US2993091A - Variable dynamic infinite damping loudspeaker enclosure device - Google Patents

Description

R. GUSS July 18, 1961 VARIABLE DYNAMIC INFINITE DAMPING LOUDSPEAKER ENCLOSURE DEVICE ATTD RN EYS United States Patent lO 2,993,091 VARIABLE DYNAMIC INFINITE DAMPING LOUD- SPEAKER ENCLOSURE DEVICE Reuben Guss, New York, N .Y. (1445 Shore Parkway, Brooklyn 14, N.Y.) Filed Apr. 2, 1957, Ser. No. 650,260 7 Claims. (Cl. 179-1) .dynamic innite damping loudspeaker enclosure which is extremely simple and inexpensiveto manufacture.

Other objects and advantages will be apparent during the coursexof the following description.

In the accompanyingdrawings, forming a part of this application, and in which like numerals are used to designate likefparts throughout thesame.

FIGURE 1 is avrear elevational view of the enclosure, with parts broken away and in section.

FIGURE 2 is a sectional view taken on. the line 2-2 ofFIGURE y1.

v FIGURE 3 is a sectional view taken on the line 3-3 of FIGURE 2.

FIGURE 4 is a perspective view .of Vthe enclosure of FIGURES lthrough 3.

FIGUREy 5 is a side elevational view of the modification,` with parts broken` away and in section.

FIGURE 6 is a perspective view of the enclosure of FIG-URE 5.

FIGURE 7 is a perspective view of a further modified enclosure. v

FIGURE 8 is a vertical sectional view taken through the enclosure of FIGURE 7 and showing sound absorbent materialy therein and showingthe loud speakers in place.

FIGURE 9 is a View :illustrating the wiring diagram of theA present invention.

Referring in detail to the'drawings, the numeral 10 esignates .an enclosure or housingl which 'can be made of any suitable material, and the housing 10` includes horizontally disposed spaced parallel topV and bottom walls 11.and 12, and the housing 10 further includes vertically .disposed spaced parallel side-walls `13 and 14.

.There is further provided a rear panel 15 which is provided with a plurality of openings 16, and arranged on the front of the housing 10` is a front panel 17 which in- Vcludesfa large. cutout or opening 18. Positioned within Vthe housing 10 and interposed between the front panel 17r and the rear panel'15 is an inner panel .19 which is provided with. a large central opening'20, for a purpose to be later described. The'inner panel 19 coacts with the panels land 15 to'dene a front compartment 21 and a rear compartment 22.l Positioned in the front compartment 21":is a directly radiating loudspeaker 23, while positioned in the rear'compartm'ent 22,V is an inner loudspeaker 24. Sounddampening material is posi- Vtioned contiguous `to' the inner surface of the walls which dene the compartment 22.

Referring to FIGURE 9 of ftheA drawings, there is showna wiring diagramtorthe present invention, and it will ibeseen that the numeral indicates wires which serve to supply'anaudio -si'gnallfrom a signal source 27, to the loudspeakers 23 and 24, thei-lloudspeakers'fbeing Patented July 18, v1961 generally by the numeral 32, and the enclosure 32 includes a front wall 33 that is provided with an opening 34 for registering with the loudspeaker 23. The loudspeaker 23 is positioned in a compartment 35 which is detined by a horizontally disposed partition 36 and a vertically disposed partition 37, and these partitions detine in the enclosure a second compartment 41. The enclosure 32 further includes a bottom wall 39 that has a plurality of openings 38 therein. The partition 37 is provided with an opening `40 for registering with the loudspeaker 24. As shown in FIGURE 8, sound deadening material 42 may be positioned in the compartment 41 and a horizontally disposed baie 43 may also be provided or positioned in the compartment 41.

From the foregoing, it is apparent that vthere has been provided a variable dynamic infinite damping loudspeaker enclosure device. VBy damping is meant the inhibition of free or distorting vibrations of the loudspeaker diaphragm, and by variable damping is meant a damping action whose amplitude may be varied at will. By dynamic damping is meant a damping action whose amplitude is directly proportional to theamplitude of the A.C. audio signal. 'By iniinite damping is meant a damping action over the entire frequency range of the directly radiating loudspeaker y23.

The apparatus is constructed so that the inner loudspeaker 24 is placed as close as possible behind a directly radiating loudspeaker 23as shown in the drawings so that the air between the two diaphragms is completely enclosed. The inner loudspeaker 24 may be less expensive but must be the same size as the directly radiating loudspeaker 23 and have about the same cone resonance. The two loudspeakers 23 and 24 are wired in parallel and in phase, with a variable resistor' 28 placed in series with the inner loudspeaker 24. This variable resistor 28 may be placed within the enclosure behind thek inner loud'- speakerV 24, with the adjustment knob projecting through t0 the outside, or the variable resistor maybe kept outside the enclosure. The directly. radiating loudspeaker 23 is attached to the front panel 17, and the inner loudspeaker24 is attached to the inner panel 19. The rear panel '15 contains about nine to twelve holes which may have a size of one quarter of an inch to one' half inch.

