US2638510A - Duplex loud-speaker - Google Patents

Description

May 12, 1953 J. BRAMI 2,638,510

DUPLEX LOUD-SPEAKER Filed Jan. 6, 1949 V 7 I l I Z! 25 25 7 Z I '9 ll D A 2:; 26

INVENTOR.

JOSEPH BRAMI ATTORNEY Patented May 12, 1953 DUPLEX LOUD-SPEAKER Joseph Brami, Baltimore, Md., assignor to Caesar David Zeitouni, Brooklyn, N. Y

Application January 6, 1949, Serial No. 69,541

23 Claims.

The invention relates to loud-speakers and more particularly to sound-chamber loud-speakers equipped with sectional reflex horns.

Loud-speakers of that type are widely used because of their compactness and light weight.

Adequate for general applications, these loudspeakers are unfortunately inappropriate for high-fidelity music reproduction owing to their restricted sound frequency range which covers generally the high to medium portion.

That is why they are mostly associated with large-diaphragm direct radiator loud-speakers which are acknowledged as good reproducers for the low frequency portion,

Such a combination, however, is expensive and cumbersome since it requires the use of two separated loud-speaker units.

A first object of the invention is to convert sectional reflex horn loud-speakers into wide-range duplex loud-speakers by replacing one of the sections of their reflex horn (preferably the external mouth-section) by the large diaphragm of a direct radiator loud-speaker separately operated.

A second object of the invention is a speciallydesigned, wide-range duplex loud-speaker achieving the aforesaid object and comprising a number of particular arrangements and advantageous features.

The invention, which furthermore includes other improvements, is illustrated in cross-section in the accompanying drawing in which Figure 1 is the wide-range duplex loud-speaker of the present application; and Figure 2, a modified portion of the same loud-speaker.

As shown in Figure l, the wide-range duplex loud-speaker of the invention is composed of four principal, easily-separable parts: a sound-chamber reproducer I, a single-fold reflex horn 2, a large-diaphragm direct radiator loud-speaker 3 and a double air gap magnetic structure 4 which is common to the sound-chamber reproducer I and to the direct radiator loud-speaker 3.

' The magnetic structure 4 consists of an annular magnet 5 clamped by bolts 6, '6 passing through its slots I, I, between a bottom of a case '8 and a ring 9 which forms an outer annular air gap In with an edge of the case 8 and an inner annular air gap I I with a central core I2 tightly fitted to a hole of'the bottom of this case 8.

The sound-chamber reproducer I comprises a small dome-shaped diaphragm I4 which, attached to a voice coil I5 located in the inner air gap I I, has its flexible edge I6 glued between two rings I71, I I which, fitted into a recess I3 provided by a shoulder I8 projecting the ring 9, are tightened by an exponential throat-case I9 which, screwing 2 on a thread 20 of the shoulder I3, has a tapped duct 2 I and makes by its inner side with the facing side of the diaphragm I4, an enclosed clearance space 22.

The single-fold reflex horn 2, composed of a section 23 and another 24 having an annularconcave deflecting bottom 25 and mounted over the section 23 by riveted or Welded brackets 26, 26, is screwed by its threaded throat 21 on the tapped duct 2| in order to communicate with the clearance space 22 of the sound-chamber reproducer I.

The large-diaphragm direct radiator loudspeaker 3 consists of a housing 28 which, welded to a rim 29 fitted and clamped by machine screws 30, 30 to the magnetic structure 4, has an edge 3I to which is glued together with a felt ring 32, a corrugated edge 33 of a large exponential bell-like diaphragm 34 having an opened concave bottom 35 which, continued without contact by the exponential throat-case I3 in order to constitute an annular-concave deflector 36, is attached to a voice coil 3! guided in the outer air gap I 0 by a corrugated spider 38 glued to a bottom edge 39.

The whole assembly is previously centered in order to insure the automatic centering of the voice coil 37 of the large diaphragm 34 in the outer air gap II), when the magnetic structure 4 fits to the rim 29.

Owing to the deflector 36, the large diaphragm 34 of the direct radiator loud-speaker 3 serves at the same time as a continuation of the singlefold reflex horn 2 by constituting the external mouth-section of a two-fold, three- section reflex horn 23, 24, 34 for the sound-chamber reproducer I. The reflexed air-column of this horn 23, 24, 34 (visualized by the successive arrows) follows this path; the throat 21, the section 23, the deflecting bottom 25, the space between the two sections 23 and 24, the deflector 36 and the space between the section 24 and the diaphragm 34.

