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Description  |
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BACKGROUND OF THE INVENTION
The present invention relates to a loudspeaker system and especially to a
loudspeaker system using an elongated hollow tube having wide range
speakers mounted in each end thereof for emanating sounds from each of the
tube.
The loudspeaker tube system in accordance with the present invention will
produce a stereophonic sound or a dual monophonic sound system which is
self-contained in a single length of pipe or tubing with a full range
loudspeaker at either end of the length of the pipe. The design simplifies
the otherwise cumbersome loudspeaker components normally associated with
higher quality sound systems by having a single module that does all of
the work for the system.
In the past, stereophonic sound systems of high quality sound reproductions
have been incorporated into two or more loudspeaker enclosures. These
enclosures employ more than one driver inside the loudspeaker box and many
employ a woofer, midrange, and a tweeter driver in at least two enclosures
separated by distance between the two speakers to achieve a sound stage.
Sometimes a subwoofer is used to handle bass frequencies below 100 Hz.
The present invention is a full range loudspeaker system which maximizes
the bass frequencies in the subwoofer range and isobaric configurations
set the two drivers out of phase with each other in the tube to increase
the lower frequency sound pressure levels while minimizing box size
requirements. This technique is commonly called "push-pull" because one
loudspeaker pushes while the other pulls using the air pressure in the
enclosure. This technique has been successfully used in low frequency
units in the past but has had severe limitations in full range
loudspeakers. One problem in full range loudspeakers has been the phase
shift in a full range loudspeaker system, particularly where a
stereophonic or discrete two channel signals are introduced. The phase
must be correct or the sound stage will be off-center. In addition, one
speaker will seem to have more bass than the other speaker, which will
sometimes appear tinny or thin. An advantage of the present system using a
length of tubing is that a discrete stereo signal can be placed in phase
to each driver by having one driver face the furthest distance from the
other inside a single pipe. The signal from channel one will cause the
associated driver to push out thereby rarifying the air within the
container and pulling the opposing driver along while doubling the SPL and
bass frequency response. The second driver, which receives a second
signal, will electrically be pulling in the opposite direction to that of
the acoustic action caused by the first signal reaction. Thus, a dual
opposing signal or extended stereo signal can create a push-pull affect on
a full range loudspeaker system if that system is contained in a single
unit where the drivers are set to the furthest point within the unit away
from each other, in phase electrically, and where the enclosure is equal
to a minimum of twice the length of the radius of one of the drivers and
assuming both drivers are of equal character, size, shape, and general
electrically acoustical response to one another.
There have also been small stereophonic systems in the past but the
advantage of the cylindrical tube is that it is a singular and small pipe
with a length of five inches or more, can put out more bass with more
sound pressure level, and more full range frequency response with more
clarity and with more perceived volume than systems three to four times
its size and weight.
In the stereophonic full range mode, the sound stage can be easily adjusted
using simple mechanical controls or walls to reflect the sound in the
direction you would have it to go. The width of the sound stage can be
spread out or brought in closer depending upon how far out you choose to
place the simple deflection walls.
Another way to create a sound stage which incorporates an acoustic center
field image is to cut a hole into the center of the pipe equal in size to
at least half the radius of either of the two drivers and force a length
of pipe, at least the length of the diameter of the hole, into the hole,
closing off all air from escaping outside the center hole. The interaction
between the two stereo signals using standard tuning procedures, like a
helmholtz or a small theile tuned port, will produce the third product of
sound which results from the tuned port or an acoustical center field.
In a dual mono-mode, where each of the two speakers are driven by a
monophonic signal, a better bass signal can be produced and two pipes can
be used driven by the same monophonic signal to produce a bigger, louder
sound capability. In the dual monophonic configuration each driver can be
wired in standard phase, which produces a single point source full range
uniform response, or out-of-phase using the isobaric configuration. In
this configuration, the bass response will increase below 150 Hz but the
length of pipe needs to be cut to be equal to at least the length of one
of the drivers radius. For instance, if the driver is 4" around, the
length between the two drivers would be approximately 4" long. The
disadvantages of this configuration is the sacrifice that some of the full
range uniformity but where two separate pipes are employed, the bass
extension or in-phase driver can be loaded towards the wall to increase
the bass by 3 db per pipe with the full range sound extended into the room
acting as the point source. The same system can be also accomplished with
a longer pipe but the electroacoustic phasing will not be as effective for
delivery of deeper bass as it would in the smaller enclosure using
generally standard type drivers.
