US 1866831 A
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July 12, 1932. I. WOLFF ETAL AUDITORIUM LOUD SPEAKER Filed Aug. 3, 1928 2 Sheets-Sheet 1 INVENTORS LW A. RINGEL R. MAY, W AT R NEY July 12, 1932. w L -r AL 1 1,866,831
AUDITORIUM LOUD SPEAKER Filed Aug. 3, 1928 Y 2 Sheets-Sheet 2 lNVENTOR I. WOLF, R MAY, AJZNGEL A ORNEY Patented July 12, 1932 UNITED TATES.
ravnwo WOLFE, or NEwlYonx, BUssELnr. MAY, or BRONX, AND ABRAHAM RINGEL,
or BROOKLYN, NEW YORK, ASSIGNORS T0 RADIO CORPORATION or AMERICA, A
CORPORATION OF DELAWARE i Application filed August Si, 1928. Serial No. 297,218."
This invention relates to the loudspeaker art and deals morespecificallywith an auditorium loudspeaker.
It is well knownthat most loudspeakers radiate sound energy better incertain directions than in others. This directional'characteristic of sound radiation" is particularly noticeable, when the lengthof the wave be ing radiated is comparable with, or smaller than, the diameter of the efl'ective radiating surface. In loudspeaker operation, this'results in the higher tones of the audible range being propagated in the form ofabea'm from the loudspeaker, while the lower tones radiate so as effectively tocover a wide area, Obviously, therefore, inauditoriumwork unsatisfactory results are obtained with the usual loudspeakers due to thefact that a certain portion of the audible spectrum is transmitted in the form of a rather narrow beam,- while the other portion of the spectrum is propagated in all directions.
It is an object of this invention, therefore, to give substantial uniformity of sound intensity over any desired area at all frequencies within the audible range.
Also, when two Or more radiating surfaces are mounted alongside of each other, there are certain positions in space, where there will usually be a difference in the path length of the sound reaching thellistener from the separate surfaces. This may result in bad interference I between the sound waves emanating from each of the radiating surfaces unless care is taken properly to place them.
It is therefore a further object of this invention so'to mount a'plurality of sound radiating surfaces with respect to each other, that interference, "due to a difference in path of-the sound emanating from each surface, is reduced to a minimum in the direction in which sound propagation is desired.
It is a further object of this invention to mount a plurality of sound radiating surfaces with respect to each other so thatthe path lengths of sound emanating from any one of these surfaces to a given point will be effectually the same at all angles in. a horizontal plane. This result is made possible py mounting the vibrating units in a vertical Arranging the diaphragms in a vertical line leads to the additional beneficial result that the radiation is concentrated in a slightly diverging horizontal disc of a height about equal to the height of the cone line. This leads to a very desirable increase in sound intensity in this disc, thus making radiation useful which would otherwise be diffused upward and downward.
Further, it; is an object of this invention to provide an auditorium loudspeaker having a plurality of vibrating surfaces each of which contributes to the required volume of sound for the auditorium, and which aid each other at low frequencies without objectionable interference between the sound waves produced art from the following description taken in connection with the accompanying drawings 2 in which Fig. 1 is a front elevation of an auditorium loudspeakerembodying the principles of this invention; Figs. 2 to 5 inclusive are sectional views taken along lines 22 to 5-5 respectively of Fig. 1, each of these sectional views showing the angular relation of only one of the sound vibrating surfaces with respect to'the bafiie; y v
Fig. 6 is a side elevation of the device shown in Fig. 1; V I
Fig. 7 is a sectional view taken along the line 7-7 of Fig. 1; p
. Fig. 8 isa top plan view of the. device shown in Fig. 9;
Fig. 9 is an elevational view of a modified form of the invention; and
Fig. 10 is a sectional view taken along the line 1010 of Fig. 9.
Referring in detail to the drawings, the loudspeaker 10 is seen to comprise a nonvibratory support or baflie member 11 formed of wood, metal or any other suitable material. Mounted centrally of the baffle 11 in vertical alignment are four vibratory sound radiating devices 12, preferably of the cone type.
Suitable driving units (not shown) are as sociated with each of the devices 12 in a man ner well understood in the art, each of these devices being connected to a common amplitier or sound source. The size of the battle is chosen of a proper magnitude to interpose a path from front to rear running around its edge, which path is long enough to prevent excessive reduction in low frequency response due to interference of sound radiated from rear with that from front.