In the modification of Figure 2 (where the same numbers designate the same parts as in Figure l) the wide-range duplex loud-speaker of the invention has its sound-chamber reproducer I placed at the back of the magnetic structure 4.

For that purpose, the ring 9 is replaced by a round plate 4| holding a core 42 which, extended by a centrally-holed convex plug 43 and provided with a tapered duct 44 ended by a tapped hole 45, forms a rear annular air gap 46 with a bottom opening of the case 8. To avoid useless magnetic losses, the plug 33 is made of insulating material, such as Bakelite, hard rubber, plastics and the like. A back extension of this case-8 furnishes a shoulder 41 with a thread 48 and a recess 49 i into which fit the rings I1, I! supporting the municate with the clearance space 5! of the,-

sound-chamber reproducer I.

It is obvious that the wide-range duplexrldudz speaker of the invention necessitates the use of. an electrical frequency-dividing"network'whifiit by separating the sound-modulated currents into two parts, permits to allocate tthemzrespecti'velyx to the voice coil 65 of the sound-chamber. repro ducer l and to the voice coil 31 of the'direct radiator loud-speaker 3.

ACCOI'diIIg-tO'thG(13116115101315 of the diaphragm" 3 4 and the =le'ngth of th'e -refiex horn '2 5 the direct radiator loud speakes 3 "and tthe -sound chambei reproducer l maybe assigned to the reproduction of the iollowing portions of-"Una soundflfrequency ran-gee- (a) the speaker statue lovwto medium" frequonoies;--' while 'the reproducer i to the frequencies (b)- the speake'r 3 to ma low? ire-- quenoies-y- While the repr-cducer l to the h'ighiuto medium frequencies;

O'fcOurse tHe -Ioud speaker of "th'eflinventiont is not limited to the indicated number of sections for-"the reflexhorus 1.": In: combination; a'zhell-ilike idiaphragm positionedkito .1 discharge sound-vibrations forwardlyfrom' within the diaphragrn; means for intro ducing 'high frequency -air vibrations rearwardlyinto the inner*partof"the diaphragm and "means for-imparting low frequency vibrations to media-- phragmr 2! In combinationv a'-smal1--sound chanmbery adiaphragm across the chamber; means fonim parting men frequency vibrations to the diaphragm a' long narrow horn communicating "atits inner end with'. said chamber and-having itsintermediate part remote from said inner end and its larger end adjacent to the inner "end alarge -=single' fold 'exponentialdirectradiator-belllik'e'vibratorydiaphragm receiving said-horn and having-its inne rend: freely 'movahly "closelv-adj e cent tothe larger end of" the horn: and form ing a= continuation thereof;- andmeans attached to saidinner" endofthe belllike "diaphragm for :im** parting low frequency-vibrations thereto:

31 Incombinationya'largersi-ngle fold exponen tial direct'radi'ator bell-like diaphragm 'mounted for fre'e vibration; and'h'aving asmall innerend; means attached to saicliinnerzend' Iof thetbel-l-likei diaphragm-forimparting lovv frequency vibrations" thereto; a;small' high" frequency sound chamber; a longnarrow refiexexponentialyhorn communi-j I eating" atitsfsmaller end with said'johamber;and having its larger endldisposedientirely within. said ,1 diaphragm Land. dischargingxtowarduthe inner end of .theidiaphragm; saidv diaphragm having its innera end,fr'eely =-movablyclosely adjacent-to the larger end of, the, horn and forming e -V. ponentialrcontinuationR of the horn whereby said:- bell=l-iketdiaphragmiserves thesmultiplei function 1 ofia: direct ,radiatorloudspeaker;- andv servesiasp. the 4 external 1 mental-section. and .,an.-. exponential continuation or saidahorni a 4. 1 combination; at large: single fold-g, ex-

ponential; direct radiators: belli-flikeis; diaphragm: 7 5.1

mounted for free vibration, and having a small inner end; means attached to said diaphragm for imparting low frequency vibration thereto; a small sound chamber to the rear of said inner end; a diaphragm across the chamber; means for imparting high frequency vibrations to the dia' phragm; a long narrow reflex exponential horn communicatingat its inner .endiwithi-said chamber anddisposed entirely within'said diaphragm and having its larger end discharging toward the inner end of the diaphragm; said diaphragm having its inner end freely movably closely adjacent to therlarger end of the horn and forming an exponential continuation of the horn; whereby said ibell'likesdiaphragnr serves the multiple function of a direct radiator loud speaker, and serves as the:external'jmouthisection of an exponential continuation oi said horn.

