US3028927A

US3028927A - Dual coaxial speaker

Info

Publication number: US3028927A
Application number: US751411A
Authority: US
Inventors: Sidney E Levy; Blumenfeld Arthur; Bernard C Sharp
Original assignee: Ling Temco Vought Inc
Current assignee: Ling Temco Vought Inc
Priority date: 1958-07-28
Filing date: 1958-07-28
Publication date: 1962-04-10
Anticipated expiration: 1979-04-10

Description

S. E. LEVY ETAL DUAL COAXIAL SPEAKER 6 Sheets-Sheet 1 m/JW ATTORNEY A ril 10, 1962 Filed July 28, 1958 I III!!! I Apnl 10, 1962 s. E. LEVY ETAL DUAL COAXIAL SPEAKER 6 Sheets-Sheet 2 Filed July 28, 1958 INVENTORS v Exp/v5) E. levy Atermne flzuMin/Fflo BERNARD (I SHARP WMKMW ATTORNEY A nl 10, 1962 s. E. LEVY ETAL DUAL COAXIAL SPEAKER 6 Sheets-Sheet 3 Filed July 28, 1958 WUUFEEI INVENTORS 5/0/1/E') E. AEI/r ATTORNEY A ril 1.0, 1962 s. E. LEVY ETAL DUAL COAXIAL SPEAKER Filed July 28, 1958 6 Sheets-Sheet 4 S/D/VE) E Zen/r JET/rue zaMi/vfifla BERNARD C. 5HAR ATTORNEY April 10, '1 s. E. LEVY ETAL DUAL COAXIAL SPEAKER 6 Sheets-Sheet 5 Filed July 28, 1958 0 S 3 4 6 R 0 9 3 O Z 2 T 5 We. 3 m MM II: N i w a I W 0 w 5 m M. r 5 s e 3 MW E 4 6 A r 1.. 2.. 2 M a 1.?

BERNARD C. SHARP ATTORNEY April 10, 1962 s. E. LEVY ETAL 3,028,927

DUAL COAXIAL SPEAKER Filed July 28, 1958 e Sheets-Sheet s A zaws 4/1/0 fi/GI/S m4 lijg; J5.

INVENTORS EERNA/QD C. SHARP BY ATTORNEY United States Patent 3,028,927 I DUAL C(EAXIAL SPEAKER Sidney E. Levy, White Plains, Arthur lilumenfeld, New York, and Bernard (1. Sharp, White Plains, N.Y., assi'gnors, by theme assignments, to Ling-Temco-Vought, lino, Dallas, Tom, a corporation of Delaware Filed July 28, 1958, Ser. N' 751,411 Ciaims. (6i. iSl--27) This invention, relating as indicated to a dual coaxial speaker, is more particularly directed to loudspeakers of the coaxial type in which a reflex horn is used as part of a high frequency speaker and a second horn is disposed annularly around this speaker and driven by a large, conical diaphragm driver.

It is a primary object of this invention to provide a new dual coaxial loudspeaker adapted to efiicient reproduction of sound over a wide range of frequencies and with greater efficiency than heretofore possible with a speaker of the same size.

Itis another object to provide this efficiency of reproduction without any of the non-linear distortion which is characteristic of small throat horns driven at high power at low frequencies.

It is another object to provide a novel unitary nioiinting arrangement for a high frequency reflex horn speaker, or tweeter, within a casing containing a low frequency speaker, or woofer, which forms part of the enclosure of the woofer.

It is another object to provide a novel, composite memher which forms part of the woofer enclosure, part of the tweeter horn, and part of the tweeter throat.

It is another object to provide such a composite memher which is extended to exercise other functions normally exercised by various other separate parts, and thus increase accuracy of acoustical design and simplify manu facture by a great reduction in number of parts.

It is another object to provide a dual loudspeaker having wider directional pattern along one axis than at 90 thereto, by making the mouth of each horn rectangular with the major axis directed in the planewhere wider distribution is desired.

