US3131783A

US3131783A - Loud-speaker enclosure

Info

Publication number: US3131783A
Application number: US67427A
Authority: US
Inventors: Santos J Mares
Original assignee: Individual
Current assignee: Individual
Priority date: 1960-11-04
Filing date: 1960-11-04
Publication date: 1964-05-05
Anticipated expiration: 1981-05-05

Description

y- 1964 5. J. MAIQQES 3,131,783

LOUD-SPEAKER ENCLOSURE Filed NOV. 4, 1960 3 Sheets-Sheet 1 mmvron Santos J. Mares fmZ/MJW May 5, 1964 s. .1. MARES 3,131,783

' LOUD-SPEAKER ENCLOSURE 3 Sheets-Sheet 2 Filed Nov. 4, 1960 INVENTOR. Santos J. Mares United States Patent M 3,131,733 LOUD-SPEAKER ENCLOSURE Santos J. Mares, 116 Muller St, Vallejo, Calif. Filed Nov. 4, 1950, Ser. No. 67,427 8 Claims. (Cl. 1811-61) This invention relates to a novel loud-speaker enclosure which will allow a directional sound dispersion which is particularly useful in stereophonic sound reproduction.

In the reproduction of stereophonic sound it is necessary that there be two sound transducers, each transducer being fed with a signal which is reproduced from separate input sources spaced apart relative to a given sound producing media. The spacial effect of the simultaneous but different rendition from the same source creates an effect similar to the effect normally observed in hearing the direct rendition of the sound wherein each of the human ears observes a somewhat different rendition of the same sound source.

In order to achieve the true stereo effect it is necessary that the sound transducers be spaced apart a considerable distance in order to give the true spacial efiect. If the transducers are located too close together the sound from each of the transducers merges and the spacial effect is lost.

The same spacial effect, however, can be obtained by the formation of specially designed loud-speaker cabinets which through bafiles and the like direct the sound from speakers contained within the cabinet in a directional pattern. In this type of device the audio energy is dispersed at an angular relationship which spaces the sound from each of the transducers so as to provide a spacial effect similar to that obtained by actual physical separation or spacing of the transducers.

The principal object of this inventoin is to provide a novel speaker baflle system which will allow two loudspeakers to be contained within a single enclosure and which will furthermore direct the sound waves emanating from each of the speakers in opposite directions to obtain the spacial effect necessary for the proper reproduction of stereophonic or binaural audio sound.

Another important object of this invention is to provide a novel speaker baffle which contains in its interior a configuration of baflies in horn like chambers arranged in a pattern that creates loading of the speaker and a folded horn like arrangement which assists in the generation and emanation of the lower frequencies. Because of the unique baflle construction of the speaker system the actual cabinetry of this speaker occupies a substantially small area while allowing extremely eflicient bass frequency attenuation.

A feature and advantage of this invention is that the unique baflie configuration of the speaker enclosure provides a clear bass attenuation without noticeable harmonic resonate distortion quite frequently occurring in speaker enclosures.

A further object of this invention is to provide a speaker enclosure having a highly directionalized audio output in such a way that both the bass and the high frequencies are directed to extend uni-directionally from the housing or enclosure. It is by the combination of two such similar elements directing the sound dispersion in opposite directions from one another that a true stereo or binaural spacial effect is created.

Still another object of this invention is to provide a relatively small or compact speaker housing capable of dispersing sound uni-directionally from each of two sound transducersv and with the further provision of a base reflex folded horn bafile network contained within the housing arranged to attenuate the base to provide a smooth base attenuation similarly directed in uni-directional sound radiation patterns.

Patented May 5, 1964 A still further object of this invention is to provide in such a single enclosure a baflle and sound deflecting network which will allow the device to be satisfactorily operated in a corner position in a room and still obtain the required spacial sound effect required for true stereophonic or binaural reproduction.

Other objects of the present invention will become apparent upon reading the following specification and referring to the accompanying drawings in which similar characters of reference represent corresponding parts in each of the several views.

In the drawings:

FIG. 1 is a perspective view showing the speaker enclosure of this invention.

FIG. 2 is a cross-sectional view taken through the middle of the enclosure and showing the position of loudspeakers in dotted lines.

FIG. 3 is a top plan view taken through the middle of a modification of the speaker cabinet particularly adaptable for corner installation.

FIG. 4 is a side elevational View of the embodiment of FIG. 3 taken from the position indicated by the arrow 4 in FIG. 3.

