US 3356179 A
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Dec. 5, 1967 L. L. TOMPKINS 3,356,179
HIGH FIDELITY SPEAKER ENCLOSURE Filed Feb. 17, 1967 2 Sheets-Sheet 1 Leo L. Tompkins 1N VENTOR.
1366- 1967 L. TOMPKINS HIGH FIDELITY SPEAKER ENCLOSURE 2 Sheets-Sheet 2 Filed Feb. 17, 1967 6 i/ 0 a o 7 z/ 2 \3 x 7 2 w 8 1 0 6 P a m a v1 2 0 H. 6 u H T, u \m ww 3 Ma i a v m. 1 (K, F 5 0 H Leo L. Tompkins INVENTOR.
United States Patent Office 3,356,179 HIGH FIDELITY SPEAKER ENCLOSURE Leo L. Tompkins, 127 Wacaster St., Jackson, Miss. 39209 Filed Feb. 17, 1967, Ser. No. 616,857 10 Claims. (Cl. 18131) ABSTRACT OF THE DISCLOSURE A sound reproducing enclosure having a bass reflex chamber rearwardly loading a single, wide range, conetype speaker and an exponential horn forwardly loading the speaker. The bass reflex chamber is ducted to conduct rearwardly radiated sound into the horn through which all sounds are propagated forwardly from a forward opening in the enclosure.
Background the invention bers disposed rearwardly of the speaker. In this manner,
the radiating cone of the speaker is stiffened by the volume of air enclosed rearwardly thereof in order to lower the natural resonance frequency of the speaker-enclosure sys- 'tem.
In order to avoid interference between sounds rearwardly radiated above the resonant frequency of the speaker system with the sounds directly radiated from the front of the speaker, some systems of the bass reflex type have been limited to bass reproduction only by use of a separate speaker for reproduction of sounds above the natural frequency of the bass reflex speaker. In an attempt to avoid such interference, the outlet ports from a bass reflex chamber have been provided with deflecting surfaces peripherally surrounding the opening from which sound is directly radiated from the speaker. This proposed solution is disclosed in Patent No. 3,089,562 to Morgillo and has been found to be somewhat disappointing in results. Thus no satisfactory solution to the interference problem has been made without the use of more than one speaker for extended bassfrequency speaker systems.
Summary of the invention In accordance with the present invention, a bass reflex type of speaker enclosure is modified by porting the rear chamber through a horn forwardly loading the speaker and through which allsounds are radiated forwardly from a front opening of the speaker enclosure. In this manner, more eflicient coupling between the air and sound directly radiated forwardly from this speaker is obtained for mid-range frequencies to more closely match the sound volume with the volume of the sound at the extended bass frequencies since the mass of the air within the horn because of its inertia amplifies and reinforces the pressure waves emerging from the reflex chamber.
Further, since the suppression of speaker movement is 3,356,179 Patented Dec. 5, 1967 are formed in the walls of the horn at different distances from the driven radiating element of the speaker.
The present invention therefore provides a method of coupling a wide range speaker capable of covering the upper end of the usable audio spectrum to the air in such a manner as to allow this same speaker to reproduce the lowest frequency sound with a reduced amount of physical motion. Frequency modulation of high frequency sounds of any noticeable degree is thereby avoided. Because of the use of a single speaker surface, reproduction of sound is accomplished Without phase shift between the various frequency components. This improves the repro duction of percussion in music and human voice.
An additional object of the present invention is to provide a speaker enclosure system which matches speaker movement to the outside air by a low natural resonant frequency arrangement so that the various frequency components of the sound will be reproduced close to the volume ratio associated with the electrical current driving the speaker. Also, by dampening the natural resonance of the speaker with a broadly resonant reflex circuit, large changes in impedance of the speaker coil with frequency particularly in the bass range, is avoided. Distortion due to mismatch is thereby held at a minimum.
Thus, the present invention is limited to speaker enclosures of the bass reflex type wherein sound rearwardly radiated from the speaker is conducted from the reflex chamber through paths terminating at ports formed in the walls and adjacent the inlet end of an exponential horn that forwardly loads the speaker and through which all sound is propagated forwardly from the speaker enclosure. These together with other objects and advantages which will become subsequently apparent reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout, and in which:
Brief description of the drawings FIGURE 1 is a perspective view showing a typical construction of a speaker enclosure in accordance with the principles of the present invention.
FIGURE 2 is a front elevational view of the speaker enclosure shown in FIGURE 1.