It is another object to provide a dual rectangular horn assembly in which the tweeter horn may be mounted at either of two 90 orientations relative to the woofer horn.

Another object of the invention is to provide a high fidelity dual range waterproof loudspeaker system designed for either indoor or outdoor use, and one that is suitable for auditoriums, restaurants, or any location requiring high fidelity public address sound distribution.

Another object of the invention is to provide a speaker with an adjustable U-bracket so that the speaker can be oriented with its longer axis extending either vertically or horizontally and also to-enable the speaker assembly to be moved throughout a large are about its pivotal mountings on the U-bracket.

A still further object of' the invention is to provide a speaker assembly pivoted to a U-bracket and one in which the tweeter horn may be moved with respect to the woofer horn. Thereby the original mounting of the bell in either a horizontal or a vertical direction, plus the adjustability of the tweeter with respect to the woofer, results in extremely wide selection of sound orientation, thus making it possible to cover to greatest advantages ice those areas where sound production is required; At the same time, by the flexibility thus afforded, undesirable feedback in auditoriums or rooms where there are ex cessive' reverberation conditions is eliminated.

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

To the accomplishment of the foregoing and related ends, said invention then comprises the features herein after fully described and particularly pointed out in the claims, the following description and the annexed draw ings setting forth in detail certain illustrative embodiments of the invention, these being indicative, however,

of but a few of the various ways in which the principle of the invention may be employed.

In said annexed drawings:

FIG. 1 is a perspective view of the loudspeaker with parts broken away; 2

FIG. 2 is a front elevational View of the same;

FIG. 3 is a rear elevational view with parts broken away to show the cone speaker mounted therein;

FIG. 4 is a sectional view taken approximately on the line 4'4 of FIG. 2;

FIG. 5 is an enlarged vertical sectional view of the magnetic system and diaphragm;

FIG. 6 is a perspective view of the front portion of the housing containing the tweeter;

FIG. 7 is a sectional view taken on the line 77 of FIG. 4;

. FIG. 8 is a sectional view taken on the line 8-3 of FIG. 4;

FIG. 9'is a sectional view taken on the line -'9of FIG. 4;

FIG. 10 'is' asectional view taken on the line Ill-1h of P16. 4;

FIG. 11 is a schematic wiring diaphragm for the dual speakers;

FIG. 12 is a plan vie-w of a chart illustrating thelower portion of the audio spectrum-of the acoustic performance of several loudspeakers;

FIGS. 13a, 13b, 13c, and 13d are diagrammatic views of the various arrangements made possible by rotating the tweeter and the woofer;

FIG. 14 is a' diagrammatic plan View of dual speakers in juxtaposition; and,-

FIG. 15 is a front elevational view of the same.

Referring now to the drawings, and more particularly to FIGS. 1 and 4, it will be seen that the assembly comprises a tweeter and a woofer disposed back-to-back. The tweeter is generally similar to the tweeter shown more in detail in a co-pending application of Sidney E. Levy et al-., Serial No. 741,601, entitled Transducer," filed on June 12, 1958, said Levy being one of the aplicants herein. This application has now issued into Patent No. 2,957,054, on October 18; 1960.

It'is to be understood that theterm tweeter, which is common in the art, refers to a'loudspeaker which is used preferentially for the high frequency end of the spectrum,- and the term woofer is used preferentially for the low frequency end thereof;

There is an important difference between thetweeter of the above-identified application and that of the present application, and this resides in the shape ofthe mouth. Iii thepresent application the mouth 5 of the tweeter is rectangular, whereas in the above-identified application the mouth is circular. In addition, the mouth 5 is provided with a rearwardly extending skirt 87.

Referring to FIGS. 1, 4, and 6 to 9, inclusive, the tweeter driver unit 21 comprises the annular magnet 22, the magnetic core 23, the annular pole piece 24, the annular nonmagnetic spacer 25 which disposes the annular pole piece 24 in such manner that a desired annular air gap 26 is formed between it and the inner core 23,

spacer washers

27, 28, and a diaphragm assembly 29.