The inside of the enclosure between the panels 19 and 15 is lined with sound absorbent material 25, and the inside of the enclosure between panel 17 and panel 19 may be lined with sound absorbent material also, but more brilliant sound is achieved or provided if this area is left unlined or is only partly lined. By using the braces or blocks 29, the quality of reproduction is improved. Also, by using the airtight cylinder 31 to coniine the air space, a better quality of reproduction is provided. Furthermore, better reproduction of the lower frequencies as well as better over-all reproduction, may' be achieved if the air space behind panel 19 is made larger.

By placing the inner loudspeaker 24 behind the directly radiating loudspeaker 23, as shown in the drawings, and connecting it in parallel as shown in FIGURE v9 so that it is activated by thesame audio signal, the air between the diaphragms ofthe'two loudspeakersv 23 and 24 will vibrate in sympathy over the entire frequency range. By placing the variable resistor 28 in series with the inner loudspeaker 24, the signal amplitude of this loudspeaker can be adjusted so that it operates at less amplitude than the directly radiating loudspeaker 23 and this causes the vibrating air between the two loudspeakers to move with less force than the force of the diaphragm of the directly radiating loudspeaker 23.

When the best value of resistance is found or determined, the variable resistor 28 may be replaced by a fixed resistor of the same value, but it is advisable to keep the variable resistor in the circuit in the event that the directly radiating loudspeaker 23 is changed, or the room acoustics are changed.

The best adjustment of the variable resistor 28 is the one `at which the signal amplitude of the inner loudspeaker 24 is such that the air behind the diaphragm of the directly radiating loudspeaker 23 is driven to move with sufficient force to permit `and encourage this diaphragm to reproduce the A.C. audio signal, while the difference in force between the moving air and the diaphragm of the directly radiating loudspeaker 23 is of suicient magnitude to inhibit the expression of free, distorting vibrations due to the forward and reverse momentum of this diaphragm.

The result is a damping `action over the entire diaphragm of the directly radiating loudspeaker 23, and over the entire frequency range, at all amplitudes. Furthermore, due to the fact that the inner loudspeaker 24 vibrates with less amplitude, the bass radiation through the holes 16 in panel 15, is too weak to cancel out the front bass radiation. Because this back radiation is so comparatively weak, the size of the loudspeaker enclosure can be kept extremely small, for example, one half to one cubic feet -for an eight inch loudspeaker, on to two cubic feet for a twelve inch loudspeaker, and two or four cubic feet for a fifteen inch loudspeaker. Furthermore, the variable tresistor 28 in series with the loudspeaker 24 permits the user to completely control the amplitude thereof, so that in view of the fact that the loudspeaker 24 does not have to be as efficient as the loudspeaker 23, the loudspeaker 24 may be inexpensive. The function of the loudspeaker 24 is to assist and damp the loudspeaker 23 and, therefore, the loudspeaker 24 does not have to have as =high a quality as the loudspeaker 23.

The advantages of the present invention are as follows: The size of the loudspeaker enclosure or housing is very small, for example, one to two cubic lfeet for a twelve inch loudspeaker. The vibrations of the enclosure are so negligible as to permit installation thereof in the same cabinet containing a chassis and phonograph without fear of feed-back. The entire diaphragm of the directly radiatingloudspeaker 23 is damped. The damping action is dynamic and infinite because the inner loudspeaker 24 is actuated by the same audio signal which actuates the directly radiating loudspeaker 23 so as to cause the air enclosed between these two loudspeakers to move at the same frequency and with a force which is the resultant of the amplitude of both loudspeakers.

Furthermore, the damping action is variable, since it can be varied in amplitude to compensate for the different loudspeaker and enclosure characteristics, as well as the different room acoustics and this is accomplished by varying the amplitude of the inner loudspeaker 24 by means of the variable resistor 28 which may be of about 150 ohms. The inner loudspeaker 24 may be less expensive than the directly radiating loudspeaker 23, and the back bass radiation is too weak to cancel out the front bass radiation so that the entire cabinet can be kept small and the total cost of the entire unit is very low. Thus, it will be seen that there has been provided a loudspeaker enclosure device which is constructed in such a manner as to permit an inner loudspeaker 24 to be placed very closely behind a directly radiating loudspeaker 23 as shown in the drawings, and the loudspeaker 23 is mounted on the front panel 17, while the inner loudspeaker 24 is mounted on the inner panel 19. These two panels have large holes 18 and 20 which are large enough to accommodate the loudspeakers that are being used, vfor example, about ten and a half inch diameter holes for twelve inch loudspeakers. The rear panel 17 contains about nine to twelve holes 16 of a quarter to a half inch diameter, and the inside of the enclosure between panels 19 and 15 is lined completely with sound absorbent material 25, while the inside of the enclosure between the panels 17 and 19 is only partly lined with sound absorbent material or left unlined if more brilliant sound is desired.

