US 3115947 A
Description (OCR text may contain errors)
Dec. 31, 1963 W. R. WOOD HIGH FIDELITY SOUND REPRODUCER Filed Feb. 25, 1962 Fig.4
INVENTOR. I Warren R. Wood Attorney United States Patent O HlGE-ll FliDlELlllfY SQUND REPRGDUCER Warren lit. Wood, Palo Alto, Calif. (R0. lllox 3211, Stanford, Calif.)
Filed Feb. 23, 1%2, SE1. No. 175,949 3 Claims. (C1. Ebb-31) This invention relates to an improved device for reproducing sound. More specifically it relates to a method of rotating and supporting a loudspeaker with relation to its environment so that greatly improved sound reproduction is obtained. Still more specifically my invention relates to a decoupled suspended speaker system which solves most of the problems in obtaining high fidelity sound reproduction in a novel and unusual manner which is contrary to what has hitherto been believed to be the proper practice in this art.
Most existing loudspeakers comprise a conical member and an electromagnetic vibrating means for actuating said conical member to produce sound waves in the air, the electro-magnetic means being responsive to the original source of the sound.
The vibration of the cone or diaphragm, as it is sometimes called, sends out sound waves from both of its opposite faces and consequently to persons standing on one side of the cone, or diaphragm, sound waves emanating from the opposite side will be 189 out of phase.
Various means have been used to overcome this problem, one of which is to surround the outer circumference of the cone, or diaphragm, with a wide bar ie which has the effect of cutting off the sound coming from the opposite side of the cone. To be effective, such a battle must be of relatively large diameter which makes it impracticable for use in most speakers.
Speakers have also been enclosed in an open-back cabinet which acts as an enclosure and is somewhat eilective in preventing the interference described above. To be eifective, however, such a cabinet must have a relatively large volume and this is likewise objectionable.
Another method which has been used is known as the bass-reflex cabinet. This utilizes an enclosed cabinet for the speaker in which is located a vent, the vent being located on the same face as the speaker and having an area equal to t e area of the speaker cone. In this type of speaker acoustical absorbing material is placed inside the back wall opposite the speaker and in one of each of two opposing walls.
Still another device utilizes the labyrinth cabinet for an enclosure. in this device the cabinet is divided into a series of labyrinth passages which connect the back of the cone to a vent. This tends to eliminate much of the undesirable elfect.
Another device is known as the folded-horn cabinet. in this device the back of the speaker cone is connected to a horn which in turn directs the sound so that undesirable effects are eliminated.
None of these devices by themselves have been found to be satisfactory for high fidelity reproduction.
A notable improvement in sound reproduction devices is that taught in United States Patent 2,775,309 to Villchur in which the speaker cone is supported in a cabinet enclosure and the latter is packed with acoustic absorbing material, such as fiber glass. This has been found to be quite effective in the lower frequencies ins far as obtaining good sound reproduction.
For high fidelity, however, not only is good response at low frequency necessary, but also in the middle and high frequency ranges, the former being of the magnitude of 260 cycles per second and the latter considerably above this up to 17 kilocycles per second.
In some embodiments the higher frequencies are taken care of by an auxiliary speaker known as a tweeter and the sound output blended with that of the main speaker. While I may use a similar device with my invention, I have found that it is unnecessary in order to attain good results.
Some of the disadvantages from a mechanical stand point of existing high fidelity speaker arrangements have been overcome by using specially designed speaker combinations, such as those described in an article by Larry Steckler in Radio-Electronics for November 1960. These likewise have proven to be not completely satisfactory, especially with regard to transient response, the phenomenon which enables one to distinguish one sound quality from another. in every type of speaker enclosure now known to the art, reflected waves and enclosure vibrations caused by the structure surrounding the speaker have a tendency to destroy or distort the transients.
It is therefore an object of my invention to provide a loudspeaker arrangement which would eliminate the problems accompanying high fidelity reproduction as mentioned above.
it is another object of my invention to provide a loudspeaker which would be simple and economical and still give satisfactory high fidelity performance.
it is yet another object of my invention to provide a speaker which would produce tone qualities superior to any now in use.
it is a final objective of my invention to accomplish the above results without resorting to an elaborate multiplicity of devices.
I have discovered that by properly suspending a conventional type of cone and eifectively isolating it from its supporting structure i am able to achieve unusual re sults insofar as high fidelity reproduction is concerned. My invention, which i am about to describe, should not be confused with United States Patent 1,613,609 to Harrison or United States Patent 1,735,417 to Bernard. Both of these devices use thread-like flexible suspension means to join the cone with its rim or enclosure. While these produce certain improvements, they still require an enclosure to complete the speaker assembly and the latter, of course, is attended by the objections enumerated above.
My invention is quite simple, but has not been hitherto discovered because of the consistent belief by those skilled in the art that an enclosure was necessary, which, of course, was true in previous embodiments.
What I accomplish in my invention is the effective mechanical decoupling of the speaker itself, comprising the usual cone plus a small circular rim, minimized in size to that required for support purposes, plus the usual electro-magnetic components of the speaker.
My invention is better understood by a reference to the figures which follow and form a part of this specification, as follows.
Referring now to the figures:
H6. 1 is a diagrammatical elevation of a typical embodiment of my invention.
FIG. 2 is a plan of the embodiment of FIG. 1.
FIG. 3 is a side elevation of a special embodiment for a particular interior application.
FlG. 4 is an end elevation of the embodiment of FIG. 3.
Referring now specifically to FIGS. 1 and 2, the speaker proper 1 comprises the usual components of a cone 2, a housing 3 in which are located the electr c-magnetic components of the speaker and a loosely connected electrical cable for receiving the signals 4. The cone is rigidly fastened to the supporting ring 5, which is of any material such as wood, but is of a minimum width required for structural purposes.