The diaphragm assembly is shown in detail in FIG. 5 and has a generally curved acoustic driving portion 36 symmetrical about a central axis 31-31, an annular, generally flat rim 32, an annular step 33 at the edge of the curved portion, a cylindrical voice coil form 34 affixed to the step, and a voice coil 35 wound on the form. The rim 32 is cemented between the

various spacer washers

27, 28.

The driver 21 is assembled into an inner compartment 49 of the mechanical acoustic body with the spacer washer 28 pressed against the diaphragm assembly contacting shelf 38 to make a tight acoustic seal. The arcuate portion 30 of the diaphragm is positioned in closely spaced relationship to the rear surface 39 of the partition 40, which is an integral part of the portion of the mechani cal acoustic body 15, such partition 40 bridging the rear end of the throat 43. The air chamber 41 formed between the arcuate portion of the diaphragm and the rear surface 39 of this partition constitutes an acoustic coupler, when used in combination with the sound ducts 42 leading through the throat 43. These ducts 42 begin as arcuate segmented apertures in the partition see FIG. 8. It should be noted that these apertures are so arranged as to provide minimal spacing between any point 44 in the acoustic coupler and the edge of the nearest aperture 42see FIG. 8.

These ducts 42 are formed continuously along the length of the throat 43 beyond the partition 40 by the elongated spaces formed between longitudinal ridges 45 on the body. The taper of these ducts is arranged to be similar to that of the outer part 60 of the tweeter horn, so that they constitute a part of the tweeter horn.

The driver is resiliently pressed against the shelf 38 by the strap 46, which is retained at the ends by screws 47, which are in turn screwed into holes in boSses'on member 19.

The rear of the driver compartment 49 may optionally be covered by a cover 50, which has apertured tongues 51 on the outside for the reception of screws to fasten it to the tweeter housing, the cover also having terminals 52.

Referring again to FIGS. 1, 4, and 6 to 9, inclusive, the reflector 56 is illustrated as a generally cup-shaped member having a coaxial core portion 57 extending internally and rearwardly from the closed end 69 thereof, this core portion 57 being adapted to fit within the conical recess of the mechanical acoustic member. The space between the outer surface of the core portion 57 and the inner surface of the forwardly extending portion 20 of the mechanical acoustic body 15 forms the throat or first traverse 43. The external surface of this core portion 57 forms part of the boundary of the ducts. In the embodiment shown in the drawings, the ridges 45 (see FIG. 9) separating the ducts 42 are integral with the internal wall of the forwardly extending portion 29 of the mechanical acoustic body, although alternatively they may be integral with the outer wall of the reflector core portion 57. The inner edge of the skirt 58 of the reflector fits in the annular groove 59 formed between the outer surface of the rearwardly extending cylindrical portion 1.9 of the mechanical acoustic body 15, such portion forming the driver unit compartment 49; and the outer skirt of forming therebetween two traverses of the horn. The said inner edge abuts radial ridges 59a (see FIGS. 4 and 7).

The annular area between the housing skirt 60 and the reflector 57 up to the section line 8-8 of FIG. 4 is tapered exponentially to form part of the horn. The

outer annular portion has greater cross-section than required for exponential taper, and this acts as a resonator to enhance acoustic response near the low frequency cut-ofi of this tweeter horn. The outer end of the tweeter horn is joined to the forward housing 87. The skirt 60 is joined to the portion 19 by part 18 extending substantially at right angles thereto. The skirt 60 and the skirt 58 form the third or outer traverse 16. A second or intermediate traverse 17, which may be termed a sound duct, is formed between the skirt 58 of the reflector and the rearwardly extending portion 19. Thus, it will be seen that three distinct communicating ducts or traverses are formed within the relatively short axial dimension of the tweeter assembly.

Referring now particularly to FIGS. 1, 4, 9, and 12 of the drawings, further details of the traverses and of the mechanical acoustic body 15 can be seen, such as partition 41') and the central projection 61 thereon.

