US1992300A - Dynamic loud speaker unit - Google Patents

Description

'Feb zfi, 1935. FANGER 1,992,300

y DYNAMIC 1.0m) SPEAKER'UNIT I Original Filed Sept. 25, 1928 k v j f I 32 g 35, E 34 T INVIENTOR Y krm xvi/77 r syww ATTORNEY Patented Feb. 26, 1935 UNITED STATES DYNAMIC LOUD SPEAKER UNIT Herman J. Fanger, Oakland, Calif.

Original application September 25, 1928, Serial No. 308,152. Divided and this application July 26, 1932, Serial No. 624,732

8 Claims.

This invention relates to devices for transforming signal carrying electrical impulses into sound waves; and more particularly to a device employing the dynamic principle whereby a movable conductor is actuated in accordance with the signals to be reproduced.

' This application is a division of an application filed in my name on September 25, 1928, Serial Number 308,152, now Patent No. 1,895,071, granted Jan. 24, 1933, entitled Dynamic loud speaker lmitn' Such units employ a magnetic field, usually produced by the aid of a field coil supplied with direct current. The magnetic circuit includes a small gap in which a coil or other conductor is movable, in such manner that the movement cuts the magnetic lines of force, When such a conductor is supplied with current carrying the impulses, this current reacts with the transverse field to move the coil, and this movement can be used to actuate an air actuator, such as adiaphragm or a cone.

The field coil, in order to secure good efliciency, must be supplied with a considerable energizing 25 current, sometimes of the order of an ampere.

In prior devices, the heat losses in the coil serves to heat the coil and the surrounding parts of the structure; and it is obvious that this heating must be taken care of by proper circulation so that it 30 may not affect the unit deleteriously.

It is one of the objects of my invention to prevent this undesirable temperature rise, and more particularly by providing a large radiating surface for the structure. I accomplish this result 35 by so arranging the magnetic circuit that it has, in addition to an external radiating surface, a

supplemental interior radiating surface. Ac-' cordingly, it is another object of my invention to provide a structure for the magnetic circuit that accomplishes these useful results.

In a single coil device, it is evident that movement of the coil in response to signaling impulses may serve partly to remove the coil from the influence of the field, and the response for a large coil movement is materially lessened. In my two coil arrangement, this effect is nicely overcome, for as one coil moves out of the field, the other can move into the field. Furthermore, the effect of the coils on the air actuator is cumulative, to 50 produce a push-pull result.

It is often desirable to provide separate speakers adapted faithfully to reproduce different reg isters in the range of audible frequencies. For example, a horn and cone are often used together, the hornbeing best adapted to reproduce the higher frequencies and the cone to reproduce the lower frequencies. It is another object of my invention to provide a single unit in which the low and high register elements are embodied in a compact and inexpensive manner.

This compact arrangement is rendered possible by so arranging the cone that it may serve as the mouth of a, horn having converging passageways leading to the cone.

My invention possesses many other advantages, and has other objects which may be made more easily apparent from a consideration of several embodiments of my invention. For this purpose I have shown a few forms in the drawing accompanying and forming part of the present specification. I shall now proceed to describe these forms in detail, which illustrate the general principles of my invention; but it is to be understood that this detailed description is not to be taken in a limiting sense, since the scope of my invention is best defined by the appended claims.

Referring to the drawing:

Figure 1 is a sectional view, mainly diagrammatic, of a loud speaker unit embodying my invention;

Fig. 2 is a diagram showing the manner in which the two sections of the movable coil used in my device are energized; and

Fig. 3 is a diagram of that form of the invention in which the device embodies the characteristic both of a horn and of a large diaphragm, such as a cone.

In Fig. 1, I show a field coil 11 in diagrammatic fashion only. It is shown as disposed on a tubular magnetic member 12. This member has an internal flange 13, forming a large central aperture at one end. It can be further provided with an external flange 14 at the opposite end, against which one end of coil 11 can rest. The exterior of coil 11 is covered by a tubular magnetic casing 15 fastened to flange 14. At its other end, this casing is provided with an annular pole piece 16 forming an aperture of substantially the same size as flange 13, but overlying it.

A short core piece 17 is held centrally of both flange 13 and pole piece 16, as by the aid of a non-magnetic bridging member 18. This bridge 18 can be fastened in tube 12, and a screw 19 passing through it can serve to hold the piece 1'7 firmly in centered or central relation to the members 13 and 16 1 It is apparent that if, say, the pole piece 16 forms a north pole, the inner edge of flange 13 must form a south pole. The core 1'7 at that portion opposite the inner edgeof pole piece 16 has a south pole induced thereby; and that portion opposite flange 13 has a north pole induced thereby. The course of the lines of force through the core 1'7 is shown by arrows 19'. Thus it is seen that two narrow air gaps are formed; in one, the lines radiate outwardly from a north pole (opposite flange 13); and in the other, the lines converge inwardly to a south pole (opposite piece 16). 1

Before proceeding with a description of the moving parts of the mechanism, attention is directed to the fact that a large interior cooling surface is presented by the interior of tube 12. Consequently the heat energy lost in coil 11 can be easily dissipated without danger of excessive temperature rise.

