CA1085745A

CA1085745A - Loudspeaker horn

Info

Publication number: CA1085745A
Application number: CA304,979A
Authority: CA
Inventors: Mark S. Ureda; Clifford A. Henricksen
Original assignee: ALTEC Corp
Current assignee: ALTEC Corp
Priority date: 1977-06-27
Filing date: 1978-06-08
Publication date: 1980-09-16
Also published as: JPS576875B2; FR2396485B1; FR2396485A1; GB2000668B; DE2827390C2; DE2827390A1; JPS5412724A; GB2000668A

Abstract

Abstract of the Disclosure A loudspeaker horn has a throat section with a rectangular cross-section to which the driver unit is coupled.
The throat section has side walls joined together by substantially flat digressing top and bottom walls. The horn has a square mouth which is formed by flat walls forming a bell section which runs between the throat section and the mouth with an angular digression corresponding to the desired horn dispersion pattern, this square mouth assuring equal low frequency directivity control both horizontally and vertically. A pair of the walls may be additionally flared outwardly at a portion thereof near the mouth to provide improved midrange directivity control. The use of planar sides between the throat section and the mouth makes for an improved directivity pattern.

Description

LOUDSPEAKER HO~N

In the design of horn type loudspeakers which are yenerally employed to provide acoustical output in the frequency range of 400-2000 hertz, it is difficult to maln control of the acoustical output to a desired dispersion pattern throughout he f;requency range of interest. Control is particularly difficult in the low frequency portion of this range wherein even the best prior art horn loudspeakers, the dispersion pattern of the acoustical energy departs considerably from the optimum desired pattern. Many of the prior art loudspeakers employ exponentially curved walls. Others, such as that described in United States Patent No. 2,537,141, employ an arcuate mouth and multiple cell elements. Neither of these types of prior art horns i8 capable of achieving the low freguency control of the present invention.
By employing a square mouth, it is possible particularly ~15 in the low frequency range of the horn to achieve equal directivity control both horizontally and vertically. The use of planar sides for the bell section of the horn and a pair of sides of the throat section thereof afford~ an improvement in the directional pattern in the midfrequency range of the horn.
'0 It is therefore the principal object of this invention to provide a loudspeaker horn having improved directivity control.
; Definition of the Invention In accordance with the present invention there is provided a loudspeaker horn for receiving and radiating acoustical , ,', , ' ' , ~

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~0857~5 energy with directivity control from an acoustical driver comprisin~;
a throat section connected to said driver havlng a rec-tangular transverse cross section and including a fir~t pair of : walls which are substantially parallel to each other, and a second S pair of walls which diverge outwardly from each other from said driver at a predetermined angle, the acoustical energy output of the driver being coupled to said throat section, a rectangular mouth portion having a substantially greater perimeter than that of the greatest transverse cro~s section of said throat section, a first pair of bell section walls which interconnect the first pair of walls of the throat section and the mouth portion, and which diverge outwardly for the entire distance between said throat sectio~ and said mouth portion, and a second pair of bell section walls which interconnect the second pair of walls of the throat section and the mouth portion and which diverge outwardly between the throat section and a point proximate to the mouth portion at the same angle as the second pair of throat section walls, the portions of said second pair of interconnecting walls connected to the second pair of throat section walls forming a continuum thereof, said first and second pairs of interconnecting walls being joined together along the edges thereof to form a flared bell ~25 section of said horn, said first pair of wall~ of said bell section ;. diverging outwardly at a substantially greater angle than said pair or bell section walls.

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- 2 -At least one of said pairs of walls of the bell section may include two portions, one of which is closer to said throat section and is flared at a first angle and a second one of which is closer to said mouth portion and is flared at a second angle greater than said first angle.
Preferably, the said mouth portion is square.
:. A particular preferred embodiment of the invention will now be described, by way of example, in connection with the accom-panying drawings, of which:
FIGURE 1 is a front elevational view of a preferred embodiment of the invention, FIGURE 2 is a cross-sectional view taken along the plane indicated by 2-2 in Figure l;
FIGURE 3 is a cross-sectional view taken along the plane indicated by 3-3 in Figure l;
FIGURES 4 and 5 are polar diagrams comparing sound radiation pattern~ of the device of the present invention with that of a prior art loudspeaker horn.

