US1722008A - Sound-reproducing apparatus - Google Patents

Sound-reproducing apparatus Download PDF

Info

Publication number
US1722008A
US1722008A US96009A US9600926A US1722008A US 1722008 A US1722008 A US 1722008A US 96009 A US96009 A US 96009A US 9600926 A US9600926 A US 9600926A US 1722008 A US1722008 A US 1722008A
Authority
US
United States
Prior art keywords
diaphragm
sound
base
gongs
armature
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US96009A
Inventor
O'donnell Patrick Shaughnessy
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Individual
Original Assignee
Individual
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Individual filed Critical Individual
Application granted granted Critical
Publication of US1722008A publication Critical patent/US1722008A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R1/00—Details of transducers, loudspeakers or microphones
    • H04R1/20—Arrangements for obtaining desired frequency or directional characteristics
    • H04R1/22—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired frequency characteristic only 
    • H04R1/28—Transducer mountings or enclosures modified by provision of mechanical or acoustic impedances, e.g. resonator, damping means
    • H04R1/2807—Enclosures comprising vibrating or resonating arrangements
    • H04R1/283—Enclosures comprising vibrating or resonating arrangements using a passive diaphragm
    • H04R1/2834—Enclosures comprising vibrating or resonating arrangements using a passive diaphragm for loudspeaker transducers
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C21/00—Alloys based on aluminium
    • C22C21/02—Alloys based on aluminium with silicon as the next major constituent
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R1/00—Details of transducers, loudspeakers or microphones
    • H04R1/20—Arrangements for obtaining desired frequency or directional characteristics
    • H04R1/22—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired frequency characteristic only 
    • H04R1/28—Transducer mountings or enclosures modified by provision of mechanical or acoustic impedances, e.g. resonator, damping means
    • H04R1/2807—Enclosures comprising vibrating or resonating arrangements
    • H04R1/2838—Enclosures comprising vibrating or resonating arrangements of the bandpass type
    • H04R1/2842—Enclosures comprising vibrating or resonating arrangements of the bandpass type for loudspeaker transducers

