US2491982A - Reflex type loud-speaker cabinet - Google Patents

Description

, 20, H49 5. M. KINCART 2,491,982

I REFLEX TYPE LOUDSPEAKER CABINET Filed Sept. 12, 1946 }i lliihlnhlimllm V ATTORNEYS.

Patented Dec. 20, 1949 6 Claims.

This invention relates to a loud-speaker tone chamber and is particularly useful in connection with loud-speakers of the cone type, whether the speaker be of the permanent magnet or dynamic type.

'A speaker of the cone type produces sound vibrations of the cone elementwhich set the adjacent air into vibration. It is, a' characteristic of a cone type loud speaker that sound is emitted from the rear, of the, cone as well as from the. front. In conventional speaker systents, various means. have been tried and adopted for mufiling orfdarnping the tone emitted from the. rear-of the speaker soas, not to interefere with, tones emanating. from the. front 'of the neake It is an object of my present invention to improve the. characteristicsof a loud-speaker of thecone type. by utilizing-sound emitted from the rear of the cone. andcausing it to travel through certain paths. and be emitted toward the, front so as to combine. with and reenforoe the tones, emitted from the. front of the speaker a no m manne It is another object of my invention to, cause the paths. for tones, emitted from the rear of hesr aker u n h and articu ar r ne low register, there will be paths which areonehalf. w en h r odd. u es er o en r l th e ie i at v ion c d the provision of a tone. chamber for a loud-v speaker in which tones, from. the front possess a gr t pr ve -response he o registers a We e m y hieh ones- These: and other objects-of my invention which will be pointed out hereinafter, or which will be.

apparent, to one skilled. in the art. upon reading these specifications, I accomplish b ythat cere tain. construction and. arrangement of parts of. wh ch shall w de cr e n exem a yem-. bodiment. Reference is, made) to the drawings qmi e a. p t he eof. a d in w h? Fig. '1 od -1 v n eniien:

Fig. 2 is a horizontal cross sectional view thereof.

While my invention may be carried out in a number of-ways and may embody-no more than the tone chamber itself for uses where the speaker is confined (as behind a motion picture screen for sound movies) I have shown it in the rese t. ase as being cor orated o a has such as maybe found in small restaurants and bars as well as in recreation rooms in. private homes. This particular embodiment, of course, forms no limitation upon my nyention.

A bar or suitable cabinet to contain the speaker and tone chamber is indicated at In. It preferably has a front panel and lateral panels exto be elongated; so that. for any. flE-r is a front elvationalview of a device respectively.

. having 'a cone l1.

which are 2. tendingrearwardly and at anangle as indicated at H. In some installations, as for example behind. a motion picture screen, the panels l I should be coplanar with the panel It, by extension of the panels 22.

The side walls and rear of the cabinet. are indicated by: the broken lines it and I3 since the, particular form of these panels is immaterial. The top and bottom bafiles of the.

tone chamber are indicated at [2a and l2b,

$ubstantial ly centrally of the front panel I0, I provide a; suitable grilleor series of slots indicated generally at l 4 Behind the grille it, upon a'sub-baille l5, I'mount a loud-speaker It emanating from the front of the cone ill will issue. through the grille M in conventional manner.

In order to utilize, tone emanating from the rear of the cone 1 provide passages in communication with merrier. of the cone and leading to grilles or apertures l8 in" the panels M. It will be noted that the grilles 13 are disposzd at an angle pointing outwardly from the axis of the cone l'L: so that tones from the speaker as a whole. are not projected oniy directly forward,

but alsojarelproj ected toward the side. I have found that afsp eaher according to my present inventionis quite directional in its character istics with maximum volume projected straight forward, a decreasing volume outwardly sub, stantially to. a 45 angle and with practically no tones projected directly to the sides or to the.

rear.

Directly behind the speaker, I provide a pair of 'ang ularly disposed baffles is meeting. in an edge 20 and serving to deflect tones which are emitted directly. to the: rear respectively to the right and to the left, Extending outwardly from the bafiles 19 are a pair of rear baffles 2! which are s1 ilostantially parallel with the front of the structure and from the baffies 2!, there extend forwardly a pair of inclined battle; 22. The

bafiles 2l' and 22 serve to reflect forwardly tones projected to the rear from the cone l1, each side of they loud-speaker cone I provide'bafiies 2 3, whichjslerve to deflect toward the reara y tones which are emitted directly towardthe side from'the cone, H. The baffles 23 are stibstant'ally parallel to the baffles l9.-

Extending rqgwaruly from the, rear edges of the baffles 23; I provide a; air. of baffles 2 3; which re ebstan a lvra ellelto the baffles.

