Sound reproducing combination

Sound reproducing combination

United States Patent [191

Ritter

[11] Patent Number:

[45] Date of Patent:

4,466,505

Aug. 21, 1984

[54] SOUND REPRODUCING COMBINATION

[75] Inventor: David Ritter, Aston, Pa.

[73] Assignee: Temporal Dynamics Research, Inc.,

Aston, Pa.

[21] App]. No.: 369,825

[22] Filed: Apr. 19, 1982

[51] Int. Cl.3 ............................................. .. HOSK 5/00

[52] US. Cl. ................................... .. 181/144; 181/155

[58] Field of Search ............. .. 181/144, 156, 163, 150,

181/199, 155, 166, 172, 145, 146, 147

[56] References Cited

U.S. PATENT DOCUMENTS

2,713,396 7/1955 Tavares ......................... .. l8l/l63 X

3,169,601 2/1965 Smith ..... .. 181/156

3,603,427 9/1971 Sotome .

3,903,989 9/1975 Bauer

4,016,953 4/1977 Butler ..... ..

4,029,170 6/1977 Phillips ........... ..

4,100,992 7/1978 Rehde et a1.

..... .. 181/166

181/144

181/144

181/155

181/166 ducer with novel upper range reproducer. Bass repro ducer is box whose height, width and depth are each between about 15 and about 21 inches, the interior of the box housing a pair of woofer loudspeakers in face to-face relation, their cones being linked together and the speakers being inter-connected so that they are

dynamically driven in oppositely phased relation, the

cone frames having side windows that pass sound gen erated by the cones, the box having on one side an essentially direct mouth permitting the direct radiation of the sound passed by one speaker frame, and the box also having on a different side a baffled outlet for dis charging the sound passed by the other speaker frame through a passive resonator that preferentially passes the lowest frequencies. Upper range reproducer has a loudspeaker cone suspended for vibration in a frame mounted in an essentially closed shallow box the face panel of which extends at least about 7 inches out from the cone for at least 270° of the cone periphery, a tweeter is mounted in the baffle adjacent the mid-range loudspeaker, the shallow box enclosing the back waves of the upper range loudspeaker and of the tweeter and being essentially free of vibratory response to sound frequencies higher than about 200 hertz.

Primary Examiner—L. T. Hix

Assistant Examiner—Brian W. Brown

Attorney, Agent, or Firm—-Connolly and Hutz

[57] ABSTRACT

High ?delity combination of low-bulk bass signal repro 11 Claims, 6 Drawing Figures

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Sheet 1 of4 4,466,505 US. Patent Aug. 21, 1984

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US. Patent Aug. 21, 1984 Sheet 2 of4 4;466,505

US. Patent Aug. 21, 1984 Sheet 3 of4 4,466,505

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U.S. Patent Aug. 21, 1984'

Sheet 4 Of 4

4,466,505

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1

SOUND REPRODUCING COMBINATION

2 tween about 15 and about 21 inches, the interior of the box housing a pair of woofer loudspeakers correspond

The present invention relates to sound reproducers,

more particularly sound reproducers using loudspeak

ing to each other in size, each having a dynamically driven speaker cone held by the face of a supporting frame, the frame faces being clamped to each other in ers or speakers in radio and recorder sound outputs.

Among the objects of the present invention is the

face-to-face relation, the cones being linked together

and the speakers being interconnected so that they are provision of novel sound reproducers that are very effective in faithfully reproducing the desired sounds.

Additional objects of the present invention include

high quality sound reproducer constructions that are‘

relatively small in size.

dynamically driven in oppositely phased relation, the

cone frames having side windows that pass sound gen erated by the cones, the box having on one side an essentially direct mouth permitting the direct radiation

The foregoing as well as still further objects of the particularly true of stereo systems, where two separate sound reproducing systems are used to separately repro

60 of the sound passed by one speaker frame, and the box also having on a different side a baffled outlet for dis present invention will be more fully demonstrated in the following description of several of its exempli?cations,

reference being made to the accompanying drawings

wherein:

FIG. 1 is a vertical sectional view, with parts broken away, of a woofer type sound reproducer according to the present invention; '

FIG. 2 is an isometric view, with parts broken away,

20 charging the sound passed by the other speaker frame through a passive resonator that preferentially passes the lowest frequencies. The box preferably contains a

partition that effectively separates the sounds passed by

the respective speaker frames. To provide the best transmission for the very lowest frequencies, the dia phragm should be at least as wide as the wider speaker frame, and be weighted to furnish optimized control for of the sound reproducer of FIG. 1 as it is arranged for operation; the interaction between the speakers and the air con

?ned within the box.