The inner loudspeaker 24 is wired in phase with and in parallel to the directly radiating loudspeaker 23, and the closeness between the diaphragms of the loudspeakers 23 and 24 causes the air between them to vibrate sympathetically `and acurately over the full frequency range of the loudspeakers so as to encourage the mechanical expression of the A.C. audio signal by the diaphragm of the directly radiating loudspeaker 23 and also the whole diaphragm is `aifected.

The variable resistor 28 of about 150 ohms is placed in series to the inner loudspeaker 24 so as to vary its signal amplitude at will and by reducing the signal amplitude of the inner loudspeaker 24, the user can reduce the amplitude of force of the vibrating air between the diaphragms of the two loudspeakers. While this air, vibrating in sympathy with the diaphragm of the directly radiating loudspeaker encourages its mechanical expression of the A.C. audio signal, the reduction in amplitude or force of this vibrating air inhibits free or distorting diaphragm vibrations, and the best adjustment of the variable resistor is the one at which this free distorting vibration is eliminated. Furthermore, in view of the fact that the inner loudspeaker 24 operates at less amplitude, the back radiation of low frequencies is too weak to cancel out the low frequencies emitted by the directly radiating loudspeaker.

The inner loudspeaker 24 is of the same size and has about the same cone resonance as the directly radiating loudspeaker, and the inner loudspeaker can be of a poorer quality than the directly radiating loudspeaker since its major functions are to assist and damp the directly radiating loudspeaker. By adding the braces 29, between the panels 17 and 19, to eliminate the ninety degree corner angles, the quality of reproduction will be improved, and these braces may be made of any suitable material such as wood, plastic or the like. Furthermore, by adding the cylinder 31 which may be made of wood, plastic or any other material, between the panels 15 and 19, the -dynamics of the sound reproduced will be substantially improved.

In increasing the size of the rear chamber behind the inner loudspeaker, and by placing holes on a bottom panel, and lining the rear chamber partly with sound absorbing material, a better reproduction of the lower frequencies as well as generally better reproduction of all frequencies can be accomplished.

The structure as previously described can be inserted into any existing loudspeaker enclosures if small size is not desired so that these structures would comprise a completely enclosed chamber. Thus, it will be seen that there has been provided a loudspeaker enclosure device which is unique and the variable dynamic infinite damping of a directly radiating loudspeaker is achieved and the result is an extremely small loudspeaker enclosure, for example, about one to two cubic feet for a twelve inch loudspeaker, which successfully rivals and even surpasses loudspeaker enclosures many times its size and cost. The shape of the enclosure can be varied by varying the shape and size of the enclosure behind the inner panel, and the shape and size of the various parts can be varied as desired, and also the parts can be made of any suitable material.

The present invention uses two different loudspeakers of `ther-same size with one operating at lower signal amplitude but at the same frequencies as the other, for the purpose ofrdamping the diaphragm of the directly rradiating loudspeaker, and the inner loudspeaker does not reproduce much sound since its only function is to damp the directly radiating loudspeaker diaphragm. In the present invention the two loudspeakers are connected in parallel which handle the same frequencies with a variable resistor connected in series with the inner loudspeaker to make it operate at a lower signal amplitude to exert damping action on the directly radiating loudspeaker. The inner loudspeaker is mounted directly behind the directly radiating loudspeaker to exert equal pressure over both diaphragms When using the present invention, any two stock loudspeakers can be used so so that the inner loudspeaker can be inexpensive, and expense in construction is therefore reduced since the labor involved in critical matching of the two loudspeaker diaphragms characteristics is unnecessary and the difference in diaphragm resonance is also unnecessary. Furthermore, the device uses a very small loudspeaker enclosure which further cuts expenses and provides the public with a small, quality loudspeaker device. The inner loudspeaker has the major function of damping the directly radiating loudspeaker and back radiation is of very low amplitude. The air space between the two loudspeakers is calculated deliberately to make the inner loudspeaker operate in considerably low amplitude so that it will not produce sound, but merely damp the directly radiating loudspeaker, and by using the variable resistor 28, not only is the signal amplitude reduced of the inner loudspeaker but also its signal amplitude is controlled so that the system can be accommodated to different room acoustics, `and to a variety of stock loudspeakers which may be selected for the directly radiating loudspeaker 23.

As a further modification, the small openings such as the openings 38 may be arranged in the front panel 33 instead of in the panel 39 and when the openings are arranged in the panel 33, they may be hidden or covered by the grill cloth.