It, will. thus be, seen by referring to the broken lines, :1: and y howftones projeoted from therear 'of the cone"'may. b8 were about so as to emerge through the, gr

Y 5J5 hd it will be seen h t se at s taeqneaerab y e l by tue of the angular construction of the baffles.

It will also be noted that a substantial space It. wilfbe clear that tone mes over behind the speaker, so as to emerge through A the grille l8 on the opposite side as indicated, for example, by the broken line a. It will be seen that the tones which cross over have a much greater effective length of path than those which do not cross over. A range of frequencies for a speaker to provide good fidelity is from 30 to 10 thousand cycles per second. Since the wave length of a tone can be determined by dividing the velocity of sound by the frequency, it may be readily calculated that the length of a half-wave of a cycle per second tone is about 218 inches. For 50 cycles per second tones, the length of a half-wave is about 130 inches and for 100 cycle per second tones, it is about 65 inches. At the other end of the scale, we find that for tones of 10 thousand cycles per second, the length of a half-wave is .66 inch and for 5 thousand cycles per second, it is 1.31 inches. From the above it is clear that there is a considerable range in half-wave length between tones of 30 cycles per second on the low end and 10 thousand cycles per second on the high end. It will also be understood that by virtue of the infinite number of directions in which tones may be reflected from the back'of the cone l'l, there will be for any individual frequency a number of paths which are one-half wave or a multiple thereof in length. Such tones will strengthen and reenforce. tones being projected from the front of the speaker. Thegeneral effect apparent to the hearing when listening to a loudspeaker according to my invention is that the high tones are sharper and clearer, while the low tones are well rounded, resonant, and free from objectional vibrations and booming. The tonal effects are also improved by the sounding board eiiect of the various baifies which are used.

While dimensions are not highly critical, I have determined that in general the distance between centers of the lateral grilles should be about five times the diameter of the speaker for best results; also that the depth of the tone chamber should be about one-quarter of the total width. These figures set the practical minimum dimensions, while the practical maximum dimensions are about double the above. Thus, for example, with a 5 inch speaker the minimum width should be about 25 inches, while the maximum width might be as high as inches with the depth of the tone chamber ranging from about 6 inches to about 12 inches; and with a 15 inch speaker the minimum width would be about 75 inches and the maximum width about 150 inches with the depth ranging from about 19 inches to about 38 inches.

While I have shown and described my invention as having two diametrically opposed branches, it will be clear that any number of branches could be symmetrically disposed about the axis of the cone, so as to constitute a polygonal or even a circular tone chamber. A circular tone chamber may be considered as a revolution of Fig. 2 about the axis of the cone.

For some special purposes it may be desirable to add one or more small supplementary speakers and these may be mounted between the bafiles 23 and 24, as indicated in brokenlines at 25 in Fig. 2 in which supplementary grilles or apertures could be provided as at 26 in Fig. 1. It

4 may also be desirable to use more than one speaker behind the grille M.

It willbe understood that numerous odiflcations may be made without departing f cm the spirit of my invention and I therefore \do not intend to limit myself except as pointedout in the claims which follow.

Having now fully described my invention what I claim' as new and desire to secure by Letters Patent is:

1. A tone chamber for a cone type loud-; speaker, comprising a bafiie upon which said 3 speaker is mounted, said baflie having an aperture coaxial with said speaker for emission of tones to the front, a pair of angularly disposed baffles behind saidspeaker, said baffles meeting in a dividing edge substantially centrally behind said speaker, a pair of angularly disposed baffles one to each side of said speaker and extending rearwardly in substantial parallelism with the respective first mentioned angular bafiles which are on the same side of the speaker axis, a pair of rear bailies to each side of said first mentioned angular bafiies, a pair of bafiles extending for-" emitted from one side of saidspeaker and refiected from said angularly disposed baflles on either side of said speaker may cross over he hind said speaker and issue from the reflective path on the opposite side of said speaker, thereby traveling an effectively longer path.

3. A tone chamber according to claim 1, in which the distance between centers of said openings is on the order of five times the diameter of said speaker.

4. A tone chamber according to claim 1, in

which there are top and bottom bafiies for said chamber, and in which the depth of said charm-- her is on the order of one quarter its length.

5. A tone chamber according to claim 1, in which the distance between centers of said openings is on the order of five times the diameter of said speaker.

6. A tone chamber according to claim 1, in which the distance between centers, of said openings is on the order of five times the diameter of said speaker, said chamber being provided with top and bottom baflies, and the depth of,

said chamber being on the order of one quarter its length.

STANLEY M. KINCART.

REFERENCES CITED The following references are of record in the file of this patent:

Klipsch Apr. 17, 1945

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