US2903084A - Speaker assembly - Google Patents

Description

Sept. 8, 1959 H. R. JOHNSON SPEAKER ASSEMBLY 4 Sheets-Sheet 2 Filed June 14, 1956 INVENTOR JOHNSON FI/G. 2

HOWARD R Mm A ORNEY Sept. 8, 1959 H. R. JOHNSON 2,903,084

SPEAKER ASSEMBLY Filed June 14, 1956 4 Sheets-Sheet 3 in m IN VENTOR HOWARD R. JOHNSON A 0' EY fig Sept. 8, 1959 Filed June 14, 1956 OQI OOI

H. R. JOHNSON SPEAKER ASSEMBLY O In m 9. 1 13 1| 1/ A I q: I I I I I WITHOUT TRANSDUCER WITH TRANSDUCER 4 Sheets-Sheet 4 INVENTOR United States Patent SPEAKER ASSEMBLY Howard R. Johnson, Collingswood, NJ. Application June 14, 1956, Serial No. 591,418 4 Claims. 01. 181-31) This invention relates to speakers for radios and particularly, but not exclusively, to high fidelity sets. The principal object of the invention is to provide a speaker assembly requiring considerably less space than is presently thought the minimum and yet to be able to reproduce accurately notes of low tones while extending the range of high notes.

An important object of the invention is to add a transducer in front of a radio speaker, touching or close to the cone, and confining a volume of air between two parallel membranes in the path of sound waves from the speaker, thus greatly smoothing out the curve of the speaker as plotted between decibels and cycles per second. While this object is had with any type of speaker, it is most noticeable in the tweeter range which is extended from about 10,000 cycles per second to 15,000 cycles, the peak of the curve extending just to the zero line and thus eliminating the characteristic crossing and recrossing into positive values that is found in most of the high fidelity tweeter speakers.

A further object of the invention is to apply a drumlike transducer to a speaker having no cone, the voice coil being directly connected with one of the two parallel membrane heads of the transducer, there preferably being a ventilating opening through the magnet so as to transmit rearwardly a certain amount of sound.

A further object of the invention is a method of increasing the purity of tone and the range in cycles of the speaker, which method includes passing the sound waves from a cone to the head of a transducer and back around the speaker frame, passing out through a baifie having a number of rather small openings, the holes preferably being at 90 apart and formed in part by coaxial semi-circles.

At the present time high fidelity sets reproduce with remarkable accuracy the original sounds but to be able to do this the apparatus has to be complicated and, most of all, the speaker cabinet is required to be of huge size, including a tweeter, a woofer, and one or more intermediate speakers. The present invention is concerned with greatly reducing the size of the speaker cabinet by adding in front of the several speakers a dead air space bounded by a pair of spaced membranes preferably, though not necessarily, parallel. When such a transducer is placed in the path of the sound waves from a speaker cone, there is a noticeable change in the sound waves and a definitely increased fidelity, especially with low volume. The present invention permits the use of much greater power without loss of accurate reproduction than can be permitted with present [day apparatus. With a woofer using a transducer as small as a cube eighteen inches on each side overall, the sound may be taken below forty cycles per second, and a sound meter will indicate a very smooth curve extending from the lowest cycle to the highest.

In the drawing:

Figure 1 is a horizontal cross section through a preferred form of the device.

Figure 2 is a front view largely broken away to show the woofer and tweeter in front elevation.

Figure 3 is a central section through the tweeter.

Figure 4 is a chart showing the frequency response curves with and without the transducer.

Figure 5 is a modified form of woofer.

The cabinet is shown as a 16 inch cube, the back 14 and the side panels 15 and 16 being solid pieces of wood, preferably soft pine suitably veneered. The front panel 12 has a central 8 inch circular opening 17 and has four smaller openings 18, preferably spaced near each corner of the front panel 12 and consisting principally of two coaxial semi-circular sides 19 and 20. The front panel, as usual, is entirely covered by the customary grill cloth 21. The case or cabinet 10 is lined at top, bottom, both sides and back with a sheet of open cell vinyl material 27 having a thickness of at least one inch and preferably more. This lining, which is shown as 1 /2 inch thick, fits snugly between the front corner bracing 28 and the rear corner bracing 2.9, the latter being triangular in cross section.