Definitions

  • This invention relates to, and has for its the diamond 4 and the middle of the armaobject the provision of improvements in, sound reproducing apparatus, of the kind described and claimed in my copending application for Letters Patent of the United States Serial No. 96,008.
  • the invention consists broadly of a loud speaker, particularly for use in connnection with wireless apparatus, of the kind in which a sound emitting diaphragm is adapted to be vibrated by means of the armature of an elcctromagnet, wherein other diaphragms or membranes are provided for the purpose of rendering the sound more mellow and pure.
  • FIG. 1 is a side elevation of a loud speaker (particularly for use in connection with wireless apparatus) in accordance with the invention, the casing thereof and certain other parts being shown in section.
  • Figure 2 is an end elevation of the same looking from the left of Figure 1.
  • Figure 3 is a similar end elevation of all those parts to the right of line XX of Figure 1, certain of the parts being shown in chain dotted lines.
  • Figure 4 is a side elevation of a detail.
  • the loud speaker therein illustrated comprises an electromagnet 1 the armature 2 of which is adapted to vibrate in accordance with the vibrations of the sound to be reproduced.
  • the vibrations of this eleotromagnet are adapted .to be transmitted to a diaphragm 3 of conical shell formation through the medium of a transmission device which comprises two diamonds 4 and 5 which .are in simple contact with one another and which are in rigid relationship respectively with said armature 2 and said diaphragm 3.
  • the diaphragm 3 is rigidly and co- .axially mounted to a rod 6 extending outwardly from its apex, and this rod carries at its remote extremity the diamond 5.
  • the armature 2 carries a cup 7 which contains the other diamond 4.
  • the rod 6 is reeiprocably mounted in a sleeve 8 carried by a bracket 9 ,so that the axis .of saidrod passes through ture. 2.
  • a spring 6 is provided. for biasing said rod with respect to said sleeve in such a way that the diamond 5 is pressed down upon the diamond 4.
  • the vibrations of the armature 2 are adapt ed to take place in a sense at right angles to the rod 6 and thus the'diamonds 4 and 5 tend to rub one another in a sense at right angles to the direction of the pressure between them.
  • the irregularity of form of the two diamonds resultsin an engagement between them such that the rod (3 together with the diaphragm 3 is vibrated. Sound waves are therefore emitted from said diaphragm.
  • the bracket 9 and the clectromagnct 1 are both supported from a common base 10 which consists of a glass disc and is supported in spaced relation from the back 11 of the loud speaker casing by means of four supporting feet 12 spaced around its circumferential periphery.
  • the electromagnet is mounted to this base in the neighbourhood of its centre and the bracket 9 is made in the form of a bridge which straddles said elcctromagnet with its columns mount-ed to said base and its bridging member carrying the aforesaid sleeve 8.
  • the loudv speaker casing is of cylindrical formation the back 11 thereof thus being disc shape.
  • the front thereof is open and has mounted thcrewithin at spaced intervals around the circumferential wall of said casing a number of tuned gongs 13 each of which represents a definite musi al note.
  • These gongs are of spiral type and are located as shown in radial planes with respect to the cylindrical casing and with their mounting points nearest the open end of the casing. They are mounted to an annular base l-l extending around the inner periphery of the casing as shown.
  • the gongs are partly isolated from one another by means of battle plates 15 also arranged in radial planes.
  • These baffle plates come between the outer halves only of each pair of the gongs (i. e. the halves nearest the open end of the casing) and are formed so that they become narrower as they approach the centre of the casing near to which they terminate. They also are mounted to said. base 15 and at their inner ends carry an annulus 15.
  • auxiliary diaphragms 16 Rigidly and coaxially mounted upon an extension of the sleeve 8 and betweenthe diaphragm 3 and the bracket 9 are a number of, say four, auxiliary diaphragms 16. These to the diaphragm 3.
  • a glass disc 17 Between the cup 7 and the armature 2 and in rigid relation with both is a glass disc 17. Extending between the disc shape base 10 and the annular base 14 are four wooden rods 18. These rods are mounted to said base 10 by means or blocks 18* cemented to, and overhanging the circumferential periphery of, said base, and are bolted to the base 14 as shown. 7
