Apex loudspeaker

A loudspeaker (10) has speaker mounting walls (11 and 12) joined at an apex angle (15) of 70.degree. or less, with a pair of tweeters (20) mounted as close to the apex as possible and a pair of woofers (25), arranged below the tweeters, and also mounted as close to the apex as possible. The width spanned by tweeter pair (20), from a viewpoint in front of apex (15), is approximately equal to the frontal width of either tweeter. Similarly, the width spanned by woofer pair (25), from a viewpoint in front of apex (15), is approximately equal to the frontal width of either woofer. The geometry of this mounting arrangement produces even acoustic intensity throughout a wide angle around both sides of the apex and preserves stereo identity by having the sound emanate from an apparently small source.

BACKGROUND 
In research and experimentation with loudspeaker design, I have discovered 
the importance of maintaining acoustic intensity for a wide angle off the 
axis of the loudspeaker cabinet. Others have attempted this by aiming 
speakers in directions oblique to the cabinet axis, but this has created 
multiple images. I have discovered a way of arranging speakers within a 
loudspeaker cabinet so as to greatly broaden the angle of acoustic 
intensity on opposite sides of the cabinet axis, while preserving stereo 
identity. A pair of my apex loudspeakers, while accomplishing this, also 
deliver a higher acoustic output, are able to handle more power, and can 
project sound from apparently small stereo sources that effectively fill a 
listening area extending between and beyond the cabinets. 
SUMMARY OF THE INVENTION 
My apex loudspeaker has a pair of speaker mounting walls that diverge from 
an apex at an angle of 70.degree. or less. The mounting walls are 
incorporated into a loudspeaker cabinet that joins the diverging ends of 
the mounting walls. A pair of tweeters are mounted in an upper region of 
the mounting walls so that the tweeter drivers are angularly juxtaposed, 
and the tweeters face outward on opposite sides of the apex. A pair of 
woofers are similarly mounted on the mounting walls below the tweeters, to 
face outward on opposite sides of the apex. The tweeters and woofers are 
both mounted as close as possible to the apex between the mounting walls 
so that a distance spanned by a pair of tweeters from a viewpoint in front 
of the apex, approximately equals the frontal width of one of the 
tweeters. Similarly, the distance spanned by the pair of woofers, from a 
viewpoint in front of the apex, approximately equals the frontal width of 
one of the woofers. This makes the tweeter pair and the woofer pair 
operate as apparently small sources, from which sound is directed over 
wide regions on each side of the apex. A single tweeter signal drives both 
tweeters, and a single woofer signal drives both woofers, and yet the 
close proximity of the tweeter pair and the woofer pair eliminate 
frequency responsive interference patterns that would otherwise occur, if 
the tweeter pair and woofer pair were spaced farther apart.