Prior art speaker systems may be seen in the following U.S. patents. In the
Ashe U.S. Pat. No. 2,905,259, a tubular speaker housing has a single
loudspeaker mounted in the middle of two truncated cones attached to form
one tube spreading in each direction. The Lanternier U.S. Pat. No.
4,905,788, shows an electro-acoustic transducer which uses a single hollow
cylindrical support for an active speaker at one end and a passive
radiator mounted at the opposite end thereof for increasing the bass
response from the tube. Two systems are required for stereo response. In
the Flanders U.S. Pat. No. 4,753,317, a trapezoidal loudspeaker enclosure
mounts a loudspeaker at one end at an angle and passively at the other
with attached base plates over each angled end of the enclosure. The
Manger U.S. Pat. No. 4,268,719, is a loudspeaker arrangement giving a pair
of back-to-back loudspeakers in an infinite baffle arrangement. The
Seville U.S. Pat. No. 4,655,315, teaches a speaker system having a
plurality of serially connected angularly disposed hollow tubes with a
loudspeaker mounted at one end, which tube can be adjusted to different
shapes. The Virva U.S. Pat. No. 4,164,988, shows a fine tuned column
speaker system in which a bellows is formed in part of tube or in which
telescoping tubes can be adjusted for a single loudspeaker to vary the
length of the back tube for the backwave of the speaker. The Robinson U.S.
Pat. No. 3,945,461, is a sound speaker system which has an adjustable
telescoping tube which can be locked in place and has a loudspeaker
mounted facing the bottom of one of the tubes.
The aim of the present invention is to have a loudspeaker system with a
single elongated hollow tube which may be a rigid tube or a telescoping
tube with a wide range speaker mounted in each end thereof and the tube
length set to accomplish the desired affect in both the wide range sound
and increased bass response and also to utilize positioned end deflectors
for directing the sound.
SUMMARY OF THE INVENTION
A loudspeaker apparatus includes an elongated hollow tube having two open
ends, which tube may be a rigid or telescoping tube, and has a wide range
speaker mounted at each end of the hollow tube. A pair of deflector
surfaces may be flat, polymer surfaces mounted to a base and are
positioned at an angle facing each speaker at each end of the tube for
deflecting the sound waves emanating from each speaker in accordance with
the positioning of the tube. The tube may also have a tuned port formed
into the side of the tube and connected to an arcuate passageway built
into the hollow portion of the inside of the tube for producing a bass
resonance from the backwaves of both speakers.
BRIEF DESCRIPTION OF THE DRAWINGS
Other objects, features, and advantages of the present invention will be
apparent from the written description and the drawings in which:
FIG. 1 is a perspective view of a sound system in accordance with the
present invention;
FIG. 2 is a sectional view of the sound system tube of FIG. 1
interconnected with a sound source;
FIG. 3 is an alternate embodiment of a sound system in accordance with
FIGS. 1 and 2 having a tuned port formed therein;
FIG. 4 is another embodiment of a loudspeaker system having a pair of
telescoping tubes in one position; and
FIG. 5 is a sectional view of the embodiment of FIG. 4 having the tubes
repositioned.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to the drawings and especially to FIGS. 1 and 2, a sound system
10 is illustrated having a rigid tube 11 which can be made of a polymer or
even of a paperboard, if desired, and is made of a predetermined length
and sits on a flat base member 12 which prevents the tube from rolling but
which base member can also be used for attaching the tube to a wall or the
like. Tube 11 has a full range speaker 13 mounted in one end 14 thereof
and a full range speaker 15 mounted in the second end 16 of the tube 11 as
far apart as possible with the length of tube, each speaker has a speaker
grill 17 covering the front of the speakers 13 and 15. Speakers 13 & 15
both are directed to emanate directly from the outside of the tube
180.degree. from each other. The tube, as illustrated in FIGS. 1 and 2, is
a rigid tube which has been carefully calculated as to length in which the
two drivers 13 and 15 are set out-of-phase with each other in the small
container to increase the lower frequency sound pressure level in each in
a push-pull arrangement and will not hurt the stereo affect and upper
range output of the drivers 13 and 15. A sound source 18 may include a
stereo amplifier receiver and may receive a sound input from a CD player
or the like which is conducted through the conductors 20 to the stereo
speaker driver 15 and through the conductors 21 to the driver 13. The
drivers 13 and 15 are carefully placed at the furthest point from each end
14 and 16 thereof and are faced back-to-back aligned on the center axis of
the tube 11 so that the audio energy emanates from the front of each
driver 13 and 15 and from each end of the tube.