FIG. 3 is an isometric view of a sound reproducer of the present invention used to reproduce sounds having

25 frequencies higher than that of a woofer, parts being

To reduce the bulk of the sound reproducer for

higher frequencies and improve their spacial distribu

broken away for clarity; tion, a separate mid-range loudspeaker has a cone sus pended for vibration in a frame about 4% inches in

FIG. 4 is a plan view of the loudspeaker of FIG. 3 with its face board removed; diameter and about 2 inches deep, the frame is mounted in an essentially closed box not more than about 2

FIG. 5 is a schematic diagram of a circuit of the

30 present invention for supplying to the sound reproduc inches deep, the face panel of which extends at least about 7 inches out from the cone for at least 270° of the ers of FIGS. 1 and 3 the electric signals to be repro

duced;

FIG. 6 is an isometric view of a particularly desirable cone periphery, the frame mounting being about one to about 3 inches away from the center of that face panel, combination of the sound reproducers of FIGS. 1 and 3.

35 a tweeter is mounted in the baffle adjacent the mid range loudspeaker, the box enclosing the back waves of

The sound reproducer combination of the present invention is of the so-called high ?delity type intended to faithfully reproduce sounds in the usual type of living the loudspeaker and of the tweeter and being essen tially free of vibratory response to sound frequencies higher than about 200 hertz. The small size of these room of a home. Such a room is generally at least about

12 feet by 18 feet in floor size and about 8 feet high, and

40 drivers relative to the wavelengths to be reproduced results in much improved spatial response. the floor is frequently covered by a rug. The sounds to be reproduced are generally those from the electrical

Turning now to the drawings, FIGS. 1 and 2 show a sound reproducer 10 for woofer frequencies. This re output of a radio, record player or tape recorder or the producer consists of a box 12 having a ?oor panel 14 like, and have a range of frequencies from as ‘low as about 20 hertz to as high as about 16 kilohertz.

45

Faithful response of a speaker calls for reproduction and four upright walls 16, 18, 20 and 22 on which walls a top panel 24 is secured. Walls 16 and 18 connect oppo site edges of the ?oor and top panels, but wall 20 is of all audible frequencies at the correct amplitude, as well as accurate reproduction of rise and decay times recessed in the box to provide an open outer chamber

26. for all such signals, and spacial distribution of the repro

Top panel 24 is in one direction a litter larger than duced sound in a manner closely corresponding to that

50 of the original sounds.

Loudspeakers or speakers have long been used as sound reproducers, different kinds being adapted to

?oor panel 14, and thus provides a short overhang 28.

Wall 22 is secured in upright position with respect to the corresponding edge 30 of the ?oor panel, and an extra outer wall 32 is mounted in spaced relation to wall

22 by being secured to the edge 34 of overhang 28 as reproduce the different frequencies. While the art has developed relatively inexpensive ampli?ers that do a

55

very good job of providing the electrical signals for high quality sound, the necessary speaker systems have

generally been quite expensive as well as bulky. This is well as to side walls 16, 18.

The foregoing combination provides an enclosed central chamber 36, and a separate open-bottomed sound-directing chamber 38 with a sound-discharging mouth 40 at its bottom. Box 10 is supported by a short hollow pedestal frame 42 secured to the lower face of duce a pair of stereo sounds. Even these expensive and

bulky systems generally fail to ‘faithfully reproduce

?oor panel 14 and recessed from all its side faces.

Wall 20 has a large circular cut-out 44 into which is sound in the comprehensive sense discussed above.

?tted a mated pair of loudspeakers 51, 52. Each of these

The bulkiest portion of such systems is the woofer,

which is supposed to reproduce sounds having frequen

cies below about 200 to 300 hertz. According to the speakers has a mounting frame 54 with an out-turned flange 56 to which is cemented the usual annular mount ing pad 58 and resilient ring that resiliently holds the present invention a woofer sound generating apparatus has a box whose height, width and depth are each be outer edge of a speaker cone 62. Flange 56 merges into a generally cylindrical section 64 of the frame, and this

4,466,505

3 section 64 of speaker 52 is shown as ?tted into cut-out

4

A very effective woofer unit 10 has its height, width and depth, without pedestal 42, each about 18% inches well as aligned mounting holes in ?anges 56 to secure measured on its exterior surfaces, with speakers 51, 52 the speakers in place face-to-face, with the help of nuts

68.

