US1750900A - Electroacoustic device - Google Patents

Description

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Mmh i8, 1930. J, P, MINTON ET AL ELECTRQACOUSTIC DEVICE Filed Aug. l5, 1924 March 18, 1930. J. P. MaNToN ET AL S ELECTROACOUSTIC DEVICE Filed Aug. l5, 1924 3 Sheets-Sheet 2 INVENToRs JOHN aRasToN mm1-0N Asn HAM ames. v

/L fm A 55 E5 ORNEY March 18,- 1930. J, P, MINTON El' AL ELECTROACOUSTI C DEVI CE File'd Aug. l5a S1924 3 Sheets-Sheet 3 INVENTORS JOHN PRESTON MINTQN ABRAHM l BY A SRNGEL.

Patented Mar. 18, 1930 LUNITED STATES PATEN'n OFFICE JOHN PRESTON HINTON, OF WHITE PLAINS, AND ABRAHAM S. RINGEL, OF BROOKLYN, NEW YORK, ASSIGNORS TO RADIO CORPORATION OF AMERICA, A CORPORATION OF DELAWARE ELECTROACOUSTIC DEVICE Appiieuon 111m August 15, 1924. serial No. 732,153.

'Our invention relates to acoustic devices and particularly to electro-acoustic devices of the so-called loud speaker type. Our invention further relates to sound reproduction and ampliication methods.

One of the principal objects of our invention is the provision of an electro-acoustic device possessing the following charactertially maximum uniform amplification over` a wide range of frequencies with the employment of a comparatively small amount of power.

4 Tonal quality control. 5 Low manufacturing costs. 6) Constructional features im arting rigidity to the device resultin in t e substantial elimination of undesirable vibrations.

Other objects and advantages of our .invention will be apparent from the followmg description taken 1n connection with the accompanying drawings, in which: I

F 1g. 1 is a perspective view of a cablnet and a preferred' embodiment of our*y loud speaker mounted therein.

Fig. 2 isa combined perspective view and schematic dia ram of connections of a preferred embodlment of our invention.

Fig. 3 is a front elevation partly in section. Fig. 4 is a side elevation of the horns. Fig. 5 is a top plan view of the horns.' Fig. 6 is a top plan View partly in section of thehorns with certain parts broken away ,to more clearly disclose their structural relationship. p

Fig. 7 is a plan view of a diaphragm actuating device.

A preferred embodiment of ourl loud speaker comprises two lelectro-acoustic units A and B of different sizes and possessing differentl electrical and Aacoustical character- ,istics The unit A is substantially resonant `to the lower range of audible frequencies while the unit B is substantially resonant to the upper range of audible fre uencies resulting in the substantially uni orm reproduction and amplification of sound over a much wider range of frequencies than is attainable with a single unit.

The unit A which is the larger of the two, comprises an exponential horn 1 and an electro-magnetic sound reproducer 2.

The horn 1, which is the longer of the two and which opens up at a slow rate, comprises an intermediate vertical tapering portion3 of quadrilateral cross section, terminating at its upper end in an open horizontal flaring portion 4 communicating with o nings 5 in cabinet 6 and at its lower end 1n a securing portion 7 of cylindrical cross section as shown.

The horn 1 may be appropriately secured to certainV of the inner surfaces of the cabinet 6 by means of substantially L-shaped brackets 8; Y

The unit B, which is the smaller of the two, comprises a straight exponential horn 10 and an electro-magnetic sound reproducer 11.

The horn 10, which is the shorter of the `two and opens up ata more rapid rate than horn 1, comprises a straight intermediate horizontal tapering portion 12 of quadrilat- 80 eral cross section terminating at one end in an open horizontal flaring portion 13 and at vthe other end in a securing portion 14 of cylindrical cross section as s own. i

The tapering portion 12 is inserted thru an opening 15 in one of the sides of the horizontal Haring portion 4 of horn 1, the opening of the'horizontal flaring portion 13 coinable metal stampings, which may be soldered,

' brazed or welded together at their' edges.

The metal em loyed should be of such a character and t ickness as `not to vibrate.

As the two electro-magnetic sound reproducers 2 and 11- are similar l'except as to size, the magnetic dia hragm of 2 being of greater diameter than -t at of ll-and the actuating coils of 2 having a larger number of turns and consequently a greater inductance than those of 11, a description of onewill suffice for both.

The electro-magnetic sound reproducer 2 comprises an enclosing cylindrical casing 18 open at its lower end and closed at its upper end by an integral closure member 19 terminating in a nipple 2O arranged to be frictionally engaged on its outside cylindrical surface by the lower securing portion 7 of horn 1 as shown. The horn 10 is similarly secured to the sound reproducer 11.

A peripheral shoulder 21 is integral with the enclosing casing 18 and is contained there- Y in. The low frequency diaphragm 22, constructed of appropriate diaphragm material, is spaced away from the closure member 19, resting against the outer surface of the shoul- -4 der 21 and is held in engagement therewith by means of a clamping ring 23 and screws 24 passing through registering holes in the periphery of the diaphragm and ring, the said screws being threaded in the body of shoulder 21. y

The lower end of the casing 18 is internally threaded for the-reception of a closure member 25 made of-some suitable non-magnetic material and having an integral upwardly extending flange 26 externally threaded for engagement with the internally threaded lower end of the enclosing casing 18.

