US2871972A - Horn for loudspeaker - Google Patents

Description

Feb. 3, 1959 c. Q. GLASSEY HORN FOR LOUDSPEAKER Filed March 12, 1958 INVENTOR. COURTNEY Q. GLASSEY BY 5 Z Z blis AGE/YT United States Patent HORN FOR LOUDSPEAKER Courtney Q. Glassey, Rochester, N. Y.

Original application May 2, 1955, Serial No. 505,367,

now Patent No. 2,835,335, dated May 20, 1958. Digizdgiggmd this application March 12, 1958, Serial No.

7 Claims. (Cl. 181-31) The present invention relates to sound-reproducing apparatus and more particularly to a multiple horn structure within a housing or cabinet in which two horns substantially encircle the speaker for increasing the speaker efliciency as well as the frequency response of the speaker and is a division of my co-pending application, Serial No. 505,367, filed May 2, 1955, and now U. S. Patent No. 2,835,335

Inexpensive speaker cabinets have used cone speakers and cabinets of the open back and closed back, or bass reflex types, and such systems vary from poor to fair in bass response and from low to moderate in expense in the order designated. The efficiency of the speaker in such cabinets varies from 3 percent to 10 percent.

While the advantages of the flared, folded horn are known to those skilled in the art, the difficulties encountered in designing such horns have resulted in many disadvantages. All of the designs utilize complicated and expensive cabinetry to form the folded horn sections and with many such horns there is a waste of cabinet space. Also, there is too high an acoustic capacitance which results in the loss of higher frequencies due to many foldings, or to 180 folding where the dimensions are unfavorable. There is also a loss of eificiency and a waste of space due to the use of a chamber or cavity enclosing the speaker to absorb the back wave. The design of horns known in the art is such that the cabinet must be placed either against the wall of a room, or adjacent a room corner, whereby the effective mouth area 'of the horn will be increased. When such horns have been compromised by being given a larger mouth and a shorter length, the bass deficiency cannot be compensated for by the use of simple bass booster circuits.

In the present invention, the above disadvantages and shortcomings of the known structures are overcome. By improving the coupling of the vibrating diaphragm of the speaker through a large mouth to the atmosphere, the horn efficiency is increased to 40 percent and uniformity over the whole frequency range is improved. The reduced cone travel resulting from the use of a horn reduces distortion, improves transientresponse, increases definition and reduces cost by permitting smallermagnet structures to be used in the speakers. For full efficiency down to the cut-off frequency, the mouth area and the horn length should be in balance and compatible with the housing or cabinet dimensions. This can be accomplished by providing a relatively long, flared horn which v has a flare in at least one plane and which couples a chamber within the housing to the atmosphere, said chamber enclosing one side of the speaker diaphragm. Such a horn substantially encircles the speaker and provides, in effect, a close approximation of an exponential horn which directs the lower frequencies of the speakerto an 7 open side, of the housing. The back of the speaker being horn-loaded gives good and extended bass. With the horn structure described hereinafter, radiation of the higher frequencies of the speaker is directed to the atmosphere by means of a short, flared horn which is partially encircled by the long horn, the open side of the housing or cabinet providing a mouth for each horn in accordance with the frequency range of each horn and being divided into a desired ratio of mouth sizes or areas by a partition which also forms a common portion of the flare for both the long and the short horns.

The frequency of the mechanical cross-over between the two horns is controlled by the design capacitance of the chamber and the long horn which directs the lower frequencies to the open side and by the designed bass cutoff frequency of the short horn which directs the higher frequencies to the open side. The loud speaker is loaded to an optimum by the use of the dual horns, one horn being arranged with respect to each side of the speaker diaphragm. The dimensions of the horn will depend on its use and the bass response that is required. A small horn of less than one cubic foot of volume can be used for paging and public address systems where bass response is unimportant. However, horns of larger volume are required in high fidelity systems wherein good bass respouse is required and necessary. The horn structure described in more detail hereinafter can be readily incorporated within a cabinet that contains a sound source such as a radio receiver, television receiver and/or record-playing equipment of either the disc or tape type.

The dual horn arrangement also possesses several inherent advantages which are not found in single horn compression systems. It is well known that a single horn is restricted in the range of frequencies which can be covered and can only give optimum performance over a range of three or four octaves. On the other hand, a dual horn system in which the horns are calculated to complement each other, a range of six to eight octaves can be attained. Also, in a dual horn system the speaker diaphragm is not susceptible to rupturing by a steep pressure wave front developed outside of the cabinet or housing in which the speaker is mounted, because such pressure is applied by the dual horns to both sides of the speaker diaphragm and not to only one side as in the case of a single horn system.

