WO1983000977A1

WO1983000977A1 - Loudspeaker horn

Info

Publication number: WO1983000977A1
Application number: PCT/AU1982/000146
Authority: WO
Inventors: Alan Maxwell Tattersall
Original assignee: Alan Maxwell Tattersall
Priority date: 1981-08-31
Filing date: 1982-08-31
Publication date: 1983-03-17
Also published as: US4635749A; EP0086801A1

Abstract

A loudspeaker horn having first vertical wall portions (6) converging to a throat (7) and then diverging at a controlled horizontal dispersion angle maintains uniform horizontal sound dispersion at up to 4KHz. In preferred forms the diverging portions are second vertical straight wall members (8) having an included angle of approximately 90<o> and third vertical straight wall members (9) diverging at a greater angle than the second vertical wall members (8); and the width of the opening (3) and its spacing from the throat (7) are such that the distance from all points on the cone of the loudspeaker (1) to the throat (7) are substantially the same.

Description

LOUDSPEAKERHORN

This invention relates to a loudspeaker horn and has been devised particularly though not solely as a low to mid frequency horn for public address, theatre and band uses. In applications where it is necessary to provide low to mid frequency sound at high volumes such as in public address, theatre and band uses it has been a problem to provide a sound output having an even dispersion in the vertical and particularly in the horizontal plane over the entire frequency range. Various types of horn enclosures have been used to control the sound emitted from the loudspeaker cone and in particular it has been common to use exponential horns and hyperbolic horns. The exponential horn lacks a control throat in the horn and gives a very high dispersion of sound at low frequencies while being very directional at high frequencies. Hyperbolic horns also have very directional high frequencies and tend to spit out the sound rather than dispersing the sound uniformly in a pleasant manner. To overcome these difficulties with the highly directional sound emitted from exponential and hyperbolic horns toward the upper end of their range it has been common to use the low frequency units with a relatively low crossover frequency for example of five hundred, eight hundred or twelve hundred Hz so that the mid-range frequencies are handled by the high frequency unit. This has the attendant disadvantage that the high frequency unit must be much larger and have a higher power handling capacity than would otherwise be required with a higher crossover frequency. Alternatively because the high frequency unit is of a light construction to give the reσuired high frequency response it tends to burn out very quickly from having to handle the - 4 -

comparatively low mid-range frequency imposed by the crossover.

It is therefore an object of the present invention to provide a loudspeaker horn which will obviate or minimize the foregoing disadvantages in a simple yet effective manner or which will at least provide the public with a useful choice. It is a further object of the invention to provide a loudspeaker horn which will give an improved horizontal dispersion of sound toward the upper portion of the sound range allowing a higher crossover frequency that has heretofore been possible.

Accordingly the invention consists in a loudspeaker horn having a vertical elongate opening adapted to be positioned in front of the speaker cone, said horn incorporating first vertical wall members extending forwardly and inwardly from either side of said opening to a throat narrower than said opening and second vertical wall members extending forwardly and outwardly from said throat.

Preferably the width of said vertical elongate opening and the spacing of said throat from said elongate opening are designed so that the distance from all points on the cone of said loudspeaker to said throat are substantially equal.

Preferably the included dispersion angle between said second vertical wall members is approximately 90 degrees.

Notwithstanding any other forms that may fall within its scope one preferred form of the invention will now be described by way of example only with reference to the accompanying drawings in which:

Fig. 1 is a cross-sectional plan view of a loudspeaker enclosure incorporating a horn according to the invention,

Fig. 2 is a frontal elevation of the loudspeaker enclosure shown in Fig. 1,

Fig. 3 is a side elevation of the loudspeaker enclosure shown in Fig. 1, Fig. 4 is a cross-sectional plan view of a loudspeaker horn according to the invention incorporated into a bass reflex cabinet having a bottom vent.

Fig. 5 is a frontal elevation of the enclosure shown in Fig. 4 and Fig. 6 is a cross-sectional elevation on the line 6-6 of Fig. 5.

