Note: Descriptions are shown in the official language in which they were submitted.
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MULTIPLE CONE TRANSDUCER
Backqround of the Invention
This invention relates to loudspeaker
construction.
Various loudspeaker constructions are known.
There are, for example the configurations illustrated and
described in U.S. Patents: 4,118,605; 4,567,959;
4,590,333; 4,908,601; 5,097,513; 5,119,431; 5,295,194; and,
5,327,985.
Configurations specifically designed to move the
large volumes of air required by woofer, subwoofer and sub-
subwoofer applications are also known. There are, for
example, the systems illustrated and described in U.S.
Patents: 4,531,025; 4,757,547; 4,763,358; 5,140,641;
5,313,127; and, 5,317,642.
Summary of the Invention
According to the invention, a loudspeaker
comprises a motor stator defining an air gap. The stator
provides a magnetic field in the air gap. A former
supports a voice coil through which current to be
transduced into audio is to be passed in the air gap. A
first diaphragm is fixed to the former at a first position
a first distance along the length of the former. The first
diaphragm has a first outer perimeter. A first compliance
for permitting relative movement between the first outer
perimeter and frame couples the first outer perimeter to
the frame. A first opening in the frame vents air from a
first face of the first diaphragm. A second opening in the
frame vents air from a second face of the first diaphragm.
A second diaphragm is fixed to the former at a second
position a second distance greater than the first distance
along the length of the former. The second diaphragm has a
second outer perimeter. A second compliance permitting
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relative movement between the second outer perimeter and
frame couples the second outer perimeter to the frame. A
third opening in the frame vents air from a first face of
the second diaphragm. A first partition disposed between
the second face of the first diaphragm and the first face
of the second diaphragm provides a fourth opening through
which the former extends. The fourth opening lies between
the first and second positions.
According to an illustrative embodiment, a first
spider movably couples the former to the first partition
around the fourth opening.
Further according to illustrative embodiments a
fifth opening in the frame vents air from a second face of
the second diaphragm.
Additionally according to illustrative
embodiments, a third diaphragm is fixed to the former at a
third position a third distance greater than the second
distance along the length of the former. The third
diaphragm has a third outer perimeter. A third compliance
permitting relative movement between the third outer
perimeter and frame couples the third outer perimeter to
the frame. A second partition providing a sixth opening
through which the former extends is disposed between the
second face of the second diaphragm and the first face of
the third diaphragm.
According to an illustrative embodiment, a second
spider movably couples the former to the second partition
around the sixth opening.
Further according to illustrative embodiments,
the frame comprises a first end closure providing the first
opening. A first housing portion having a first
configuration provides the second opening and the first
partition. A first housing portion having a second
configuration provides the third opening. A second housing
portion having the first configuration provides the fifth
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opening and the second partition. A second housing portion
having the second configuration provides a seventh opening
for venting air from a first face of the third diaphragm.
Additionally according to illustrative
embodiments, a third housing portion having the first
configuration provides an eighth opening for venting air
from a second side of the third diaphragm and a third
partition defining a ninth opening through which the former
extends.
Additionally according to an illustrative
embodiment, a third spider movably couples the former to
the third partition around the ninth opening.
According to illustrative embodiments, the frame
further comprises a third housing portion having the second
configuration. A fourth diaphragm is fixed to the former
at a fourth position a fourth distance greater than the
third distance along the length of the former. The fourth
diaphragm has a fourth outer perimeter. A fourth
compliance permitting relative movement between the fourth
outer perimeter and frame couples the fourth outer
perimeter to the frame. The third housing portion having
the second configuration defines a tenth opening for
venting air from a first side of the fourth diaphragm.
Further according to illustrative embodiments of
the invention, the frame further comprises a second end
closure defining an eleventh opening for venting air from a
second side of the fourth diaphragm.
Additionally according to illustrative
embodiments, the first opening, the third opening, the
seventh opening and the tenth opening all open generally in
a first common direction and the second opening, the fifth
opening, the eighth opening and the eleventh opening all
open generally in a second common direction generally
opposite to the first direction.