Speaker frames 54 are preferably of metal and have identical to each other, both having l0 inch frames, a total Q (QT) of about 0.4 and a resonant frequency below 30 hertz. The walls of the box structure should be large windows 70 to expose the outside of their cones to the ambient air. In addition cone 62 of speaker 52 has a rigid enough so that they are not vibrated by the sounds generated at the speakers, and preferably made of parti number of spaced openings 72 punched out of its side. cle board at least about 2 inch thick.

These openings can have a circular, rectangular, oval, or any other general outline and can be from about %

Co-acting with the foregoing speakers, vibratory

diaphragm panel 88 is preferably a disc about 11 inches inch to about 1% inches in width. Also the small ends 74 of both cones are linked together by a light-weight tube in diameter, and chamber 38 about 1% inches thick. A pedestal 42 also about 1% inches thick is enough for use

80 of paper for example, extending between and ce on floors covered with deep-pile rugs. mented to those ends. The ends of tube 80 can be just

The top as well as sides of box 10 can be covered, as large enough in diameter to ?t snugly around or inside with cushiony material, and whether or not so covered the'end of the voice coil form 82 to which the cone is is strong enough to serve as a rugged table top, and can secured.

Wall 22 has a cut~out opening 84 even larger than opening 44. Across this opening is cemented a resilient

20 be sat on or stood on by even heavy people without damage. The completely equipped box can weigh as supporting ring 86 that holds a diaphragm panel 88 so wires 98 can enter chamber 26 via a hole drilled in ?oor that it vibrates when very low frequency sounds im

14. Where crossover or compensation circuits are used, pinge on it. The diaphragm panel 88 is preferably of their components can be mounted on the ?oor of cham such mass as to signi?cantly reduce the travel of the ber 26, and an additional hole through wall 20 permits speaker cones at the lowest frequencies. A disc of

25 running leads to the inner speaker 52. pressed wood weighing at least about % gram per square

' FIGS. 3 and 4 illustrate a sound reproducing combi centimeter of area that it spans, is a very effective dia nation in the general form of a shallow box 110. The box

phragm when resiliently mounted at its edges.

has a facing panel 112, a rear panel 114, and a set of

The open face 90 of chamber 26 can be covered by speaker grill cloth 92 which can be secured in lace by its

30 inner spacers 121, 122, 123, 124, 125, 126, 127, 128 and edges. If desired face 90 may remain uncovered in use.

129, and outer spacers 131, 132, 133 and 134 sandwiched

Velcro~type fastener strips 94 can be cemented to the between the panels. A pocket 140 is routed out of the corners of the mouth, preferably over wedges 96 ce inner surface of the rear panel to receive the rear por mented just inside those corners, and mating strips tion of a mid-range speaker 142. As shown by the nar sewed to the inner face of the grill cloth at its corners. 35 row peripheral margin 144, the outer spacers 131, 132,

If desired two-faced pressure-sensitive tape can be used

133 and 134 have their outer edges recessed inwardly instead of the velcro-type fasteners. from the outer edges of the rear panel.

Mouth 40 faces downwardly and is close to the sur

Speaker 142 is mounted inside an opening in the face face on which box 10 is placed, so that this mouth needs no cover. Grill cloth 92 need not be very strong, inas much as it does not serve as signi?cant protection for

’ panel 112, and has a frame with a peripheral ?ange 145

40 that is screwed or bolted to the outer face of that panel.

The overall depth of the speaker is about two inches so the delicate speaker cones. that the panels and the spacers can each conveniently be

Such a speaker combination reduces the volume from about 3 to about if inch thick pieces of particle equivalent compliance of the combination so that en board to provide a speaker-accommodating pocket 140 closed chamber 36 may be optimally reduced to half the

45 otherwise required volume. Also, in a stero system the that does not penetrate completely through the rear panel. bass frequenceis may be added together mechanically by application of right and left low frequency signals to the terminals of speakers 51 and 52 respectively with the phasing connection to 51 reversed relative to 52.