At the outer end of reflector 56 is a shallow recess 65 adapted to receive an identifying escutcheon 66, which can be cemented in place.

It may be seen that the mechanical acoustic member 15 of the tweeter, shown in FIGS. 1 and 4, constitutes a mechanical acoustic body having many functions, such as forming the acoustic coupling chamber 41, tweeter horn traverse 16, driver compartment 49, and one surface of each of a plurality of reflex horn traverses or ducts 17 and 43. The reflector 56 constitutes a coordinating member which completes the configuration of the composite ducts and contains the opposite surfaces of the reflex horn traverses or ducts 16, 17, and 43.

In order to secure optimum low frequency response from the woofer 96, it is necessary not only to load the diaphragm properly with a horn 110 on the driving side but to enclose the non-driving side with an enclosure sufficiently large so as to impose negligible stiffness on the diaphragm. Such an enclosure is formed between the diaphragm 95, the forward housing 37, and the rear housing 90, described hereinafter.

A substantially cylindrical housing 90 envelops the nondriving side of woofer 96, and this is joined to the forward extension 87 around the tweeter, along the line of junction 99, first becoming dome-shaped and then rectangular at the mouth 5 thereof, the same housing wall 90-87 forming or generating the inner annular wall of the horn of the woofer 96. It may be seen that this constitutes the most eflicient possible use of the air space available Within the outline of the inner annular portion of the woofer horn for minimizing stiifness loading of the woofer diaphragm 95. In addition, the shape of the inner annular wall of the woofer horn 110 generated in this manner is the optimum shape for that horn, whereas any variation in the annular cross-section 100 between the dome 87 or the portion 90 of the woofer enclosure and the horn skirt 112 would insert a discontinuity into the flare of the woofer horn, which would impair the efiiciency of the horn.

Although the line of junction 99 between the tweeter skirt 87 and the woofer housing 90 is shown disposed in a plane approximately midway between the annular seat 91 of the woofer and the mouth 5 of the tweeter, this line 99 may be disposed nearer the tweeter mouth if desired, so long as the object of this junction is fulfilled; namely, that a junction be made between the rim of the tweeter horn and the rim of the woofer housing 90 which will not cause the contour of the woofer horn to be disturbed and which can be assembled to have a substantially air tight seal without costly hand-fitting.

The annular line of division 99 at which the cylindrical portion 90 of the housing is separated from the domed portion 87, and the manner by which the domed portion and the

rectangular portions

1, 2, 3, and 4 are integrally die cast with the tweeter horn structure, constitutes a wide departure from known prior art structures.

The baffle 97 is made of felt or any other suitable sound i) absorbing material. Any standing wave in the chamber bounded by the diaphragm 95, forward housing 87, and the rear housing 90 may be controlled or damped by the porosity or permeability of the baffle 97, as well as the dimensions of the orifices 76-77.

It is an important feature of the present invention that the extra or outermost skirt 87 on the tweeter horn is circular at the rearward end 88 and has four screws 98 disposed at 90 intervals, located at the bases of tapering grooves 37 which permit easy access With a screw driver. It is also important that the skirt 87 can be assembled with the major axis of the mouth 5 along either of two 90 axes, one being parallel to the major axis of the Woofer month 104 and the other being parallel to the minor axis thereof. This rectangular horn mouth 5 and skirt shape 87 isfabricated without extra expense, once the dies are made.

The material selected for the tweeter housing is die cast metal; that for the reflector, molded plastic; and that for the woofer horn bell, molded fibreglass. These materials are preferred but not essential, and it is to be understood that any of these parts may be formed of any of these three materials.

The performance of this dual speaker is better than that of any other speaker of comparable dimensions. It has higher efliciency and wider frequency range. There is no non-linear distortion due to throat distortion, since the woofer throat size is large, this type of distortion being characteristic of small throats. The directional pattern is wider in the plane of the major axis of either horn. The feature of mounting the tweeter with its major axis either parallel or perpendicular to that of'the Woofer permits greater control of directional patterns.

