US1964977A - Condenser speaker - Google Patents

Description

Emy 3, 1934. p E EDELMAN 1,964,977.A

CONDENSER SPEAKER .Y Filed June 3, 1929 3 Sheets-Sheet l j@ f5 j# 4,

3 Sheets-Sheet 2 July 3, 1934. P, E. EDELMAN CONDENSER SPEAKER Filed June 3. 1929 my 9, 1994. R E, EBELMAN 1,964,977

CONDENS ER SPEAKER Filed June 3, 1929 5 Sheets-Sheet 3 Fatented July 1i, 1934 NETES TATES PATENT GFFCE CONDENSER SPEAKER Chicago, Ill.

Appiication .lune 3, 1929, Serial No. 368,157

4 Claims.

rIlois invention relates to improvements in condenser speakers and the method of making and using the sa -e. An object of the invention is to 'provide an iinproved structure for the speaker apparatus, and for operating the saine with more perfect reproduction than has heretofore been possible in this type of device.

This and other objects are accomplished by this invention, which is fully described in the following specification and shown in the accompanying Idrawings, in which- F'igure l is a diagram showing suitable circuit connections for the condenser speaker;

Fig. 2 is a rear elevation of a suitable mounting frame for the acoustic condenser;

Fig. 8 is a front elevation of a portion of the frame of Fig. 2;

Fig. 4 is a sectional view of a part of the condenser assembly showing the relation of the operating parts;

Fig. 5 is a sectional View of a portion of the dielectric diaphragm and its conductiveI coating;

Fig. 6 is a sectional View of a suitable structure "for the flexible electrode diaphragm of the condenser;

Eig. 7 is a section showing part of the condenser diaphragms in a modified structure suit- 'able for use on a collapsible mounting frame;

Fig. 8 is a rear elevation showing a collapsible frame mounting for the condenser structure of Fig. 7;

Fig. 9 is a diagram showing the use or" a plurality of acoustic condensers according to my in- Ivention;

Fig. 10 is a side View, partly cut away and seetic-ned showing a suitable assembly for a plurality of acoustic condensers connected as in Fig. 9; and

Fig. 11 is a diagram showing a circuit for the co-operative use of my acoustic condenser together with an electrodynainic type reproducer.

1n Fig. 1, the acoustic condenser l consists of two operative diaphragms, of which diaphragm 2 'is a porous electrode permeable to air flow and flexible, while diaphragm 3 is impermeable to air iiow, flexible, and carries a conductive coating or electrode 4. Condenser 1 is supplied with operating potential from the output transformer 5 of a vacuum tube amplifier 11, 12 of customary push-pull design, having an input circuit 18 which may be connected to a radio set or a talking niotion picture apparatus. The vacuum tubes 11, 12 are supplied with energy by a power unit 10 operated through a plug 9 in usual manner. A condenser 6 in series with speaker 1 is supplied with (Cl. Mii-111) polarizing potential at about 400 lVolts by polarizer power unit 7 operated through plug connector 8.

As shown in Fig. 2 and. Fig. 3, the condenser 1 is supported on a wooden frame 14 having a rim 50 lining l5 of rubber material. The soft rubber strips 15 tend to assist in cushioning the con denser 1 and in maintaining same taut in use. Wedges 16 permit frame 14 to be expanded to initially stretch frame 14 to make condenser 1 taut, and may be held in place by glue. Rubber strips 15 may be cemented to frame 14.

As shown in Fig. 4, a minute air gap 17 separates flexible porous electrode diaphragm 2 from dielectric diaphragm 3. A Contact strip 18 of soft lead connects to electrode coating 4 carried on diaphragm 3. Diaphragm 8 is preferably made from empire cloth, varnished with japan goid size and coating with metal foil 4. A soft flexible lead ribbon 19 is fastened to contact strip 18 and reinforced by tinsel ribbon connector 20 to bring a terminal from electrode 4 to lug terminal 23 carried on frame 14 by tacks 21. A varnished silk insulator strip 22 insulates strips 19 and from tacks 21 which hold dielectric diaphragm 3 and flexible electrode 2 to frame 14. A terminal 24 is fastened at 25 to flexible diaphragrn velectrode 2, and fastened to frame 14 by a tack 21. Mucilage containing lamp black or aluminum bronze, or black lead powder is suitable for fastening strips 20, 19, 18 respectively to electrode 4. A small amount of conducting powder in the mucilage is sufficient for the pur- 13.05,

Another mode of using the conductive mucilage aforesaid is shown in Fig. 5. The flexible porous electrode 2 is made from tinsel metal cloth, to which cross connector soft lead foil strips 27 are glued by conductive mucilage 28 in order to join the tinsel strands of cloth 26 together electrically.