The primary object of the invention is, therefore, to provide a sound-reproducing apparatus in which separate horns are utilized for directing the lower and higher frequencies of a speaker to the same open side of the structure housing the speaker, both horns having-a flare in one plane and the horns substantially encircling the speaker and being concentric thereabout.

Another object of the invention is to provide a soundreproducing apparatus in which the lower frequencies of the speaker are directed to the atmosphere by a relatively long, flared horn which couples an opening in a chamber within the housing enclosing one side of the speaker diaphragm to an open side of the housing and which substantially encircles the speaker, and the higher frequencies of the speaker are directed to the atmosphere by a short, flared horn which couples an opening in the chamber on the other side of the speaker diaphragm to the same open side with one side thereof common to and forming a portion of one flared side of the long horn.

A still further object of the invention is to provide a simplified design for a dual horn sound-reproducing apparatus which, by varying the size of the apparatus, can be readily adapted to paging, public address and high fidelity 3 skilled in the art by the description of the invention which follows. Reference is now made to the accompanying drawing in which like reference numerais designate like parts throughout, and wherein:

Fig. 1 is a perspective view with one side of the housing or cabinet removed and showing a structure of sheet metal by means of which the speaker is enclosed and by which 'two horns are formed with the mouths thereof contiguously arranged with respect to the same open side;

Fig. 2 is a perspective view similar to Fig; 1 in which the speaker enclosure and the horns are fabricated-of a formable non-metallic material; and V Fig. 3 is a perspective viewof a wall-type speaker in which the housing is given a shape other than rectangular,

the horns being formed in a manner similar to that shown in Figs 1 and 2.

In the embodiment of the invention disclosed in Figs.

l and 2, a cabinet 19 is shown with a diaphragm-type loud speaker Silt arranged within the cabinet. Cabinet is substantailly rectangular and comprises the two larger and opposed sides -12 and 13 and the three smaller sides 14, 15' and 16, enclosing the opposed sides and having an open side 17. Open side 17 permits communication between the interior of cabinet 10 and the atmosphere. If desired, an opening can be provided in one of sides 12 .or 13 to permit direct radiation to the atmosphere from a supplementary treble speaker mounted within cabinet 10. In the embodiment disclosed in Fig. 1, speaker 80 is enclosed by a structure 83 which can be formed of sheet metal and arranged between opposed sides 12 and 13. Structure '83 is formed so as to provide a chamber 85 about speaker '80 and is provided with an opening 84 which permits communication of the lower frequencies from the one side of the speaker between chamber 85 and the interior of cabinet 19, the chamber being formed about speaker 80 by walls 86, 87 and 88 together with opposed sides 12 and 13. Speaker 30 is mounted on wall 88 and aligned with opening 90 which permit the higher frequencies from the other side of the speaker diaphragm to be communicated to the atmosphere.

From opening 84, walls 86, $7 and 88 are formed so .as to provide a relatively long, flared horn 82 together with the interior surfaces of sides 16, 15 and 14 respectively, the flare being in a plane parallel to that of opposed sides 12 and 13 and increasing from opening 84 to open side 17 in only one dimension.

In. order to direct the higher frequencies of speaker 8t) to theopen side, a partition 91 is arranged'between sides 12 and 13 to provide a short, flared horn 81 connecting opening $5 to open side 17. Horn 81, therefore, comprises a portion of wall 88, partition 91 and opposed sides 12 and 13, the partition 91 being common to both horns 81 and 82 and dividing the open side 17 into two contiguous horn mouths in a predetermined ratio of areas depending on the cross-over frequency desired from the speaker. frequencies from the front side of the speaker to the atmosphere via opening 90 and open side 17, whereas the lower frequencies from the rear side of speaker 80 are communicated to the atmosphere via opening 84 and horn 82 to open side 17. While the higher frequency Horn 81 permits communication of the higher p horn 81 is short as compared with the lower frequency ft will shift along wall 38 or 37, depending on the rota-' tion of speaker .819 and partition 91 will be extended and still form a wall common to each horn. Although the inner length of born 82 ( walls 85, 87, and partition 91) much shorter than the outer length ( sides 15, 16

and 14), this can be partially equalized by covering the 'Walls and partition with'a good insulator and by using sound diffractors to retard the wave front shorter path.

The structure disclosed in Fig. 2 is similar to that of Fig. 1, except that walls 86 and 8'7 andpartition A are shown as comprising a single sheet which can be formed or molded from plywood, 'Fiberglas, metal or a plastic material. Such a structure can provide a smooth and continuous horn surface together with low installation cost.

