US1733232A - Electrodynamic sound-reproducing system - Google Patents

Description

Oct. 29, 1929. B. F. MlEssNER 1,733,232 v ELECTRODYNAMIC SOUND REPRODUCING SYSTEH I Filed )lax-ch 6, 1929 wwf/MM f 3% www Patented Oct. 29, T1929.. y i 1 UNITED'STATES PATENT OFFICE BENJAMIN' F. MIESSNER, 0F SHORT HILLS, NEW JERSEY if ELECTRODYNAMIC SOUND-REPRDUCING SYSTEM Application filed March 6, 1929. Serial No. 844,883.

The present invention relates to sound reor an electrolytic rectifier, both kinds being producing systems, and particularly to such so used. systems employing signal reproducing de- The armture coil A is shown energized by vices requiring energizing for operation, such the signal currents to be reproduced as sound as the so-called electrodynamic type of re- .through a transformer T2, which may be for; producer. instance the output element of a cascaded am- Anobject of the invention is t0 energize a plifier system. The signal currents flowing reproducer requiring a strong magnetic field through coil A react on the field produced by from a readily available source of unsteady coil to produce motion of coil A and atcurrent, such as rectified alternating current tached cone C in accordance with the sound 60 of a commercially available 60 cycle source, representing signal currents. However, the without encountering an annoying degree of rectified field energizing current through coil, hum, F is not steady, thus producing an unsteady A further object is to employ the current of field tending to produce hum reproducing a filter system associated with an alternating motion of coil A. This I oppose by introe5 current rectifier as a source for energizing a ducing a selected amount of current of the system of vacuum tube amplifiers in the adsame character as that in field coil F into arditional function of energizing the reproducer A mature coil A by way of coupling resistance associated with the system, while keeping R, the amount of current being selected in,

hum effects adequately small to be non-disany desired Way, as by a tap S on resistance I0` turbing. R, which tap may be permanently setonc'ethe The invention is readily understood from desired adjustment is found. The connecthe following description with the aid of the tion of the coil A to the resistance R is so figures of the accompanying drawing in poled that the effect of the fiuctuating current which like reference characters represent like in Coil A opposes the effect of the fluctuating 75 parts so far as possible in the several figures. current in coil F.

Fig. 1 is an illustration in diagram of an The device of course can be usedwin fashion electrodynamic form of sound reproducer reverse to that of Sound reproduction; that iS., connected to employ my invention. as a sound pick-up or microphone, in which Fig, 2 illustrates 9, modification 0f the 3,1'- CaSe Creating SOllnd in the Vicinity 0f C0116 C 80 rangement 0f Fig- 1. sets the coil A in motion to generate sound Fig. 3 diagrammatically illustrates an elecrepresenting currents which may bepassed to trodynamicreproducer associated with a filan amplifier or other device through transter system in a manner to employ features of former T2.

x5 my invention. In Fig. 2 I show a transformer T3 substi- 85 Fig. 4 illustrates a modication of the artuted for the resistance R of Fig. 'l for transrangement of Fig. 3. ferring the hum-bucking energy to coil A` in Referring to' Fig. l, the usual electrothis Way avoiding introducing any of the didynamic reproducer is shown as having a rect current component into the coil A circuit.

40 magnetic core M on which is wound an ener- Of course an auto-transformer, or any other 90 gizing or field producing coil F. A movable suitable form of coupling between the two or armature coil A is shown associated with circuits may be used. Other than this couthe field of the core M, and having attached pling, Fig. 2 is the same as Fig. 1. thereto a cone or other suitable sound gen- In Fig. 3 I show the field coil F of the reerator. v producer used as the choke coil of a filter sys- 95 The field coil F is shown energized from antem of general character, shown to have filter alternating current source through a suitable condensers C, and C2. The filter is shown fed transformer T1 by Way of a rectifier D, which from the usual rectifier system having a recmay be either a full wave or single wave rectifier tube D energized through secondarie tifier of'suitable kind, such as a tube rectifier `S, and S2 cfa transformer T1 connected into 100 an alternating current supply system. The filter system 1s shown to supply a load E, conventionally shown, which may be for eX- ample the plate circuits of a cascaded series of vacuum tubes.

As before the reproducer is shown to have a movable coil A associated with a reproducing cone C. Input of sound representing current to coil A is by way of transformer T2, which may be for instance the output of an amplifier system the plate circuits of the tubes of which form the load E on the filter system.

I show a resistance R, coupling the movable coil circuit with the filter circuit, so that some of the same character of current that flows through coil F is introduced into coil A for hum neutralizing as described in connection with Fig. 1, it being understood that the circuits may be coupled by a transformer as in Fig. 2, or through other suitable form of coupling. In Fig. 3 the field coil F serves the additional useful function of acting as a filter choke. thereby saving from the system the weight and cost of such an element.