  • the gongs operate to break down echoes and false vibrations and to enhance the true notes. Each gong responds to its own proper note and tends to swamp false notes.
  • the auxiliary diaphragms 16 and the disc 17 have the effect or" further increasing the mellowness and purity of the tone produced. The scientific explanation of this is not however quite clear.
  • the connection between the base 10 and the base 14 by means of the rods 18 has the effect of increasing the sensitiveness of the gongs. Very slight vibrations are transmitted from said base 10 to said base 14 and thus the gongs themselves are maintained in a slightly tremulous state in which they are more read ily susceptible of sympathetic response to their proper notes than when they are in a state of rest.
  • the clectromagnet 1 consists of a core 1? having energizable pole pieces 1 arranged one each side of the armature 2 and adapted alternately to attract and repel the same.
  • the armature 2 is mounted to a somewhat resilient bridging piece 2 one end of which is rigidly mounted to the base 1 to which the core 1 is mounted and the other end of which is mounted to said base in such a way as to be adjustable with respect thereto in a vertical sense. adapted to be effected by means of an adjusting knob 2 underneath the glass base 10. the adjusting column passing through a hole in said 10.
  • the base 1 is secured to the base 10 by means o a suitable cement.
  • the cup 7 is made in one unit with the disc
  • the transmission through the contacting diamonds probably has the eitect oi
  • Such adjustment is 17 and with a suitable screw 19 by which said unit is screwed to sai l arm; turc 2.
  • a Washer 20 say or" ebonitc is in erposed between said screw 19 and the armature 2.
  • the diaphragm 3 and also the auxiliary diaphragms 16 are made or" silk.
  • the silk may be mounted on a light frame-work and coated with a very thin solution of celluloid followed by thin coating of sairit mastic varnish, or it may be self supporting being stiitcned by means of a suitable stiffening solution.
  • the former method is adopted and the frame members of the diaphragm 3 are shown in Fig. 2 at 8
  • the bafiic plates 15 are shown superimposed over the radial frame members 3 This is purely tortuitous and should not cause confusion.
  • the tour supporting feet 12 are provided with grooves as shown in which the edge of the 10 fits. These grooves are provided The with rubber or like pads12 above and below the edge of said base.
  • a loud speaker comprising a diaphragm for producing sound waves and a plurality of tuned gongs in the path whichsaid sound waves are adapted to take and battle plates located between adjacent pairs of said gongs, as such a loud speaker is described and claimed in my copending application for'Letters Patent of the United States for sound amplifying devices for sound reproducing Serial No. 96,010.
  • a loud speaker comprising a sound emit-ting diaphra m havin an unclamped g and pluralityof nonresonant damping diaphragms also having unclamped edges 10- eated behind said sound emitting diaphragm.
  • a loud speaker comprising a sound emitting diaphragm having an unclamped edge and a plurality of nonresonant damping diaphragms, also having unclamped edges located coaxially with, and behind, said sound emitting diaphragm.
  • a loud speaker comprising a sound emitting diaphragm having an unclamped edge and a plurality of nonresonant damping diaphragms of smaller diameter than said sound emitting diaphragm, also having unclamped edges, located behind said sound emitting diaphragm.
  • a loud speaker comprising a sound emitting diaphragm, a rod supporting said sound emitting diaphragm and adapted to transmit vibrations thereto, a support for reciprocably supporting said rod and a plurality of nonresonant damping diaphragms mounted on said support.
  • a loud speaker comprising a sound emitting diaphragm having an unolamped edge and a plurality of nonresonant damping diaphragms of smaller diameter than said sound emitting diaphragm, also having unclamped edges, located behind said sound eiui'tlin diaphragm, said nonresonant damping diaphragms being of progressively varying diameters, the largest being closest to said sound emitting diaphragm.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Health & Medical Sciences (AREA)
  • Otolaryngology (AREA)
  • Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Audible-Bandwidth Dynamoelectric Transducers Other Than Pickups (AREA)
  • Obtaining Desirable Characteristics In Audible-Bandwidth Transducers (AREA)
  • Details Of Audible-Bandwidth Transducers (AREA)