In the foregoing embodiments, the cabinet 16 has been described and shown as a rectangular cabinet suitable for receiving the signal output from a radio, television receiver, record player, or as part of a cabinet suitable for housing any' combination of these sound reproducers. However, as will be readily apparent to those skilled in the art, the cabinet may be varied in shape depending on the size of the speaker and its application. For example, the dual, concentric horn arrangement described hereinabove can very well be utilized for public address systems in which the housingor cabinet can be of a form shown in Fig. 3. Accordingly, the reference herein to housing or cabinet can be used interchangeably whether of a rectangular form as shown in Figs. 1 and 2 or of a type having a bell-shaped mouth and molded of a plastic,

along the Fiberglas, or similarly suited material, as shown in Fig. 3.

The embodiment shown in Fig. 3 comprises a housing 70 molded of plastic or Fiberglas and of two parts which are joinedto form a complete unit. Opening 84 and 90 are provided, as in the above-described embodiments, and the interior surface of the curved wall 71 together with the outer surface of partition 91 and the curved interior surface of the housing forms the long, flared horn 82, the short flared horn 81 being formed by a portion of the housing and the other surface of partition 91. As in the embodiments described above, speaker is mounted within the chamber 72 with horn 82 permitting the lower frequencies to be communicated via opening 84 to the open end and the atmosphere and horn 81 permitting the higher frequencies to be communicated viaportion of sides 75 and 76 beyond the flare are actually parallel to the median plane. Also, it may be desired to flare horns 8 1 and 82 in two dimensions so that sides 75 and 76 will not be parallel with respect to the median plane but will be symmetrical thereto. The arrangement and shape of the sides of housing 70 will not, however,

alter the relationship of horns 31 and 82.

Since many modifications of the invention will be apparent to those skilled in the art, the invention is not to be limited to the disclosed embodiments but is defined by the appended claims.

Having now particularly describedmy invention, what I desire to secure by Letters Patent of the United States and what I claim is: a

1. Asound-reproducing apparatus comprising in combination,-a hollow housing having an aperture for establishing communication between theinterior of said housing and theatmosphere, at least one vibrating-diaphragm type loud speaker arranged within said housing, a chamber within said housing enclosing said speaker and having a first opening for establishment communication between the rear side of the speaker diaphragm and-the interior of said housing and a second opening for establishing communication between the front side of the .speakendiapbragmand the interior of said housing, .a :part'itionarranged' within said housing, said partition dividingsaid "aperture'into two contiguous horn mouths of a predetermined ratio of areas,.a first horn substantially encircling said chamber and having a flare increasing in at least one dimension from said first opening to said aperture for directing the lower frequencies of said speaker from said first opening to one of the horn mouths, and a second horn having a flare increasing in at least the same one dimension as said first horn from said second opening to said aperture for directing the higher frequency of said speaker from said second opening to the other of the horn mouths, a portion of said first horn being arranged about said second horn with said partition forming a portion common to each of said horns. I

2. A sound-reproducing apparatus comprising in combination, a hollow housing having an aperture for establishing communication between the interior of said housing and the atmosphere, at least one vibrating-diaphragm type loud speaker arranged within said housing, a chamber within said housing enclosing said speaker and having a'first opening for establishing communication between the rear side of the speaker diaphragm and the interior of said housing and a second opening for establishing communication between the front side of the speaker diaphragm and the interior of said housing, a partition arranged within said housing and extending from said second opening to said aperture, said partition dividing said aperture into two contiguous horn mouths of a predetermined ratio of areas, a first horn substantially encircling said chamber and having a flare increasing in at least one dimension from said first opening to said aperture for directing the lower frequencies of said speaker from said first opening to the larger of the horn mouths, and a second horn having a flare increasing in at least the same one dimension as said first horn from said second opening to said aperture for directing the higher frequency of said speaker from said second opening to the smaller of the horn mouths, a portion of said first horn being arranged about said second horn with said partition forming a portion common to each of said horns.

3. A sound-reproducing apparatus comprising in com bination, a hollow housing having at least two sides substantially symmetrical to a median plane and an open side normal to said median plane, at least one vibratingdiaphragm type loud speaker arranged within said housing, a chamber within said housing enclosing said speaker and having a first opening for establishing communication between the rear side of the speaker diaphragm and the interior of said housing and a second opening for establishing communication between the front side of the speaker diaphragm and the interior of said housing, a partition arranged within said housing and extending from said second opening to said open side, said partition dividing said open side into two contiguous horn mouths of a predetermined ratio of areas, a first horn formed by the interior surface of said housing, a portion of the exterior surface of said chamber and said partition, substantially encircling said speaker and having a flare increasing in at least said median plane from said first opening to one of the horn months for directing the lower frequencies of the speaker from said first opening to the open side, and a second horn formed by a portion of the exterior surface of said chamber and said partition, arranged within said first horn and having a flare increasing in said same median plane as said first horn from said second opening to the other of the horn months for directing the higher frequencies of said speaker from said second opening to said open side.

