U.S. patent number 3,923,124 [Application Number 05/429,514] was granted by the patent office on 1975-12-02 for back loaded folded corner horn speaker.
Invention is credited to John P. Hancock.
United States Patent |
3,923,124 |
Hancock |
December 2, 1975 |
Back loaded folded corner horn speaker
Abstract
A back loaded, folded corner horn speaker adapted to be placed
in the corner of a room comprises direct radiating low, mid-range,
and high frequency drivers mounted on a baffle at the front of the
enclosure and a hyperbolic-exponential folded corner horn fitted
into the enclosure so as to back load the low frequency speaker.
The length of the horn is one-quarter of the wavelength of the low
frequency cut-off frequency of the horn. The horn follows an
inwardly converging spiral path in an upper compartment of the
speaker enclosure and then passes downwardly into a lower
compartment, wherein it follows an outwardly expanding spiral path
to a horn outlet in the back of the speaker, which faces directly
into the corner of the room. The horn continues to expand from the
horn outlet through a space between the side panels of the
enclosure and the walls forming the corner of the room to a mouth
of the horn at the front of the speaker. The speaker employs an
eight-inch low frequency driver that operates over its full
frequency range; a mid-range driver that cuts in at 800 hertz; and
a high frequency driver that cuts in at 5,000 hertz.
Inventors: |
Hancock; John P. (Belmont,
MI) |
Family
ID: |
23703581 |
Appl.
No.: |
05/429,514 |
Filed: |
January 2, 1974 |
Current U.S.
Class: |
181/156; 181/152;
181/147; 181/199 |
Current CPC
Class: |
H04R
1/2865 (20130101) |
Current International
Class: |
H04R
1/28 (20060101); H04R 1/02 (20060101); H05K
005/00 () |
Field of
Search: |
;181/156,152,147,189,199 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Tomsky; Stephen J.
Attorney, Agent or Firm: McGarry & Waters
Claims
The embodiments of the invention in which an exclusive property of
priviledge is claimed are defined as follows:
1. A back loaded, folded corner horn speaker comprising:
a corner speaker enclosure having a front and a back and an open
interior and including:
a front panel having at least one baffle opening therein;
a pair of side panels connected to opposite side edges of the front
panel and converging inwardly therefrom to the back of the speaker
enclosure, said back comprising a horn outlet therein, said side
panels being formed such that when the speaker is placed in the
corner of a room with the side panels facing the walls of the room,
said side panels are spaced from the walls of the room such that
the space between the side panels and the walls forms the final
segment of a folded horn fitted in the enclosure; and
a top and a bottom enclosing open ends of the speaker
enclosure;
a low frequency driver having a front and back and mounted in the
baffle opening such that the front of the low frequency driver
radiates directly outwardly from the speaker enclosure into the
room and the back of the low frequency driver radiates into the
interior of the speaker enclosure;
a folded hyperbolic-exponential horn fitted in the interior of the
speaker enclosure so as to back load the back of the low frequency
driver, said horn extending from a horn throat acoustically
connected to the back of the low frequency driver to the horn
outlet at the back of the speaker enclosure, said horn thereafter
extending through a final segment of the horn formed along the
outer surfaces of the side panels to a horn mouth at the front of
the speaker enclosure, the length of said horn being approximately
one-fourth of the wavelength of the low frequency cut-off frequency
of the horn;
the interior of the speaker enclosure comprising upper and lower
compartments that are separated by a horizontal divider, with a
divider opening in the divider forming a passage from the upper to
the lower compartment;
the upper compartment comprising the baffle opening and the driver
and a first section of the horn formed by a series of
interconnected partitions extending between the top and the
divider, said first section of the horn extending from the throat
connected to the back of the low frequency driver to the divider
opening leading to the lower compartment; and
the lower compartment comprising the horn outlet and a second
section of the horn formed by partitions extending between the
divider and the bottom, said second section of the horn extending
from the divider opening to the horn outlet of the enclosure.
