US3055451A

US3055451A - Speaker cabinet

Info

Publication number: US3055451A
Application number: US767592A
Authority: US
Inventors: Kenney George Robert
Original assignee: Individual
Current assignee: Individual
Priority date: 1958-10-16
Filing date: 1958-10-16
Publication date: 1962-09-25
Anticipated expiration: 1979-09-25

Description

Sept. 25, 1962 G. R. KENNEY SPEAKER CABINET Filed 001'.. 16, 1958 Qt INVENTR Q en/gef?. [Ye/weet@ ATTORNEYS Patented Sept. 25, 1962 3,655,451 SPEAKER CABINET George Robert Kenney, 39 Kingsley Ave., Rutland, Vt. Filed oet. 16, 195e, ser. No. 767,592 9 Claims. (Cl. 181-31) The present invention relates generally to a speaker cabinet and is more particularly directed to a specially constructed tone cabinet or lound speaker cabinet adapted to be used in conjunction with standard cone type high fidelity speakers.

One of the principal objects of the present invention is to provide a tone cabinet which increases the efficiency of the speaker by augmenting the sound emanating from the front of the speaker in the cabinet by directing sound waves from the back of the speaker to a port in the cabinet adjacent and facing the same direction as the front of the speaker.

Another object of the invention is to provide a tone cabinet of the type described in which the low frequency sound waves, down to a frequency of 32 cycles per second, emitted from the rear of the loud speaker will be directed in a novel manner through a 16 foot path entirely within the cabinet, or in other words through one-half its full wave length, to and out of a port in that portion of the cabinet near the front of the speaker and facing in the same direction.

A further object of the invention is to provide a sound cabinet of the type described which is especially adapted for use with so-called high fidelity cone type speakers and which is constructed in such novel manner that it is possible to produce full bodied tonal responses of the speaker from the middle C of 256 cycles per second of a 4 foot wave length, down to 32 cycles per second C of a 35 foot wave length.

A still further object of the invention is to construct a tone cabinet of the type described which is capable of producing full bodied audio frequencies well below 30 cycles and yet which by reason of its unique construction, is quite small and Imay be placed in small areas and is independent of the trihedral of a room corner.

Another important object of the invention is to provide a cabinet structure of the type described in which the sound waves from the front of the speaker are augmented by the sound from the rear of the speaker and projected into the upper level of a listening room, where there are relatively few sound absorbing or reflecting obstructions.

The present invention generally utilizes a cabinet which may be said to be neither a horn nor a tuned baffle type of construction. In the cabinet which is adapted to accommodate either a single low range or a full range speaker, a chamber is incorporated behind and surrounding the back of the speaker. This chamber is so constructed that it provides a very tigat air coupling load against the back of the speaker cone, causing compression of the mid low sound wave frequencies emitted from the back of the speaker. The chamber is shaped in a novel manner so as to compress substantially all of the sound waves emitted from the back of the speaker, except those of a very high frequency, and to direct them in the form of relatively flat sheets through a prescribed path lying entirely within the cabinet to a port adjacent the front of the speaker.

The novel features that I consider characteristic of my invention are set forth with particularity in the appended Claims. The invention itself, however, both as to its construction and method of operation, together with additional objects and advantages thereof, will best be understood from the following description of a preferred embodiment thereof, when read in connection with the accompanying drawing in which:

FIGURE y1 is a front elevational view of the cabinet largely broken away in vertical section to illustrate the interior construction, and

FIGURE 2 is a vertical sectional View of FIGURE 1 taken on line 2-2 thereof looking in the direction of the arrows.

Referring now in somewhat greater detail to the iigures of the drawing, the reference numeral 4 generally designates the -tone cabinet which is generally of quadrangular shape and is provided with a solid bottom 6 and a pair of spaced upstanding side walls 8 and 10 secured thereto in any convenient manner. Upstanding end panels 12 and 14 are secured to the bottom 6 and to the side walls 8 and 1t) to define a box-like cabinet open at its top and having a width considerably narrower than its length.