FIGURE 3 is a sectional view taken substantially through a plane indicated by section line 33 in FIG- URE 2.
FIGURE 4 is a sectional view taken substantially through a plane indicated by section line 44 in FIG- URE 3.
FIGURE 5 is a sectional view similar to that of FIG- URE 3 but showing a modified form of speaker enclosure.
FIGURE 6 is a sectional view through a speaker enclosure illustrating another form and further arrangement in accordance with the present invention.
Description of the preferred embodiments Referring now to the drawings in detail, FIGURES 1 through 4 illustrate one form of speaker enclosure generally denoted by reference numeral 10 which includes an outer housing formed by a top wall 12, a bottom wall 14, side walls 16, and a back wall 18. The front opening of the housing through which all sounds emerge, may be closed by a mesh material 20 as is customary. It will also be appreciated that the dimensions of the housing and the volumes enclosed therein will be selected pursuant to the principles of the present invention dependent upon the size and rating of its associated single speaker 22.
As shown in FIGURES 2 and 3, the speaker 22 is of a commercially available type having a forwardly diverging, conical radiating element 24 supported by the mounting frame 26 and driven by a coil assembly 28. In the illustrated form of the invention shown in FIGURE 3, the speaker is fixedly mounted within the enclosure by means of a partition wall 30 having a central sound emitting opening 32 through which the conical, radiating element 24 of the speaker is exposed. The wall 30 also encloses within the enclosure, a rear, bass reflex chamber 34 into which sound is radiated rearwardly from the low pressure side of the conical radiating element 24. In order to prevent resonance at undesirable frequencies, sound absorbing material 36 is mounted on the rear wall 18 of the enclosure within the chamber 34.
The central opening 32 in the wall member 30 through which the speaker is exposed, is formed with straight vertical sides 38 conforming to the inlet end of an exponential born 40 formed by a pair of curved vertical walls 42 that are connected to the partition wall 30 and extenL from the opening 32 forwardly to the open end of the enclosure housing constituting the outlet of the horn. All sounds directly radiated fro-m the speaker as well as those which pass through the bass reflex chamber 34, emerge from the horn at the forward open end of the enclosure housing. Thus, the sounds rearwardly radiated into the bass reflex chamber 34 are conducted through passage spaces disposed laterally of the horn and forwardly of the partition wall 30 within which sound absorbing material 44 is placed in the corners in an amount suflicient only to prevent resonance at undesirable frequencies without resisting the flow of sound waves at the bass frequencies.
In the form of the invention illustrated in FIGURES 1 through 4, the volume of the rear bass reflex chamber 34 is maintained at a reduced value by ducting the chamber 34 through the laterally disposed passage spaces between the chamber 34 and the horn 40. Toward this end, a pair of symmetrically disposed deflector elements 46 extend in vertical planes from the vertical partition wall 33) at approximately 45 degrees thereto in order to form a folded duct on either side of the horn, The folded ducts communicate with the reflex chamber 34 through a plurality of distributed outlet openings 48 formed in the partition wall 30 in laterally spaced relation to the central opening 32 so as to establish a plurality of extended paths of different lengths for the travel of sound into the horn 40. Sound from the reflex chamber as shown by the arrows in FIGURE 3, enters the sound passage chamber enclosed by the horn 40 at locations adjacent the inlet end thereof in front of the forward side of the radiating cone 24 through reflex ports 50 formed in the walls 42 of the horn and ports 52 formed alongside of the central opening 32 in the partition wall 30. The ports 50 as shown in FIGURE 2 are distributed at different distances from the inlet of the horn or radiating element 24 to broaden the tuning of the speaker system.
The provision of a plurality of distributed openings 48 prevent propagation of high frequency sounds through the folded ducts as well as to broaden resonance of the bass reflex enclosure without impeding the flow of air at bass frequencies by establishing paths of different lengths for the travel of sound as aforementioned. The loading effect of the horn 40' on the speaker is also increased because of the placement of the ports 50 adjacent the speaker. The bass response of the enclosure will therefore more closely match the resonance curve associated with the speaker in order to achieve more complete balance. Also, tighter coupling is obtained between the speaker and the air particularly during the reproduction of sound at the lower bass frequencies.