The audio output energy is controlled by a pair of audio deflectors 22,
each having a plate 23 for deflecting the energy, which is illustrated as
a flat plate but also can be a shaped arcuate plate, if desired, and each
defector surface 23 is mounted to a base 24 which allows it to stand up
right on a surface and to be aligned at any angle desired depending upon
the placement of the tube 11 resting on its base 12. For instance, a
different angle is shown in FIGS. 1 and 2 which deflects the energy at an
opposite angle from each end. It should be clear that the deflector
surface 23 can be rotated 360.degree. and thus has variations of angles
over 180.degree..
The enclosure pipe section 11 is set to be a minimum of twice the length of
the radius of the drivers 13 and 15 and each drive is selected to be equal
in character, size, shape and general electro-acoustical response to the
other. In addition, it will be clear that a dual mono source input can
also be utilized within the sound system. The system allows a very small
sound system incorporated into one enclosure which can produce a full
range of audio output and which can vary the sound stage for a stereo
system and which can be made in a very small size.
Turning to FIG. 3, a second embodiment of the sound system 25 is
illustrated having a rigid tube 26 having an audio driver 28 mounted in
the other end thereof, which are both full range drivers in accordance
with the embodiments of FIGS. 1 and 2. In this embodiment, an opening 30
within the rigid tube 26 is used to create an acoustic centerfield image,
which opening is sized to at least half the radius of one of the drivers
27 or 28 and includes a passageway or length of tubing 31 which is
arcuately shaped to follow the wall of the rigid pipe 26. The pipe 31 is
the same length as the diameter of the hole 30 and is set to produce a
tuned helmholtz or small theile signal to produce an acoustical
centerfield for the system 25.
Turning to FIGS. 4 and 5, another embodiment 32 is illustrated having a
rigid tube 33 acting as an outer telescoping tube and an inner telescoping
rigid tube 34, which tubes 33 and 34 slid within each other. The sliding
is adjusted by a pressure fit but can have with one of the tubes having
raised thin ridges 35 to slightly space the tube 33 from the tube 34 to
allow the escape of air pressure from between the two tubes. Tube 33 has
an acoustical driver 36 mounted at one end thereof while tube 34 has an
acoustical driver 37 mounted in the end thereof so that the tubes 33 and
34 act as one tube which can have the volume in the space 40 adjusted by
telescoping the tubes in and out to a predetermined length in a
predetermined internal volume for producing the best bass frequency. In
addition, the tubes may or may not have the ridges 35 which allows the
escape of air pressure from the backwave of the drivers 36 and 37 through
the arcuate spacing formed by the ridges slightly spacing the tubes one
from the other while maintaining a tight fit of the tubes to each other.
It, of course, will be clear that a small screw or the like can lock the
tubes together to any predetermined length without departing from the
spirit and scope of the invention.
It should be clear at this point that a loudspeaker system has been
provided which is easily incorporated into one enclosure for producing an
improved sound output from a small enclosure are which can be easily
placed and located and can easily have the sound directed for maximum
benefit. For instance, the tube 11 can be placed in front of a television
set or even mounted in the housing of a television to extend slightly from
either side thereof and can be used in connection with computer monitors
with very small amplified signals to produce sound in connection with
computer programs and CD ROM drives or it can be made larger for
incorporation into home sound systems. However, the present invention
should not be construed as limited to the forms shown which are to be
considered illustrative rather than restrictive.
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