In Fig. 4 I show for example the output tube VT of a cascaded amplifier system connected to the same supply and filter system of Fig. 3 for energizing the plate circuit thereof, the input circuit being shown to include as a sound representing current input element a transformer T which may be the output of a series of cascaded nt-ubes also energized by the filter system.

The energizing of the filament and grid electrodes of tube VT is shown in accordance with standard practice. and requires no detailed description, not being a feature of the present invention.

In this Figure 4 arrangement I sh ony the armature coilAof thereproducer energizedivith sound representing currents from the output of tube VT through transformer Tg. For hum bucking I provide a coil B associated with core M to pickup some of the fluctuations due to unsteady current through field coil F. and introduce these hum bucking currents into armature coil A by way of the grid circuit of tube VT, and thus, after amplification, into transformer T2 to coil A. and of course can pole either transformer T2 or coil B to get the desired neutralizing phase. I show coil B to have a tapped connection S, but this may be determined and permanently fixed by the design of the coil in a given design.

The adaptation of the features of my invention to various like systems will be apparent to those practiced in the art from the description Ihave given. and I intend no limitations by reason of having confined my description to a limited number of typical examples of its employment, the scope of tue invention being set forth in the accompanying claims.

Having thus described my invention, what I claim is:

1. In a device for translating electrical signal energy into sound energy, the combination of a source of alternating current energy, a rectifier for convertingsaid alternating current into unidirectional current having a ripple component, a coil connected between the electrodes of said rectifier whereby a strong magnetic field of constant polarity is developed around said coil, a conductive element mounted for vibrational movement within said field, means for passing signal currents through said conductive element whereby said conductive element is vibrated at the signal current frequency, and means for transferring a. regulable portion of said ripple component of the unidirectional current from said source to said conductive element, of a phase to substantially eliminate vibrationof said conductive member by thel variation in field intensity caused by the ripple component of said unidirectional current.

2. In a device. for translating electrical signal energy into sound energy, the combination of a source of alternating current energy, a rectifier for converting said alternating current into unidirectional current having a ripple component, a coil connected between the electrodes of said rectifier whereby a strong magnetic field of constant polarity is developed around said coil, a conductive element mounted for vibrational movement within said field, means for passing signal currents through said conductive element whereby said conductive element is vibrated at the signal current frequency, means for diverting a regulable portion of said ripple component of said unidirectional current from said coil, and means for introducing this diverted portion into said conductive element of a phase to substantially eliminate vibration of said conductive member by the variation in field intensity causedby the ripple component of said unidirectional current.

3. In a device for translating electrical signal energy into sound energy the combination of a source of. alternating current energy, a rectifier for converting said alternating current into unidirectional current having a ripplekcomponent, a coil connected between the electrodes of said rectifier whereby a strong magnetic field of constant polarity is developed around said coil, a conductive element mounted for vibrational movement within said field. means for passing signal currents through said conductive element whereby said conductive element is vibrated at the signal current frequency, a second coil coupled to the coil-rectifier circuit for diverting a regulable portion of the ripple component of said unidirectional current therefrom, and means for introducing this diverted portion into said conductive element of a phase to substantially eliminate vibration of said conductive member by the variation in field intensity caused b the ripple component of said unidirectiona current.

4. In a device for translating electrical signal energy into sound energy the combination of a source of alternating current en ergy, a rectifier for converting said alternating current into unidirectional current having a ripple component, a coil connected between the electrodes of said rectifier whereby a strong magnetic field vof constant polarity is developed around said coil, a conductive element mounted for vibrational movement Within said field, means for passing signal currents through said conductive element Iwhereby said conductive element is vibrated f at the signal current frequency, a second coil coupled to the coil-rectifier circuit for diverting a regulable ortion of the ripple component of said unidirectional current therefrom, a third coil conductively coupled to said element and associated with said second coil for introducing this diverted portion into said conductive element of a phase to substantially eliminate vibration of said conductive member by the variation in field intensity caused by the ripple component of said unidirectional current.

5. In a device for translating electrical signal energy into sound energyr the combination of a source of alternating current energy, a rectifier for converting said alternat- A ing current into unidirectional current having a ripple component, a coil connected between the electrodes of said rectifier wherebv a strong magnetic field of constant polarity is developed around said coil, a conductive element mounted for vibrational movement A within saidfield, means for passing signal currents through vsaid conductive Velement whereby said conductive element is vibrated at the signal current frequency, a second coil coupled to the 'coilrectifier circuit for diverting therefrom a regulable portion of the ripple component of said unidirectional current, a vacuum tube having a grid, filament and plate, said second coil being connected to said grid, a transformer, the rimary of which connects said plate to said) coil-recti fier circuit, the secondary of said transformer being associated with said conductive element of a phase to substantially eliminate vibration of said conductive member by the variation in field intensity caused by the ripple, component of said unidirectional current.

In witness whereof, I have hereunto subscribed my name this first day of March,

BENJAMIN F. MIESSNER.

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