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~ -t~ , ,~: 1219 ',.'' . . , ~085745 1 sriefly described, my invention is as follows: The 2 throat section of a loudspeaker horn is rectangular in cross- ¦

3 section with acoustical energy being coupled thereto from a

4 driver unit. The throat section has a constantly expanding I ' cross-sectional unit and side walls which are generally of a 6 truncated triangular configuration, the side walls being joined A 7 together by top and bottom walls which diverge outwardly from c f4ng ~ pr~ ~c r ~ 6/y S9 4 0~
8 each other. The mouth of the horn is/equarc and is formed by a 9 bell section having planar walls which diverge outwardly from the throat section, there being a first pair of diverging top and 11 bottom walls, and a second pair of diverging side walls which 12 join with the top and bottom walls along the edges thereof to form¦
13 an integral unit. The top and bottom walls may be flared out-14 wardly an additional amount at a portion thereof immediately 16 adjacent to the mouth to provide improved control in the 16 midfrequency range of the speaker. The dispersion angle 17 between the top and bottom walls and that between the side 18 walls generally determines the dispersian angle of the acoustical 19 energy. , ' Referring now to the figures, the acoustical oUtput of 21 audio driver unit 11 i~ coupled to throat section 15. T,hr,oat 22 section 15 has a pair of opposite walls 15a and lSb which ' 23 are in'the shape of a truncated triangle, and which are ~
24 joined together by divérging top and bottom planar walls 15c , and 15d. The mouth 20 of the horn is square in shape and 26 is formed by a bell section 19 having a pair of diverging , 27 planar side walls 21 and 22 which flare outwardly from throat 28 section 15, and a pair of outwardly diverging planar top and 29 bottom walls 24 and 25 which also flare outwardly from throat section 15 and are joined along their edges to the edges of 32 ~ .

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` ~ ' ''''`, , ~ 1219 ' 1 walls 20 and 22. Walls 24 and 25 have first portions 24a and 25a 2 which diverge outwardly at a first lesser angle, and second ~,, 3 portions 24b and 25b which diverge outwardly at a second greater 4 angle. Wall portions 24a and 25a are coplanar with walls 15c and 15d respectively. The angle of divergence of wall portions 6 24b and 25b is generally fifteen degreeq greater than that of q wall portions 24a and 25a. It has been found that the additional 8 dispersion between wall portions 24b and 25b provides better 9 control in the midrange of the frequencies of interest (2 - 5kHz).
Referring now to FIGS 4 and 5, po],ar graphs showing the 11 sound radiation patterns of the speaker of the present invention 12 as compared with a typical prior art speaker are shown. Referring 13 to FIG 4, graph line 32 shows the dispersion pattern of the 14 acoustical energy at 800 Hz from a loudspeaker horn designed in accordance with the present invention. The optimum dispersion 16 pattern designed for in this instance was one generally pie-shaped 17 and having an angle of 45 (i.e., with thè half power points 18 separated from ea~h other by 45). As can be~ seen, the half poWer 9 points 33 and 34 are separated from each other by 43. Graph line 37 ~hows the acoustical dispersion pattern at 800 ~z of a prior 21 art horn having the best directivity control characteristics here-22 toore known. As in the first instance, the design attempt was 23 for a 45 dispersion. As can be seen, the acoustical output of 24 thi~ prior art horn has its half power points 38 and 39 separated 2~ by 84 and has a dispersion pattern which is a considerably 26 greater departure from the optimum than that of the present 27 invention.
28 Reerring now to FIG 5, the,acoustical dispersion patterns 29 of the speaker of the present invention and that of the same prior 32 ` . ' r ~,. ` ~ 1219 10~5745 1 art speaker as for FIG 4 are illustrated for 2500 Hz (the mid-2 range of the speaker outputs). Graph line 40 shows the pattern 3 for the speaker of the present invention, while graph line 41 4 shows that of the prior art speaker. As can be seen, the half power points 43 and 44 of the instant speaker are 45 apart as 6 compared with 58 for the half power points 47 and 48 of the prior ~ art speaker. There is also a considerable difference between 8 the two directivity patterns, indicating a substantial improvement 9 in directivity control in the midfrequency range for the speaker of the present invention.
11 The device of the present invention thus provides a 12 substantial improvement over the prior art in its directivity 13 control characteristics in the low and mid-frequency ranges of 14 the horn.
While ~e device of this invention is described and 16 illustrated i~ detail, it is to be clearly understood that this 17 is lntended by way of illustration and example only and is not to 18 be taken by way of limitation, the spirit and scope of this inventio~ being limited only by the ~erm~ of the following clai .