Although it is desirable, from the point of view of quality of reproduction, for the inner loudspeaker to be of the same size as the directly radiating loudspeaker, and to locate directly behind it, it is to be understood that according to the present invention a smaller inner loudspeaker can be used and it may be placed on any one of the panels which comprise the chamber between the two loudspeakers and such a concept cornes under the scope of this invention if the two loudspeakers are wired so as to conform to the principle of the invention as embodied in the claims since it is still possible to achieve a large degree of damping `action on the diaphragm of the directly radiating loudspeakers. When -an adjustment is found which is best tted to the loudspeakers contained, a iixed resistor of the same value as the valuable resistor may be substituted. The sound absorbing material may be of a suitable acoustical type.

I claim:

1. In a variable dynamic infinite damping loudspeaker enclosure device, an enclosure, a directly radiating loudspeaker mounted in said enclosure, and an inner loudspeaker mounted in said enclosure directly behind said directly radiating loudspeaker, said loudspeakers being of the same size, said inner loudspeaker serving the purpose of damping the diaphragm of the directly radiating loudspeaker, said loudspeakers being connected in parallel and being responsive to the same frequencies, and said loudspeakers having an audio signal supply connected thereto, and a variable resistor connected in series with the inner loudspeaker.

2. In a variable dynamic iniinite damping loudspeaker enclosure device, an enclosure, a directly radiating loudspeaker mounted in said enclosure, and an inner loudspeaker mounted in said enclosure directly behind said directly radiating loudspeaker, said loudspeakers being of the same size, said inner loudspeaker serving the purpose of damping the diaphragm of the directly radiating loudspeaker, said loudspeakers being connected in parallel and being responsive to the same frequencies, and said loudspeakers having an audio signal supply connected thereto, and a variable resistor connected in series with the inner loudsepaker, and sound absorbent material lining the inside of the enclosure adjacent the inner loudspeaker.

3. The structure as defined in claim 2 and further including braces arranged in certain of the corners of the enclosure.

4. The structure as defined in claim 2 and further i11- cluding a cylindrical member surrounding said directly radiating loudspeaker.

5. In a variable dynamic infinite damping loudspeaker enclosure, a housing including horizontally disposed spaced parallel top and bottom walls, vertically disposed spaced parallel side walls, braces mounted in certain of the corners of the housing, a rear panel on said housing provided with a plurality of spaced apart openings, a front panel on said housing provided with a central opening, an inner panel positioned in said housing and interposed between said front and rear panels and coacting therewith to define a front and rear compartment, a di rectly radiating loudspeaker positioned in said front compartment, an inner loudspeaker positioned in said rear compartment, sound damping material arranged in said inner compartment, means for supplying an audio signal to said loudspeakers, said loudspeakers being connected in parallel, and a variable resistor connected in series with the inner loudspeaker.

6. In a variable dynamic infinite damping loudspeaker enclosure, a housing including horizontally disposed spaced parallel top and bottom walls, vertically `disposed spaced parallel side walls, braces mounted in certain of the corners of the housing, a rear panel on said housing provided with a plurality of spaced apart openings, a front panel on said housing provided with a central opening, an inner panel positioned in said housing and interposed between said front and rear panels and coacting therewith `to define a front and rear compartment, a directly radiating loudspeaker positioned in said front compartment, an inner loudspeaker positioned in said rear compartment, sound damping material arranged in said rear compartment, means for supplying an audio signal to said loudspeakers, said loudspeakers being connected in parallel, a variable resistor connected in series with said inner loudspeaker, said loudspeakers having the same size, said inner loudspeaker serving the purpose of damping the diaphragm of the :directing radiating loudspeaker, said loudspeakers being responsive to the same frequencies.

7. In a variable dynamic infinite damping loudspeaker enclosure, a housing including horizontally disposed spaced parallel top and bottom walls, vertically disposed spaced parallel side walls, a vertically disposed and a horizontally disposed partition arranged in said housing and deining a iirst and second compartment, said vertically disposed partition having an opening therein, a front panel on said housing provided with an opening, a directly radiating loudspeaker positioned in said first compartment, an inner loudspeaker positioned in said second compartment, sound damping material arranged in said second compartment, means for supplying an audio signal to said loudspeakers, said loudspeakers being connected in parallel, a variable resistor connected in series with the inner loudspeaker, said loudspeakers having the same size, said inner loudspeaker serving the purpose of damping the diaphragm of the directly radiat- UNITED STATES PATENTS References Cited in the le of this patent 5 Blattner July 3, 1934 Olson Sept. 7, 1954 8 FOREIGN PATENTS Great Britain Aug. 25, 1930 Great Britain Feb. 13, 1936 Great Britain May 30, 1938

Images