2. A back loaded, folded corner horn speaker as claimed in claim 1
wherein:
the divider opening is located in an interior portion of the
divider;
the path of the first section of the horn in the upper compartment
is a generally inwardly converging spiral leading from the back of
the driver at the front panel to the divider opening; and
the path of the horn in the lower compartment is a generally
outwardly expanding spiral leading outwardly from the divider
opening in the interior of the compartment to the horn outlet at
the back edge of the speaker enclosure.
3. A back loaded folded corner horn speaker as claimed in claim 2
wherein the horn path formed by the partitions comprises a
plurality of individual interconnected segments, each having a
straight axis and expanding in a generally straight line
approximation of a hyperbolic-exponential curve.
4. A back loaded, folded corner horn speaker as claimed in claim 3
wherein no more than two adjoining horn segments in the enclosure
are immediately adjacent each other so as to share a common
partition.
5. A back loaded, folded corner horn speaker as claimed in claim 3
wherein the horn is formed so that there are no more than two bends
of approximately 180.degree. in the horn within the enclosure.
6. A back loaded, folded corner horn speaker as claimed in claim 3
wherein the partitions are positioned so that separate partitions
forming adjoining segments are not parallel.
7. A back loaded, folded corner horn speaker as claimed in claim 1
wherein the horn has a flare parameter T of approximately 0.5.
8. A back loaded, folded corner horn speaker as claimed in claim 1
wherein the length of the horn is no less than about 7 feet.
9. A back loaded, folded corner horn speaker as claimed in claim 8
wherein the length of the horn is at least 8 feet.
10. A back loaded, folded corner horn speaker as claimed in claim 9
wherein the length of the horn is approximately 9 feet.
11. A back loaded, folded corner horn speaker as claimed in claim 1
wherein the horn has a cut-off frequency of less than 40 hertz.
12. A back loaded, folded corner horn speaker as claimed in claim 2
wherein the horn has a cut-off frequency of about 30-35 hertz.
13. A back loaded, folded corner horn speaker as claimed in claim 8
wherein the speaker is less than 3 feet high.
14. A back loaded, folded corner horn speaker as claimed in claim 9
wherein the height of the speaker from top to bottom is no more
than about 27 inches.
15. A back loaded, folded corner horn speaker as claimed in claim
14 wherein the volume of the speaker is no more than about 3 cubic
feet.
16. A back loaded, folded corner horn speaker as claimed in claim 2
wherein the low frequency driver has sufficient transient response
characteristics to satisfactorily reproduce audio signals in the
middle range of frequencies.
17. A back loaded, folded corner horn speaker as claimed in claim 1
wherein the low frequency driver is a 6 to 12-inch diameter
driver.
18. A back loaded, folded corner horn speaker as claimed in claim
17 wherein the low frequency driver is an 8-inch driver.
19. A back loaded, folded corner horn speaker as claimed in claim 1
and further comprising a direct radiating mid-range driver and a
direct radiating high frequency driver mounted in separate baffle
openings in the front panel.
20. A back loaded, folded corner horn speaker as claimed in claim
19 wherein the low frequency driver is an 8-inch driver.
21. A back loaded, folded corner horn speaker as claimed in claim
20 wherein the 8-inch driver operates through its full frequency
range, the mid-range driver is connected so as to cut in at about
800 hertz and operate through its full high frequency range, and
the high frequency speaker is connected so as to cut in at 5,000
hertz and operate through its full high frequency range.