In the preferred form of the invention a loudspeaker enclosure incorporating a horn according to the invention for use with a 15 inch loudspeaker driver is constructed as follows although it will be appreciated that the proportions of the enclosure according to the invention may be scaled up or down to suit other loudspeaker sizes.

The loudspeaker which is represented in Fig. 1 by the cone 1 shown in broken outline is nounted on a baffle board 2 by bolting the periphery of the loudspeaker to the baffle board in the normal manner. The baffle board is provided with a vertical elongate opening or slit 3 centralized in front of the speaker cone and extending from the top 4 to the bottom 5 of the speaker enclosure.

The enclosure is provided with a horn extending forwardly and generally outwardly from the opening 3 and in the preferred form of the invention shown in the accompanying drawings the top and bottoz surfaces of the horn are defined by the parallel top 4 and bottom 5 of the loudspeaker enclosure. It will be appreciated however that in other forms of the invention the top and bottom surfaces of the horn may diverge slightly. The sides of the horn are formed from first vertical

c..;? wall members 6 extending forwardly and inwardly from either side of the vertical opening 3 to a throat area 7 which is narrower than the opening 3. The horn further comprises second wall members 8 which diverge forwardly and outwardly from the throat 7 and which preferably have an included angle of approximately 90 degrees. In the preferred form of the invention the horn is completed by third wall members 9 extending forwardly and outwardly from the forward edges 10 of the second vertical wall members and which diverge at a greater angle than the second vertical wall members 8.

The remainder of the loudspeaker enclosure is completed in the normal manner with sides 11 and a back 12 and in the form of the invention shown in Figs. 1 to 3 the enclosure is vented through ports 13 down the sides of the enclosure whic communicate throug openings 14 to the rear of the loudspeaker cone 1.

The. general design criterion for the positioning of the throat 7 is to construct the width of the opening 3 and the length of the first vertical wall members 6 so that the paths from all points on the speaker cone 1 to the throat 7 are as close to equal in length to one another as it is possible to make them. The response Figures for the horizontal dispersion of a loudspeaker show that to achieve a horizontal dispersion of 90 degrees up to a crossover frequency of 3.5 KHz it is necessary to use a "piston diameter" of 5 inches. The throat 7 has therefore been sized to a throat width of 5 inches to give an effective piston diameter and an even dispersion of sound in a horizontal plane over 90 degree at up to' 3.5 KHz. It would be possible to use an even narrower throat to extend the frequency response over an even 90 deσree horizontal dispersion even hiσher

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but it is felt that this would lead to distortion due to higher pressures in the throat area.

In this manner the sound waves from the loudspeaker cone 1 passing forwardly into the throat 7 are defracted through the throat passing outwardly in an even horizontal dispersion of 90 degrees controlled by the second vertical wall members 8 which define an* included angle of 90 degrees. The third vertical wall members 9 diverge even further outwardly to provide improved base dispersion at the low frequency end of the range.

The width of the vertical elongate opening 3 has been found, to be effective at 8 inches for a 15 inch speaker cone and could in practice be wider than this. It has been found however that most of the higher frequencies leaving the cone driver are within this 8 inch width and that there is little mid to high frequency sound generated from the edges of the speaker cone. In this manner a loudspeaker horn is provided wherein the sound waves passing through the throat 7 defract outwardly to give an almost perfect horizontal throw of sound. The dispersion angle is controlled by the width of the throat 7 and by the included angle of the vertical wall members 8, to give a 90 degree dispersion in a horizontal plane which is considered to be generally desirable for public address or band work. The horn configuration according to the invention when used^" in conjunction with a high frequency unit allows a higher crossover frequency to be used and gives a fairly even frequency response over the entire range with no "hole in the middle" which is generally present in previously known forms of horn enclosures. Because the frequency response is rrain- tained over a horizontal dispersion angle of 90 degrees up to at least 3.5 KHz it is -possible to use the unit described above - έ -

a much higher crossover frequency than has hereto¬ fore been possible. This then enables a lighter high frequency unit to be used resulting in superior high frequency response and a longer life for the high frequency unit.