Near the top portion of the cabinet on the inside thereof, and spaced from the end Walls 12 and 14 there is provided a cone speaker support and back loading chamber designated generally by reference numeral 15 and which, as illustrated, includes a bottom l16 extending the full width of the cabinet and is supported by cleats 18 and 2@ attached to the inner sides of the walls `10 and 8. A cone-shaped speaker 21 is supported by a baffle 22 having a centrally disposed hole therein through which the speaker extends. The baflie 22 in turn is supported adjacent the top of the cabinet in spaced relation to the bottom 16 by [means of a cleat 24 on the inner side of the end panel 14 and a pair of cleats 26 secured in any convenient manner to the inner faces :of the side walls 8 and 10. The cone speaker 21 may be secured to the baffle support 22 in any convenient manner as by means of the screws 40.

The free end of the speaker supporting baille 22 (at the left as seen in FIG. l) and the adjacent free end of the bottom 16 terminate short of the inner face of the end panel 12 and are secured together by an end closure panel 28 which extends the full width of the cabinet. It will thus be seen that the space between the end panel 28 and the inner' face of the end wall 12 of the cabinet defines an outlet port designated generally by reference numeral 29. The other free end of the bottom 16 (at the right as seen in FIG. l) terminates short of the inner face of the end panel 14 and has secured thereto an inclined end wall 30. This end wall 30 is of the same width as the inside of the cabinet and its upper transverse edge portion terminates in spaced relation to the inner face of the speaker supporting baille 22 thereby defining a transversely extending, slot-like opening 36 opening from the interior of the chamber 15 to the interior of the cabinet 4. The inclined end wall is held in position by means of the vertical support 32.

lt will be observed that the baffle 22, bottom 16, and end walls 28 and 30 defining, with the cabinet walls 8 and 10, the chamber 15, are shown to be secured to the interior of the cabinet by means of cleats; however, if so desired, angle members may be used or the same may be held it position by gluing or the like.

Referring now particularly to FIGURE 1, the upper transverse end of the Wall 30 is shown to be tapered outwardly in such manner as to form a lip which, in conjunction with a similarly spaced and shaped lip on a wedge 34 secured to the underside `of the baie 22, defines what might be termed the sound outlet throat or opening 36 of the chamber 15. A transversely extending wedge shaped primary reflector 38 is secured in any convenient manner to the inner face of the cleat 24 on end panel 14 so that the hypotenuse or reecting side of the reiiector 33 is directly in front of the throat opening 36 and in spaced relation thereto. Thus it will be apparent that sound waves produced in chamber 15 by the back of speaker 21 are directed substantially in sheet form from the chamber 15 through the throat 36 to the reflecting surface of the reflector 3d. The interior of the loading chamber as illustrated is lined with acoustically absorbent material 42 which serves to absorb the higher frequencies of sound but not the lower frequencies and the throat portion 36 .of the chamber is not lined.

The top of the cabinet 4 is fitted with a removable frame 44 in which there is secured in any suitable manner an acoustically transparent screening 45 through which the sound from the front or upper portion of the speaker 21, augmented with the sound from the back of the speaker through port 29, proceeds upwardly.

In the operation of the speaker substantially all frequencies emanating from the front or top side of the speaker 21 proceed upwardly through the acoustical screening 45, being somewhat diffused as they pass therethrough. However, all frequencies emanating from the rear of the cone speaker, except those of a high order which are absorbed by the acoustical lining material 42, are compressed substantially into a sheet by passing through the restricted mouth-like opening 36 and are directed against the angled refiecting face of the primary reflector 38. This sheet of compressed sound, composed of a finite number of pulses, travels downwardly at a predetermined angle striking the floor 6 of the cabinet and being reflected therefrom. It then travels up to the outer side of the bottom 16 of the chamber 15 and is reflected away therefrom again to the inner face of the bottom 6 of the cabinet, this process repeating and continuing with the angle of incidence equal to the angle of reflection until the pulse is nally reflected up through the outlet port 29 as indicated by the chain line and arrows in FIG. 1.