This maintains complete electrical isolation between channels. The push-pull symmetric nature of the combi nation signi?cantly reduces asymmetric cone motion in face panel 112 near mid-range speaker 142. Inasmuch as tweeter speakers are quite shallow in overall depth, no pocket is needed in rear panel 114 to accommodate speaker 150. The hollow interior of box 110 provides between the spacers, ample room for locating crossover and therefore reduces asymmetric distortion in a man ner similar to the reduction achieved by push-pull type

55

electronic ampli?ers.

With cones so coupled such that no motion of a single and/or compensation circuits, such as is shown in FIG.

4 by the circuit components 152, 154, 156, 158, 160 and

162. There are appropriately wired together, to the leads of the speakers, and to incoming terminals 164 that are bolted through the rear panel. The components can cone relative to the other is possible, and with one cone vented to the chamber in the box, the possiblity of reso also be ?xed in position as by cementing or clamping them in place. nances in the frequency range from 200 to 1000 hertz is eliminated. Prior art con?gurations with face-to-face

Before completing the assembly of the structures, a caulking or similarly soft ?ller material is placed in drivers and a sealed inner air volume between cones as the coupling medium, as in US. Pat. No. 4,016,953, present resonance problems in this range. pocket 140, so that the rear of speaker 142 presses against such soft ?ller and thus supports and strengthens the relatively thin wall at the bottom of the pocket, and

The cones need not be identical to each other and

65 keeps it from vibrating in resonance to the sounds gen need not be driven by identical drivers, but identical speaker constructions are less expensive to manufac erated by the speakers. The remainder of the panels, and the spacers, are too thick for such vibration, and need ture. no further attention in this respect.

5

4,466,505

The combination of FIGS. 3 and 4 does an extremely

good job of reproducing sound frequencies above about

200 Hertz, with a mid-range speaker having a frame no

6 delivered by an ampli?er having a stereo output each channel of which has an eight ohm output impedance.

A terminal board 200 which can be mounted in the larger than 4% inches, a cone that resonates at about 70

Hertz, and a QTof from about 0.5 to about 1, where the face of the box extends laterally at least about seven woofer box 10, has a series of eight external connector terminals 211, 212, 213, 214, 215, 216, 217 and 218, and a companion series of eight internal connector terminals inches from the cone of speaker 142, for about three fourths of the cone perimeter. For the remaining one best results are obtained where the cone of speaker 142 is made of paper and‘ the resilient surround is cloth rather than foam. I

The circuit diagram of FIG. 5 illustrates a very desir

221, 222, 223, 224, 225, 226, 227 and 228, each of which is conductively linked to its companion terminal. Leads fourth of the cone periphery, that face extends out at least 4 inches from the cone. This is accomplished by. from the left stereo channel are connected to terminals

213, and 214, which leads from the right stereo channel dimensioning the face panel so that it is about 18 inches by 18 inches or slightly smaller, and having speaker 142 are connected to terminals 215 and 216. The phasing of the leads is shown by the plus and minus marks. offset about two inches from the center of that panel.

Conductor 230 connects terminals 223 to conductor rear panel 114, so that the box can be readily hung on a wall that is provided with a conventional picture book.

232 which runs from terminal 221 to the minus terminal of speaker 52. Conductor 234 connects one terminal of bipolar electrolytic cross-over capacitor 236 to board

Hanging the box in this way so that its tweeter is about terminal 222, while conductor 238 connects the other terminal of capacitor 236 to board terminal 224. Also four to ?ve feet up from the ?oor, is preferred. The box is so thin and blocks all sound directed backwardly from its speakers, so that when so hung the sound prop connected to conductor 238 is one terminal of cross over inductor 240, the other terminal of which ties through conductor 242 to the plus terminal of speaker agated forwardly behaves very much like that from a speaker in a planar baffle of in?nite size.