22. A back loaded, folded corner horn as claimed in claim 3
wherein:
the upper compartment comprises:
a triangular speaker compartment formed in a front corner of the
upper compartment between one side panel of the compartment and the
front panel, the baffle opening being formed in the front panel of
said speaker compartment, a vertical speaker compartment partition
forming the third side of the speaker compartment and extending
between the first side panel and the front panel, the horn throat
opening being formed in the speaker compartment partition;
a first horn segment extending from the throat to an outer end away
from the speaker compartment in a direction generally perpendicular
to the speaker compartment partition;
a second horn segment leading from the outer end of the first horn
segment to an outer end adjacent the speaker compartment partition
in a path that runs adjacent the first segment;
a third segment connected to the outer end of the second segment
and extending away from the speaker compartment partition to an
outer end adjacent the back corner of the enclosure;
a fourth segment extending from the outer end of the third segment
along the second side panel of the compartment to an outer end
adjacent the corner of the compartment formed by the second side
panel and the front panel;
a fifth segment extending from the outer end of the fourth segment
along the front panel of the compartment to an outer end adjacent
the speaker compartment partition; and
an upper open section formed between the first, fourth, and fifth
segment of the horn, said upper open section having a triangular
horizontal cross section and opening on one side thereof into the
outer end of the fifth segment;
the divider opening mates with the upper open section;
the lower compartment comprises:
a lower open section that mates with and is positioned immediately
below the upper open section and the opening in the divider, said
lower open section being triangular in horizontal cross section and
being formed by three partitions, an outlet opening being formed in
one of the partitions;
a sixth segment connected to the outlet opening in the lower open
section and running along one of the partitions surrounding the
lower open section to an outer end at the end of said
partition;
a seventh segment connected to the outer end of the sixth segment
and running between a second of the partitions surrounding the
lower open section and one of the side panels of the lower
compartment, said seventh segment terminating at an outer end at
the front panel of the lower compartment;
an eighth segment connected to the outer end of the seventh segment
and running along the front panel to an outer end adjacent the
corner of the compartment formed by the front panel and the other
side panel;
a ninth segment extending from the outer end of the eighth segment
to the horn outlet at the back of the enclosure;
a vertically disposed corner deflection plate means is connected to
the lower compartment outside the enclosure so as to face directly
into the horn outlet, said deflection plate means being adapted to
deflect audio output emanating from the horn outlet into the space
between the respective side panels of the enclosure and the side
walls of the room; and
the final segments of the horn formed adjacent the outer surfaces
of the side panels of the enclosure extend from the horn outlet to
the mouth of the horn at the front of the enclosure.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to high fidelity loud speakers and more
particularly to a back loaded, folded corner horn speaker, wherein
the mid-range and high frequency drivers are direct radiating to
the front and the low frequency driver is direct radiating to the
front and horn loaded at the rear with a one-quarter wavelength
hyperbolic-exponential horn.
2. Description of the Prior Art
The performance of most speakers is enhanced when the speaker is
placed in the corner of a room, and this effect is enhanced when
the speaker is specifically designed for placement in the corner of
a room. In such a design, the speaker is usually generally
triangular in shape, with the front panel facing outwardly into the
room and side panels converging inwardly from the sides of the
front panel to the back edge or corner of the enclosure facing the
corner of the room. Two features of speaker response generally
enhanced by corner placement of the speaker are an improvement in
bass response and an improvement in sound direction and dispersion
within the room.
Another device commonly used for enhancing base response is "horn
loading" of a low frequency driver with a long expanding horn.
Ideally, the horn should be equal in length to the wavelength of
the desired low frequency cut-off frequency of the horn, which for
a 30 hertz cut-off frequency (fc) would be equal to approximately
36 feet in length. The horn itself may be formed in several shapes,
principally, conical, exponential, and hyperbolic-exponential, with
the concavity of the horn increasing in the order named. In most
applications, the shape of the horn employed is exponential.
Because of the unusual size of a straight axis horn that is a full
wavelength in length, it is most common to employ a horn that is
only a fraction of the wavelength of the cut-off frequency of the
horn, with a one-quarter wavelength horn being next most desirable.
Because of space limitations, a one-eighth wavelength horn is
frequently used. Also, in order to avoid the problem of undue
length of the horn projector, speakers have been designed wherein
the horns are folded so as to fit into a speaker enclosure of more
conventional dimensions.