Description

my 23, 1929. P, a ODONNELL 1,722,008
SO UND REPRODUCING APPARATUS Filed March 19. 1926 2 Sheets-Sheet l A July 23, 1929. A P. s. ODONNELL 1,722,008
SOUND REPRODUC ING APPARATUS Fi'led March 19, 1926 2 Sheets-Sheet 2 Patented July 23, 1929.
UNITED STATES PATENT OFFICE.
PATRICK SHAUGHNESSY ODONNELL, OF LONDON, ENGLAND.
SOUND-REPRODUCING APPARATUS.
Application filed March 19, 1926, Serial No. 96,009, and in Great Britain September 30, 1925.
This invention relates to, and has for its the diamond 4 and the middle of the armaobject the provision of improvements in, sound reproducing apparatus, of the kind described and claimed in my copending application for Letters Patent of the United States Serial No. 96,008.
The invention consists broadly of a loud speaker, particularly for use in connnection with wireless apparatus, of the kind in which a sound emitting diaphragm is adapted to be vibrated by means of the armature of an elcctromagnet, wherein other diaphragms or membranes are provided for the purpose of rendering the sound more mellow and pure.
One embodiment of the invention is illustrated in the accompanying drawings and the same will now be described, it being understood that the particular construction and arrangement illustrated are susceptible of variousmodifications without departing from the scope of the invention as defined in the appended claims.
In these drawings Figure 1 isa side elevation of a loud speaker (particularly for use in connection with wireless apparatus) in accordance with the invention, the casing thereof and certain other parts being shown in section.
Figure 2 is an end elevation of the same looking from the left of Figure 1.
Figure 3 is a similar end elevation of all those parts to the right of line XX of Figure 1, certain of the parts being shown in chain dotted lines.
Figure 4 is a side elevation of a detail.
Referring to the drawings the loud speaker therein illustrated comprises an electromagnet 1 the armature 2 of which is adapted to vibrate in accordance with the vibrations of the sound to be reproduced. The vibrations of this eleotromagnet are adapted .to be transmitted to a diaphragm 3 of conical shell formation through the medium of a transmission device which comprises two diamonds 4 and 5 which .are in simple contact with one another and which are in rigid relationship respectively with said armature 2 and said diaphragm 3.
Thus the diaphragm 3 is rigidly and co- .axially mounted to a rod 6 extending outwardly from its apex, and this rod carries at its remote extremity the diamond 5. The armature 2 carries a cup 7 which contains the other diamond 4. The rod 6 is reeiprocably mounted in a sleeve 8 carried by a bracket 9 ,so that the axis .of saidrod passes through ture. 2. A spring 6 is provided. for biasing said rod with respect to said sleeve in such a way that the diamond 5 is pressed down upon the diamond 4.
The vibrations of the armature 2 are adapt ed to take place in a sense at right angles to the rod 6 and thus the'diamonds 4 and 5 tend to rub one another in a sense at right angles to the direction of the pressure between them. In practice the irregularity of form of the two diamonds resultsin an engagement between them such that the rod (3 together with the diaphragm 3 is vibrated. Sound waves are therefore emitted from said diaphragm.
The bracket 9 and the clectromagnct 1 are both supported from a common base 10 which consists of a glass disc and is supported in spaced relation from the back 11 of the loud speaker casing by means of four supporting feet 12 spaced around its circumferential periphery. The electromagnet is mounted to this base in the neighbourhood of its centre and the bracket 9 is made in the form of a bridge which straddles said elcctromagnet with its columns mount-ed to said base and its bridging member carrying the aforesaid sleeve 8.
The loudv speaker casing is of cylindrical formation the back 11 thereof thus being disc shape. The front thereof is open and has mounted thcrewithin at spaced intervals around the circumferential wall of said casing a number of tuned gongs 13 each of which represents a definite musi al note. These gongs are of spiral type and are located as shown in radial planes with respect to the cylindrical casing and with their mounting points nearest the open end of the casing. They are mounted to an annular base l-l extending around the inner periphery of the casing as shown. The gongs are partly isolated from one another by means of battle plates 15 also arranged in radial planes. These baffle plates come between the outer halves only of each pair of the gongs (i. e. the halves nearest the open end of the casing) and are formed so that they become narrower as they approach the centre of the casing near to which they terminate. They also are mounted to said. base 15 and at their inner ends carry an annulus 15.
Rigidly and coaxially mounted upon an extension of the sleeve 8 and betweenthe diaphragm 3 and the bracket 9 are a number of, say four, auxiliary diaphragms 16. These to the diaphragm 3.
CPI
the bracket 9.
Between the cup 7 and the armature 2 and in rigid relation with both is a glass disc 17. Extending between the disc shape base 10 and the annular base 14 are four wooden rods 18. These rods are mounted to said base 10 by means or blocks 18* cemented to, and overhanging the circumferential periphery of, said base, and are bolted to the base 14 as shown. 7