FIGURE shows an outer enclosure housing 54 similar to the enclosure housing shown in FIGURES 1 through 4. In this form of the invention, a mounting wall 56 mounts the speaker 58 non-symmetrically within the enclosure so as to form a folded duct on only one lateral side of a forwardly loading horn 60 to correspondingly form a rear bass reflex chamber 62 of larger volume tha'nthatassociated with the speaker system shown in FIGURES 1-4. The hour 60 therefore forms a passage through which all sound is propagated forwardly between the non-symmetrically mounted speaker 58 and a forward opening 64 of the reduced dimension. The horn is provided with reflex ports 66 on only one side thereof in communication with the folded duct established by the deflector wall 68 interconnected between the mounting wall 56 and a front wall 70 in laterally spaced relation to the speaker 58. Distributed openings 72 in the form of the invention illustrated in FIGURE 5, are formed in the duct wall 68 functioning similar to the distributed openings 48 associated with the enclosure shown in FIGURES 14. Except for the lack of symmetry, the reduced ducting and correspondingly enlarged volume of the reflex chamber 62, the speaker enclosure shown in FIGURE 5 operates in a fashion similar to that described in connection with FIGURES 1-4.
In FIGURE 6, the speaker enclosure 74 is volumetrically increased to form a larger bass reflex chamber 76 rearwardly of the speaker 78. The speaker is fixedly mounted in non-symmetrical relation between the side walls of the enclosure housing by an open spider frame 80. The volume of the reflex chamber 76 is enlarged inasmuch as no ducting is utilized in the form of the invention shown in FIGURE 6. Further, in view of the enlargement of the reflex chamber volume, no ducts are necessary. However, both sides of the horn 82 which forwardly loads the speaker are provided with reflex ports 84 as in the case of the horn 40 shown in FIGURES 1-4 so as to obtain the advantages hereinbefore indicated with regard to such reflex ports.
The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly all suitable modifications and equivalents may be resorted to, falling within the scope of the invention as claimed. 3
What is claimed as new is as follows: i
1. In combination with a speaker having a sound radiating element, an enclosure comprising a bass reflex chamber loading one side of said element, a horn having side walls enclosing a forward sound chamber loading the other side of said element through which all sounds are radiated and passage means extending between said bass reflex and forward sound chambers including ports formed in the side walls of the horn adjacent to said other side of the sound radiating element to establish air paths of different lengths between said chambers.
2. The combination of claim 1 wherein said passage means further includes a folded duct establishing fluid communication between said chambers through said ports.
3. The combination of claim 1 wherein said passage means further includes distributed outlet openings in the bass reflex chamber.
4. In combination with a speaker having a sound radiating element and an enclosure having a front opening, means mounting the radiating element within the enclosure spaced from the front opening forming a bass reflex chamber rearwardly of the radiating element, a horn extending forwardly from the radiating element to said front opening radiating all sounds forwardly and having distributed ports formed therein, and passage means extending laterally of the radiating element from the bass reflex chamber to said ports in the horn, said distributed ports being spaced by different distances from the radiating element in the direction in which sound is propagated through the horn.
5. The combination of claim 4 wherein said passage means further includes a deflector connected to the mounting means extending forwardly from the bass reflex chamber in spaced relation to the horn to form a folded duct between the chamber and said ports in the horn.
6. The combination of claim 5 wherein said mounting means includes a partitioning wall mounted internally of the enclosure having a sound emitting opening adjacent an inlet end of the horn, said partitioning wall having a plurality of distributed outlet openings laterally spaced from the radiating element between the bass reflex cham her and the passage means.
7. The combination of claim 4 wherein said mounting means includes a partitioning wall mounted internally of the enclosure having a sound emitting opening adjacent an inlet end of the horn.
8. The combination of claim 6 wherein said passage means includes a deflector connected to the mounting means extending forwardly from the bass reflex chamber in spaced relation to the horn to form a folded duct.
9. The combination of claim 8 wherein said deflector is provided with distributed openings spaced from the radiating element and the horn.
10. The combination of claim 4 wherein said horn is formed by walls enclosing an exponential passage having an inlet extending forwardly from the radiating element, said distributed ports being formed in the walls adjacent to the inlet.
References Cited UNITED STATES PATENTS 1,843,524 2/1932 Stenger 181-31 1,866,921 7/1932 Black 179-115 1,875,171 8/1932 Sprague et a1. 181-31 1,878,018 9/1932 Stephens 18131 2,167,625 9/4939 Albano 181-31 2,801,704 8/1957 Martin 181-31 2,900,040 8/ 1959 Novak 181-31 STEPHEN I. TOMSKY, Primary Examiner.