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According to illustrative embodiments, the frame
further includes mounting flanges extending generally
outwardly from the frame between at least one of the first,
third, seventh and tenth openings on the one hand and the
second, fifth, eighth and eleventh openings on the other
hand. The flanges permit mounting of the frame in a baffle
with the first, third, seventh and tenth openings opening
on a first side of the baffle and the second, fifth, eighth
and eleventh openings opening on a second side of the
baffle opposite the first side of the baffle.
Additionally according to illustrative
embodiments, the first end closure further comprises means
for mounting the motor stator in the frame.
Brief Description of the Drawings
The invention may best be understood by referring
to the following description and accompanying drawings
which illustrate the invention. In the drawings:
Fig. 1 illustrates conceptually and schematically
a longitudinal sectional view of an embodiment of the
invention;
Fig. 2 illustrates an exploded longitudinal
perspective view of an embodiment of the invention; and
Fig. 3 illustrates a fragmentary perspective view
of the embodiment of Fig. 2 mounted in a baffle.
Detailed Description of the Drawings
Referring now to Fig. 1, an audio transducer 10
for such applications as a mid range loudspeaker, woofer
loudspeaker, subwoofer loudspeaker or sub-subwoofer
loudspeaker includes a motor 12, a generally right circular
cylindrical coil former 14 and a generally right circular
cylindrical frame 16. The motor 12 is fixed to one end
wall 18 of the frame 16. Motor 12 includes a front plate
20 providing a generally right circular cylindrical outer
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pole 22, an annular permanent magnet 24 and a back plate 26
providing a generally right circular cylindrical center
pole 28. Coil former 14 supports a voice coil 30 in the
air gap 32 defined between poles 22 and 28.
In accordance with the invention the coil former
14 extends substantially beyond air gap 32. While coil
former 14 is illustrated as continuing for its full length
as a generally right circular cylindrical tube, it is to be
understood that other configurations of coil former 14
outside of air gap 32 can be employed in practicing the
invention. For example, coil former 14 at some distance
outside of air gap 32 can assume the shape of a
substantially reduced cross-section right circular
cylindrical rod or other reduced or enlarged cross
sectional shape, such as square, rectangular, elliptical,
and so on.
In any event, a first diaphragm 34 of a stiff,
light weight material is fixed at its apex 36 to coil
former 14 at a distance 38 from front plate 20. A vent 40
is provided through the generally right circular
cylindrical sidewall 42 of frame 16 for air moved by a
first face 44 of first diaphragm 34 during the voice coil
30 excursion in air gap 32 in response to excitation of
voice coil 30 by a current to be transduced into audio. A
vent 46 is provided through sidewall 42 of frame 16 for air
moved by a second face 48 of first diaphragm 34 during the
voice coil 30 excursion in air gap 32. Terminals 50, 52
are provided for the application of current to voice coil
30. The sidewall 42 of frame 16 need not be circular.
Other configurations would serve equally well. For
example, and not by way of limitation, elliptical and
rectangular transducer frame configurations are known in
the art. See, for example, U.S. Patents 4,554,414 and
1,913,645. Such frame configurations are also contemplated
by the present invention.
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A compliance 54 extends from the outer perimeter
56 of first diaphragm 34 and couples perimeter 56 to
sidewall 42 at 58. Compliance 54 is attached at its
perimetrally inner extent to perimeter 56 and at its
perimetrally outer extent at 58 to support first diaphragm
34 for relatively free reciprocating motion longitudinally
of frame 16. Compliance 54 also seals the chamber 60
defined in part by the first face 44 of first diaphragm 34
from the chamber 62 defined in part by the second face 48
lo of first diaphragm 34. This prevents cancellation effects
adjacent the outer perimeter 56 of first diaphragm 34.
Beyond the second face 48 of first diaphragm 34,
a partition 64 extends across frame 16 generally
transversely to the longitudinal extents of coil former 14
and frame 16. Partition 64 in part defines chamber 62.