In operation the vibrations are transmitted as described by means or the diamond con tact transmission device from the armature 2 Sound waves are thus emitted from said diaphragm and pass out through the open end or the casing past the gongs 13. The purity of the sound thus pro duced is enhanced on account of the said transmission device and also as a result of the gongs 13.
making the vibrations of the diaphragm 3 more nearly simple harmonic vibrations than are the vibrations of the armature 2 but this is not certain. The gongs operate to break down echoes and false vibrations and to enhance the true notes. Each gong responds to its own proper note and tends to swamp false notes. The auxiliary diaphragms 16 and the disc 17 have the effect or" further increasing the mellowness and purity of the tone produced. The scientific explanation of this is not however quite clear. The connection between the base 10 and the base 14 by means of the rods 18 has the effect of increasing the sensitiveness of the gongs. Very slight vibrations are transmitted from said base 10 to said base 14 and thus the gongs themselves are maintained in a slightly tremulous state in which they are more read ily susceptible of sympathetic response to their proper notes than when they are in a state of rest.
Describing now certain constructional dc tails of the device, the clectromagnet 1 consists of a core 1? having energizable pole pieces 1 arranged one each side of the armature 2 and adapted alternately to attract and repel the same. The armature 2 is mounted to a somewhat resilient bridging piece 2 one end of which is rigidly mounted to the base 1 to which the core 1 is mounted and the other end of which is mounted to said base in such a way as to be adjustable with respect thereto in a vertical sense. adapted to be effected by means of an adjusting knob 2 underneath the glass base 10. the adjusting column passing through a hole in said 10. The base 1 is secured to the base 10 by means o a suitable cement.
The cup 7 is made in one unit with the disc The transmission through the contacting diamonds probably has the eitect oi Such adjustment is 17 and with a suitable screw 19 by which said unit is screwed to sai l arm; turc 2. A Washer 20 say or" ebonitc is in erposed between said screw 19 and the armature 2.
The diaphragm 3 and also the auxiliary diaphragms 16 are made or" silk. The silk may be mounted on a light frame-work and coated with a very thin solution of celluloid followed by thin coating of sairit mastic varnish, or it may be self supporting being stiitcned by means of a suitable stiffening solution. In the particular construction illustrated the former method is adopted and the frame members of the diaphragm 3 are shown in Fig. 2 at 8 In this figure the bafiic plates 15 are shown superimposed over the radial frame members 3 This is purely tortuitous and should not cause confusion.
The diaphragm 3 is provided with a boss 3 by which it is screwed onto the end of the rod (3 and said diaphragm is also supported from eriphery by means of strings 3 secured o tne inner periphery of the casing. oi" phragms 16 are formed with bosses whereby hey are spaced apart as shown.
The tour supporting feet 12 are provided with grooves as shown in which the edge of the 10 fits. These grooves are provided The with rubber or like pads12 above and below the edge of said base.
No claim is made in this specification to a loud speaker comprising a diaphragm for producing sound waves and a plurality of tuned gongs in the path whichsaid sound waves are adapted to take and battle plates located between adjacent pairs of said gongs, as such a loud speaker is described and claimed in my copending application for'Letters Patent of the United States for sound amplifying devices for sound reproducing Serial No. 96,010.
What I claim and desire to secure by Let ters Patent is l. Aloud speaker comprising a sound emitting diaphragm having an unclamped edge and a nonresonant'damping diaphragm also having an unclamped edge located behind said sound emitting diaphragm.
2. A loud speaker comprising a sound emit-ting diaphra m havin an unclamped g and pluralityof nonresonant damping diaphragms also having unclamped edges 10- eated behind said sound emitting diaphragm.
3. A loud speaker comprising a sound emitting diaphragm having an unclamped edge and a plurality of nonresonant damping diaphragms, also having unclamped edges located coaxially with, and behind, said sound emitting diaphragm.
4. A loud speaker comprising a sound emitting diaphragm having an unclamped edge and a plurality of nonresonant damping diaphragms of smaller diameter than said sound emitting diaphragm, also having unclamped edges, located behind said sound emitting diaphragm.
5. A loud speaker comprising a sound emitting diaphragm, a rod supporting said sound emitting diaphragm and adapted to transmit vibrations thereto, a support for reciprocably supporting said rod and a plurality of nonresonant damping diaphragms mounted on said support.
6. A loud speaker comprising a sound emitting diaphragm having an unolamped edge and a plurality of nonresonant damping diaphragms of smaller diameter than said sound emitting diaphragm, also having unclamped edges, located behind said sound eiui'tlin diaphragm, said nonresonant damping diaphragms being of progressively varying diameters, the largest being closest to said sound emitting diaphragm.
In Witness whereof I aflix my signature.
PATRICK SHAUGHNESSY ODONNELL.
US96009A 1925-05-11 1926-03-19 Sound-reproducing apparatus Expired - Lifetime US1722008A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB1722007X 1925-05-11

