CA2342746A1

CA2342746A1 - Sound speaker system

Info

Publication number: CA2342746A1
Application number: CA002342746A
Authority: CA
Inventors: David Chu
Original assignee: Individual
Current assignee: SHEER SOUND TECHNOLOGIES Inc
Priority date: 2000-04-10
Filing date: 2001-04-02
Publication date: 2001-10-10
Also published as: US20020036113A1

Abstract

A speaker cabinet system having a cabinet with front and back walls and side walls, and a location for supporting at least one speaker in one of the walls, and having several stress elements connected to two of the walls opposed to one another, stress elements being stressed to develop tension biasing the opposed walls towards one another.

Description

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 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 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.

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.

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.

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.

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.

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.
s 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 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 any of the specific features as described, but comprE:hends all such variations thereof as come within the scope of the appended claims.

Claims

1. A speaker cabinet system as claimed in claim 1 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.

2. A speaker cabinet system as claimed in claim 2 and which further provides such a speaker cabinet system in which there are a plurality of said stress element means being parallel to one another.

3. A speaker cabinet system as claimed in claim 3 wherein the stress element means are provided with threaded tensioner means whereby they can be stressed to a desired tension.

4. A speaker cabinet system as claimed in claim 4 in which there are a plurality of said speakers in said wall of said cabinet.

5. A speaker cabinet system as claimed in claim 5 wherein the stress element means comprise elongated thin metallic rods.

6. A speaker cabinet system as claimed in claim 6 wherein the stress element means are tensioned to a resonant frequency of between about 200 MHZ
and about 600 MHZ.

7. A speaker cabinet system as claimed in claim 1 wherein the speaker cabinet walls are made of injection molded thermoplastic material.

8. A speaker cabinet system as claimed in claim 1 wherein said speaker cabinet walls are formed of wooden particle board.

9. A speaker cabinet system as claimed in claim 1 wherein there is a first plurality of said stress element means connected between a front wall and a back wall of said cabinet and wherein there is a second plurality of said stress element means connected between opposite side walls of said cabinet.