We have found in actual practice that sat isfactory results may be obtained with a baille extending outwardly from the edge of the vibrating surface by an amount equal to 4 to of the longest wavelength which the device is designed to reproduce. Thus, for a loudspeaker designed to reproduce 60 cycles as the lowest frequency, which corresponds to a wave length of about 16 feet, the battle was made to extend about 3 feet outwardly from the edge of the vibrating surface.
By virtue of this structure, interference between sound vibrations emitted from the front and from the rear of the vibrating surfaces is eliminated at the lower frequencies, at which frequencies it has been found tha the waves are propogated substantially in all directions, as distinguished from the beam effect manifest at the higher frequencies.
In order to obtain a uniform sound pat tern for an auditorium, the radiating surfaces or cones 12 are disposed at different angles with respect to the bafile, each surface being adapted to furnish a certain predetermined sector of the room with sound mate rial. Obviously, the number of radiating surfaces used, and the angles at which they are placed, may be varied widely as the acoustic conditions of the auditorium may require. We have found, however, that in most cases, four units mounted at the angles indicated in Figs. 2 to 5 inclusive give satisfactory results.
In order to mount the radiating surfaces 12 upon the baffle 11, the housings 13, which may be of either wood or metal, are provided, each housing being suitably shaped as shown in Figs. 1 to 6 to cause the front faces of the cone 12 to lie in the desired plane. Each of the housings 13 is provided with an extending edge 14- which is attached to the angle member 15 carried by the baffle 11. Theunion between the members 14 and 15 may be effected in any suitable manner such as, for example, by rivets or bolts 16.
Referring in detail to Figs. 81O there is shown a modified form of the invention in which each of the vibrating surfaces is mounted for rotation about an axis lying in the plane of the bafile member. To accomplish thisresult the baffle 111 is provided with the cut-out portions 112 arranged cent-rail of the bafile 111 in vertical alignment. upporting members 113 shaped to fit the openings 112 are pivot-ally mounted at. 11 1 as shown. Each of the members 113 has a cutout circular portion to which is attached the edge'of the vibrating surface 115. Each of the sound producing surfaces 115 is provided with suitable driving units, which are fixedly joined to it respective support 113 inthe usual manner. It will thus be seen that the variable sound pattern may be provided for, by suitably adjusting the angle of the supports 113 with respect to the bafilelll. In accordance with a. preferred embodiment of this invention we have adjusted the first and third vibrating surfaces from the top to lie in the plane of the baffle 111, while the second and fourth are displaced at anangle of 15 with respect to the bafiie in opposite directions as shown. 7 o o It will be seen that when the supports are turned at an angle with respect to the baliie the lower frequencies will circulate around the edge of the supporting members 113 from the rear to the front sides and vice versa. This counteracts the useful effect resulting from the employment of baffle 111. We, therefore, provide the auxiliary bafiie members 117 having circular side walls joined to the baffle 111 by any suitable means such as rivets or screws 117a. The opposite ends of the members 117 are covered by segmental portions 118 as shown in Fig. 8. It will be understood that the auxiliary bafiies are mounted one on the front and one on the rear of 111 for each vibrating surface 115, depending upon the angular relation of the vibrating surface 115 with respect to the bafile 111. Under certain conditions, however, itmay be found desirable to reverse the cones .115 in such a way that the portion which extends rearwardly of 111 is made to extend forwardly thereof, and vice versa. Accordingly, the auxiliary baflies may be provided with detachable means for joining them to the member 111 as required.
Obviously, many changes in the specific embodiments of the invention disclosed here in will readily suggest themselves to those skilled in the art. For example, the radiat ing units may be mounted in a vertical plane without being in exact alignment, or, alternatively they may be in alignment at an angle to the vertical. ,lVe therefore do not intend to be limited in the details of struc ture except as defined in the appended claims.
Having thus described our invention, we claim: I a
1. A loudspeaker comprising a supporting member, and a plurality of sound radiating elements in vertical alignment carried by said member, said sound radiating elements beingarranged to radiate sound Waves directly to the open air in directions substantially perpendicular to the line of vertical align-1 surface being of a size sufficiently great tov prevent objectionable interference between the sound waves from the rear and the front of the vibrating elements, substantially over the range of the entire audible spectrum, and said vibrating elements being mounted to radiate sound waves in different directions all of which lie within an angle of less than 180.