Publications (1)

Publication Number Publication Date
US1722008A true US1722008A (en) 1929-07-23

Family

ID=10889181

Family Applications (3)

Application Number Title Priority Date Filing Date
US96008A Expired - Lifetime US1722007A (en) 1925-05-11 1926-03-19 Sound-amplifying device for sound reproducing and recording instruments
US96009A Expired - Lifetime US1722008A (en) 1925-05-11 1926-03-19 Sound-reproducing apparatus
US96010A Expired - Lifetime US1730286A (en) 1925-05-11 1926-03-19 Sound-producing apparatus

Family Applications Before (1)

Application Number Title Priority Date Filing Date
US96008A Expired - Lifetime US1722007A (en) 1925-05-11 1926-03-19 Sound-amplifying device for sound reproducing and recording instruments

Family Applications After (1)

Application Number Title Priority Date Filing Date
US96010A Expired - Lifetime US1730286A (en) 1925-05-11 1926-03-19 Sound-producing apparatus

Country Status (5)

Country Link
US (3) US1722007A (en)
BE (3) BE335672A (en)
DE (2) DE463897C (en)
FR (3) FR613216A (en)
GB (3) GB256677A (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3015366A (en) * 1956-12-14 1962-01-02 George M Bishop Speaker system

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE943412C (en) * 1951-06-13 1956-05-17 Elbau Elektrotechnik Aappbau Protective body for sound emitters
DE949406C (en) * 1953-06-07 1956-09-20 Wilhelm Silberkuhl Dipl Ing Sound cabinet with several loudspeakers that stimulate resonators

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3015366A (en) * 1956-12-14 1962-01-02 George M Bishop Speaker system

Also Published As

Publication number Publication date
BE335672A (en)
FR613218A (en) 1926-11-12
FR613217A (en) 1926-11-12
BE335673A (en)
BE335674A (en)
DE463898C (en) 1928-08-06
US1730286A (en) 1929-10-01
GB256677A (en) 1926-08-11
US1722007A (en) 1929-07-23
GB259103A (en) 1926-10-07
FR613216A (en) 1926-11-12
GB261154A (en) 1926-11-18
DE463897C (en) 1928-08-06

Similar Documents

Publication Publication Date Title
US1808149A (en) Electrodynamic speaker
US3609253A (en) Loudspeaker with improved voice coil suspension
US1722008A (en) Sound-reproducing apparatus
US1866090A (en) Sound reproducing device
US2071828A (en) Loudspeaker, sound reproducing instrument, and the like
US1743194A (en) Radio loud-speaker
US1756838A (en) Sound-reproducing apparatus
US1552914A (en) Telephone device
US1931885A (en) Resonance box
US1733013A (en) Sound-reproducing device
US1893049A (en) Sound producing device
US1803892A (en) Loud speaker
US1653045A (en) Loud-speaker unit
US1735862A (en) Push-pull-actuated radial resonator
US1859921A (en) Acoustic device
US1868019A (en) Acoustic device
US1621562A (en) Electromagnetic sound reproducer
US1645051A (en) Sound-reproducing device
US1452827A (en) Telephone device
US1548740A (en) Sound-reproducing device
US1475754A (en) Sound box
US1656446A (en) Apparatus for reproducing sound
US1763056A (en) Sound-producing device
US1218799A (en) Phonograph recorder and reproducer.
US1484509A (en) Microphone transmitter