Cooperating with the two narrow annular air gaps, are a pair of coils 20, 21, supported on a thintube 22 attached to a cone 23. This cone can be fastened in any appropriate manner at its edges, whereby the whole movable structure is constrained for axial movement. Then as these coils are axially moved, the cone 23 is actuated to set up corresponding sound waves. In order that these coils have a cumulative effect on the cone, they must of course carry currents that circulate in opposite directions because the lines of force in the two air gaps extend in different directions. Thus for coil 20, influenced by the gap formed by flange 13, currents must be supplied that circulate, say, in a clockwise direction; while for coil 21, influenced by the gap formed by annular member 16, currents must be supplied that circulate in a counterclockwise direction. The coils can be supplied from a circuit 24 (Fig. 2) that carries the signaling impulses by having one terminal of the circuit connecting to a common point 25 for both coils; and the other terminal connects to the outer terminals of both coils, thus providing a parallel connection for the coils; and if the coils are wound in the same direction on tube 22, the currents will then circulate in opposite directions. The magnetic effects of coils 20, 21 are indicated by arrows 26, 27, and since both coils are of equivalent number of turns, these two effects cancel each other. There is thus no magnetic reaction, due to these coils on the core.

Preferably, I arrange coils 20 and 21 so as to.

be not quite centrally disposed in the gaps when these coils are unexcited; coil 20, say, has its medial line passing to the'right of the medial line of flange 13; and the coil 21 has its medial line passing to the left of the medial line of annular member 16. In this way, when these coils are pole pieces 29, 30, one at each end. A central core 31 passes entirely through the coil 28, and forms with the pieces 29, 30, a pair of gaps that function in a manner analogous to the form of Fig. 1. Coil 32, at the right hand side of the device, is connected directly to a cone or large diaphragm 33. Coil 34, at the left hand end, is supported on a cup-like member 35, the end or which forms the center portion of a diaphragm 36, fastened to a stationary support at its edges.

The movement of coil 34 actuates this diaphragm,

and the sound waves caused thereby can be led through a diverging central opening 37 in the core 31 and finally out through the cone 33.

It is evident that cone 33 serves not only as a diaphragm air actuator, but also to lead the sound waves out from another, smaller diaphragm. The coils 32, 34, can be connected either in parallel or in series to a common source of signaling currents. Diaphragm 33 correctly reproduces the lower notes, while the smaller diaphragm 35-36 correctly reproduces the higher notes. Some of the advantages of the structure of Fig. 1 are also present; there is an internal radiating surface, and two moving coils are used.

I claim: v

1. In a dynamic signaling device, a core, a pair of annular pole pieces, one at each end of the core to form annular gaps, a movable coil in each gap, and diaphragms operatively associated respectively with each movable coil, said core having a tapering aperture therethrough for leading sound waves through the core.

2. The'combination as set forth in claim 1, in which the'larger diaphragm or cone is in the form of a large mouthpiece forming an extension for the aperture in the core.

3. In a dynamic loud speaker, a pair of dynamic coils axially displaced from each other, a core passing through both coils, an air actuator adapted to reproduce the lower register of sound waves, operated by one of the coils, and an air actuator adapted to reproduce the higher register, operated by the other coil, the core having an axial aperture forming with the low register actuator, a horn-like air passage from the higher register actuator.

4. A sound reproducing system comprising in combination a loud speaking receiver having a diaphragm and a horn amplifier and a second loud speaking receiver having a free radiating diaphragm, the diaphragm of said second receiver having a central opening substantially equal to the opening of the horn mouth of saidv first receiver and being located circumferentially around the mouth of said horn.

5. In combination a moving coil loud speaker having a horn radiator, is. second moving coil loud speaker having a free radiating diaphragm, and a common field magnet system for the moving coilsof both of said loud speakers.

6. In combination, a loud speaking receiver having a diaphragm and a horn radiator, and a second loud speaker comprising a diaphragm, a driving coil mounted on said last recited diaphragm, and a cylindrical shell type magnet providing a magnetic field for said driving coil, said magnet having a hollow central core the interior wall of which is formed to provide the horn for said first loud speaker.

7. A sound reproducing system in accordance v with claim 6 in which the diaphragm of the second loud speaker is a free radiating cone having a'central opening and is mounted circumferentially of the horn opening of the first loud speaker.

8. In combination, a loud speaking receiver having a diaphragm and a horn radiator, and a second loud speaking receiver comprising a free radiating diaphragm, a driving coil mounted on said free radiating diaphragm, and a cylindrical. shell type magnet providing a magnetic'fleld for said coil, the horn of said first loud speaker being located centrally and coaxially' within said magnet and said free radiating diaphragm having a central opening substantially coinciding with the horn mouth.

HERMAN J. FANGER.

Images