Partition 64 is provided with a voice coil former opening
66 through which voice coil former 14 passes beyond the
attachment 36 of voice coil former 14 to first diaphragm
34. A low-friction sliding seal 70 is provided between
coil former 14 and opening 66 so that movement of coil
former 14 in response to current flow in voice coil 30 is
not substantially impaired by seal 70.
A second diaphragm 134 is fixed at its apex 136
to coil former 14 at a distance 138 from front plate 20. A
vent 140 is provided through sidewall 42 for air moved by a
first face 144 of second diaphragm 134 during voice coil 30
excursion in air gap 32. A vent 146 is provided through
sidewall 42 for air moved by a second face 148 of second
diaphragm 134 during voice coil 30 excursion in air gap 32.
A compliance 154 extends from the outer perimeter 156 of
second diaphragm 134 and couples perimeter 156 to sidewall
42 at 158. Compliance 154 is attached at its perimetrally
inner extent to perimeter 156 and at its perimetrally outer
extent at 158 to support second diaphragm 134 for
relatively free reciprocating motion longitudinally of
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frame 16. Compliance 154 seals the chamber 160 defined
between the first face 144 of second diaphragm 134 and
partition 64 from the chamber 162 defined between the
second face 148 of diaphragm 134 and a partition 164.
Partition 164 extends across frame 16 generally
transversely to the longitudinal extents of coil former 14
and frame 16. Partition 164 is provided with a coil former
opening 166 through which coil former 14 passes beyond the
attachment 136 of coil former 14 to second diaphragm 134.
A low friction sliding seal 170 is provided between coil
former 14 and opening 166 so that movement of coil former
14 in response to current flow in voice coil 30 is not
substantially impaired by seal 170.
A third diaphragm 234 is fixed at its apex 236 to
coil former 14 at a distance 238 from front plate 20. A
vent 240 is provided through sidewall 42 for air moved by a
first face 244 of third diaphragm 234 during voice coil 30
excursion in air gap 32. A vent 246 is provided through
sidewall 42 for air moved by a second face 248 of second
diaphragm 234 during voice coil 30 excursion in air gap 32.
A compliance 254 extends from the outer perimeter 256 of
third diaphragm 234 and couples perimeter 256 to sidewall
42 at 258. Compliance 254 is attached at its perimetrally
inner extent to perimeter 256 and at its perimetrally outer
extent at 258 to support second diaphragm 234 for
relatively free reciprocating motion longitudinally of
frame 16. Compliance 254 seals the chamber 260 defined
between the first face 244 of diaphragm 234 and partition
164 from the chamber 262 defined between the second face
248 of third diaphragm 234 and a third partition 264.
Third partition 264 extends across frame 16 generally
transversely to the longitudinal extents of coil former 14
and frame 16. Partition 264 is provided with a coil former
opening 266 through which coil former 14 passes beyond the
attachment 236 of coil former 14 to second diaphragm 234.
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A low friction sliding seal 270 is provided between coil
former 14 and opening 266 so that movement of coil former
14 in response to current flow in voice coil 30 is not
substantially impaired by seal 270.
A fourth diaphragm 334 is fixed at its apex 336
to the remote end 337 of coil former 14 at a fourth
distance 338 from front plate 20. End 337 is provided with
a dust cap 339. A vent 340 is provided through sidewall 42
for air moved by a first face 344 of fourth diaphragm 334
10 during voice coil 30 excursion in air gap 32. A vent 346
is provided through sidewall 42 for air moved by a second
face 348 of fourth diaphragm 334 during voice coil 30
excursion in air gap 32. A compliance 354 extends from the
outer perimeter 356 of fourth diaphragm 334 and couples
15 perimeter 356 to sidewall 42 at 358. Compliance 354 is
attached at its perimetrally inner extent to perimeter 356
and at its perimetrally outer extent at 358 to support
fourth diaphragm 334 for relatively free reciprocating
motion longitudinally of frame 16. Compliance 354 seals
20 the chamber 360 defined between the first face 344 of
fourth diaphragm 334 and partition 264 from the chamber 362
defined between the second face 348 of fourth diaphragm 334
and an end closure 364.