In one popular version of a folded horn enclosure, the horn is
folded into an enclosure designed for corner placement of the
speaker, and the outlet of the horn emanates at the back of the
speaker directly into the corner of the room. The side walls of the
speaker enclosure are spaced apart a predetermined distance from
the side walls, so that the audio output emanating from the back of
the enclosure passes between the side walls of the enclosure and
the side walls of the room and emanates from the speaker enclosure
at the front of the speaker. In such a speaker, the side panels of
the speaker enclosure and the walls of the room constitute an
integral part of the horn projector, with the mouth of the horn
being the area between the walls of the room and the side panels of
the projector at the front of the speaker enclosure. By using the
space between the enclosure and the side walls of the room, the
effective length of the horn and the effective size of the speaker
enclosure can be increased without actually increasing physical
dimensions of the speaker enclosure. This type of speaker also
enhances the directivity of the speaker.
In the speaker referred to above, with the exception of the horn
outlet, the enclosure is a sealed container, and the low frequency
speaker is mounted on the interior of the speaker enclosure with
the front of the speaker being connected to the horn projector.
Thus the entire output of the speaker is projected from the speaker
through the horn via the corner of the room. The length of the horn
is approximately one-eighth of the wavelength of the cut-off
frequency of the horn. Some of the performance potential of this
speaker enclosure is lost in this manner, since a one-eighth
wavelength horn is not as desirable as a full wavelength horn. Nor
is a one-eighth wavelength horn as desirable as a one-quarter
wavelength horn.
There also are several other types and designs of corner placement
speaker enclosures that employ folded horns (generically referred
to as "folded corner horns"), and each of these horns has a
particular design that is unique with that particular model of
horn. In one well known design, the low frequency driver radiates
directly from an opening in the front of the enclosure, and is horn
loaded at the back of the driver with a hyperbolic-exponential horn
between six and seven feet long. The low frequency driver is
located at the bottom of the speaker enclosure, and the horn leads
from the bottom of the speaker enclosure upwardly to the top of the
speaker enclosure and then is directed out of the front of the
speaker enclosure through an opening in the top of the front
panel.
One of the problems with this speaker is that the horn is of
insufficient length to produce a desirably low horn cut-off
frequency of 30-35 hertz. In this speaker, the cut-off frequency is
calculated to be about 40 hertz, with the length of the horn being
about one-fourth of the wavelength of the cut-off frequency.
Another problem with this horn is that there is relatively little
fold to the horn -- it simply runs from the bottom to the top of
the enclosure -- so in order to achieve proper horn length, it is
necessary to make this enclosure unusually tall, on the order of
fifty inches, or over four feet high. Aesthetically, a speaker of
these dimensions is unsatisfactory in the average sized room, so
the usefullness of this speaker is effectively limited to extra
large rooms or auditoriums. Also, this speaker seems to have design
limitations that impair the performance of the speaker.
One of the principal problems encountered in designing a speaker
enclosure for home use is optimizing design characteristics so as
to reach a suitable compromise between two continuously conflicting
design parameters, one being the acoustic performance of the
speaker and the other being aesthetic and financial considerations
that place practical limitations on the size and the expense of any
speaker. Heretofore it has not been possible to design a back
loaded foldec corner horn speaker employing a one-quarter
wavelength horn (i.e., the length of the horn is one-fourth of the
wavelength of the cut-off frequency of the horn) wherein excellent
acoustic performance and a desirably low horn cut-off frequency
have been achieved in a speaker of sufficiently modest cost and
size to make the speaker acceptable for normal home use.
SUMMARY OF THE INVENTION
In accordance with the present invention, an improved high fidelity
speaker of modest size and cost comprises a corner mounted speaker
enclosure housing a low frequency driver that is direct radiating
to the front and is back loaded at the rear by means of a folded
corner horn that is fitted within the speaker enclosure. The length
of the folded horn is one-fourth of the wave length of the cut-off
frequency of the horn, and the outlet of the horn from the speaker
enclosure is directed out of the back of the speaker into the
corner of the room. From there the horn extends between the side
panels of the speaker enclosure and the walls of the room to a
mouth of the horn at the front of the speaker.
The speaker enclosure employed in the present invention comprises a
vertical front panel that faces away from the counter and into the
interior of the room and two vertical side panels that are attached
to outside edges of the front panel and converge inwardly to a back
portion of the speaker enclosure that fits into the corner of the
room.