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Claims

The embodiments of the invention in which a particular property or privilege is claimed are defined as follows:

1. A loudspeaker horn fox receiving and radiating acoustical energy with directivity control from an acoustical driver comprising:
a throat section connected to said driver having a rec-tangular transverse cross section and including a first pair of walls which are substantially parallel to each other, and a second pair of walls which diverge outwardly from each other from said driver at a predetermined angle, the acoustical energy output of the driver being coupled to said throat section, a rectangular mouth portion having a substantially greater perimeter than that of the greatest transverse cross section of said throat section, a first pair of bell section walls which interconnect the first pair of walls of the throat section and the mouth portion, and which diverge outwardly for the entire distance between said throat section and said mouth portion, and a second pair of bell section walls which interconnect the second pair of walls of the throat section and the mouth portion and which diverge outwardly between the throat section and a point proximate to the mouth portion at the same angle as the second pair of throat section walls, the portions of said second pair of interconnecting walls connected to the second pair of throat section walls forming a continuum thereof, said first and second pairs of interconnecting walls being joined together along the edges thereof to form a flared bell section of said horn, said first pair of walls of said bell section diverg-ing outwardly at a substantially greater angle than said pair of bell section walls.

2. The loudspeaker horn of Claim 1 wherein at least one of said pairs of walls of the bell section includes two portions, one of which is closer to said throat section and is flared at a first angle and a second one of which is closer to said mouth portion and is flared at a second angle greater than said first angle.

3. The loudspeaker horn of Claim 1 wherein the mouth portion is square.

4. The loudspeaker horn of Claim 2 wherein the mouth portion is square.

5. The loudspeaker horn of any one of Claims 1 to 3 wherein the first pair of walls of the throat section form the side walls thereof and the second pair of walls of the throat section are substantially planar and form top and bottom wall portions which diverge outwardly from each other between the driver and the bell section, said side wall portions joining said top and bottom wall portions together to form an integral unit.

6. The loudspeaker horn of any one of Claims 1 to 3 wherein the bell section walls are planar.

7. The loudspeaker horn of any one of Claims 1 to 3 wherein the bell section walls are planar, and wherein the first pair of walls of the throat section form the side walls thereof and the second pair of walls of the throat section are substantially planar and form top and bottom wall portions which diverge outwardly from each other between the driver and the bell section, said side wall portions joining said top and bottom wall portions together to form an integral unit.

8. The loudspeaker horn of any one of Claims 1 to 3 wherein the separation between the first pair of walls of the throat section at their interconnection with the bell section is no greater than the wavelength of sound at the highest frequency of the sound waves to be controlled.

9. The loudspeaker horn of any one of Claims 1 to 3 wherein the bell section walls are planar, and wherein the separation between the first pair of walls of the throat section at their interconnection with the bell section is no greater than the wave-length of sound at the highest frequency of the sound waves to be controlled.

10. The loudspeaker horn of any one of Claims 1 to 3 wherein the first pair of walls of the throat section form the side walls thereof and the second pair of walls of the throat section are sub-stantially planar and form top and bottom wall portions which diverge outwardly from each other between the driver and the bell section, said side wall portions joining said top and bottom wall portions together to form an integral unit, and wherein the separation between the first pair of walls of the throat section at their interconnection with the bell section is no greater than the wavelength of sound at the highest frequency of the sound waves to be controlled.

11. The loudspeaker horn of any one of Claims 1 to 3 wherein the bell section walls are planar, wherein the first pair of walls of the throat section form the side walls thereof and the second pair of walls of the throat section are substantially planar and form top and bottom wall portions which diverge outwardly from each other between the driver and the bell section, said side wall portions joining said top and bottom wall portions together to form an integral unit, and wherein the separation between the first pair of walls of the throat section at their interconnection with the bell section is no greater than the wavelength of sound at the highest frequency of the sound waves to be controlled.