5"." In combination, a magnet having outer and inner air gaps; a diaphragm flexibly marginally secured to--said magnet a high-"frequency -voice coil in the-inner gapand attache'd to the dia phragm; -athroat case spaced over said dia phra-gmand having-a-duct therethrough; and an exponential f ace 1 around the duct a reflex-"horn comprisingan innersection-mounted in'said duct, and anouter section'closed at the outer endand" sp aced from the 131181 seotion and said" f ace alarge-exponential dii'ect' radi'atorsingle foldbel'l like diaphragm substantially' coaxialwith the h'orn and-having a-flexi-blysupported fiaringiouter edge "and an inwardlycurved-"bottom freely-mov ably'closely -spaced around; and forming a con-- tinuation of, said face; low-frequency-coil in: said outer 'airgap-attached to the-=ihhereedg ofSthe large diaphragm:

6. In combination, a magnetic-case having a bottom and a large 'opening 'opposite the' bottom; a core seoured to said bottom; an annular- -magnet secured to said bottom'raroundjsaid zcorer' aa'mag' netic'r ring secured on; said-magnet and spaced from said core and the =edgeot theopeningr to form outer and inn'erai-ragaps a" diaphragmwdispose d over the freeend 0f said core and fl'exibly secured 1 to said ring; a "high frequency-'"voice (coil in th'e' inner: gap and attached 'to :thediaphragm;- a: throattcase secured over-rsai-d" diaphragm. to: form therewith a sound chamber and. having'am axia-ltdu'ct anda-fhaving am exponential face therearound; arbowl-lilre exponential diaphragm: ham:

1 ing "am inner margin freely movablmaround said face andforming-an :exponentiat continuationaof thexfaoe; means tfo'rzrimpartingi lowrfrequenoy-wi brations to said inneramargin: of thezdiaphragm'at ancexponenti'al-*reflexahorn: having: its small end inzrsaid ductyand its; large; end .di'reoted.;- towardi said'zfaceei 7 lntcombination'," a. member having;- a ducts therethrough; andcan exponential face-around the duct? a reflex: norm-comprising," an inner-rsection-'- seoured iat'itsinner endinzsaid duct, ;and an;outer section spacedzzaround {the inner :sectiomandtexs 1 tendingto nean'said 1f aces-and havingsat; the outer end 1 an end-icaps spaced'ifromi th-BFiIlHBI rsectiongw a! large-"exponential idirect radiator tsinglesfold 1 bell-like w diaphragm substantiallw coaxial with;

secured to said bottom and terminating substantially centrally of said opening in the plane of the opening; an annular magnet secured to said bottom around and spaced from the core and terminating near said plane; a magnetic ring secured on said magnet and spaced from said core and the edge of the opening to form outer and inner air gaps; a dome-shaped diaphragm disposed overv the free end of said core and having a. flexible marginal extension secured to said ring; a, high frequency voice coil attached to the edge of the diaphragm and disposed in the inner air gap; an exponential throat case marginally secured to said ring over and conformably spaced from said diaphragm to form therewith a sound chamber and provided with an axial duct communicating with the sound chamber, and an exponential face around the duct; a bowl-like diaphragm having a freely movable inner margin forming a continuation of said face; a horn having its small end in said duct and its large end directed toward said face; and a low frequency voice coil attached to the inner edge of the large diaphragm and disposed in said outer air gap.

9. In combination, a member having a duct and an exponential face around the duct; a single fold reflex horn comprising an inner section tapering toward and secured at its inner end in said duct, and an outer section spaced from and enclosing the inner section and flaring toward and extending to near said face of the member and having at the outer end an end cap having an inner concaved face facing and spaced from the inner section; a bell-shaped loud speaker housing substantially coaxial with the reflex horn and having an inner end secured fast on said member around said face and having at its free edge a belt ring disposed in a plane transverse to the axis of the horn slightly beyond the outer end of the horn; a large exponential direct radiator single fold bell-like diaphragm conformably spaced from the loud speaker housing and having a transversely outwardly disposed flexible edge secured to said belt ring and a downwardly inwardly curved inner margin freely movably closely spaced around the edge of and forming a continuation of said face of the throat case; means connected to said inner margin for imparting low frequency vibrations to the large diaphragm; and means for supplying high frequency vibrations in said duct.