The front face of box 110 is shown in FIG. 3 as pla

52. A very effective crossover frequency of about 200

Hertz is provided by a capacitor 236 of 100 microfarads, and an inductor 240 of 6.8 millihenrys having a maxi nar, but if desired that face can be made frusto conical mum of about 0.5 ohm resistance, where speaker 52 has with speaker 142 at the frustrum. The thickness of the box can then taper down from a maximum of about two a voice coil of 7 to 8 ohm impedance. As a matter of precaution capacitor 236 can have a 100 volt operating inches at speaker 142 to a thickness of as little as a half inch or so at the box periphery. Such a tapered con struction may be more conveniently made in the form of potential, in which case it is preferably a non-polarized electrolytic capacitor or a parallel pair of SO-microfarad

100-volt non-polarized electrolytics.

a disc, as in FIG. SI of US. Pat. No. 3,964,571 so that the box has a generally circular outline. Box 110 can

Between conductors 232 and 242, there is connected also be made with a circular outline and without the tapered thickness. . a compensation network consisting of a series-con nected resistor 244 and capacitor 246, along with a bridging capacitor 248. With a speaker 52 having the

In FIG. 3, box 110 is shown as having its face covered

- with grill cloth 165 that is stretched‘ over a marginal stand-off frame of quarter-round rods 166. The margins foregoing impedance, a very effective value for resistor

244 is 7.5 ohms, while capacitor 246 is 50 microfarads and capacitor 248 33 microfarads. These two capacitors of the grill cloth are secured as by stapling to the ex posed faces of outer spacers 131, 132, 133 and 134, and the secured edges covered by trim strips 168 that span need not be rated for operation at voltages greater than about 50 volts.

The combination of resistor 244 and capacitor 246 across the outer edges of the rear panel as well as of the foregoing spacers. Using a grill cloth that has a stretch weave enables it to be more readily and neatly stretched provides a high pass electrical impedance whose time constant is computed to match the time constant of the over and around corners.

For best results with the mid-range speaker, it is treated to spot stiffen the resilient ring 170 that resil iently holds the outer margin of its cone 172. During

45 electrically inductive and resistive components of the voice coil in speaker 52. This provides a desirable con stant load for crossover elements consisting of capacitor

236 and inductor 240 and greatly enhances their opera tion. operation there is a tendency for local resonances to cause ringing instead of abrupt sound decay, and thus distort the'generated sound. Applying adhesive dabs

Where speaker 51 has about the same voice coil impe dance as speaker 52, its crossover and compensation network components 256, 260, 264, 266 and 268 and

173 about i inch in diameter about 1 inch apart on the resilient ring 170 where it is cemented to the cone, signi?cantly reduces this type of distortion. Any adhe sive can be used, even those like rubber cement that leave a resilient deposit. A heavy deposit of resilient wiring 252, 254, 258 and 262 can be exactly the same as the corresponding parts for speaker 52. However the conductors 252, 262 are connected in opposite phase with respect to the terminals of speaker 51.

FIG. 5 also shows a very desirable crossover and rubber on a spot of the ring very effectively reduces the resiliency of that spot as compared to the remainder of the resilient ring. The dabs can vary in width from about i to about % inch, and can if desired be placed as much as two inches apart although such spacing might compensation network for a set of speakers 142, 150 that reproduce the higher frequency sounds in one of the stereo channels. The other stereo channel can be identi cally treated. For the illustrated network, conductor

270 ties minus terminal 217 directly to the minus termi

not always provide the desired damping. In general the

nal of speaker 142 as well as to the plus terminal of speaker 150. Conductor 272 leads from plus terminal

218 through conductor 274 and inductor 276 to the plus terminal of speaker 142. Conductor 272 also connects through capacitor 278 to the minus terminal of speaker able cross-over and compensation network that coacts with the various speakers of FIGS. 1 and 3 to produce

excellent sound‘ reproduction from electrical signals

150. Across the terminals of speaker 142 is bridged a series-connected capacitor 280 and resistor 282, while bridged across the terminals of speaker 150 is a series

4,466,505 connected inductor 284 and capacitor 286. Series con

8 that opening. The lower portion of upright 302 is rod nected capacitor 280 and resistor 282 perform the same compensation function for mid-range speaker 142 as resistor 244 and capacitor 246 provide for woofer speaker 52. Series connected inductor 284 and capacitor

286 compensate for the fundamental resonance of speaker 150. Compensation of a tweeter with such a series connected bridge has been found to give particu larly good square wave response in a microphone, as

5 shaped as at 304 and is seated in a socket 306 secured to

?oor panel 14. The upper portion of the upright is shaped like a board 308 having the height and width of a speaker box 110. Two such boxes are hung, one each on‘the respective faces‘of board 308, as by recessed hooks. Opening 300 can be made so tight ?tting with respect to rod 304 as to keep the upright from rotating in its socket unless forcefully moved. well as improved sound reproduction. '

Placing box 10 so that its mouth 90 faces a wall of a

With the voice coil of speaker 142 of about 7.5 ohms impedance, and that of speaker 150 of about 6.8 ohms ‘ room and is at least about 6 inches, preferably 8 to 12

inches, from that wall, then permits adjustment of the

impedance, a four-microfarad capacitor 278 and a 0.37 upright so that its upper portion does not obstruct any millihenry inductor 276 wound from 18 gauge copper wire provide a desirable crossover at about 4500 hertz.