Performance data of the present speaker is shown in I FIG. 12, wherein the solid line 53 represents the sound pressure characteristic measured on the speaker as described herein, and the line 54 is a curve defining the relative characteristic of the closest approach in the prior art, for a speaker of similar size, to the speaker of the present case.

The dotted line 55 represents the unretouched charac teristic of the speaker when the damper baffie 97 is omitted, whereas the solid line represents the same structure with the damper inserted and suitably proportioned as to thickness, porosity, and similar. vibration controlling parameters. The

orifices

76 and 77 are helpful in permitting low frequencies to be passed from the diaphragm side of the bafile to the tweeter side, thereby minimizing stiffness loading on the diaphragm.

It will be noted that the woofer skirt 90 is provided with diametrically oppositely spaced struts 93, these being integral with the skirt 90. The struts permit pivotal mounting of the horn bell. Generally indicated by the reference numeral 110, since they extend from the horn bell skirt 112 and may be provided with wing nuts 113 so as to fix the horn bell with respect to the U-shaped bracket 115. Friction Washers 117 may be employed on both sides of the skirt 112.. The U-shaped bracket is also apertured as shown at 116 in the legs 115 of the U, as well asthe base portion 118 of the U-bracket.

The woofer assembly 96 is bolted to the peripheral inwardly extending flange 9 1 on the skirt 90 by means of the bolts 103.

FIGS. 13a, 13b, 13c, and 13d depict various ways in which either the horn hell or tweeter bell may be rotated one with respect to the other so as to obtain the ultimate sound distribution for any particular type of application.

In cases where a wider pattern is desired in a given plane, together with increased power handling capacity, an array may be made of two or more of these dual coaxial speakers, juxtaposed at the front and having their axes divergent as indicated in FIG. 14. In that case the major axis of the tweeter may be disposed in the plane crossing the mouths of both speakers, as indicated in FIG. 15. In this manner the spacial distribution of the high frequencies may be substantially equivalent to thatof the low frequencies.

The circuit is shown in FIG. 11, wherein 106 and 107 represent the input leads and 101 and 102 represent the leads going to the tweeter, 114 being a condenser interposed in line 101.

From the foregoing it will be noted that there has been provided a dual coaxial speaker including an inner tweeter horn and an outer woofer horn bell. It will be noted that, due to the provision for the means for orienting one horn with respect to the other and the provision of and adjustable U-bracket, directional characteristics may be controlled.

The direction of the sound propagation of the high frequency section may be readily changed relative to the low frequency section to accommodate the necessary dis persion requirements. For example, under normal horizontal operating conditions the orientation of the high frequency section is as shown in FIG. 13a. When it is desired to increase the high frequency dispersion in a vertical direction for purposes of reaching up into balcony areas or down onto auditorium floors, the high frequency. tweeter may be reoriented into an alternate position, as shown in FIG. 1311. This may also be utilized to reduce acoustic feedback due to excessive reflections from walls that would otherwise reflect back upon the microphone of a sound amplifying systems and cause oscillations.

This reorientation is simply and speedily accomplished by moving the four screws 98 and then rotating the body of the tweeter housing 87. In this connection it will be seen that the screws are easily accessible from the front of the speaker since there is considerable space between the

skirts

87 and 112 and a screw driver may be readily inserted in such space so as to contact the screws 98.

It is well known that ordinarily non-linear distortion occurs when high power is transmitted at low frequencies through a small throat. However, the speaker, as described herein, completely eliminates low frequency nonlinear throat distortion because a large throat is used for low frequencies.

The invention has been described as embodied in a loudspeaker, though it is to be understood that the same construction is usable as a sound pickup device. Other modes of applying the principle of the invention may be employed, change being made as regards the details described, provided the features stated in any of the following claims or the equivalent of such be employed.