FIG. 5 is a top plan view of the speaker enclosure of FIGS. 3 and 4 shown installed in the corner of a room.

FIG. 6 is a top plan view of a modification of the speaker cabinet particularly adapted for larger speakers.

FIG. 7 is a side elevational view of the embodiment of FIG. 6 taken from the subject indicated by arrow 6.

The speaker enclosure of FIGS. 1 and 2 is formed by an enclosed cabinet divided in the middle by a partition 20 separating the enclosure into A and B sound chambers.

The exterior formation of the enclosure is formed by a straight back panel 23 having at its ends two side panels 24 extending at right angles from back panel 23.

The forward or front portion of the cabinet is formed by two converging front panels 25 and a front face plate 26 which caps the two converging front panels 25 forming a truncated front face for the cabinet.

Partition 20 bisects the interior portion of the cabinet being mounted midway between the ends of front face plate 26 and back panel 23 so as to provide an equal spacial area in each of the sound chambers A and B.

Loud-speaker openings indicated at 30 are formed in converging front panels 25. The two panels 25 are positioned at a 90 angle relative to each other so that the two speaker openings will carry speakers such as indicated at 31 disposed at a 90 relationship to each other.

The interior of each of the sound chambers A and B is divided into three sound control areas indicated at 4th, 41 and 42by two

baffle members

44 and 45.

Baffle member 45 extends from the inside face of converging front panel 25 to the face of the dividing partition 20. The position of joinder of batiie member 45 to partition 20 is located a short distance, in the order of approximately two inches, from the inside face of back panel 23. The opposite end of baffle member 45 is located a sufficient distance away from the joinder between side panel 24 and converging front panel 25 to allow for the formation of a base frequency output port 50, in converging front panel 25 between batlle member 45 and side panel 24. This allows bass frequency output ..port 50 to be on the same plane as speaker outlet opening 30.

Bafile member 44 is mounted on the inside face of front face plate 26 and the base of baflie 45. The forward end of bafile 44 is mounted substantially midway between the dividing partition 20 and the juncture of converging front panel 25 and front face plate 26 and extends rearwardly from front face plate 26 at an angle of approximately relative to front face plate 26 to mate with bafile 45 at a position somewhat closer to dividing parenemas tition 20 than to converging front panel 25. Bafifle 44 is positioned so that sound control area 4% provides a suflicient cubic air space Within the chamber to provide satisfactory back loading for speaker 31. The forward end of baffle 44 is provided with an air port 55 which allows air communication between

chambers

40 and 41.

Bafile 45 is provided with a relatively small aperture 56 opening close to partition 26 It can thus be seen that the air path from sound control area 49 is allowed to go through aperture 55 wherein there is a rectangular cross section horn like configuration in sound control areadl for the passage of air to and through aperture '56. Thence the air passage is in another rectangular cross section horn like area 42 terminating in bass frequency output port 59.

- Area 40 therefore functions to provide the back loading for the speaker and

sound control areas

41 and 42 function in a folded horn like arrangement to cause the attenuation of the bass frequency.

The top and bottom of the enclosure, of course, is provided with a cap so that each of the sound control areas is sealed from the other and to atmosphere in substantially air tight relationship except for the ports and passageways 30, Q, 55 and 56. These passageways provide the sole communicating passageways between the compartments and-the compartments and atmosphere.

The exterior of converging front panel "25. is provided with sound deflecting board 58 which extends at an angle of 58 outwardlyfrom the outer' face of the two converging front panels 25. Board 58 extends the entire height of converging front panel 25 and passes over speaker opening 30 at a position about three-fourths the.

distance between the midway point of the speaker opening and the extreme forward end. The precise positioning of the interior end of board 5% is limited'to the particular design of loud-speaker 31 employed.

As it can be seen with the board in position, as indicated, there is asmall opening of the loud-speaker opening'iltlindicated at 60 located on the forward portion of deflecting board 58 and a substantially larger opening 61 locatedto the rear of deflecting board 58. The front por- 7 .tion of board 58 terminates "at a position overlying opening 30 at a position approximately equal to the inboard spacing of board 58 from the center of speaker opening 30, but, of'course, in the .opposite side of the opening.

Most loud-speakers are characterized by the fact that the high frequency generating region of the speaker is located in the'central portion of the speaker and the lower or lower and middle frequency ranges are generated at the-ends or at least throughthe entire diaphragm of the speaker. -Opening 60 should therefore beat a position located outwardly from the area of the speaker responsible for the generation of the higher frequency ranges so that the opening 60 is facing only thelower low frequency generating region of the speaker. It has been found in this system that deflecting boards 58 disperse the mid-range and higher frequencies in a' substantially unidirectional pattern outwardly from the speaker cabinet so that the sound emanating from sound chambers 'A and 'B is emanated at substantially 90 angles relative to each other.