DETAILED DESCRIPTION 
The mounting geometry of a pair of tweeters and a pair of woofers is what 
accomplishes the improved sound from my loudspeaker 10. This mounting 
geometry involves an apex 15 between a pair of angled mounting walls 11 
and 12. These form sides of a preferably pentagonal cabinet having three 
other sides 16, 17, and 18. I prefer that no two sides of cabinet 10 be 
parallel with each other, because this helps strengthen the mechanical 
rigidity of cabinet 10. It is also possible to make cabinet 10 in a 
triangular shape or to give cabinet 10 some other number of sides; but I 
prefer the illustrated pentagonal shape, for effectiveness and good looks. 
To eliminate baffle reflections from loudspeaker 10, I prefer that apex 15 
have a small radius of less than 10 mm and preferably less than 7 mm. This 
assures that baffle reflections along the bisector of the apex do not come 
in phase with the direct sound below about 23,000 Hz. 
The angle between mounting walls 11 and 12, or the angle of apex 15, is 
preferably 70.degree. or less. Through mentation, I have found that 
desirable angles lie between 60.degree. and 70.degree., and I prefer 
66.degree. for the apex angle between mounting sides 11 and 12. 
The bisector of the apex angle, extending outward from apex 15, forms an 
axis of loudspeaker 10 and is aimed generally into a listening area. Two 
loudspeakers 10, spaced apart to form a stereo pair, have their axes and 
apexes 15 aimed into a listening area, where stereo sound can be heard. 
The mounting of a pair of tweeters 20 and a pair of woofers 25 relative to 
apex 15 is important to the geometry of the sound pattern produced by 
loudspeaker 10. Tweeters 20 are mounted as close to apex 15 as possible. 
This crowds tweeters 20 nearly together at apex 15 and leaves their 
drivers 21 angularly juxtaposed, as shown in FIG. 3. With mounting walls 
11 and 12 being mounted at 70.degree. or less with tweeters 20 mounted as 
close to apex 15 as possible, a distance d spanned by tweeters 20, from a 
viewpoint in front of apex 15, as shown in FIG. 3, is approximately equal 
to the frontal width w of either tweeter 20. In effect, this makes the 
paired tweeters 20 apparently no wider than a single tweeter, to keep the 
apparent source of the sound small and preserve stereo identity. As a 
listener moves through different positions on opposite sides of apex 15, 
the apparent size of the paired tweeter source 20 does not increase or 
diminish. Also, tweeters 20, being closely juxtaposed at apex 15, do not 
create frequency responsive interference patterns, which would occur if 
tweeters 20 were arranged on opposite sides of a cabinet axis. 
Tweeters 20 preferably have a flat acoustic response throughout a wide 
angle, rather than projecting sound in a relatively narrow beam, so that 
the response is flat throughout wide angles on both sides of apex 15. To 
accomplish this, tweeters 20 preferably maintain their acoustic intensity 
in a horizontal plane, through an arc of 120.degree. at frequencies up to 
12,000 Hz. This provides full acoustic intensity through an arc of 
240.degree. around apex 15, which is a much wider sound pattern than 
previous loudspeakers have been able to obtain, while maintaining an 
apparently small source, to preserve stereo identity. 
The mounting of woofers 25 in mounting walls 11 and 12 is similar to the 
mounting of tweeters 20 in that woofers 25 are also mounted as close to 
apex 15 as possible. The larger drivers 26 of woofers 25 would interfere 
with each other if both woofers were crowded all the way to the apex 15, 
so one woofer 25 is moved slightly away from apex 15, as shown in FIG. 4. 
This may not be necessary for all designs of woofers; and to the extent 
possible, woofers 25 are crowded close to apex 15. When one woofer 25 has 
to be spaced at a small distance from apex 15, to avoid interference with 
its juxtaposed woofer driver, I prefer that the outboard woofers of a 
stereo pair of loudspeakers 10 be the ones that are spaced from apex 15. 
In most listening areas, sound from the outboard woofers will reflect off 
walls enroute to listeners so that less distortion will occur by choosing 
the outboard woofers as the ones to be spaced from apex 15, if absolutely 
necessary. 
Like tweeters 20, a distance D spanned by woofer pair 25, from a viewpoint 
in front of apex 15, approximately equals a frontal width W of either 
woofer 25. Woofers 25 are also chosen to have an even acoustic intensity 
throughout a wide angle on each side of apex 15. 
Since a single tweeter signal drives both tweeters 20 and a single woofer 
signal drives both woofers 25, tweeter pair 20 and woofer pair 25 are able 
to handle more power than single tweeters or woofers could handle. This 
allows loudspeaker 10 to handle more powerful signals and to produce sound 
of greater acoustic intensity. At the same time, the apparently small size 
of the paired tweeter source and the paired woofer source preserves stereo 
identity so that the stereo effect throughout a listening area between and 
beyond a stereo pair of loudspeakers 10 is excellent. 
I prefer that tweeters 20 and woofers 25 be used without any mid-range 
speakers, so that a single crossover can be made in the acoustic signal. 
Listening tests have shown that the distortion produced by a single 
crossover between tweeters and woofers is less than the distortion of two 
crossovers between tweeters, mid-range, and woofers.