It is a further advantage of the loudspeaker enclosure as shown in Figs. 1 to 3 that its overall size is easy to handle and transport which is particularly advantageous in band or public address use. In this form of the invention the enclosure is vented through the side vents 13 resulting in a low flat enclosure -which is easy to transport. Becaμse the horn gives a controlled horizontal dispersion of sound it is necessary when using multiple units to stack the enclosures one on top of the other and the enclosure configuration shown in Figs. 1 to 3 ideally lends itself to this application. Because each enclosure is only 18 inches tall for a 15 inch speaker driver 1 it is possible to to stack four such enclosures in a height of only 6 feet.

Where it is desired to give enhanced base response such as in a high fidelity or domestic use situation it is possible to incorporate the horn according to the invention into a larger bass reflex cabinethavingbottom venting as shown in Figs. 4 to 6. In this configuration the horn is provided in exactly the same manner as in the enclosure shown in Figs. 1 to 3 and the horn components are referenced by the same reference numerals as previously described. The horn is incorporated into a cabinet having sides 20 and 21 and a back 22. The cabinet is narrower than the cabinet shown with reference to Figs. 1 to 3 as the side vents 13 are eliminated and replaced with a bottom vent 23. The bottom vent is tuned for length in a manner well known with bass reflex cabinets. The advantage of the enclosure shown in Figs. 4 to 6. is that a larger enclosed volume 24 can be provided giving enhanced bass frequency response.

It is a further advantage of the loudspeaker horn according to the invention that the horn may be constructed using flat surfaces only and is therefore comparatively simple and cheap to construct.

Although the horn has been described as an integral part of a loudspeaker enclosure, it will be appreciated that a horn of the configuration described could readily and simply be attached to the front of an existing unit, directly in front of the bass driver.

To maintain correct exponential expansion of the horn the vertical elongate opening 3 could be reduced in height to a centralised 8 inch square throat from which extend diverging upper and lower members meeting the top and bottom panels 4 and 5 at the throat 7. It is to be understood that all references in this specification to the vertical elongate opening include this configuration.

Claims

" % -CLAIMS

1. A loudspeaker horn having a vertical elongate opening adapted to be positioned in front ofa loudspeaker cone, said horn incorporating first vertical wall members extending forwardly and inwardly from either side of said opening to a throat narrower than said opening, and second vertical vertical wall members extending forwardly and outwardly from said throat.

2. A loudspeaker horn as claimed in claim 1 wherein the width of said vertical elongate opening and the spacing of said throat from said elongate opening are designed so that the distancesfrom all points on the cone of a loudspeaker, placed at said vertical elongate opening, to said throat are substantially equal.

3. A loudspeaker horn as claimed in either claim 1 or claim 2 wherein the width of said throat corresponds to the theoretical piston diameter corresponding to the desired horizontal dispersion and upper frequency range of the horn.

4. A loudspeaker horn as claimed in claim 1 where the said second vertical wall members define an included angle of approximately 90 degrees.

5. A loudspeaker horn as claimed in claim 1 including third vertical wall members extending forwardly and outwardly from the forward end of the second vertical wall members and defining a larger included angle than the included angle defined by said second vertical wall members.

6. A loudspeaker horn as claimed in claim 1 wherein the first vertical wall members and the second vertical wall members are substantially planar.

7. A loudspeaker horn as claimed in claim 1 - 1 -

incorporating top and bottom surfaces which are substantially planar and parallel to one another.

8. A loudspeaker horn as claimed in claim 1 when adapted for use with a 15 inch loudspeaker driver wherein the vertical elongate opening is approximately 8 inches wide, the throat is approximately

5 inches wide,and the throat is spaced approximately

6 inches forwardly from the elongate opening.

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