US2025388A

US2025388A - Sound reproducing system

Info

Publication number: US2025388A
Application number: US745019A
Authority: US
Inventors: Harley A Henning
Original assignee: Bell Telephone Laboratories Inc
Current assignee: AT&T Corp
Priority date: 1934-09-05
Filing date: 1934-09-22
Publication date: 1935-12-24
Anticipated expiration: 1952-12-24

Description

Dec, 24, 1935.. H. A. HENNING 2,025,338

SOUND REPRODUC I NG SYSTEM Filed Spt. 22, 1934 FIG. I

AME LATERAL 5J2 AMI? :11? VERTICAL I/Vl/EN TOR H. A. HENN/NG A TTORNE Y Patented Dec. 24-, 1935 UNITE STATES orries SOUND REPRQDUQHNG SYSTEM Application September 22, 1334, Serial No. 745,019

3 Claims.

This invention relates to sound reproducing systems and more particularly to systems for reproducing simultaneously a plurality of recordings in a single track or groove.

It has been proposed heretofore to cut in a sin gle groove two independent sound records, one consisting of vertical undulations and the other of lateral undulations of the groove. In a copending application of H. C. Harrison, Serial No.

19 742,761, filed Sept. 5, 1934, is disclosed a double moving coil type reproducer in which both coils are responsive to both vertical and lateral stylus vibrations, and when a duplex record of the type already mentioned is played with such a repro- 5 ducer the output is a combination of the reproductions of both recordings.

The object of this invention is a simple, efiicient system for simultaneously and separately reproducing both recordings of a record of the 20 duplex type.

According to the invention a reproducer of the double generating element type is connected to two reproducing circuits by means of transformers with double secondary windings. One sec- 25 ondary winding of each transformer is connected to each circuit in such a way that the output 01 both elements of the reproducer due to vertical undulations is conducted to one circuit and the output of both elements due to lateral undula- 39 tions is conducted to the other circuit. This result is conveniently obtained by connecting the windings in the vertical circuit either series or parallel aiding and the windings in the lateral circuit either series or parallel opposing. In the reproduction of the lateral record, the reproducer elements move in opposite directions and generate the voltages of opposite polarity which are balanced out in the vertical circuit and in the reproduction of the vertical record, the elements move in the same direction and generate voltages of the same polarity which are balanced out in the lateral circuit.

The two sound records may, of course, be entirely unrelated, but the invention is particularly useful in reproducing auditory perspective efiects since only a single record is needed and the operation is the same as for an ordinary phonograph.

The invention will be more clearly understood from the following detailed description and the accompanying drawing in which:

Fig. l is a circuit diagram of a reproducing system according to the invention; and

Figs. 2 and 3 are sectional views of the moving system and associated portions of the magnetic circuit of a reproducer suitable for use in the system of Fig. 1.

The magnetic circuit at the reproducer comprises a permanent magnet (not shown) and pole pieces H and I2, the pole piece it having two end 5 portions 53 and id projecting into the circular hole to in the pole piece E2 to form working gaps to the coils it and ill. The portions is and I4 of the pole piece i l are somewhat oval cross-section and contoured to iorm short air gaps l8 and is for the outer active sides 2%, 2i of the coil. The coil supporting cup 22 is supported on a tube 23 having a stylus it for engaging the record and this moving system assembly is supported by

parallel springs

25 and 25. The lower spring 25 is free to deflect both vertically and laterally, but the upper spring 2% is triangular in shape and hence relatively stifi in a lateral sense, but free to deflect both vertically and torsional.

The coils iii and ll are connected to the prlmary windings of the transformers 2i and 28, each of which has two secondary windings 29, 3E], and 3!, 32 respectively. Winding 30 of transformer 2i and winding 32 of transformer 28 are connected in aiding relationship to an amplifier S3 and a loud-speaker receiver 34 for reproducing the vertical recording and winding 29 of transformer 2i and winding 311 of transformer 28 are connected in opposing relationship to an amplifier 35 and a loud-speaking receiver 36 for reproducing the lateral recording. I

When the reproducer is cooperating with a record 39 having both hill-and-dale and lateral undulations, the stylus 24 will be vibrated simultaneously in both lateral and vertical modes. Assume the flux in the gaps i8 and E9 to be in the directions indicated by the arrows in Fig. 3, then for vertical vibrations of the stylus, the coils will move vertically in the same direction and the varying potentials impressed on the primary transformer windings 3'5 and 38 will be equal and in phase. Since the

secondary windings

30 and 32 are in aiding relationship, the sum or these potentials is impressed on the amplifier 33 and these vertical stylus vibrations are reproduced by the receiver 34, but the equal potentials in the

secondary windings

29 and 3| are opposed to each other so that no sound is heard from the receiver 36.

The lateral vibrations of the stylus imparted to it by the lateral recording will deflect the spring 26 torsionally and the coils l6 and ll will vibrate vertically in opposite directions. Under this condition the variations in the potentials impressed on the

transformers

21 and 28 will always be 180 degrees out of phase with each other. The potentials in the aiding

windings

30 and 32, will also be 180 degrees out of phase so that the lateral recording is not reproduced by .each coil and transmits it only to the receiver 38.

It will be understood that the two recordings in the record 39 may be recordings of entirely unrelated sounds, or of related sounds of any one of a number of kinds. For example, one recording might be a solo rendition and the other the accompaniment or the recordings may be related recordings of the same sound for producing spacial distribution effects as taught by Rosenberg in British Patent 23,620 of 1911 or by Wier in Patent 1,508,432, granted September 16, 1924. When the system is used for producing spacial distribution effects, it will be understood that the receivers 36 and 38 should be suitably spaced as taught in the patents referred to above.

What is claimed is:

1-. In a reproducing system, the combination with a record combining in one track two independent recordings of the same sound picked up at difierent positions, a reproducer having a stylus and two generating elements each responsive to both of the recordings and two reproducing circuits terminating in spaced loud-speaking receivers, of a transformer for each of the elements having a primary winding connected to the element and two secondary windings, one of the secondary windings of each transformer being connected to each receiver.

2. In a reproducing system, the combination with a record combining in one groove a Vertical cut and a lateral cut recording and a reproducer for the record having two generating elements each responsive to both recordings, of two independent receiving circuits and means for transmitting the lateral output of the reproducer to one of the circuits and the vertical output to the other circuit comprising a separate transformer for each of the elements and double secondary windings on the transformers, one of the secondary windings of each transformer being connected to each of the circuits.

' 3. In a reproducing system, the combination with a record combining in one groove a vertical cut and a lateral cut recording and a reproducer for the record having two generating elements adapted to be driven in the same direction by the vertical recording and in opposite directions by the lateral recording, of a transformer for each element having a primary winding associated with the element and double secondary windings, conductors between the transformers connecting the secondary windings in aiding and opposing pairs, and an independent receiving circuit connected to each pair of windings.

HARLEY A. HENNING.