The thread-like suspension numbers 6 may be made of any suitable thin, flexible material of minimum diameter consistent with the required tensile strength. I have found Teflon very well suited to this purpose. The structural supports 7, which may also be made of wood, are positioned vertically on a wooden base 8, as shown. The upper surface of wooden base 8 may be covered with a layer of acoustic absorbing material 9, such as fiberglass, although I have obtained excellent results without the use of any such absorber.
The actual dimensions and physical sizes of the above parts will vary with the area (its size, and acoustical propcities) which the speaker is intended to serve. Furthermore, the cone need not be positioned horizontally in every case, as shown in FIGS. 1 and 2, but may be inclined at an angle alpha to the horizontal as shown in FIGS. 3 and 4, said angle being varied to suit the acoustics of a given room in the case of an interior application. I have found, for example, that the larger the room having a normal ceiling height and acoustical properties, the greater the angle alpha should be made for best results.
Furthermore, the speaker proper need not be located centrally between the support posts 7, but may be shifted horizontally depending on the proximity of the entire assembly to walls or other sound reflecting surfaces.
Referring now to FIGS. 3 and 4, there are seen two views of a special embodiment which I have found to be extremely satisfactory in the typical living room 20 feet by 24 feet, with 8 foot ceiling height in a typical residence using average construction materials.
The speaker 1 1 is a typical commercial vibrating coil transducer type, the latter components being located in housing 13 and having a cone 12, the face of which is approximately 6 inches in diameter. The speaker is connectcd to the sound source by cables 14. The Wooden rim 15 may be 1 inch in width, while suspension members 16a and 1612 may be two inches and 6 inches in length, respectively. The vertical structural supports 17 may be composed of 1 /2 inch square wooden sections of any suitable soft wood. The vertical support 17 may be 18 inches in height and rest upon a wooden base /1 inch thick and 18 inches by 24 inches in width and length, as shown at 1.8. Using this configuration, the face of the speaker cone r12 makes an angle alpha of approximately 30 with the horizontal. This, of course, is not critical but may be varied or Without any noticeable change in quality of sound reproduction in the average room.
The open sides between the vertical posts may be covered with grill cloth for purposes of appearance, but this was found to have no effect upon the sound properties of the assembly. The four sides and top are in effect, completely open to the surrounding atmosphere. In the embodiment shown in FIGS. 3 and 4 I have obtained excellent results without the use of any fiberglass over the bottom base 18.
Those skilled in the art will appreciate that by substantially eliminating the enclosure around the speaker, I have eliminated undesirable vibration effects caused by such enclosure, as well as undesirable reflections and out of phase interference. Those skilled in the art will further appreciate that this is highly important in the midrange frequencies which I mentioned above.
Phase distortion is not a problem with my invention since contrary to what has been the previous belief, most existing enclosures actually accentuate this eflect rather than to minimize it.
What little distortion I get with my arrangement is not noticeable in most cases and where it is may be overcome by the use of the fiberglass absorber, which I mentioned above. The reasons for the superior performance of my invention are not clearly understood in complete detail, but it has been definitely verified by experiment.
It is felt that the need for enclosures was originally thought necessary for the speakers then in use, and the application of various types of enclosures was encouraged for esthetic rather than technological reasons. With the advent of high fidelity, attempts were made to modify and compound existing enclosure concepts to obtain the desired results. My discovery of the decoupled suspension speaker system solved the problem by eliminating the source of the problem itself.
I have shown a general embodiment and one specific preferred embodiment, but I do not limit myself to those disclosed, except as I do so in the claims which follow.
1. A sound reproducing device comprising:
means for vibrating said diaphragm in response to sound actuated electrical impulses;
support means fixedly positioned around the outer periphery of said diaphragm;
a plurality of suspension means comprising thin, flexible, members, one end of each of said members be ing fixedly positioned on said support means, the other end of each of said members being positioned the upper end of each of a plurality of thin, vertical columns, thereby suspending said diaphragm in space;
said structure being characterized by the absence of sound reflecting surface exposed to said diaphragm.
2. In a loudspeaker assembly comprising:
a diaphragm and electro-magnetic vibrating means, the
improved means of support comprising:
a plurality of thin, flexible, suspension members, one end of each of said members being fixedly positioned on the outer edge of said diaphragm, the other end being positioned on a plurality of thin vertical supports positioned on a base, thereby suspending said loudspeaker in a substantially horizontal plane;
said supports being of suflicient length to eliminate undesirable sound reflection from said base, whereby said loudspeaker may reproduce sound without the distortion caused by enclosures or bafiies;
thereby effecting high fidelity reproduction.
3. In a loudspeaker assembly comprising a diaphragm and electro-magnetic vibrating means the improvement comprising:
a plurality of thin, flexible, suspension members, one end of each of said members being fixedly positioned on the outer edge of said diaphragm, the other end being position on a plurality of thin, vertical supports positioned on a base thereby suspending said loudspeaker in a substantially horizontal plane;
porous, sound-absorbing material positioned over said base;
said vertical supports being of such length with relation to said sound-absorbing material as to eliminate undesirable sound reflection from said base.
References Cited in the file of this patent UNITED STATES PATENTS 1,735,417 Bernard Nov. 12, 1929 1,877,294 George Sept. 13, 1932 2,297,218 Henrich et al Sept. 29, 1942 2,315,896 Dumas Apr. 6, 1943 2,820,526 Tavares .M Jan. 21, 1958 2,927,657 Patla et al Mar. 8, 1960 3,090,461 Gray May 21, 1963