In the claims the term transducer is used to indicate a sound translating device used either as, a loudspeaker or a microphone.

We claim:

1. in a transducer of the type'described, a tweeter diaphragm with a generally curved acoustic driving portion symmetrical about a central axis, a generally flat annular rim and a voice coil concentric therewith, a tweeter magnetic system having a concentric air gap, a forwardly disposed mechanical acoustic body symmetrical about said central axis comprising a wall perpendicular to said axis having a rearwardly facingsurface generally conformant to the diaphragm, a plurality of apertures therein, and an annular concentric portion adapted to support the rim and thereby dispose said acoustic driving portion at a narrow spacing from the rear surface of said wall whereby to define an acoustic coupling chamber, a tubular concentric portion extending forwardly from said wall, a concentric generally cylindrical portion extending rearwardly from said wall and surrounding said tweeter magnetic system,

a flange extending outwardly from the rear end of said cylindrical portion, a first skirt extending forwardly from the outer edge of said flange and symmetrically surround ing the aforementioned portions, and a second skirt extending rearwardly from the outside of the forward region of the forwardly extending first skirt, a generally cupshaped reflector member having a coaxial core portion extending internally from the closed end thereof, said core of said reflector being seated within the tubular portion of said mechanical acoustic body and coordinate with the inner surface and the apertures thereof whereby to form the throat of a reflexed tweeter horn, the inner surface of the reflector cooperating with the outer surface of said tubular portion and of the generally cylindrical portion whereby to form an intermediate annular reflexed portion of a tweeter horn, and the outer surface of said reflector cooperating with the inner surface of the forwardly extending first skirt whereby to form the final annular reflexed portion of the tweeter horn, a cone-type loudspeaker unit adapted for use as a woofer, having an annular peripheral mounting seat, a rearwardly disposed housing comprising an annular seat for engaging the mounting seat of said woofer, a forwardly extending shell adapted to substantially surround said woofer and having a forward edge adapted to engage with the rearward edge of the rearwardly extending skirt of the forwardly disposed mechanical acoustic body whereby to form an enclosure for the forward side of the woofer, a generally cup-shaped outer horn bell having the closed end thereof disposed in spaced relationship to the rearward surface of the Woofer and the side walls spaced progressively from the outside surfaces of the forwardly extending shell of said housing and said rearwardly extending skirt whereby to form therebetween an annular woofer horn concentric with said tweeter born.

2. A transducer as set forth in claim 1, wherein said horn bell has a U-shaped supporting bracket pivotally attached thereto.

3. A transducer as set forth in claim 1, wherein said tweeter is adjustably mounted with respect to said woofer, whereby the rectangular mouth of said tweeter may have the longer axis of its mouth alined with the longer axis of said horn bell mouth or at right angles thereto.

4. In a transducer of the type described, a one-piece integral mechanical acoustic body having a central axis, said body including an interior wall perpendicular to the axis having a rearwardly facing surface, said surface having an annular portion concentric with said axis adapted to support the rim of a diaphragm and thereby dispose other portions of the diaphragm at a preselected spacing from said surface, at least one aperture in said wall within said annular portion, said body having at least one annular portion concentric with said axis extending forwardly from said wall and terminating in a frontal edge; a tubular portion extending rearwardly from said wall terminating in a flange and a second forwardly extending tubular portion extending from said flange and terminating in a forward edge, and a second tubular portion extending rearwardly from said forward edge surrounding the aforementioned portions and terminating in an annular seating surface.

5. A transducer as described in claim 4 characterized by a plurality of equal spaced apertures through said wall.

6. In a transducer of the type described, a one-piece integral mechanical acoustic body having a central axis, said body including an interior rearwardly directed diaphragm seat perpendicular to said axis, an interior annular portion extending forwardly from said seat, said portion having a central recess; a first annular portion extending rearwardly from said seat and terminating in a flange, a second annular portion extending forwardly from said flange spaced from said first annular portion and terminat ing in a front edge; and a third annular portion extending rearwardly from said front edge surrounding the aforementioned portions and adapted for mounting at the rear edge.

