to the axis of the diaphragm. Such waves, however, will immediately in addition to the direction so imparted travel likewise towards the sides, and the wave fronts expanding towards the sides from thernouths 15 and 18 may interfere with and substantially destroy one another, as indicated at 23. At the same time, however, the wave fronts which have advanced further from the mouths ofthe horns become substantially contiguous with one another without superposition, as indicated at 24 and thus produce a composite, substantially hemispherical wave front from the entire device. It will be apparent, however, that since waves from the separate horns are not superposed on one another there can be no interference from varying phase between the waves.

The presence of the annular, concaved space external to the sound passages, which is formed between the

walls

10 and 16, aids materially in preventing destructive interference between the waves from the separate horn mouths. This space may be termed an equalizing chamber, and provides a reentrant space wherein the interfering portions of the waves are confused and destroyed, without causing any substantial effect on the wave fronts advancing from the radiator. This equalizing chamber'thus serves to equalize the composite wave fronts into a smooth, even wave of approximately equal intensity throughout, whereby practically a complete hemispherical radiation is obtained. 1

Fig. 3 shows a form. of. the invention diiierin from Fig. 1 in the size, shape and design of the horns and equalizing chamber.. The operation of this horn is similar to that of Fig. l, but the radiating characteristics differ due to the change in form of the horns. Both of the horns are in general shorter and of greater cross" sectional area, and have larger mouths, than in Fig. 1, and the equalizing chamber has a cross section which is elliptical in form. In some instances it may be desirable to omit the equalizing chamber, and in'such, case a partition or closure 25 is placed across the opening thereof.

Figs. 4 and 5 show a form of the invention somewhat modified in the shape of the horns, but analogous'to the embodiment of Fig. 1 in principle of operation'and in construction. In this embodiment the horn 14 is shown as of somewhat greater length than in Fig. 1, but having a less rate of taper and a smaller mouth, whereas the horn 16 is shorter than that of Fig. l and has a greater rate of taper and a larger month. These variations in the horns serve to control the loading and radiating characteristics of the radiator when designed to meet dif ferent conditions.

Fig. 6 shows a form of the radiator in general similar to the form shown in Figs. 1, 3 and 4, but differing therefrom in the loading and radiating characteristics of the two horns and in the general shape of the sound radiator, thus being analogous in principle and operation. I

In order to obtain greater length of one or both of the horns from the diaphragm to the mouths thereof without excessive overall dimensions of the radiator, it may be advantageous to provide horns having curved or reversely curved passa es.

Figs. "1, 8 and 9 show two forms of the in vention having this feature. In the particular forms shown, the axially directed horn is greatly increased in length by flaring the same outwardly and reversey curving the passage to form an annular passage surrounding the first portion, and in again reversely curving said annular passage to form a second annular passage sur rounding said first two passages, said horn having an annular mouth emitting waves axially of the diaphragm. Referring to Figs. 7 and 8, the base member is conically shaped, comprising a sup-. porting plate 26, and a conical member 27 integral with said plate 26 or secured thereto in any suitable manner, and supported and strengthened by a central tubular post 28. Spaced from and approximately parallel to the conical mem ber 27 is a second conical member 29, forming a radially directed sound passage 30 terminating in a mouth 31 and adapted to receive energy from one surface of the diaphragm. Said diaphragm is clamped between the conical member 29 and a tubular member 32 extending axially relative to. the diaphragm and forming the first section of a second horn loading the other surface of the diaphragm. The tubuar wall 32 is flared radially with respect to its axis and reversely curved at 33, forming a second annular portion 34 concentric with and surrounding the tubular wall 32. The wall 34 is again reversely curved at 35 and is continued to form a third annular wall 36 surrounding the tubular wals 32 and 34. Cooperating with and generally following the contour of the

wall

33, 34, 35, 36, but spaced therefrom, is a member 37 forming with said

wall

33, 34, 35, 36, a generallyannular, reverse'y curved sound passage comprising the sections 33', 34', 35', 36 which progressively increase in transverse section. The section 36 terminates in an annular mouth 38, which emits sound waves axially of the diaphragm. The wall 37, the

walls

32, 34, 35, 36 and the base member 26, may be spaced from one another by any suitable means such as bolts 39 and

spacers

40 and 41. The operation of this form of the invention is in general similar to that of the preceding forms, but the cngth of the axially directed horn has been roughly tripled by means of the reverse curves without increasing the overall dimensions of the radiator. It will be apparent that the comtruction and d1 sign of the horns loading the two surfaces of the diaphragm may be widely varied to obtain any desired operating conditions.

Fig. 9 shows a modified form of Fig. 8, the horns being of somewhat greater cross section. and having greater length. which is obtained by increasing the radius of the radiator but without increase in the depth thereof.