10. In combination, a magnetic case having a bottom having a large central opening and a larger opening in the top; a core spaced in said large opening of said bottom to form an inner air gap and terminating substantially centrally of said larger openin in the plane of the larger opening, and having an axial duct therethrough; an annular magnet secured to said bottom around and spaced from the core and terminating near said plane; a magnetic ring secured on said magnet and around the upper end of said core and spaced from the edge of said large opening to form an outer air gap; a convexed plug mounted on the rear end of the core and having a duct alined with the duct of the core; a dome-shaped diaphragm conformably disposed over the plu conformably spaced from said plug to form therewith a sound chamber and communicating with said ducts, a high frequency coil attached to the diaphragm and disposed in the inner air gap; a freely vibratory bell-shaped diaphragm having a low frequency coil secured to its inner end and disposed in said outer gap; and a horn having a small end in said duct, and a large end in said diaphragm.

11. In combination, a small sound chamber; a diaphragm across the chamber; means for imparting high frequency vibrations to the diaphragm; a single fold horn comprising an inner horn section tapering toward and communicating with said chamber, and an outer horn section spaced from and enclosing the inner section and flaring toward and spaced from said inner end and having at the outer end an end cap having an inner concaved face facing and spaced from the inner section; a large exponential direct radiator single fold bell-like diaphragm having a downwardly inwardly upwardly curved bottom freely movably closely spaced around the inner end portion of said inner section and forming exponential continuation of the outer section; and means attached to the inner part of the large diaphragm for imparting low frequency vibrations thereto.

12. In combination, a large direct-radiator diaphragm mounted for free vibration, and having a large outer end and a small inner end; means for imparting low frequency vibration to said diaphragm; a high-frequency chamber; a narrow horn communicating at its smaller end with said chamber and having its larger end near and forward of and discharging inwardly toward and against the inner face of the inner end part of the diaphragm; said diaphragm forming a continuation of the horn and reflecting the sound waves received from the horn; whereby said belllike diaphragm serves the multiple function of a reflector and as a reflex wall for the horn and as a direct radiator loud speaker, and serves as the external mouth section and continuation of said horn.

13. In combination, a large single fold exponential direct radiator bell-like diaphragm mounted for free vibration, and having a large outer end and a small inner end; means attached to said diaphragm for imparting low frequency vibration thereto; a small high frequency compression chamber; a long narrow exponential horn communicating at its smaller end with said chamber and disposed within said diaphragm and having its larger nd near and forward of and dischargin toward the inner end of the diaphragm; said diaphragm having its inner end freely movably closely adjacent to the larger end of the horn and forming an exponential continuation of the horn and reflecting the sound waves received from the horn; whereby said belllike diaphragm serves the multiple function of a reflector and as an outer reflex wall for the horn and as a direct radiator loud speaker, and serves as the external mouth section and as an exponential continuation of said horn.

14. In combination, a horn; means for introducing air vibrations into the horn; a hollow diaphragm mounted for free vibrations independently of the horn and positioned with its inner side facing the mouth of the said horn to form a reflex contiuation of and an external mouth section for the horn; and means for imparting vibrations to the diaphragm.

15. In combination, a horn; means for introducing high frequency air vibrations into the horn; a hollow direct radiator diaphragm mounted for free vibrations independently of the horn and positioned with its inner side facing the mouth of the said horn to form a reflex continuation of and an external mouth section of the horn; and additional means for impart- :acsaiero ing low '--rrequency' vibrations tovthe' diaphragm. 16.. In combination, a vibratory "diaphragm :positioned to direct sound vibrations forwardly -from thezffront fa-certhereof; means for impart- 'ing sound vibrationsto .the;:diaphragm for :pro-

:jecting. the -.vioration's forwardly; an additional source \ofxsound vibrations; a horn communicating:at itsxsmaller end with said source and'having .its larger end near anddirected-rearwardly toward the .intramarginal part of the forward face: oi-ithe diaphragm, to :project the vibrations from the :horn rearwardly "from said larger end against thesdiaphragm'to be combined with-the 'vibrationssthereof, "to be reflected by the v.dia-

"phragm, and: proj ected'with them forwardly from ithleifaifle' of the diaphragm.