4: way that there is a definite directional characteristic also given to the lower directional regions. It is also noted that the two ports are located on the same plane as loudspeaker opening 3B so that the loud-speaker and the reflex port or bass frequency output port 50 are emanating from the same plane.

The connecting members of the cabinet are held together by brace members such as indicated at "it! and 71 to add greater rigidity to the cabinet. In addition insulating materials can be placed on one or more walls of one of the chambers to dampen any resonant effect that might exist within the respective chambers. The purpose of the insulation which may be Fiberglas or other cotton mat or other material conventionally used for this purpose is to dampen resonance that might exist.

The embodiment of FIG. 3 is identical inits general construction to the embodiments of FIGS. 1 and 2 and bear, identical reference numerals.

The embodiment of FIG. 3, however, is provided with additional bafiles and sound deflecting channels. In addi tion dividing partition 20 is formed in two pieces 20 and 2t)" spaced apart by an air space 85 The interior of sound control area 41 is provided with three air deflectors 81, S2 and 83. Deflectors 81 and 83 extends inwardly and rearwardly also at an angle'of about Small opening allows a small amount of direct fora ward sound radiation particularly in the lower load areas. This effect creates a pleasing effect in that it tends to reduce the characteristic commonly referred to as the hole in the middle which is the effect that is created when two speakers are spaced apart and-the sound appears to be void in the area between the speakers This is undesirable in that for ideal stereo reproduction the sound should appear to be coming from inbe twieen the two loud speakers but yet there should be the stereo separation required to obtain the spacial effect of stereo;

The two ports 56 emanate the bass in 'a bass reflex action through sound control areas :1 and 42 contained within the enclosure. It is noted that these ports are dis persed at 45 angles relative 'to each other and in such a are mounted on the two pieces 26' and 20" and extend inwardly and rearwardly at an angle of about 70 relative to the connected wall. Air deflector 82 is mounted between

air deflectors

81 and 83 on baflie member 4A and Air deflectors til, 82 and 83 all define deflectors or air generators which control and smooth out the flow of air pressure through baffle member 41. The spacing between divider partition 20 and 2t) facilitates the installation of

deflectors

81 and 83 and also provide a superior separation between the A and B sound deck generating sections of the enclosure.

The exterior of the speaker system of the embodiments of FEGS. 3, 4 and 5 is provided with threeadditional'exterior deflecting or

bafile boards

0, 91 and 92 in addition to board 58.

Deflector boards 95), 91 and 92 function to improve directionality of the enclosure which makes the-enclosure particularly suitable for corner installations as indicated in FIG. 5 wherein the corner there is a greater requirement that the sound be separated due to the effect o'f-the corner tending to cause the sound emanating from the A and B chambers of the cabinet to be directed between Walls of the room inwardly to' a central point. The purpose of

deflector boards

90, 91 and 92 is to cause the sounds to ride along the Wall of the room rather than be deflected outwardly to a central point in the room area.

Deflecting board is located at an approximately- 62 angleforwardly extending of the end of speaker opening 3t This causes a greater directional control in opening at of speaker opening 3t Defiecting board M is mounted at approximately 63 angle rearwardly of the panel 25:

and is located at a position approximately in line with a the termination of the end of deflecting board 58. This adds a further directional channel in the rearward area'of the speaker and also provides a horn like channel between deflecting ports 91 and 5% which still further improves'the directional characteristics of the sound emanating from the speaker. V v

Defiecting board 92 ismounted at a rearwardly extending 70 angle on converging front panel 25 slightlyforward of bassfrequency output port 50. This adds dire'cs V tional control to the sound output from port5l} andalso forms a'channel between deflecting boards E92 and 91 still adding further to the directional characteristics of the Deflecting sound einanatingdirectly from speaker 31. board 91 is about half the length of deflecting board 58 and deflecting boards 99 and 92 are slightly shorter than deflecting board 91.

In FIG. 6 and FIG] there is provided anotherembodia ment of the invention which is particularly adapted for carrying larger size loud-speakers or particularly loudspeakers having an extended depth.

The structure of FIGS. 6 and 7 includes an outer housing which is identical to the housing of the embodiment of FIGS. 1 and 2 and bearing identical reference numerals for all parts contained therein.