7. A transducer as set forth in claim 6, characterized by said diaphragm seat having a bridging partition asso ciated therewith and disposed in front thereof, said par- -tion being provided with a central forwardly extending portion having a screw socket therein.

8. In a transducer of the type described, a one-piece integral mechanical acoustic body having a central axis, said body including a wall perpendicular to the axis having a rearwardly facing surface, said surface having an annular portion concentric with said axis adapted to sup port the rim of a diaphragm and thereby dispose other portions at a preselected spacing from said surface, at least one aperture in said wall within said annular portion, said body having an annular portion concentric with the central axis extending rearwardly from said wall and adapted to surround a magnetic unit, and said body having at least one annular portion concentric with said axis extending forwardly with respect to said wall to a frontal edge and a tubular portion extending rearwardly from said edge surrounding the afore-mentioncd portions and terminating in an annular seating surface.

9. In a transducer of the type described, a one-piece integral mechanical acoustic body having a central axis; said body including a wall perpendicular to the axis having a rearwardly facing surface, said surface having an annular portion concentric with said axis adapted to support the rim of a diaphragm and thereby dispose other portions of said diaphragm at a preselected spacing from said surface; at least one aperture in said wall within said annular portion; said body having an annular portion concentric with said axis extending forwardly from said wall; an annular portion concentric with the central axis extending rearwardly from said wall and adapted to surround a driver unit; a flange portion extending outwardly from the rear end of the rearwardly extending annular portion; a flared tubular portion extending forwardly from the outer edge of said flange surrounding the aforementioned portions in spaced relationship and terminating in a frontal edge; and a tubular portion extending rearwardly from said frontal edge surrounding the aforementioned portions and terminating in an annular seating surface.

10. In a dual coaxial transducer of the type described having a tweeter and a woofer; a tweeter diaphragm with a generally curved acoustic driving portion symmetrical about a central axis, a generally flat annular rim and a voice coil concentric therewith; a magnetic unit having an air gap concentric with said axis; a one-piece integral mechanical acoustic body having a central axis coincident with said first-named axis; said body including a wall perpendicular to the axis having a rearwardly facing surface generally conformant to the driving portion of the diaphragm, said surface having an annular portion concentric with said axis adapted to support said rim and thereby dispose the acoustic driving portion at a narrow spacing from said rearwardly facing surface, whereby to define an acoustic coupling chamber; a plurality of apertures through said Wall connecting with said coupling chamber; said body having an annular portion concentric with said axis extending forwardly from said wall; an annular portion concentric with the central axis extending rearwardly from said wall and surrounding said driver unit; a flange portion extending outwardly from the rear end of the rearwardly extending annular portion; a flared tubular portion extending forwardly from the outer edge of said flange surrounding the aforementioned portions in spaced relationship and terminating in a frontal edge; and a tubular portion extending rearwardly from said frontal edge surrounding the aforementioned portions and terminating in a first annular seating surface; an annular member having a mating surface affixed to said first seating surface and extending rearwardly to a flange, said flange being directed inwardly to form a second seat; said woofer being aflixed to said second seat facing rearwardly; a generally cup-shaped horn bell having a bottom and sides, the bottom of the cup conforming generally to the surface of the woofer in spaced relationship thereto and the sides surrounding said tubular member and the mechanical acoustic body in progressively spaced relationfor the woofer.

References Cited in the file of this patent UNITED STATES PATENTS Perla et a1 Dec. 3, 1929 Betts et a1. Oct. 27, 1936 Massa Sept. 10, 1940 Levy Mar. 20, 1951 10 11 Kamimori Oct. 26, 1954 Levy May 22, 1956 Hoodwin Oct. 14, 1958 Levy Oct. 21, 1958 Harris Oct. 21, 1958 Levy Oct; 28, 1958 FOREIGN PATENTS France Jan. 7, 1953 Great Britain Jan. 4, 1956