.=1:7.. In combination, a concaved vibratory diaphragm positioned. to direct sound vibrations ior- "wardlytr'romcthe concaved race thereof; means for-imparting low frequency sound vibrations I to the diaphragm for projecting the low frequency vibrations forwardly .fromsaid concaved face;: .asource of high frequency sound vibrations; a :horn communicating'at its smaller end with said. source and having its larger end near :and :directed. irearwardly toward :the 'mid part oftheuforward concavedface of the-diaphargm,

.to project the high frequency vibrations rear-- *wardly from said larger end against the dia- ,phra gm tobe reflected bythe diaphragm, added 130 13116110! frequency vibrations and projected "with them together forwardly from the forward .face "of the" diaphragm.

-l8..-In.combination, aibell-like vibratory diayphragm positioned to direct sound vibrations .iorwardly from the: concaved race thereof means for imparting low irequency sound vibrations to the inner part of the diaphragm forprojecting the low frequencyvibrations'iorwardly; :a source of high frequency sound vibrations; :a horncommunicating at its smaller end with said :source and having-its larger end near and directed rear- Wardlytoward the mid-part of the forward face of the bell-like diaphragm, to project the high frequency vibrations rearwardly-from said larger end against the diaphragm.

.19. In combination, a vibratory diaphragm positioned to direct sound vibrations forwardly from .its forward. .face thereof; means for. im- .-.parting low frequency sound vibrations. to. the diaphragm fOr projecting the low frequency vi brations forwardly; a source of .high frequency sound vibrations; a long narrow horn communicating atits. innerend with said sourceandhav- .ing its intermediate part remote from said inner .end' and its larger end adjacent .to its inner rend I .and' directed .rearwardly toward the. mid-part.of thejorward faceof the diaphragm, to project the high frequency vibrations rearwardly from said larger. end against. the diaphragm to be reflected by the .diaphragmcombined with the low ...fre,quency vibrations and projected with them forwardly.

20. In combination, ,a. high frequency sound chamber; a long narrowhorncommunicatingat its. smaller end with said.chamber;..a.large direct radiator concaved vibratorydiaphragm receiving the larger end and intermediate ,part of said-horn'and having its inner part-freely mov- =ably closely adjacent to "the larger "end "of "the horn; :arrdmeans attached :torsaid send-:of

the; :diaphragm for imparting: low frequency avibrations-zthereto. I

21. In combination, .alsound chamber; :a long narrow horn communicating :at its smaller :end

with; said chamber and having its larger: end radjacent to thezinnerzend; a large .concavedzd'irect radiator vibratory diaphragm receiving; saidcends initsv concavity and. havinginner part'moyably -closely adjacent to :the :larger end of the .rhorn and forming a 'continuatiomthereof and. means attached to the diaphragm .for imparting vibrations thereto.

.22. In :combination, a high frequency .soun

.' chamber; along :na-rrow horn:communicatingat .its: inner end with; said. chamber and having its intermediate part .remotezrrom 'said inn-eriend and its larger end adjacent -.to the-innerxend;

a Iargedirect radiator bell-like vibratory diaphragm receiving *said horn in the space be tween theinnerand outer ends of the diaphragm andhaving-its innerend freely movablyrlosely adjacent-to the larger end of the. horn and forming-a continuation'of, and external mouth for,

\ the. horn; and means-attached to, said inner end ofv the diaphragm for-imparting low frequency vibrations thereto.

23. In -.combination, a concaved bell-like :loW frequency vibratorydiaphragm positioned to direct sound vibrations forwardly from the 'con- .caved .face thereof; low frequency means -operatively connected to the mid-part of therdialphragmflfor imparting low frequency sound vibrations to the diaphragm for projecting the .low frequency vibrations forwardly from said concaved face;v a separatesource or high Fire.-

guency sound vibrations additional-to said 10w .frequencymeans; a horn communicating atl-ts smallerrendwith said source andhaving its larger end-.near and directed .rear-wardiy toward the mid-part of the forward concaved face of the .diaphragm, to project thehigh frequency vibrationsrearwardly from said larger end. againstithe vibrating low frequency diaphragm to be re- .iflectedby the low frequency diaphragmadded to and combined withthe low frequency vibrations and projected in combination with them forwardly from the forward face of the dia- ,phragm,. as. anintegralvibration, thusgiving unifieid, firm, .musical tone pattern.

JOSEPH BRAMI.

References Cited in the file of thispatent UNITEDSTATES PATENTS

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