Each of the sections of the cabinet are indicated at A and B. The interior of both sections are identical except formed of basically opposite configurations as are the embodiments of the other modification.

The interiors of each of the sections A and B include a speaker compression chamber 100 opening to a horn chamber 101 which in turn opens to the final horn chamber 102.

Compression chamber 105) is formed by a baflle wall 105 which extends from panel25 to the partition 20. Wall 195 is mounted in the division between loud-speaker opening 30 and base frequency outlet port 50 and extends angularly to partition 26 at an angle to allow a loudspeaker, such as indicated in dotted lines at 198, to be installed within the cabinet without making contact with the speaker.

An aperture 109 is formed in wall 105 which forms the air opening into horn chamber 101. Horn chamber 101 is defined by bafile wall 1&5 and another partition 110. Partition 110 extends from a point immediately adjacent the connection of wall 105 to side wall 25 to a position adjacent the corner of partition 20 and straight back panel 23. The two

walls

105 and 110 thus are angularly disposed so that the distance between the two walls increases toward partition 20. Thus the two walls form a horn like configuration.

Air deflectors 115 can be installed in the interior of horn chamber 101 in the same manner and for the same purpose as described in the embodiments shown in FIGS. 3 and 4.

Partition llti is provided with an aperture 120 at a point slightly disposed from partition 20. This opening opens in the beginning of a substantially horn like area 102 which is defined by partition 110 and straight back panel 23 of the enclosure.

Thus in operation speaker 108 creates audio vibrations against the back loading effect of the area within compression chamber 100. The vibrations are emitted through aperture 109 into the apex of partition 110 and thereafter pass through aperture 120 into the apex of horn chamber 102. The sound is then dispersed through bass frequency output port 50.

It can thus be seen that the structure in the interior of the cabinet forms the two section folded horn sup ported by the loading area immediately behind the speaker.

It is believed that an essential element of the invention is the provision of the folded horn contained within the enclosure together'with the combination of the compression chamber immediately to the rear of the speaker.

Another important feature of this invention is the provision of the bass reflex outlet and the front opening of the speaker on identical planes with the concurrent provision of the deflecting boards which cause the deflection of the emitted audio vibrations on an axis of approximately 180 from each other.

Although the foregoing invention has been described in some detail by way of illustration and example for purposes of clarity of understanding, it is to be understood that certain changes and modifications may be practiced within the spirit of the invention as limited only by the scope of the appended claims.

What is claimed:

1. A loudspeaker enclosure particularly adapted to create binaural audio reproduction comprising: enclosure box means forming a pair of complementary sealed chambers; each said chamber having a first vertical side wall relatively mounted in a substantially 90 relationship to the first side wall of the other chamber; each said first side wall forming a loudspeaker receiving aperture of complementary size to allow a loudspeaker to be mounted within the chamber over the aperture; a vertical deflector plate extending outward at a rearward angle from said first side wall to cover less than all of the speaker aperture; an air outlet port formed by each said first side wall spaced from said loudspeaker receiving aperture; partition means dividing each said chamber into a compression area immediately adjacent the loudspeaker receiving aperture; a first rectangular horn area, and a second rectangular horn area; said partition means being angularly disposed to provide a wider area at the second end of each horn area than at the first end of each horn area; a passageway formed by said partition means to form an air communication port between said compression area and the first end of said first horn area; and a second passageway formed by said partition means forming an air communication port between said first and second horn areas located adjacent the second end of said first horn area and the first end of said second horn area; said air outlet port formed by said first side walls being located adjacent and opening into the second end of said second horn area.

2. A loudspeaker according to claim 1 and wherein said first passageway is an elongated aperture and said second passageway is a circular aperture.

3. A loudspeaker enclosure particularly adapted to create the spacial effect of binaural audio reproduction comprising: a loudspeaker enclosure cabinet means form ing a pair of complementary sealed chambers; each said chamber having a first vertical side wall relatively mounted in a substantially relationship to the first side wall of the opposite chamber with the walls being positioned so that extended imaginary planes of said walls intersect along a vertical line at the front of the cabinet of the enclosure; each said side wall forming a loudspeaker receiving aperture of complementary dimension to allow a loudspeaker to be mounted over the opening in the interior of said chamber; a vertical air outlet port formed by said first side wall spaced rearwardly from said loudspeaker receiving aperture; vertical partition means in the interior of each said chamber dividing the chamber into a compression area immediately adjacent the speaker receiving aperture and a first and second serially connected folded horn means, the second of said horn means opening through said air outlet port; a passageway formed by said partition means to form an air communication port between said compression area and the first end of said first horn means; and a vertical de flector plate mounted on the exterior of each said first side walls extending outwardly from said side walls at a position rearwardly of the forward end of the speaker receiving aperture and forwardly of the center point of the speaker receiving aperture; said deflector plates extending to a position rearwardly of the center point of said speaker receiving aperture.

