Note: Descriptions are shown in the official language in which they were submitted.
CA 02342746 2001-04-02
FIELD OF THE INVENTION
The invention relates to speaker cabinets for use with audio speakers,
and in particular to a speaker cabinet system in which the cabinet is tuned by
means of internal stress elements, stressing two opposed sides of the cabinet
towards one another.
BACKGROUND OF THE INVENTION
Audio speakers are conventionally mounted in boxes known as speaker
cabinets.
Usually the cabinets are rectangular boxes with front and back panels and side
panels and top and bottom panels, and are madE; of wood or wood composition
board material, although other materials have been know in some cases.
The speakers are usually mounted in a front wall or panel of the cabinet.
Audio
frequency sound waves from the speakers are propagated both forwardly and
rearwardly of the speaker cone of each speaker. l-he sound waves forwardly of
the cabinet simply propagate out into the room or apace in which the cabinet
is
located.
However the sound waves propagated rearwardly of the speaker are caught
within the interior of the cabinet. It is well known, although not entirely
understood , that the size and shape of the cabinet , and the material of the
cabinet walls or panels, will have a significant effect on the overall quality
of the
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sound which is heard by listeners. Usually the cabinet panels are made of
relatively thick heavy material such as wooden particle board, in the hope
that
this will somehow improve the quality of the sound reproduction. Apparently,
it is
believed, the thicker and stiffer the panels, the beater will be the sound
quality.
In practice however even heavy cabinets made of costly materials do not always
result in improved quality sound. Varying the dimensions of the cabinet is
also
believed to have an effect on the quality of the sound, but in spite of
various
different makers producing cabinets of widely differing shapes and sizes and
materials , a significant improvement in sound quality has not been achieved.
It
appears that the action of the sound waves within the cabinet is still not
totally
understood. The clear quality of sound which should be achieved in theory is
not
reached in practice.
The speaker cabinet construction is now believed 1'o create random noise or
distortion due, at least in part, to the propagation of the sound waves from
the
rear of the speaker which are trapped within the cabinet. Apparently, the
problem is at least party due to the fact that the propagation of the sound
waves
within the cabinet set up random noise signals which, when heard in
combination
with the original sound signal, cause unpleasant sounds which interfere with
the
enjoyment of the original sound. The low frequency noise generated by the
feed back of the sound waves within the cabinet ane regarded as relatively
powerful and destructive. The low frequency sounds from the speaker are, in
fact, propagated forwardly through a speaker cabinet port (as a canal) to
reduce
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the pressure from inside the cabinet generated by the low frequency of sound
from the back of the speaker .
However, the random noise signals in the mid and high frequency ranges
generated within the speaker cabinet are regarded as undesirable. Accordingly,
it has been the practice in the past to incorporate sound damping materials
within the cabinet. These materials may include, i'or example, thermal
insulation
material which have sound absorption or sound damping capabilities. The intent
is to absorb and hide the higher and mid range frequency random noise signals.
This practice has led to a reduction in the overall volume and feed back of
the
higher and mid range frequencies, whereas the low range frequency sound have
remained at a higher volume. Clearly this is undesirable and, if possible,
should
be avoided.
The adjustment of the speakers within the cabinet to separate high, medium and
low frequencies, and the distortion of original sound is usually controlled by
the
electronic cross-over circuitry, and amplification of the speakers. Moreover,
the
process of adjusting the tones and sound waves within the cabinet has been
attempted in the industry through electronics.
It is desirable to provide a means of "tuning" the cabinets mechanically so
that
the sound waves can be restored to near original sound which can develop
crisp,
clear, high quality, audible sound, and thus combine with the sound waves
propagated from the front of the speaker, and proviide an overall audible
sound
which is clear and free from distortion.
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BRIEF SUMMARY OF THE INVENTION
With a view to providing a speaker cabinet which goes some way towards
achieving these results the invention comprises a speaker cabinet system
having
a cabinet construction defining front and back walls and side walls, and means
for supporting at least one speaker in one of said walls, and stress element
means connected to at least two of said walls opposed to one another, and said
stress element means being stressed to develop tension therein thereby biasing
said opposed walls towards one another.
The invention further provides such a speaker cabinet system in which said
speaker support means is located in said front wall and in which said stress
element means extends between said front wall and said back wall of the
cabinet.
The invention further provides such a speaker cabiinet system in which there
are
a plurality of said stress element means being parallel to one another
preferably
it will be between two and sixteen stress elements.
The invention further provides such a speaker cabinet system in which the
stress
element means are provide with threaded tensioner means whereby they can be
stressed to a desired tension.
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The invention further provides such a speaker cabinet system in which there
are
a plurality of said speakers in said wall of said cabinet .
The invention further provides such a speaker cabinet system in which the
stress
element means comprise elongated thin metallic rods.
The invention further provides such a speaker cabinet system in which the
stress
element means are tensioned to a resonant frequency of between about 200
MHZ and about 600 MHZ.
The invention further provides such a speaker cabinet system in which said
speaker cabinet walls are formed of wooden particle board.
The invention further provides such a speaker cabiinet system in which stress
element means extend between the front wall and the back wall, and also from
one side wall to the other side wall within said cabinet.
The various features of novelty which characterize the invention are pointed
out
with more particularity in the claims annexed to and forming a part of this
disclosure. For a better understanding of the invention, its operating
advantages
and specific objects attained by its use, reference should be had to the
accompanying drawings and descriptive matter in ~rvhich there are illustrated
and
described preferred embodiments of the invention.