The angle at which the pulse is initially reflected downwardly is established by the setting of the angle of the primary reflector 38. The dimensions of the cabinet, including the length of the bottom of the chamber and the distance between the parallel opposed Afaces of the bottom 16 of the chamber and the bottom 6 of the cabinet, are such as to provide a path for the traveling of the pulse through to the port 29 of a minimum length of 16 feet. When the focused pulse arrives at the port 29 after its travel in this manner, it will have expanded just enough t-o fill the port opening. However, lateral dispersion of the focused pulse during its 16 feet lof travel is held to a minimum, which forces the pulse to disobey the physical law of intensity of sound in free air, commonly referred to as the law of inverse squares.

Under the conditions as outlined immediately above, after passing through the mouth 36, nearly the total energy of the sound waves in the focused pulse will reach the room `atmosphere through the port 29. At this point the vigorous impact of the pulse containing nearly all the frequencies from the speaker back now attacks the room iair at conditions resembling an explosion of a small order. Substantially all of the energy from the rear of the speaker has been concentrated upon a relatively small point in space, resulting in an extremely wide range of clean and sharp sound from a very small speaker-cabinet combination. Low frequency notes are felt as well as heard. All partials and `odd harmonics, which because of their low energy level are usually lost in conventional arrangements, `are clearly heard upon being emitted from the cabinet opening port 29, whether the system is being operated at a high, medium or very low listening level. The use of this type of cabinet construction, which gives assistance to soft overtones and harmonics, brings tone color back into true perspective and balance at the listeners ear,

As one example of the extremely small cabinet dimensions made possible in accordance with the present invention, if the angle of the reflecting surface of the primary reflector 38 is chosen so as to direct the sound pulse downwardly and inwardly of the cabinet at an angle of 51/2 to the vertical, the sound pulse will strike the bottom 6 of the cabinet 4 and be reflected upwardly at an angle of 11 to itself striking the bottom 16 of the chamber 15 and being reflected toward the bottom 6 again at this same angle on itself. If the spaces between the inner ends of the panels 14 and 12 and the ends of the chamber 15 are 2.1/2 and 51/2 inches, respectively, and the overall length of the bottom of the chamber 15 is 16 and the distance between the bottom 16 of the chamber 15 and the bottom 6 of the cabinet is 17 inches, all approximately, the sound pulse will have traveled a minimum of 16 feet before it leaves the port 29.

As will be readily apparent from the foregoing illustrative example, it is possible to produce full bodied tonal response from the middle C of 256 cycles per second (2 ft. pitch) down to 32 cycles per second (16 ft. pitch) in a cabinet having overall dimensions of only approximately 2 ft. by 2 ft. by 9 in. Entirely apart from the apparent advantage of such compact cabinetry, it will be equally clear that the absence of relatively complicated ductwork and multiple baffles such as customarily found in horn type cabinets lends itself readily to the production and sale of cabinets in accordance with the present invention in kit rform for assembly and finishing by the user.

Throughout the specification I have referred to the emission of sound waves from the Iback loading chamber as being substantially in the form of a relatively thin sheet or focused pulse as observation indicates that such phenomenon does actually occur in practice. While the size of this sheet may vary to match the specic speaker design, I have obtained generally satisfactory results from sheets having a cross sectional area generally about one-f0urth of the projected area of the speaker.

While there is shown for the purpose of illustration a preferred embodiment of the invention it is apparent that various modifications of the structure and embodiments are possible without departing from the spirit and scope of the invention. It will also be clear that, while the invention has been described as applied to a vertical cabinet arrangement, various arrangements of the speaker from vertical to horizontal will affect only the design of the back loading chamber but not the operation of the wave sheet pattern as described.

I claim:

1. In a tone cabinet of the class described, a quadrangular shaped cabinet open at its top and having front, rear and end walls and a at bottom, a sound chamber supported in operative relationship with said cabinet Aadjacent the top thereof in spaced relation to the end walls and bottom of the cabinet and having a flat bottom portion in parallel relation and spaced from the flat bottom of the cabinet, the space between one of the end walls and the chamber defining a sound outlet port, a cone type speaker secured in said chamber with the back of the speaker confined within said chamber and the front thereof open to the atmosphere adjacent the sound outlet port, said chamber having a sound mouth outlet opening therein, a sound reflecting baffle adjacent the mouth opening of the chamber and having a reflecting surface at an angle to direct the sound waves emanating from the mouth of the chamber to the flat bottom of the cabinet for successive reflection between the bottom of the chamber and the bottom of the cabinet and final emission from the outlet port adjacent the front of the speaker.