A circular transducer 30 fits snugly in the central space in the cabinet leaving four fairly large corner air spaces 31. The shell 32 of the transducer may be of metal, pasteboard, plastic, or similar material and need be only one eighth of an inch thick. This transducer uses the cone 33 of the speaker as its forward head and there-' fore has only one other head 35 of membrane material, preferably rayon cords imbedded in neoprene. The head 35 is made taut by the tensioning hoop 37 which is moved axially by turning the tension screws 38 threaded into sleeves 39 carried by the transducer shell 32 prefer-.

ably by screws 40 spaced either 60 or apart; The

gaged by hooks 42 carried by brackets 43 in which the screws 38 freely turn. The shell 32 frictionally engages the thick walls of the lining 27 and is therefore securely anchored to the cabinet.

A half inch by one inch closed cell vinyl gasket 44 is positioned between the shell 32 of the transducer and the peripheral edge 45 of the speaker frame 46, usually having a pasteboard annulus 47 secured within its flange. The speaker cone 33 is made fast to the edge 45 in usual fashion and is connected to the voice coil 50 within the magnet 51. The central opening in the magnet casing has the usual fabric cover 52 coaxial with the central opening 17 in the front panel 12 of the cabinet. The vibrations from the cone pass through the closed space bounded by the dust cap 53, the cone 33, the transducer shell 32, and the flat membrane 35 and are returned through the cone and the several openings 55 in the speaker frame and pass out through the fairly large opening 17.

In Figure l the details of the tweeter 59 are omitted for clearness of illustration. It is located in the upper right hand corner of this figure which is a horizontal section. The tweeter is better shown, however, in Figure 2 in its proper location in one of the four corners of the cabinet and is shown in cross section in Figure 3 with a transducer 60 cylindrical in section and of an axial length giving better results where there is ample available space. In Fig. 2 the transducer is of cross-section corresponding to the elliptical shape of the tweeter speaker cone and is between such cone and the front panel, discharging its sound through the small opening 18 immediately in front.

The transducer 60 in each case is quite small, having a tone may be had by moving the cone very slightly away from the head. The tweeter 59 is of standard form and is either circular with 4 /2" diameter or it may carry a 4" :by 6" loud speaker. The transducer for such a tweeter is 6" in diameter and 7" in length.

The chart, Figure 4, has a full line curve 68 showing the frequency response plotted between decibels and cycles per second. It should be noted that this curve runs from 250 cycles to 10,000 cycles and is quite irregular. Curve 69 represents the frequency response with the transducer in place. Here the curve extends quite smoothly from 140 cycles to 15,000 cycles and at no time does this curve pass above the zero line and into the positive values.

In Figure is shown a cross section through a woofer in which the cone has been omitted. The magnet 70 has the usual air passage 71 and the voice coil 72 is connected as by a sleeve 73 of very light weight material to the membrane 74 forming one head of the transducer 75; the other head, which is covered, being 76. The shell of the transducer as in the preferred form is surrounded by a lining of open vinyl material at least an inch thick. There is an air space 77 between the speaker frame 78 and the head 74.

What I claim is:

1. A radio speaker assembly comprising a cabinet having a sheet of open cell vinyl compound at its rear, top, bottom, and both sides of the cabinet, a radio speaker frictionally engaging said sheet so as to be securely anchored to the cabinet thereby and having a cone, a closed cell vinyl gasket engaging the periphery of the speaker cone, and a drum with a membrane facing said cone and forming with the cone and the shell of the drum a dead air space circular in cross-section.

2. A speaker assembly comprising a cabinet having a back, top, bottom, and two sides all lined with -a sheet of open cell vinyl, also a front panel having a central opening; a woofer speaker and a tweeter speaker within the cabinet, each speaker having a cone, a two-headed drum transducer positioned in front of each cone and each forming a dead air space within the cabinet, and means within the side sheets of vinyl for tightening one head of one of the transducers.

3. The speaker assembly of claim 2 in which the shell of the woofer speaker transducer is snugly engaged by the vinyl linings, and a ring gasket engaging one end of said shell, the cone of the woofer speaker, and the lining of the cabinet.

4. A radio speaker assembly comprising a cabinet having a sheet of open cell vinyl compound at its rear, top, bottom, and both sides of the cabinet, a radio speaker frietionally engaging said sheet so as to be securely anchored to the cabinet by said sheet, a cone for the speaker, a two-headed drum transducer firictionally engaging said sheet and having a cylindrical shell of greater axial length than the axial length of the cone, the cone forming one of the two heads of the drum transducer, the other head of the drum being positioned perpendicularly to the axis of the drum, and means for tensioning said other head.

References Cited in the file of this patent OTHER REFERENCES Plastics (publication), vol. XV, Issue 155, pp. 9395, April 1950. (A copy in the Scientific Libraly, US. Patent Oflice.)

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