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IN THE DRAWINGS
Figure 1 is a perspective on a typical speaker cabinet partially cut away to
reveal
its construction, illustrating the stress element means in one embodiment;
Figure 2 is a section along line 2-2 of Fig 1;
Figure 3 is a section along line 3-3 of Fig 1; and,
Figure 4 is an enlarged side elevation of both end~~ of a typical stress
element.
DESCRfPTION OF A SPECIFIC ENIBODIMENT
Referring to Fig. 1, it will be seen that this preferred ernbodiment of the
invention is
to illustrated, in this case, in the form of a speaker cabinet indicated
generally as 10.
Cabinet 10 is a typical rectangular box-shape defining a front wall 12, a rear
wall 14,
and side walls 16-16. A top wall 18 and a bottom wall (not shown) are also
included as part of cabinet 10. Typically the walls of the cabinet are made of
for
example wooden particle board. Other materials such as injection molded
thermoplastic materials may also be used.
Front wall 12 is provided with speaker mounting locations in the form of
opening 20,
for a bass speaker, opening 22 for a mid-range speaker, and opening 24 for a
high-
2 o range speaker. Although conventional, speakers namely bass speaker 26, mid
range speaker 28, and high frequency speaker 30 are mounted on front wall 12
in
registration with their respective openings.
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The number of speakers depends on the design of the system. A cabinet may have
only one speaker and may have more than three speakers in some cases.
Typically the cabinet panels or walls will be made of wooden particle board,
although other materials are not excluded and will depend upon the choice and
taste of the manufacturer.
The speakers are connected through suitable cross over circuits of a type
known per
se and are connectable to a source of audio signals. The signal source is not
relevant to the invention and is omitted for the sake of clarity.
The cross over circuits (not shown) divide the signals from the signal source
into
bass, mid-range, and high range signals, and connecl: the divided signals to
their
respective speakers. All of this is well known in the s~>eaker art and
requires no
special description. In the case of single speaker systems all the audio
signals are
fed to the single speaker. Although not shown, the cabinet may incorporate one
or
more speaker cabinet ports (not shown) of a type well known per se, mounted on
the front wall and extending rearwardly into the interior of the cabinet, for
propagating sounds within the cabinet forwardly.
Also, as is well known, the speakers are almost alway;> of the moving cone
type. As
signals pass through the speaker coils the cones vibrate and sound waves are
propagated both forwardly and rearwardly of the spew;er cones.
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The sound waves moving forwardly in the speakers are propagated within the
room
and produce audible sound with whatever degree of clarity is possible from
those
speakers. However, it has been found that the sound waves propagated
rearwardly
of the speakers do not reproduce clear audible sound, but instead generate
unwanted audible noise which appears to distort the itrue sound quality which
is
desired. In order to combat this there is provided, in .accordance with the
invention,
a form of speaker cabinet tuning means in which stress elements are connected
between one side of the cabinet and the other side, and are tensioned to a
predetermined tension.
The precise effect of the stress element means is not as yet totally
explained. All
that is known at present is that a cabinet with the addition of the stress
elements will
develop a far clearer high quality sound than a cabinet without them.
By way of illustration Figs. 1, 2 and 3 show the speaker cabinet having a
plurality of
stress element means indicated generally as 32. The stress elements extend
from
the front wall 12 to the rear wall 14 within the interior of the cabinet.
Preferably the stress elements will extend from the wall supporting the
speakers to
the wall directly opposite to it.
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The stress elements 32, in this embodiment, are thin rods of metal, preferably
steel.
However in some cases they may be steel cables, and it is possible that
strings from
stringed musical instruments will function in the same' way.
Steel rods are convenient because they are substantially non-stretchable, they
can
easily be adapted for stressing, and they are readily <~vailable.
Preferably in a three-speaker cabinet there will be several such stress
elements 32
spaced about over the area of at least two walls. The stress elements are
located
parallel to one another, and preferably normal to the planes of the two walls.
There
may also be further elements 32 extending between opposite side walls 16-16
(phantom in Fig. 3).
In the case illustrated, there are eight such stress elernents 32 parallel
with one
another and normal to the planes of the front and rear walls. Fig. 1 also
shows six
transverse stress elements 32 between side walls 16-16.
Tensioning of the elements is achieved in this embodiment by the means shown
in
Fig. 4. This illustrates the ends of one stress element 32. It will be seen
that one
end (32A) is threaded as at 34. A socket 36 is provided having internal
threads.
Socket 36 has a head 38 with a torque device, in this case a slot 40 extending
there
across. In this embodiment there is one such socket for each stress element,
at one
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end. Each stress element is provided at the other end 32B with a fixed plug 42
secured thereto by any suitable means.
Each of front and rear walls 12 and 14 (and side walla 16-16, if transverse
stress
elements are used) is drilled with small openings 44 and 46 registering with
one
another. Plugs 42 are received in openings 44. The openings 46 are sized so as
to
receive sockets 36 therein, but their heads 38 are too large to pass through,
and
retain the sockets in their openings 46. Threaded ends 34 of each stress
element
32 are introduced into the threaded sockets, and the ;sockets are then rotated
by a
suitable tool engaging their respective slots 40. In this way, the stress
element is
progressively tensioned between the front wall 12 and the rear wall 14 (and
between
side walls 16-16 in some cases).
Generally, the stress elements will be tensioned so as. to vibrate at a
frequency of
between 200 MHZ and 600 MHZ.
Experiments have shown that when the stress elements are tensioned to a
frequency is this frequency range, the speaker cabinet will demonstrate a
marked
improvement in quality and clarity of sound reproduction.
The foregoing is a description of a preferred embodiment of the invention
which is
given here by way of example only. The invention is not to be taken as limited
to
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any of the specific features as described, but comprE:hends all such
variations
thereof as come within the scope of the appended claims.
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