4. A sound-reproducing apparatus comprising in combination, a hollow housing having at least two substantially parallel sides and an open side normal to said parallel sides, at least one vibrating-diaphragm type loud speaker arranged within said housing, a chamber within said housing enclosing said speaker and having a first opening for establishing communication between the rear side of the speaker diaphragm and the interior of said housing and asecond opening for establishing communication between the front side of thespeaker diaphragm and the interior of said housing, a partition arranged within said housing and extending from said second opening to said open side, said partition dividing said open side into two contiguous horn mouths of a predetermined ratio of areas, a first horn formed by the interior surface of said housing and said parallel sides, a portion of the exterior surface of said chamber and said partition, substantially encircling said speaker and having a flare increasing in one dimension from said first opening to the larger of the horn months for directing the lower frequencies of the speaker from said first opening to the open side, and a second horn formed by a portion of the exterior surface of said chamber and said partition, arranged within said first horn and having a flare increasing in the same one dimension as said first horn from said second opening to the smaller of the horn mouths for directing the higher frequencies of said speaker from said second opening to said open side.

5. A sound-reproducing apparatus comprising in combination, a substantially rectangular cabinet having two opposed and substantially parallel sides and four sides enclosing said two opposed sides to form said cabinet, one of said four sides being open for establishing communication between the interior of said cabinet and the atmosphere, at least one vibrating-diaphragm type loud speaker arranged within said cabinet, a chamber enclosing said speaker and having a first opening for establishing communication between the rear side of the speaker diaphragm and the interior of said cabinet and a second opening for establishing communication between the front side of the speaker diaphragm and the interior of said cabinet, a first horn substantially encircling said chamber and having a flare in a plane substantially parallel to the plane of the opposed sides for directing the lower frequencies of said speaker from said first opening to the open side, and a second horn having a flare in the same plane as said first horn for directing the higher frequencies of the speaker from said second opening to the open side, said second horn being shorter than said first horn and having one flared side thereof in common with a portion of one flared side of said first horn and dividing the open side into two horn mouths of a predetermined ratio of areas.

6. A sound-reproducing apparatus comprising in combination, a substantially rectangular cabinet having six sides, two of the opposed sides being larger than the four sides enclosing said two opposed sides to form said cabinet and one of said four sides being open for establishing communication between the interior of said cabinet and the atmosphere, at least one vibrating-diapln'agm type loud speaker arranged within said cabinet, a chamber enclosing said speaker and having a first opening for establishing communication between the rear side of the speaker diaphragm and the interior of said cabinet and a second opening for establishing communication between the front side of the speaker diaphragm and the interior of said cabinet, a partition arranged between said opposed sides and extending from said second opening to the open side, said partition dividing the open side into two areas of a predetermined ratio, a first horn substantially encircling said chamber and having a flare in a plane parallel to said opposed sides for directing the lower frequencies of said speaker from said first opening to the open side, and a second horn having a flare in the same plane as said first horn for directing the higher frequencies of the speaker from said second opening to the open side, the flare of said first horn being defined by the exterior surface of said chamber, one side of said partition and the inner surface of the three sides of said cabinet and the flare of said second horn being defined by a portion of the exterior surface of said chamber and the other side of said partition.

7. A sound-reproducing apparatus comprising in combination, a rectangular cabinet having six sides, two of the opposed sides being larger than thefour sides enclosing said two opposed sides to form said cabinet and one of said four sides being open for establishing communication between the interior of said cabinet and the atmosphere, at least one vibrating-diaphragm type loud speaker arranged within said cabinet, a chamber enclosing said speaker and having a first opening for establishing communication between the rear side of the speaker diaphragm and the interior of said cabinet and a'second opening for establishing communication between the front side of the speaker diaphragm and the interior of said cabinet, a first horn substantially encircling said chamber and having a flare increasing in one dimension and toward the open side for directing the lower frequencies of said speaker from said first opening to the open side, and a second horn having a flare increasing in the same one dimension'as said first horn and toward the open side for directing the higher frequencies from said second opening to the open side, said second horn being shorter than said first horn and having one flared side thereof common to a portion of one flared side of said first horn'and dividing the open side into two contiguous horn mouths of a predetermined ratio of areas.

No references cited.

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