An alternative mode of making the flexible electrode diaphragm 2 is shown in Fig. 6, in which two pieces of tinsel metal cloth 29, are fastened together by conductive mucilage 28, the width of cloth 29 being crosswise to the length of the cloth 30 in order to increase the strength thereof in all directions of tension, and in order further to electrically connect the individual tinsel strands of said cloths/"29, 30. I prefer to have cloth 80 of coarser weave tliana cloth 29, and made with wider tinsel strands in order to secure greater push on the air when diaphragm 2 is flexed in operation.

As shown in Fig. 7, the condenser 1 may be made flexible for portable shipment by the addition of porous fabric cloth pieces 31 and 32 stitched thereto at the rim thereof by threads 33. Cross lead foil strips 18 electrically join the individual tinsel strands of tinsel cloth 26, as aforesaid.

As shown in Fig. 8, the flexible roll condenser assembly of Fig.. '7 may be unrolled and stretched on a collapsible frame 34 having a center support 35 and adjusting members 36 to stretch or expand frame 34, so that end pieces 37 of frame 34 stretch condenser 1, as shown for operation.

In Fig. 9, a circuit is shown for using a plurality of co-operating condenser speakers as aforesaid, whereby different sized condenser speakers 38, 39, respectively more predominantly responsive to varying pitch sounds can be selectively connected in correct proportion for most pleasing reproducing through terminals 44, by means of adjusting resistance 41 having variable terminals 42 and 43 to proportion the volume of response from each speaker unit 39 and 40 with respect to the largest acoustic condenser 38 of the assembly. A variable choke coil may also be used for member 4l, if desired.

As shown in Fig. l0, the condensers 38, 39 and 40 are mounted in an open frame 49 provided with air holes 52 and porous fabric coverings 51 and 50. Frame 52 holds condenser speaker 38 through bracket supports 46. Frame 52 holds condenser 39 through brackets 47. Frame 52 holds acoustic condenser 40 through brackets 48. A distance of at least two inches separates the condensers 38, 39, 40 from each other to allow free passage of sound waves therefrom. This permits the grouping of regulated volume of controlled pitch responding condensers in co-operative group mounting in small space suitable for mounting at the rear of talking motion picture screens or in a radio cabinet, as desired.

In Fig. 11, I show how to combine my acoustic condenser reproducer with a dynamic speaker already in use to supplement same with brilliant overtones missed on the dynamic speaker. A vacuum tube amplifier 53 has an input 54 connected to a phonograph electrical pick-up device or a radio set output. Vacuum tube ampliner 53 feeds a coil 55 which serves as the field coil of dynamic speaker 58, as well as the primary of transformer 56 which feeds output energy to the dynamic reproducers moving coil 59 controlled by resistance 57 to proportion the volume with respect to the volume of response of acoustic condenser 1. Power unit 10 and polarizer power unit 7 supply operating energy in customary manner when energized through connector plug 9n attached to a source of operating current.

Acoustic condenser 1 receives its audio inputpotential from the terminals of coil 55, that is to say, directly from the plate to filament circuit of amplifier vacuum tube 53. The co-operative assembly of Fig. 1-1 affords very pleasing results in that the relative volumes of response in high and low pitch frequencies can be regulated by resistance 57.. v

It may be remarked that both diaphragms 2 and 3 of condenser 1 function co-operatively and simultaneously with unusually efcient and brilliant response to pure tones and accompanying overtones.-

While I- have shown and described but a few embodiments of my invention, it is to be understood that it is capable of many modifications. Changes, therefore, in the construction may' be made which do not depart from the spirit and scope of the invention as disclosed in the appended claims.

I claim:

l. In an acoustic condenser employing a stretched metal fabric, the improvement which comprises making the fabric in two separate sheets of thin tinsel cloth one of which is woven i with wider tinsel strands than the other, and disposing one of said tinsel cloth sheets crosswise with respect to the lengthwise tinsel strands of the other sheet, whereby the combined two cloth sheets are strengthened and electrically connect separated tinsel strands of each other.

2. An acoustic reproducer combination comprising a vacuum tube amplifier, a dynamic speaker connected thereto and having a trans` former, a power unit to energize said amplifier and dynamic speaker, and a condenser speaker connected to said vacuum tube amplifier and said dynamic speaker, characterized by the fact that the transformer of said dynamic speaker serves as a choke coil for said amplifier output, and as an audio potential feeder to operate said condenser speaker.

3. An acoustic reproducer combination comprising a vacuum tube amplifier, a dynamic speaker having a transformer, a condenser speaker connected in parallel with the transformer, and means for polarizing the condenser speaker.

4. An acoustic reproducer combination comprising a vacuum tube amplifier, a dynamic speaker having a transformer with primary and secondary coils, a condenser speaker connected in parallel with the primary coil of the transformer, and means for polarizing the condenser speaker, said primary coil serving as a choke coil for said amplifier output and as an audio potential feeder to operate said condenser speaker.

PHILIP E. EDELMAN.

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