4. A loudspeaker enclosure particularly adapted to create the spacial effect of binaural audio reproduction comprising: a loudspeaker enclosure cabinet means forming a pair of complementary sealed chambers; each said chamber having a first vertical side Wall relatively mounted in a substantially 90 relationship to the first side wall of the opposite chamber with the walls being positioned so that extended imaginary planes of said walls intersect along a vertical line at the front of the cabinet of the enclosure; each said side wall forming a loudspeaker receiving aperture of complementary dimension to allow a loudspeaker to be mounted over the opening in the interior of said chamber; a vertical air outlet port formed by said first side wall spaced rearwardly from said loudspeaker receiving aperture; vertical partition means in the interior of each said chamber dividing the chamber into a compression area immediately adjacent the speaker receiving aperture, and a first and second serially connected folded horns, the second of said horns opening through said air outlet port; a passage way formed by said partition means to form an air communication port between said compression area and the first end of said first horn; a first vertical deflector plate mounted on the exterior of each said first side walls at a position rearwardly of the forward end of the speaker opening end and forwardly of the center; said first deflecting plates extending to a position rearwardly of the center point of said speaker receiving aperture; second vertical deflecting plates extending forward from each of said first side walls at a position immediately forward of the forward end of said speaker receiving aperture; third vertical deflecting plates extending angularly rearwardly from a position slightly rearward of the center point of said speaker receiving aperture and extending to a position forward of the rearward extension of said speaker receiving aperture; and fourth vertical deflecting plates connected to each said side plates mounted on said side plate between said speaker receiving aperture and said vertical air outlet ,port; said fourth vertical deflecting plate extending angularly rearwardly to a position forwardly of the rearward edge of the vertical air outlet port. t

5. A loudspeaker enclosure particularly adapted to create the spacial effect of binaural audio reproduction comprising: enclosure box means forming a pair of complementary sealed chambers; each said chamber having a first vertical side wall relatively mounted in a substantially 90 relationship to the first side wall of the other chamber; each said first side wall forming a loudspeaker receiving aperture of complementary size to allow a loudspeaker to be mounted within the chamber over the aperture; vertical deflecting plates extending outward at a rearward angle from said firstside'wall to vertically project upon less than all of the speaker aperture; an air outlet port formed by each said first side wall spaced from said loudspeaker receiving'aperture; partition-means dividing each said chamber into a compression area immediately adjacent the loudspeaker receiving aperture; a first horn area, and a second horn area; said partition means being angularly disposed to provide a wider area at thesecond end of each horn' area than at the first end of each horn area; a passageway formed by said partition means to form an air communication port'bethe widest end of said second horn area; and a plurality. of air deflectors mounted on the interior of said first horn.

area extending inwardly from one wall portion of the partition. means and spaced from the other wall portionof the partition means forming the horn area.

6. A loudspeaker enclosure particularlyadapted to side wall of the opposite chamber with the walls being positioned so that extended imaginary planes of said walls intersect along a yerticalline at the front of the cabinet of the enclosure; each said side wall forming a loudspeaker receiving aperture of complementary dimension to allow a loudspeaker to be mounted over the opening in the interior of said chamber; vertical sound deflecting board extending outward and at a rearward angle 7 from 1 said firstvertical side wall from a position .betweenthe center and forward edge of said speaker aperture; a vertical air outlet port formed by said first side wall spaced rearwardly from said loudspeakerreceiving aperture; first vertical partition means extending from the inside of the first side wall of each of said chambers to the opposite wall of said chamber to form a compression area immediately adjacent the speaker receiving aperture; a second partition means extending'from the first side wall to another wall of said cabinet means in each of said chambers angled outwardly relative to said first partition means; said first and second partition means mounted between the vertical air outlet port and the loudspeaker receiving aperture; a vertical aperture formed by the first partition means immediately adjacent said first side walls; and a circular aperture formed in said second partition means on the rearward extension thereof opening into the area carrying the vertical air outlet port opening whereby the partition means form a serially connected pair of folded horns opening to saidvertical air outlet port.