The interior of the speaker enclosure is divided into an upper horn
compartment and a lower horn compartment, with a divider having an
interior opening therein separating the two horn compartments. The
path of the horn in the upper compartment comprises a generally
inwardly converging spiral from the back of the low frequency
driver to the opening in the divider. The lower compartment horn
path comprises a generally outwardly expanding spiral running from
the opening in the divider to a horn outlet at the back of the
speaker facing the corner of the room. The sides of the speaker are
spaced apart from the wall so that the space between the sides of
the speaker and the walls form a final segment of the horn, with
the area between the side panels of the speaker and the side walls
of the room at the front of the speaker enclosure forming the mouth
of the horn.
The horn of the present invention is hyperbolic-exponential in
shape, employing a T factor of 0.5. The length of the horn is
designed to be one-fourth of the wave length of the low frequency
cut-off frequency of the horn (including the final segment between
the speaker and the walls of the room). The length of this horn
should be greater than seven and preferably at least eight feet for
a high fidelity speaker. Ideally the length of the horn should be
about nine feet. This produces a desirable cut-off frequency of
about 30 hertz.
The horn is folded so that there are a minimum number of
180.degree. bends in the horn path and so that there are a minimum
number of parallel surfaces in the horn path, because both of these
factors cause diffraction effects that adversely affect the
performance of the horn.
The present invention also includes direct radiating mid-range and
high frequency speakers, which are mounted in the front panel of
the upper compartment of the speaker enclosure. The low frequency
driver is an eight-inch driver and is electrically connected in the
apparatus so as to be operating continuously through its full
frequency range. The mid-range driver is connected to cut in at 800
hertz, and the high frequency driver is connected to cut in at
5,000 hertz.
These and other advantages and features of the present invention
will hereinafter appear, and for purposes of illustration but not
of limitation, an illustrative embodiment of the present invention
is described in detail below.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of the speaker of the present
invention.
FIG. 2 is a schematic side view of the speaker of the present
invention, showing schematically the audio paths provided in the
present invention.
FIG. 3 is an exploded view of the speaker enclosure of the present
invention.
FIG. 4 is a sectional view taken along line 4--4 of FIG. 2.
FIG. 5 is a sectional view taken along line 5--5 of FIG. 2, with
the speaker being shown in position in the corner of a room.
FIG. 6 is a schematic electrical diagram showing the cross-over
network of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to the drawings, a speaker 10 embodying the
principals of the present invention is shown in perspective view in
FIG. 1. Speaker 10 comprises a speaker enclosure 12 and three
drivers 14, 16, and 18. Driver 14 is a low frequency driver or
"woofer"; driver 16 is a mid-range driver or "squawker"; and driver
18 is a high frequency driver or "tweeter."
Speaker enclosure 12 is a generally triangular speaker enclosure
commonly known as a corner speaker enclosure. Speaker enclosure 12
comprises a front panel 20 and side panels 22 and 24 which are
attached to outside edges of front panel 20 and converge inwardly
to a back corner 26 of the enclosure, so that the back of the
enclosure fits into the corner of the room, with the side panels of
the enclosure being spaced from the side walls of the room. A top
32 and bottom 37 enclose the top and bottom of the enclosure.
Preferably, the front panel and top are formed of three-quarter
inch veneer plywood and the remaining panels are formed of one-half
inch veneer plywood.
Speaker enclosure 12 comprises an upper compartment 28 having a
generally triangular horizontal cross section and a lower
compartment 30, also having a generally triangular horizontal cross
section. A divider 34 separates the upper and lower compartments.
Divider 34 has a triangular opening 36 therein that provides a
passage from the upper compartment downwardly into the lower
compartment.
The speaker enclosure as a whole is about 24 inches wide, 12 inches
deep, and about 27 inches high, with the upper compartment being
about nine inches high and the lower compartment being about 18
inches high. Thus, the structure is easily small enough for home
use in a conventional sized room.
Upper compartment 28 comprises a front panel 38 and side panels 40
and 42 which are joined together to form a triangular structure.