End closure 364 and/or vent 346 can be omitted
25 from frame 16. If the end 372 of frame 16 is left open,
however, cancellation effects between the open end and
vents 40, 46, 140, 146, 240, 246 and 340 may be aggravated,
depending upon the mounting orientation of frame 16. While
horns are not illustrated, vents 40, 46, 140, 146, 240,
30 246, 340 and/or 346 can, if desired, be loaded via horns of
any conventional configuration either formed integrally
with side wall 42 or made separately and attached to side
wall 42.
A realization of the transducer 10 of Fig. 1 is
illustrated in Fig. 2. The elements of the transducer
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illustrated in Fig. 2 which perform the functions of the
transducer illustrated in Fig. 1 are referred to by the
same reference numbers, and the detailed description of
Fig. 1 can be referred to for the explanation of those
functions. The transducer 10 illustrated in Fig. 2 is made
up of a stack of rings of two different basic
configurations. Rings 380 provide the ports 140, 240, 340.
Rings 382 provide the ports 46, 146, 246 and the partitions
64, 164, 264. A ring 384, like rings 380 except that it is
provided with a region 386 for locating the motor assembly
20, 24, 26, provides port 40. Rather than being provided
with sliding seals 66, 70, 166, 170, 266, and 270, more or
less conventional dampers 388 are mounted to extend between
respective partitions 64, 164, 264 and the adjacent surface
of coil former 14. Rings 380, 382, 384 and end closure 364
can be constructed from, for example, filled or unfilled
resin and their adjacent edges 390 joined adhesively,
ultrasonically, by longitudinally extending bolts, or
otherwise, with the outer extents 58, 158, 258, 358 of
compliances 54, 154, 254, 354, respectively, captured
therebetween during assembly. In this way, a transducer 10
having any desired number of diaphragms 34, 134, 234, 334,
. . ., rings 380 and rings 382 can be built up in a
"stack." The transducer 10 can be custom tailored to the
desired transducer 10 characteristics.
Undesirable cancellation effects can be reduced
substantially by any number of mounting techniques, one of
which is illustrated with reference to Figs. 2-3. Each
ring 380, 382, 384 and end closure 364 is provided with
outwardly extending, flat mounting flanges 394. Some or
all of the flanges 394 are provided with mounting holes
396. A rectangular opening 398 having substantially the
external dimensions of transducer 10 excepting flanges 394
is provided in a baffle 400 such as, for example, a rear
package tray or rear seat back of a passenger vehicle.
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Ports 40, 140, 240, 340 are oriented to vent into the
passenger compartment of the vehicle. Ports 46, 146, 246,
346 are oriented to vent into the trunk of the vehicle.
Transducer 10 is mounted to baffle 400, for example, by
fasteners of any desired type through mounting holes 396
and baffle 400.
It should be understood that, although a four-
diaphragm, or four stage, transducer has been illustrated
and described, any number of stages, either more or fewer
than the illustrated four, can be incorporated into the
transducer to provide the desired volume of air movement
and/or other transducer characteristics. Further, and as
previously mentioned, although a transducer having a
circular cross section transverse to its longitudinal
extent is illustrated, any desired cross section and indeed
any desired cross sectional area within the limits of other
acoustical constraints can be implemented into a transducer
constructed according to the present invention. It should
also be understood that the coil former 14 can be extended
into the area of end closure 364 and provided with another
voice coil wound in the opposite manner to voice coil 30.
Another motor stator of the same or substantially the same
or similar configuration to motor stator 20, 24, 26 can be
provided on the inside of end closure 364 with this
additional voice coil suspended in the air gap of the
additional motor stator. The two voice coils can then be
driven with the same program material signal to provide
twice the acceleration of diaphragms 34, 134, 234, 334 as
taught by the above identified U.S. Patent 5,119,431.