7. A loudspeaker enclosure particularly adapted to create the spacial efiect of binaural audio reproduction comprising: a loudspeaker enclosure cabinet means forming a pair of complementary sealed chambers; each said chamber having a first vertical side wall relatively mounted in a substantially relationship to the first side wall of the opposite chamber with the walls being positioned so that extended imaginary planes of said walls intersect along a vertical line at the front of the cabinet of the enclosure; each'said side wall forming a loudspeaker receiving aperture of complementary dimension to allow a loudspeaker to be mounted over the opening in the inte rior of said chamber; a vertical air outlet port formed by said first side Wall spaced rearwardly from said loudspeaker receiving aperture; partition means mounted within each of said chambers to form a' compression area immediately adjacent the loudspeaker receiving aperture and a serially connected folded horn passageway opening to said vertical air outlet port; a passageway formed by said partition means to form an air communication port between said compression area and said folded horn passageway; and vertical deflecting plates mounted on each of said first side walls at a position rearwardly of the forward end of said loudspeaker receiving aperture and forwardly of the center of the loudspeaker receiving aperture; said deflecting plates extending through the entire height of the loudspeaker enclosure cabinet.

8. A device according to claim 7 and wherein each said deflecting plate is mounted on an angle of approximately ing aperture.

References Cited in the file of this patent UNITED STATES PATENTS 2,050,575 Krau se Aug. 11, .1936 2,224,919 7 Olson Dec; 17, 1940 2,805,729 Read Sept. 10, 1957 2,811,215 Rudd Oct. 29, 1957 2,904,123 Nigro Sept. 15, 1959 2,975,852 .Chave Mar. 21, 1961 7 FOREIGNPATENTS 841,440 Great Britain July 13,1960

7 7 970,228 Germany Aug. 28, 1958 OTHER REFERENCES Cohen: Hi-Fl Loudspeakers and Enclosure, 1956, John F. Rider, Publisher. (Page206 relied upon.)

Claims

1. A LOUDSPEAKER ENCLOSURE PARTICULARLY ADAPTED TO CREATE BINAURAL AUDIO REPRODUCTION COMPRISING: ENCLOSURE BOX MEANS FORMING A PAIR OF COMPLEMENTARY SEALED CHAMBERS; EACH SAID CHAMBER HAVING A FIRST VERTICAL SIDE WALL RELATIVELY MOUNTED IN A SUBSTANTIALLY 90* RELATIONSHIP TO THE FIRST SIDE WALL OF THE OTHER CHAMBER; EACH SAID FIRST SIDE WALL FORMING A LOUDSPEAKER RECEIVING APERTURE OF COMPLEMENTARY SIZE TO ALLOW A LOUDSPEAKER TO BE MOUNTED WITHIN THE CHAMBER OVER THE APERTURE; A VERTICAL DEFLECTOR PLATE EXTENDING OUTWARD AT A REARWARD ANGLE FROM SAID FIRST SIDE WALL TO COVER LESS THAN ALL OF THE SPEAKER APERTURE; AN AIR OUTLET PORT FORMED BY EACH SAID FIRST SIDE WALL SPACED FROM SAID LOUDSPEAKER RECEIVING APERTURE; PARTITION MEANS DIVIDING EACH SAID CHAMBER INTO A COMPRESSION AREA IMMEDIATELY ADJACENT THE LOUDSPEAKER RECEIVING APERTURE; A FIRST RECTANGULAR HORN AREA, AND A SECOND RECTANGULAR HORN AREA; SAID PARTITION MEANS BEING ANGULARLY DISPOSED TO PROVIDE A WIDER AREA AT THE SECOND END OF EACH HORN AREA THAN AT THE FIRST END OF EACH HORN AREA; A PASSAGEWAY FORMED BY SAID PARTITION MEANS TO FORM AN AIR COMMUNICATION PORT BETWEEN SAID COMPRESSION AREA AND THE FIRST END OF SAID FIRST HORN AREA; AND A SECOND PASSAGEWAY FORMED BY SAID PARTITION MEANS FORMING AN AIR COMMUNICATION PORT BETWEEN SAID FIRST AND SECOND HORN AREAS LOCATED ADJACENT THE SECOND END OF SAID FIRST HORN AREA AND THE FIRST END OF SAID SECOND HORN AREA; SAID AIR OUTLET PORT FORMED BY SAID FIRST SIDE WALLS BEING LOCATED ADJACENT AND OPENING INTO THE SECOND END OF SAID SECOND HORN AREA.