Since the enclosure fits into the corner of a room, the shape of
the triangle is approximately a 45.degree. right triangle, with the
90.degree. angle being formed opposite the corner of the room, so
that the front panel is at a 45.degree. angle with respect to the
walls of the room. The triangle is not precisely a 45.degree. right
triangle, however, because the side panels are adapted to taper
slightly away from the walls of the room as they run from the back
corner of the enclosure to the front of the enclosure to form a
final expanding segment of a hyperbolic-exponential horn (as shown
in FIG. 5).
Front panel 38 is provided with a baffle opening 44 for the low
frequency driver on the left side of the panel (FIG. 3 orientation)
and baffle openings 46 and 48 for the mid-range and high frequency
drivers, respectively, on the right side of the panel. Front panel
38 is rectangular, and side panels 40 and 42 are attached to the
front panel at the respective outside edges thereof and converge
symmetrically inwardly to the back corner of the compartment.
The interior of upper compartment 28 is subdivided by a series of
interconnected partitions into a triangular speaker compartment 50
for the low frequency speaker and a first or upper section of a
hyperbolic-exponential horn 51 connected to the back of low
frequency driver 14. Speaker compartment 50 is formed between side
panel 40 and front panel 38 by means of a speaker compartment
partition 52 which extends between side panel 40 and front panel
38. Speaker partition 52 and all other partitions employed in the
upper and lower compartments of the speaker enclosure are
vertically disposed and extend the entire height of each
compartment. An opening 54 is formed in speaker compartment
partition 52, and this opening constitutes the throat of horn
51.
Mid-range driver 16 and high frequency driver 18 are mounted
outside of speaker compartment 50 and out of direct contact with
throat 54 of the horn. The mid-range and high frequency speakers
are direct radiating through the front of panel 38. The backs of
these speakers are located in the path of the
hyperbolic-exponential horn, but are acoustically isolated from any
effective backloading of the speakers by the horn.
Horn 51 is formed in upper and lower compartments 28 and 30 by
means of a series of vertically oriented partitions that extend the
full height of each compartment so that the space between the
partitions and the top and bottom of each compartment forms a
sealed cavity or conduit. Horn 51 is designed as a
hyperbolic-exponential horn, using a T factor 0.5. Horn 51
comprises a throat 54 leading into the speaker compartment 50 and a
mouth 56 formed between the side panels of the lower compartment
and the side walls of the room at the front of the speaker
enclosure. The space between the side panels of the enclosure and
the walls of the room thus forms an integral part of horn 51. As
shown in FIG. 5, the side panels of the enclosure taper outwardly
from the back of the enclosure to the mouth of the horn in
accordance with the straight line approximation of the
hyperbolic-exponential curve of the horn.
The length of the horn is selected to be one-fourth the wavelength
of the cut-off frequency selected for the horn, which was selected
to be 30 hertz. The wavelength of a 30 hertz signal is
approximately 36 feet, so a one-quarter wavelength horn was
selected to be approximately nine feet or 114 inches in length. The
length of this horn is computed from throat 54 to mouth 56 and
includes the distance between the side panels of the enclosure and
the side walls of the room. The shape of hyperbolic-exponential
horn 51, including the area of the throat and mouth, as well as the
volume of speaker compartment 50 are all readily calculable in
accordance with conventional mathmatical formula and are dependent
upon the cut-off frequency selected for the apparatus and the
characteristics of the driver selected for use in connection with
the horn.
Although the length of the horn of the present invention is about
nine feet, it is possible that satisfactory results could be
obtained within the spirit and scope of the present invention by
selecting a higher cut-off frequency for the horn and using a
correspondingly shorter horn. For good bass performance, however,
the cut-off frequency selected should be 40 hertz or less and
preferably 35 hertz or less. The minimum horn length roughly
corresponding to 40 hertz and 35 hertz signals are about seven and
eight feet respectively. Therefore, horn length should in any case
be greater than seven feet, should preferably be at least eight
feet, and ideally should be nine feet.