2. In a tone cabinet of the class described, a quadrangular shaped cabinet open at its top and having front, rear and end walls and a flat bottom, a sound chamber supported in operative relationship with said cabinet adjacent the top thereof in spaced relation to the end walls and bottom of the cabinet and having a flat bottom portion in parallel relation and spaced from the flat bottom of the cabinet, the space between one of the end walls and the Ichamber defining a sound outlet port, a cone type speaker secured in said chamber with the back of the speaker confined within said chamber and the front thereof open to the atmosphere adjacent the sound outlet port, said chamber having a transversely extending sound mouth outlet opening therein, a sound reflecting baille adjacent the mouth opening of the chamber and having a reflecting surface at an angle to direct the sound waves emanating from the mouth of `the chamber to the flat bottom of the cabinet for successive reflection between the bottom of the chamber and the bottom of the cabinet and final emission from lthe outlet port adjacent the front portion of the speaker, the length of travel of the sound Waves in the cabinet being a minimum of 16 feet.

3. In a tone cabinet of the class describ-ed, a quadrangular shaped cabinet open at its top and having front, rear and end walls and a flat bottom, a sound chamber supported in operative relationship with said cabinet adjacent the top thereof in spaced relation to the end walls and bottom of the cabinet and having a flat bottom portion in parallel relation and spaced from the flat bottom of the cabinet, the space between one of the end walls and the chamber defining a sound outlet port, a cone type speaker secured in said chamber with the back of the speaker confined within said chamber and the front thereof open to the atmosphere adjacent the sound outlet port, said chamber having a rectangularly shaped, transversely extending sound mouth outlet opening therein, a sound reflecting baffle adjacent the mouth opening of the chamber and having a reflecting surface at an angle to direct the sound waves emanating from the mouth of the chamber to the flat bottom of the cabinet for successive reflection between the bottom of the chamber and the bottom 0f the cabinet and nal emission from the outlet port adjacent the front portion of the speaker, the length of travel of the sound waves in the cabinet being a minimum of 16 feet.

4. In a tone cabinet of the class described, a quadrangular shaped cabinet open at its top and having front, -rear and end walls and a flat bottom, an acoustically lined sound chamber supported in operative relationship with said cabinet adjacent the top thereof in spaced relation to the end walls and bottom of the cabinet and having a flat bottom portion in parallel relation and spaced from the flat bottom of the cabinet, the space between one of the end Walls and the chamber defining a sound outlet port, a cone type speaker secured in said chamber with the back of the speaker confined within said chamber and the front lthereof open to the atmosphere adjacent the sound outlet port, said chamber having a sound mouth outlet opening therein, -a sound reflecting baille adjacent the mouth opening of the chamber and having a reflecting surface at an angle to direct the sound Waves emanating from the mouth of the chamber to the fiat bottom of the cabinet for successive reflection between the bottom of the chamber and the bottom of the cabinet and final emission from the outlet port adjacent the front portion of the Speaker.

5. In a tone cabinet of the class described, a quadrangular shaped cabinet open at its top and having front, rear and end walls and a flat bottom, an acoustically lined sound chamber supported in operative relationship with said cabinet adjacent the top thereof in spaced relation to the end walls and bottom of the cabinet and having a flat bottom portion in parallel relation and spaced from the flat bottom of the cabinet, the space between one of the end Walls and the chamber defining a sound outlet port, a cone type speaker secured in said chamber with the back of the speaker confined within said chamber and the front thereof open to the atmosphere adjacent the sound outlet port, said chamber having a transversely extanding sound mouth outlet opening therein, a sound reflecting baffle adjacent the mouth opening of the chamber and having a reflecting surface at an angle to direct the sound waves emana-ting from the mouth of the chamber to the flat bottom of the cabinet for successive reflection between the bottom of the chamber and the bottom of the cabinet and final emission from the outlet port adjacent the front portion of the speaker, the length of travel of the sound waves in the cabinet ibeing a minimum of 16 feet.