Figs. 10 and 11 show respectively in perspec tive and in section a further form of the invention which may be employed when it is desired to impart a directional characteristic to the emitted sound waves. This form of the invention 's in general simiar to that shown in Figs. 1, 2 and 3. with the exception that the pas-age 14. instead of terminating in a mouth which emits waves at right angles to the axis of the diaphragm. is extended and reversely curved to form an annular sound passage 42 surrounding the portion of the passage 14 immediately adjacent the diaphra m and surrounding the horn 18. and terminating in an annular mouth 4'1. Both sides of the diaphra m are thus loaded with suitable horns having the desired characteristics, and emitting separate waves which unite to form a composite wave front, in the manner heretofore described. with the exception that the sound waves are all emitted axia ly oi the dia hragm and not in planes at right angles to its axis.

Figs. 12 and 13 show respectively in perspective and in section'the use of a p'urality of dia phragms with a sound radiator of the type hereinbefore described. For purposes of exemplification, these figures show an embodiment of the invention similar to that shown in Figs. 10 and 11, but it will be understood that a plurality of diaphragms may be employed with any or all of the embodiments heretofore shown and described. As shown in Figs. 12 and 13 the base member 1 and the wall 10 cooperate to form a passage 14 which is reversely curved to form the annular passage 42 terminating in the mouth 43, analogously to Figure 11. The wall 10 is likewise extended by the wall 16 forming a second horn terminating in a mouth 17. In the present instance, however, a plurality of dlaphragms are interposed between the

horns

16 and 14, and for purposes of convenience in mounting and supporting the said diaphragms, a member 44 is inserted in the sound passage intermediate the horns l4 and 16, which member is supported by engagement with the walls of the sound passage and with the central boss 7 of the base member 1, or is made integral with the latter. The member 44 being circular in shape, is provided with a-plurality of radial y placed openings 45, which gradually increase in cross section and substantially merge into the circular and of the passage 14. Each of the openings 45 thus forms the beginning of a horn for one of the diaphragms, and each of these individual horns merges into the single horn 14 as above described.

Sound radiators such as heretofore described are capable of use in widely varying ways, some of which have been illustrated in the drawings. For example, in Fig. 2 the sound radiator is hung on a wall by means of the ring 2, and emits from itself as a center a hemispherical wave front. It has been found that the sound waves traveling toward the sides of the device are just as strong, clear and distinct as those traveling towards the front of the device. In Fig. 1, the sound radiator is suspended from overhead, as on a ceiling by means of the ring 4. In this positionthe radiator distributes the sound waves equally over a very large area below.

Furthermore, in some instances it may be de-- sirable to employ more than one sound radiating unit. In Fig. 14, for example, two sound radiators are suspended back to back and are thus adapted to emit an entire spherical wave front, such as normally emitted by a natural source of sound, and entirely without restricted directional characteristics. In the example shown in Fig. 15, two separate sound radiating units may be hung on the opposite walls of a room whereby the sound is equally distributed throughout the ,entire space.

It will be observed that the present invention provides means whereby'the energy output from both surfaces of a diaphragm may be combined in the useful output thereof. Owing to the novel combination of the sound passages and the equalizing chamber, the sound waves from the two surfaces are combined in a single output to produce a combined wave front having contiguous portions which may be of different phase but which are not superposed, whereby interference and distortion areeliminated. Moreover, the directional output of the apparatus may be extended to include a complete hemisphere or sphere, whereby sound waves are radiated equally in all directions to the listeners.

Furthermore, both surfaces of the diaphragm may be suitably loaded by true horns, and by controlling the design of the horns the radiating characteristics of the combined radiator output may readily be controlled. The sound waves thus produced may vary over a wide range of speech frequencies without suppression or distortion at any frequency. Moreover the loading of the opposite surfaces and the combination of the energy outputs thereof is accomplished in such a way that all danger of surge and of interference and consequent distortion is avoided. The device constitutes a sound radiator complete in itself, which is readily portable and may be placed in any desired position, and moreover is simple and economical to construct and manufacture, being adapted to be moulded if desired from a suitable substance such as 'a plastic.

While several embodiments of the invention have been described and illustrated in the accompanying drawings, it will be apparent that it is capable of a variety of other expressions which will readilyoccur to those skilled in the art, and

that changes may be made in the construction,

tween relatively flaring, similarly curved surfaces of revolution, and a separate horn loading the other side of said diaphragm.

3. A device of the class described comprising a diaphragm and a pair of expanding horns loading opposite sides thereof, at least one of said horns being formed between walls having relatively flaring, similarly curved surfaces of revolution.

4. A device of the class described comprising a diaphragm, an expanding horn loading one side thereof, said horn being formed between walls having relatively flaring, similarly curved surfacesof revolution, and a separate expanding horn loading the other side of said diaphragm.