In laying out the horn path to be employed in the speaker enclosure
of the present invention, several important design criteria were
followed in order to minimize any distortion effects by the folded
path of the horn. One important design criteria is that there be a
minimum number of 180.degree. turns or bends in the horn. Another
criteria is that there be a minimum number of parallel partition
surfaces in the horn. When surfaces are parallel and there are a
substantial number of 180.degree. turns, the performance of the
horn is adversely affected.
The path followed by the horn in the upper compartment of the
enclosure is generally in an inwardly converging spiral. The path
starts at throat 54 and extends perpendicularly away from speaker
compartment partition 52. Partitions 58 and 60 form the side walls
of this first segment 62 of the horn. The outer end of segment 62
is then connected to a segment 64 of the horn that extends along
the outer side of partition 60 back to speaker compartment
partition 52. Partition 65 forms the other side of segment 64. The
outer end of segment 64 is connected to a third segment 66 of the
horn which leads from the speaker compartment partition along side
panel 40 away from the speaker compartment partition to the back
corner of the upper compartment. A partition 67 forms the inner
side wall of segment 66, and a short section of partition 69 joins
partitions 67 and 65 at the ends thereof adjacent partition 52.
This latter partition provides a gradual bending of the horn around
this corner and avoids a sharp 180.degree. turn.
The outer end of segment 66 is connected to a fourth segment 70
that leads from the outer end of segment 66 along side panel 42 to
the corner formed by side panel 42 and front panel 38. Partition 71
forms the inner wall of this fourth segment, and this partition is
attached to the ends of partitions 67, 65, and 58.
The path of the horn then turns at the outer end of the fourth
segment, and a fifth segment 74 runs along front panel 38 to
speaker compartment partition 52, with a separate partition 73
forming the inner side wall of fifth segment 74. The outer end of
fifth segment 74 is then connected to an open upper section 76 in
the upper compartment, which is formed by partitions 58, 71, and
73. This open upper section is directly over and mates with opening
36 in divider 34.
The horn then leads downwardly through divider 34 into a
corresponding open lower section 78 in lower compartment 30 of the
speaker enclosure. Open lower section 78 forms the beginning of the
lower or second section of horn 51. This second section of the horn
follows a generally outwardly expanding spiral and emanates from
the enclosure directly into the corner of the room at the back of
the lower compartment.
Open lower section 78 is bordered by vertical partitions 79, 81,
and 83, with an open space being formed between the end of
partition 79 and partition 83 so as to form the outlet of open
section 78. The outlet of section 78 is connected to a sixth
segment 80 of the horn with one side of sixth segment 80 being
formed by partition 79 and the other side of the segment being
formed by partition 85. Partition 85 is connected at one end to the
end of partition 83 and at the other end to a short partition 87,
which is positioned so as to properly direct the output of the horn
directly into the corner of the room. Partition 87 is in turn
connected to a side panel 89 of the lower compartment. Side panel
89 fits directly under side panel 42 in the manner shown in FIG.
1.
The outer end of the sixth segment 80 is connected to a seventh
segment 82 which runs between side wall 89 and partition 81 to the
corner formed between side panel 89 and front panel 92 of the lower
compartment. An eighth segment of the horn 84 leads from the outer
end of seventh segment 82 along front panel 92 to a partition 95
extending between the other side panel 96 of the lower compartment
and front panel 92. The outer end of eighth segment 84 of the horn
is connected to a ninth segment 86 of the horn which runs from the
outer end of the eighth segment to a horn outlet 88 at the back of
the lower compartment. One side of this ninth segment is formed by
partitions 85 and 87, and the other side of the segment may be
formed by panels 97 and 99, with panel 99 being formed so as to
direct the output of the horn directly into the corner of the room.
To simplify the subject structure, it would be possible to
eliminate panels 97 and 99 and have the outer side of ninth segment
86 formed by side panel 96 of the enclosure. It would also be
possible to eliminate the extra partition 87 and extend partition
85 all the way into side panel 89. These simplifications would be
at the expense of some directional advantages.