6. In a tone cabinet of the class described, a quadrangular shaped cabinet open at its top and having front, rear and end walls and a fiat bottom, an acoustically lined sound chamber supported in operative relationship with said cabinet adjacent the top thereof in spaced relation to the end walls and bottom of the cabinet and having a flat Abottom portion in parallel relation and spaced from the flat bottom of the cabinet, the space between one of the end Walls and the chamber defining a sound outlet port, a cone type speaker secured in said chamber with the back of the speaker confined within said chamber and the front thereof open to the atmosphere adjacent the sound outlet port, said chamber having a transversely extending sound mouth outlet opening therein, -a sound reflecting baille adjacent the mouth opening of the chamber and having a refleeting surface at an angle to direct the low frequency sheet-shaped sound waves emanating from the mouth of the chamber to the flat bottom of the cabinet for successive reflection between the bottom of the chamber and the bottom of the cabinet and nal emission from the outlet port ladjacent the front portion `of the speaker, the length of travel of the sound waves in the cabinet being a minimum of 16 feet.

7. In a t-one cabinet of the class described, a cabinet open at its top and having front, rear and end Walls and a flat bottom, a sound chamber supported in operative relationship with said cabinet adjacent the open top thereof in spaced relation to one end wall and the bottom of the cabinet and having a flat bottom portion in parallel rela-tion and spaced from the flat bottom of the cabinet, a cone type speaker secured in said chamber with the back of the speaker confined within said chamber and the front thereof open to the atmosphere, the space between the sound chamber and the one end wall of the cabinet defining a sound wave outlet port adjacent the front `of the speaker, said chamber having a transversely extending, rectangularly shaped sound outlet mouth opening therein, a sound reflecting baffle adjacent the mouth outlet opening of the chamber and having a sound reflecting surface at an angle to direct the sound waves emanating from the mouth of the chamber to the flat bottom of the cabinet for successive reflection between the bottom of the chamber `and the bottom of the cabinet and final emission from the outlet port, the length of travel of the sound waves being of a distance within the cabinet to produce sound waves from the outlet port to augment the sound waves from the front of the speaker.

8. In a tone cabinet of the class described, a cabinet open at its top and having front, rear and end walls and a flat bottom, an acoustically Ilined sound chamber supported in operative relationship with said cabinet adjacent the open top thereof in spaced relation to one end wall and the bottom of the cabinet and having a flat bottom portion in parallel relation and spaced from the flat bottom of the cabinet, a cone type speaker secured in said chamber with the back of the speaker confined Within said chamber and the front thereof open to the atmosphere, the space between the sound chamber and the one end Wall of the cabinet defining an outlet port adjacent the front of the speaker, said chamber having a transversely extending, rectangularly shaped sound outlet mouth opening therein, a sound reflecting baille adjacent the mouth outlet opening of the chamber and having a sound reflecting surface at an angle to direct the sound waves emanating from the mouth of the chamber to the flat bottom of the cabinet for successive reflection between the bottom of the chamber and the bottom of the cabinet and final emission from the outlet port, the length of travel of the sound waves being of a distance Within the cabinet to produce sound waves from the outlet port to augment the sound Waves from the -front of the speaker.

9. In a. tone cabinet of the class described, a cabinet open at its top and having front, rear and end walls and a tion and spaced from the at bottom of the cabinet, a 5

cone type speaker secured in said chamber with the back of the speaker confined Within said chamber and the front thereof open to the atmosphere, the space between the sound chamber and the one end wall of the cabinet deiining a sound Wave outlet port adjacent the front of the speaker, said chamber having a sound outlet mouth opening therein, a sound reflecting baiile adjacent the mouth outlet opening of the Ichamber and having a sound reflecting surface at an angle to direct the sound Waves emanating from the mouth of the chamber to the flat bottom of the cabinet `for successive reflection between the bottom of the chamber and the bottom of the cabinet and linal emission from the outlet port, the length of travel of the sound waves being at a distance within the ycabinet to produce sound Waves from the outlet port to augment the sound Waves from the front of the speaker.

References Cited in the le of this patent UNITED STATES PATENTS OTHER REFERENCES Publication: Stromberg-Carlson Custom Pour Hun- 5 dred; advertising pamphlet published by Stromberg-Carlson (now General Dynamics Corp.) Sound Equipment Division, Rochester, N.Y.