' 5. A device of the class described comprising a diaphragm, a horn loading one side thereof, and a horn loading the other side thereof and terminating in an annular mouth surrounding the mouth of said first horn, one of said horns being formed between Walls'having relatively flaring, similarly curved surfaces of revolution.

6. A device of the class described comprising in combination, a diaphragm, a horn of expanding cross-section loading one side thereof, and a horn of expanding cross-section loading the other side thereof and terminating in an annular mouth surrounding the mouth of said first named horn, one of said horns comprising an amplifying passage formed between relatively flaring, similarly curved surfaces of revolution.

7. A device of the class described comprising a diaphragm, an amplifying horn loading one side thereof, and an amplifying horn loading the other side thereof and terminating in an allnular mouth, said horns being so arranged that the direction of wave emission from said annular mouth is at a large angle to the direction of wave emission from the other horn.

8. A device of the class described comprising a diaphragm, an amplifying horn loading one side thereof, and anamplifying horn loading the other side thereof and terminating in an annular mouth, at least one of said horns being formed between walls having relatively flaring, similarly curved surfaces of revolution, said horns being so arranged that the direction of wave emission from one'of said horn mouths is at a large angle to the direction of wave emission from the other horn mouth.

9. A device of the class described comprising a diaphragm, an amplifying horn loading one side thereof, and an amplifying horn loading the other side thereof and terminating in an annular mouth, said last named horn being formed betweenwalls having relatively flaring, similarly curved surfaces of revolution, said horns being so arranged that the direction of wave emission from one horn mouth is at a large angle to the direction of wave emission from the other horn mouth.

10. A device of the class described comprising a diaphragm, a horn loading one side thereof and emitting'waves axially relative to the diaphragm, and a horn loading the other sidethereof and terminating in an annular mouth emitting waves at large angles to the diaphragm axis, at least one of said horns comprising an amplifying passage between walls having relatively flaring, similarly curved surfaces of revolution.

11. A device of the class described comprising a diaphragm, a horn loading one side thereof and emitting waves axially relative to the diaphragm,

a horn loading the other side thereof and termi- 5 nating in an annular mouth surrounding the mouth of said first named horn and emitting waves at large angles to the diaphragm axis, said second named horn comprising 'an amplifying passage formed between walls having relatively flaring, similar surfaces of revolution.

12. A device of the class described comprising a diaphragm and a pair of amplifying horns loading opposite sides thereof, one of said horns having an annular mouth surrounding the mouth oi. the other of said horns.

13. A device of the class described comprising a diaphragm and a pair of amplifying horns loading opposite sides thereof, one of said horns having annular mouth surrounding the mouth of I the other of said horns and having a mean direction at any section of said annular. mouth which is at large angles to the mean direction of said other horn.

14;. A device of the class described comprising 35 a diaphragm and a pair of amplifying horns loading opposite sides thereof, one of said horns extending axially relative to the diaphragm and the other horn having an annular mouth surrounding the mouth of said first named horn and having a mean direction at any, section of said annular mouth which is at large angles to the diaphragm axis.

15. A device of the class described comprising a diaphragm and an amplifying horn loading each side of said diaphragm, said horns being of suificient length to prevent surge between. opposite surfaces of the diaphragm and having separated mouths arranged in axial alignment to emit contiguous portions of a composite wave front.

16. A device of the class described comprising in combination a diaphragm and a pair of arm plifying horns loading opposite sides thereof, said horns being of suflicient length to prevent surge between opposite surfaces of. the diaphragm and having separated months so arranged that separate waves are emitted therefrom in angularly related directions to become contiguous por- 150 horns receiving sound waves from the diaphragm and arranged one to emit the waves substantially axially relative to the diaphragm and another to emit the waves at a large angle to the diaphragm axis.

18. A sound radiator comprising in combination a diaphragm and a plurality of amplifying horns receiving sound waves from both surfaces of said diaphragm, one of said horns extending axially relative to the diaphragm and the other horn being arranged to emit waves in directions at large angles to the diaphragm axis.

19. A sound radiator comprising a diaphragm, an axially-extending horn on one side thereof, and a horn on the other side thereof extending transversely of the diaphragm axis and coaxially therewith.

20. A sound radiator comprising a diaphragm, an axially-extending horn on one side thereof, a horn on the other side thereof extending transversely of the diaphragm axis and being coaxial therewith, and an external equalizing chamber between the outlets of said first two horns.

. axially-extending sound amplifying passage on one side of the diaphragm and a sound amplifying passage on the other side thereof, said last named passage being axially directed adjacent the diaphragm and curving outwardly therefrom transversely of the diaphragm axis and concentrically therewith, the walls of said passages forming an external reentrant. space between the mouths of said passages.