The diaphragm actuatingf'mechanism (of which Fig. 7 is a plan view) comprises a substantially U-shaped permanent magnet 27 suitably secured to the inner surface of the closure member 25. The freeends 28 and 29 of the permanent magnet are vjoined together arecomposedofa plurality of similar lami- .nations united together, have two integral pole pieces 32, 32 extending toward'the diaphragm 22. Magnetizing coils 33, 33 are mounted around said pole pieces and held in place thereon by means of suitable insulated washers 34, 34. The operation of the dia-- phragm actuating mechanism, being well known in the art, requires no description here. The leads from the coils 33, 33 and 33,', 33 may be connected to. insulated terminals 35,

' 35 and 35', 35 respectively mounted in the closure members 25 and 25 respectivelyfas shown. g

Independent control of the volume of sound emanating from the units may be effected by independently screwing the closure members 25 and 25 clockwise or counterclockwise to thereby vary the spacing between the poles 32 and 32 and the diapliragms 22 and 22 respectively. This results in tonal quality control.

The coils of the electro- magneticsound reproducers 2 and 11 are eonnecte'd in series across the output terminals of the"source of received signals assliown in Fig. 2. A con .denser 36 is connected across the coils of the reproducer 2 for a purpose to be hereinafter described.

The horn 1 and the diaphragm 22 of the sound reproducer 2 are arranged to be substantially resonant tothe lower band of audible frequencies which are to-'be reproduced and amplified. The horn 10 and the diaphragm 22 of the sound reproducer 11 are arranged topbe substantially resonant to the upper band of audible frequencies which ar to be reproduced and amplified.

The coils of sound reproducers 2 and 11 and the condenser -36 are so arranged as to result in a substantially uniform impedance substantially equal to the impedance of the source of received signals over theentire' range of audible frequencies to be reproduced and amplified. Substantially maximum uniform reproduction and amplification of the frequencies to be reproduced and amplified over the entire range of audible frequencies with a minimum amount of power thereby results, or conversely, a maximum and substantially uniform volume of sound results over the entire range of audible frequencies with la given amount of available power.

The condenser 36 together with the comparatively large inductance of the coilsv33, 33

prevents the higher band of frequencies from influencing the operation of the sound reproducer 2.- 'I he 4coils 33', 33', possessing comparativel small inductance, arel readily influenced by the upper band of frequencies while the comparatively small diaphragm 22 of the sound reproducer 11 is substantially non-responsive to the lower band of frequencies. The substantial elimination of the effects of interfering frequencies is therefore effected.

1. In combination, a plurality of intersecting sound amplifying horns each substantially resonant to a different portion of the audible range of frequencies, and an electroacoustic device attached to eachof said horns. 2. In combination, a pair of intersecting stantially resonant to the upperportion of the` audible. spectrum, the other of which is sub stantially resonant to the lower portion of the audible spectrum,- and a pair of electro-acoustic `devices attached to, and having similar frequency characteristics to, the horns.

' 3. A pair of intersecting sound amplifying Asound amplifying horns one of which is sub horns, rigidly attached together at their vline of intersection and at points along the pneripheries of their outlets, each of said horns being substantially resonant to a different portion of the audible range of frequencies, and an electro-acoustic device attached to each of the horns, leach device having frequency characteristics similar to the horn to which it is attached. i

4. In an apparatus for the transformation of electrical undulations into sound vibrations, the combination of a plurality of electro-acoustic devices each substantially resonant to a predetermined portionof the audi ble frequency spectrum, each having independent means for varying the amplitude of vibration of a diaphragm in each of said electro-acoustic devices, said devices having intersecting sound amplifying horns" rigidly united together at their line of intersection and partly along the peripheries of their outlets.

5. In an apparatus for the transformation of electrical undulations into sound vibrations, a pair of electro-acoustic devices one of which is substantially resonant to the lower range of the audible spectrum and the other of which is'substantiall'y resonant to the upy per range of the audible spectrum, each of said devices having independent Ameans for varying the amplitude ofvvibration of a diaphragm in each of them, said devices having intersecting sound amplifying horns rigidly united together at their line of intersection and, in substantially one plane, partly along the peripheries of their outlets.

6. In combination, apair of horns, one of which intersects and passes through at least one part of the other horn,`each of said horns being resonant to a different portion of the audio frequency spectrum, and a separate source of sound energy for each horn.

7. In combination, a pair of intersecting horns, one'of said horns adapted for amplifying frequencies of the lower portion of the audio frequency spectrum, the other horn being relatively short with reference to said first described horn, said other horn being adapted for amplifying the frequencies of the upper portion of the audio frequency Spectrum, and a separate source of sound energy v for each horn.

8. A pair of intersecting sound amplifying horns attached together at their intersection and at their outlets.

9. A pair of sound amplifying different' size and shapeintersecting intermediate their inlets and outlets, the outlets 'of the horns lying in substantially the same plane and united together at a plurality of points in said plane, the intermediate portions of the horns being rigidly fastened together at their intersection. A

`10. In combination, a plurality of interseating sound amplifying horns, each sublhorns of' stantially, resonant to a different portion of the audible range of frequencies, an electroacoustic device attached'to each of said horns, and said horns being attached together at their outlets.

11. vIn combination, a plurality of intersectv

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