As diagrammatically indicated, capacitor 278 need not be a non-polarized electrolytic; is is preferably a polyes desired view or interface with movement around it.

Another pair of back-to-back boxes 110 can then be provided on a different support to complete the stereo ter ?lm capacitor. The compensation network for inasmuch as no signi?cant stereo perception is obtained speaker 142 desirably has its capacitor 280 of 10 micro from the bass sounds. Thus arranged, performance even farads rated for 50 volt operation and its resistor 282 a

20 better than that of the wall mounted unit is achieved.

7.5 ohm 10 watt resistor. Speaker 150 has its leads in

The output of the rear speaker of such a back-to-back verted and in addition its compensating network in pair behaves like a re?ection from the front speaker cludes a capacitor 286, preferably a 20 microfarad 50 volt capacitor, in series with inductor 284 preferably a

' vides a response similar to that of the wall-mounted

1.8 millihenry 5.6 ohm inductor. This compensation is particularly suitable where the tweeter is mechanically

25 when the front speaker is hung on a wall and so pro

unit, but the back-to-back pair yields signi?cantly

greater reverberant sound adding a desirable increase in resonant at about 900 hertz, and has a soft dome con

_ perceived depth and imaging. . ' struction, a 9-ounce magnet, and an'aluminum coil bob

Where a bass box 10 is in. contact with upper range bin. Capacitor 286 and inductor 284 should resonate at the mechanical resonance frequency or within or about

30 box 110,'the running of the wires to the boxes is some what simpli?ed. Thus in FIG. 6 the leads to boxes 110 plus or minus 10% of that frequency, and the resistance can run down a groove in the face of the upright rod of the compensation circuit can if desired be further

.304, or can run through a passageway drilled through selected to provide minimum ringing. Such selection "is that rod, and thus be directly connected to a supply best made by trial and error measurements, using differ network that can be mounted in box 10. ent capacitance and inductance values that maintain the

35 foregoing electrical resonance. ‘

Obviously many modifications and variations of the

present invention are possible in the light of the above

The quality of the sound reproduction of the present teachings. It is therefore‘to be understood that within invention is even further improved when instead of the scope of the appended claims the invention may be having one FIG. 3 box per stereo channel with that box practiced otherwise than as speci?cally described. mounted on the wall of a room, two such boxes‘ are 40

What is claimed: " > mounted back-to-back spaced from‘a wall. Thus a sim

1. A woofer sound generating apparatus for deliver ple stand can be provided with a thin upright holding ing sounds having frequencies down to below 30 hertz, hooks at the desired height on its opposite faces, and said apparatus having a box whose height, width and separate boxes mounted on the respective hooks. Both depth are each between about l5'and 21 inches, the such boxes should then have the voice coils of their

45

‘interior of the box housing a‘pair of woofer loudspeak corresponding speakers connected to receive the elec ers corresponding to each other in size, each having a trical signals for the same stereo channel, but the cross over network 256, 260 having its values modi?ed to dynamically driven speaker cone held by the face of a

supporting frame, the frame faces being clamped to

allow for the extra speakers. Where the speakers added for the doubling are identical with the single set of

50 each other in face-to-face relation, the cones being me

chanically linked together and the speakers being inter

speakers, it is enough to merely double the capacitance connected so that they are dynamically driven in oppo of crossover capacitor 256. Crossover networks can sitely phased relation, the cone frames having side win also be built into the outputs of ampli?ers, if desired. dows that pass sound generated by the cones, the

Alternatively when doubled boxes are used, their speaker frames being mounted so that the cone of one speakers can have voice coils with twice the impedance frame radiates sound directly out one side of the box, of that for a box when used alone. No changes are then and the box also having on a different side a baffled needed in the crossover network. outlet containing a passive resonator that preferentially

The foregoing box doubling can be effected with passes the lowest frequencies to an outer vertically either channel alone, or with both channels, and the doubled boxes for any channel can have their outputs in

60 directed duct open at its bottom to discharge said low

est frequencies downwardly.

on the top panel 24 of the woofer box 10, or the individ ual boxes of the pair mounted on adjacent side panels of

2. The combination of claim 1 in which the box con

'‘tains' a partition that effectively separates the sounds

passed by the respective speaker frames.

the woofer box.