At the horn outlet 88, the audio output of the horn has expanded in
a hyperbolic-exponential fashion to a size almost equal to the
mouth area of the horn. The horn outlet, however, is not the mouth
of the horn, as the audio output emanating from the horn outlet
continues its path through a tenth segment 98 formed between the
side panels of the enclosure and the walls of the room. The audio
output emanating from horn outlet 88 is propagated toward the
corner 100 of the room and is reflected back toward the front of
the enclosure by means of a deflector plate 102 that is spaced a
predetermined distance away from the horn outlet and fits into the
corner of the room at a 45.degree. angle. Deflector plate 102 is
connected to the back of the lower compartment 30 of the speaker
enclosure by means of horizontal mounting plates 104 and 106 at the
top and bottom of the deflector plate.
The audio output emanating from horn outlet 88 is deflected to the
front of the enclosure between the side panels of the lower
compartment and the side walls of the room. As shown in FIG. 5,
side panel 96 is formed so that it continues to expand as it runs
opposite side wall 108 of the room, and side panel 89 tapers
similarly away from wall 110 as it runs from the back of the
enclosure to the front of the enclosure. Mouth 56 of the horn is
formed at the front of the enclosure between side panels 96 and 89
and side walls 108 and 110, respectively. This enclosure thus
produces a horn that is longer and occupies a greater area than the
enclosure itself.
The drivers and electrical crossover network of the present
invention are shown schematically in FIG. 6. Low frequency driver
14 should be a 6 to 12 inch driver having good transient response
characteristics. The driver is operated over its full frequency
range and larger speakers or speakers with poor transient response
are unsatisfactory in such an application. Conversely, most drivers
smaller than six inches are incapable of producing sufficient bass
response to be used as a low frequency driver. In the present
invention an eight inch driver is deemed most satisfactory, and
this driver is connected in the enclosure to operate over its full
frequency range. It is customary in most speaker enclosures to
choke or filter the low frequency speaker so that it will not
reproduce signals above a certain cut-off frequency. However, by
using a relatively small driver with good transient response, it is
not necessary to choke the low frequency speaker. This avoids
possible adverse effects introduced by choking and provides an
important reinforcement of the mid-range signal of the speaker. A
C.T.S. eight inch driver (Model No. 8E8540 custom design) works
well as a woofer in the present invention.
The other drivers found to be satisfactory are a C.T.S. three and
one-half inch mid-range (Model No. TS7171); and a Norelco Tweeter
(Model No. AD0160/T8). Each of these drivers is connected to work
from its low cut-off point to its maximum high frequency
capability. Preferably, the mid-range cuts in at about 800 cycles
and the tweeter cuts in at about 5,000 cycles. In order to achieve
these results, the crossover network requires only non-polarized
capacitors employed as high pass filters. These capacitors are
connected in parallel configuration, with a constant K, quarter
section network, with a roll-off of 6 db per octave. The preferred
embodiment of the present invention employes a capacitor 112 of 15
mfd and a capacitor 114 of four mfd. The individual levels of the
mid-range and high frequency drivers are adjustable by means of
L-pads 113 and 115, respectively.
Several important advantages are achieved by the speaker of the
present invention. One of the principal advantages of the present
invention is an improved bass response achieved from components
costing a modest amount of money. The eight inch woofer maintains
fundamental radiation through the horn down to about 35 hertz,
while the upper frequency response remains extremely flat to 22
kilohertz. Also, very low harmonic distortion levels are maintained
throughout the pass-band, most notably in the crucial bass region
through the use of horn loading.
Another advantage of the present invention is that the fidelity and
effeciency of a one-quarter wave-length horn is achieved within
size and cost limitations applicable to home speakers. The speaker
is less than three feet high (actually about 27 inches high), about
24 inches wide, and about 12 inches deep. Thus the volume occupied
by the speaker is less than three cubic feet and actually is only
about two and one-fourth cubic feet, which is much smaller than
other folded corner horns having much shorter horns. Moreover, the
cost of the speaker of the present invention is much lower than the
cost of other folded corner horn speakers presently available
commercially.
It should be understood that the embodiment described herein is
merely exemplary of the preferred practice of the present invention
and that various modifications and changes may be made in the
arrangements and details of construction of the embodiment
described herein without departing from the spirit and scope of the
present invention.
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