4. A. loudspeaker comprising a non-vibrating surface and a plurality of vibrating diaphragms mounted thereon and, directed in different directions, said non-vibrating surface lying in a single plane and being of sufiicient size to constitute a baflle whereby material circulation of sound waves between the rear and front of the vibrating diaphragms is prevented over substantially the entire range of the audible spectrum.
' 5. A loudspeaker comprising a non-vibratory baflle member, said baflle member being substantially in a single plane, and a plurality of vibratory elements carried by said memher and angularly disposed with respect thereto.
6. A loudspeaker comprising a non-vibratory baffle member, and a plurality of sound radiating bodies mounted on said member,
said member extending outwardly from each of said bodies by adistance at least as great as one fifth of the longest wave length which said bodies are adapted to radiate, wherebyv to prevent circulation between opposite sides of said surfaces. i
7 A loudspeaker comprising a non-vibratory baflle member, and a plurality of sound radiating elements mounted on saidmember at angles to each other, said member extending outwardly from each of saidelements a distance, at least one fifth as great as the longest wave length which said elements are adapted to radiate, whereby said member prevents circulation between opposite sides of said surfaces. 8. A loudspeaker comprising a lurality of sound radiating members adapte to radiate sound vibrations from both the front and rear sides'thereof, and a baflie member sur-' rounding each of said members and serving to prevent interference between the sound vibrations emitted from the front and rear sides of said members, the entire surface of said baffle member being substantially in a single plane. i
9. A loudspeaker comprising a plurality of sound radiating members adapted to radiate sound vibrations from both the front and rear sides thereof, and a bafiie member surrounding each of said members and serving to prevent interference between the sound Vibrations emitted from the front and rear sides of said members, each of said members being angularly disposed with respect to each other.
10. A loudspeaker comprising in combination a bafile member, a first radiating diaphragm angularly mounted thereon and adapted to radiate a maximum of sound energy over a predetermined area, and a second radiating diaphragm mounted at an angle difierent from said first mentioned angle with respect to said member and adapted to radiate a maximum of sound energy over an area not included in said first mentioned area.
11. A loudspeaker comprising in combination a baffle member, a first radiating element angularly mounted thereon and adapted to radiate a maximum of sound energy over a predetermined area, and a second radiating element mounted at an angle different from said first mentioned angle with respect to said member and adapted to radiate a maximum of sound energy over an area not included in said first mentioned area, said bafiie being of sufiicient size to prevent circulation of sound vibrations between the front and rear sides of each of said radiating elements.
12. A loudspeaker comprising abaflie member, and a plurality of sound radiating elements pivotally mounted with respect to said member, whereby said elements may be adjusted angularly with respect to each other.
13. A loudspeaker comprising a supporting member, and a plurality of sound vibrating elements in vertical alignment carried by said member, each of said elements being angularly adjustable with respect to each other. I
14. A loudspeaker comprising a supporting member, and a plurality of sound vibrating elements in Vertical alignment carried by said member, each of said elements being rotatable about an axis parallel to said member.
15. A loudspeaker comprising a baflie memher and a plurality of sound radiating dia phragms pivotally mounted thereon.
16. A loudspeaker comprising a baflie member, and a plurality of sound radiating devices mounted on said bafile, each of said devices being mounted in a difierent horizontal plane and disposed at a different angle with respect to said baflie, and each of said devices being designed to radiate sound Waves substantially straight out in its horizontal plane and in different vertical planes.
1?. A loudspeaker comprising a battle memher, and a plurality of sound radiating deices mounted on said bafiie, each of said devices being mounted in vertical alignment and disposed at a different angle with respect to said baflle, and each of said devices being designed to radiate sound Waves substantially straight out in its horizontal plane and in difiierent vertical planes.
18. An acoustic device comprising a battle, and a member having a sound radiating sur face, said member being pivotally mounted with respect to said bafiie.
19. A loudspeaker device comprising a member having a sound radiating surface, a supporting member, and means for pivotally mounting the first mentioned member in said supporting member.
20. An acoustic device comprising a loudspeaker having a sound radiating surface, a support for said loudspeaker, and means for adjusting the position or" said loudspeaker in said support to vary the direction of radiation of sound waves froinsaid sound radiating surface.
IRVING WOLFF. RUSSELL P. MAY. ABRAHAM R-INGEL.