FIG. 6 diagrammatically illustrates a very desirable

65 speaker combination according to the present inven

3. A woofer for receiving electrical signals and con verting them to sounds, said woofer having a closed chamber with a volume of from about 2400 to about tion. Here a bass box 10 has an opening 300 in its upper panel 24, and a paddle-shaped upright 302 is ?tted into

5000 cubic inches, one wall of the chamber having an aperture which is ?lled by a sound generator having

4,466,505

Ill electrically driven cone elements that generate sounds being about one to about 3 inches away from the center which have a frequency not over about 200 hertz, a different wall of the chamber having an opening cov of that face panel, a tweeter is mounted in the face panel

adjacent the mid-range loudspeaker, the box enclosing

ered by a passive resonator panel at least as wide as the opening for the sound generator, the chamber volume being matched to the effective volume compliance of the cone elements for accentuating the lowest sound frequencies generated by the speakers, the resonator

panel being weighted to preferentially respond to those

5 the back waves of the loudspeaker and of the tweeter and being essentially free of vibratory response to sound

frequencies higher than about 200 hertz.

8. The combination of claim 7 in which the face panel is at least about 5 inch thick, and the box has a rear panel as well as a set of rigidifying spacers between the panels, lowest sound frequencies and trasmit those lowest fre

the panels being rigidly secured together sandwiched

quencies to a baffled sound outlet duct open at its bot- tom to discharge the lowest frequencies downwardly.

4. The combination of claim 2 in which the sound about the spacers to help prevent the vibratory re spouse. generator has two woofer speaker cones mounted face to-face, the small ends of the cones being mechanically

9. The combination of claim 7 in which the suspen sion of the cone in its frame includes a resilient ring as connected to each other to cause both cones to vibrate as a unit. the only connection between the frame and the outer edge of the cone, and spaced dabs of stiffening material about 5 to about % inch in size are applied to the ring to

5. The combination of claim 4 in which each speaker cone is heldin a 10-inch frame and the sound generator locally reduce its resilience and reduce the tendency for ringing at the operating frequencies of that cone. has a low sonic resonance below about 30 hertz. '

6. A woofer sound generating apparatus having an enclosure containing a pair of woofer loudspeakers corresponding to each other in size, each with a dynam ically driven speaker cone held by the face of a support ing frame, the frame faces being clamped to each other

25 in face-to-face relation, the cones being mechanically linked together so that they vibrate as a unit, the speak ers being interconnected so that they are dynamically

10. The combination of claim 1 in which the box contains a support for an upright, a paddle-shaped up right has its handle portion positioned in said support, and a pair of sound reproducers are secured to the op posite faces of the paddle portion of the upright to face outwardly, each of said pair including a mid-range loud speaker having a cone suspended for vibration in a frame about 4% inches in diameter and about 2 inches driven in oppositely phased relation, the cone frames having side windows that pass sound generated by the deep, the frame is mounted in the face panel of an essen tially closed box not more than about 2 inches deep, the cones, and one of the cones having a number of cut-outs face panel extending at least about 7 inches out from the that open into the interior of the enclosure and establish cone for at least 270° of the cone periphery, the frame communication between the air in the enclosure and the air between the speaker cones. mounting being about one to about 3 inches away from the center of that face panel, a tweeter is mounted in the

7. In a sound reproducer for faithfully reproducing

35

sound from electric signals having frequencies higher

face panel adjacent the mid-range loudspeaker, the last

mentioned box enclosing the back waves of the last than about 200 hertz, a mid-range loudspeaker having a mentioned loudspeaker and of the tweeter and being cone suspended for vibration in a frame about 4% inches essentially free of vibratory response to sound frequen in diameter and about 2 inches deep, the frame is cies higher than about 200 hertz. mounted in the face panel of an essentially closed box

40 not more than about 2 inches deep, the face panel ex tending at least about 7 inches out from the cone for at

11. The combination of claim 1 in which the outer duct is a shallow duct about as wide and about as high as the box. least 270° of the cone periphery, the frame mounting

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