23. A device of the class described comprising a diaphragm and a pair of amplifying horns loading opposite sides thereof, each of said horns comprising an amplifying passage formed between relatively flaring, similar surfaces of revolution.

24. A device of the class described comprising a diaphragm and a pair of amplifying horns loading opposite sides thereof, each of said horns comprising an amplifying passage formed between relatively flaring, similar, surfaces of revolution, the walls of one of said passages being reversely curved.

25. A device of the class described comprising a diaphragm and a pair of amplifying horns loading opposite sides thereof, each of said horns comprising an amplifying passage formed between walls having relatively iiaring, similar surfaces of revolution, one of said passages terminating in an annular mouth and being directed axially relative to the diaphragm, and the other of said passages terminating in an annular mouth transverse to the diaphragm axis and coaxial therewith.

26. A sound radiator comprising in combination a plurality of diaphragms, a horn loading one side of each of said diaphragms, and another horn loading the other side of said d phr gm.

said horns having separated mouths, at least one of said horns comprising an amplifying passage formed between walls having relatively flaring, similarly curved surfaces of revolution.

27. A device of the class described comprising'a diaphragm and a pair of amplifying horns loading opposite sides thereof, one of said horns having an annular mouth surrounding the mouth of the other of said horns and having a mean direction at any section of said annular mouth which is substantially parallel to the mean direction of said other horn.

28. A device of the class described comprising a diaphragm and a pair of amplifying horns loading opposite sides thereof, one of said horns extending axially relative to the diaphragm and the other horn having an annular mouth surrounding the mouth of said first named horn and having a mean direction at any section of said annular mouth which is substantially parallel to the diaphragm axis.

'29. A device of the class described comprising a diaphragm and a pair of horns arranged in axial alignment and loading opposite sides thereof, said horns having different characteristics.

30. In a sound-producing device, a substantially freely suspended diaphragm, and a. plurality of concentric baffle-devices associated with said diaphragm, certain of said baffle-devices being arranged in nested relation to define a restricted sound passage.

31. In a sound-producing device, a diaphragm, actuating means for said diaphragm, a horn concentrically arranged on one side of said diaphragm, and a plurality of baffle-devices concentrically arranged on the other side of said diaphragm, said baflie-devices comprising a plurality of partitions'cooperating to define a second horn.

32. A sound projecting apparatus comprising, in combination with the/sound projecting cone of a loud-speaker, means for projecting the sound waves emanating from the outside surface of the cone in the same direction as those emanating from the interior of the cone, and with approximately the same volume.

33. A sound projecting apparatus comprising, in combination with the sound projecting cone of a loud-speaker, means for catching the sound waves thrown from the. back surface of the cone and projecting them forwardly about and in spaced relation to the cone.

34. A device of the kind described comprising a sound passage having an inlet end and terminating at the other end in an annular mouth, and a sound reproducing unit disposed at said inlet end, said sound reproducing device comprising a conical diaphragm having its outer or back surface arranged to project energy into said sound passage and having its inner or front surface arranged to project energy in substantially the same direction as said mouth.

35. A device of the kind described comprising an annular sound passage having an inlet end, and a sound reproducing unit disposed at said inlet end and comprising a diaphragm having one side arranged to project energy into said sound passage and having its other side arranged to project energy directly away from the device.

36. A deviceof the kind described comprising an annular member, a dished member forming a sound passage with said annular member and provided with a central lug projecting toward said annular member, and a reproducing unit carried by said annular member and provided with a conical diaphragm, the back or outer side of the diaphragm being arranged to project energy into said sound passage and the front or inner side of said diaphragm being arranged to project energy directly away from said device.

37. A device of the kind described comprising a sound passage having an inlet end and terminating at the other end in an annular mouth and a sound reproducing unit disposed at said inlet end, said sound reproducing unit comprising a diaphragm having one surface arranged to project sound into said sound passage and having its other surface arranged to project sound in substantially the same direction as said mouth. 38. A device of the kind described comprising a dished member, an annular member disposed in said dished member and co-operating therewith to form an annular sound passage, and a sound reproducing device carried by said annular member, said sound reproducing device having a diaphragm of which one side projects sound into said annular sound passage and of which the other side projects sound directly into the air in front of the device.

39. A device of the kind described comprising a dished member, an annular member disposed within said member, saiddished member and said annular member co-operating to form a sound passage whereof the central aperture of said annular member is the inlet, and a sound reproducing unit disposed at said inlet, and provided with a diaphragm, one side of said diaphragm being adapted to project sound into said sound passage and the other side thereof being adapted to project sound into the air in front of said dished member;

SELDEN T. WILLIAMS.