US3009528A - Electro-acoustical device for reproducing low pitch notes - Google Patents

Electro-acoustical device for reproducing low pitch notes Download PDF

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Publication number
US3009528A
US3009528A US672832A US67283257A US3009528A US 3009528 A US3009528 A US 3009528A US 672832 A US672832 A US 672832A US 67283257 A US67283257 A US 67283257A US 3009528 A US3009528 A US 3009528A
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US
United States
Prior art keywords
air
apertures
cone
box
loudspeaker
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
US672832A
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English (en)
Inventor
Mayr Hans
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.)
Industrie Magneti Marelli SRL
Marelli Europe SpA
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Magneti Marelli SpA
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Publication date
Application filed by Magneti Marelli SpA filed Critical Magneti Marelli SpA
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Publication of US3009528A publication Critical patent/US3009528A/en
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    • 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
    • H04R1/2815—Enclosures comprising vibrating or resonating arrangements of the bass reflex type
    • H04R1/2819—Enclosures comprising vibrating or resonating arrangements of the bass reflex type for loudspeaker transducers
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R7/00—Diaphragms for electromechanical transducers; Cones
    • H04R7/02—Diaphragms for electromechanical transducers; Cones characterised by the construction
    • H04R7/12—Non-planar diaphragms or cones
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R7/00—Diaphragms for electromechanical transducers; Cones
    • H04R7/02—Diaphragms for electromechanical transducers; Cones characterised by the construction
    • H04R7/12—Non-planar diaphragms or cones
    • H04R7/122—Non-planar diaphragms or cones comprising a plurality of sections or layers

Definitions

  • the present invention relates to electroacoustical units and more particularly to loudspeakers for reproducing low pitch notes.
  • conventional loudspeakers are not well adapted to reproduce low pitch notes, the wave 5 lengths of which are greater than the dimensions of the loudspeaker. This is due to the fact that the two faces of the vibrating cone of a conventional loudspeaker act as two sources of sound with opposed phases. If, for instance, the cone moves forward, the front face tends to compress air while the rear face tends to rarify it. The differences of pressure so produced tend to be eliminated, creating only a current of air around the cone of the loudspeaker, and thus no sensible acoustic radiation is produced.
  • a better system which is also well-known, is to use a box inwhich there are provided apertures of suitable dimensions so that air can leave the box if compressed or can enter if the air inside of the box is rarified.
  • the air passing through the apertures opposes movement due to inertia of its mass and forms a resonant system with the air in the interior of the box, which reacts against compression like a spring.
  • the frequency of that system is made to coincide with that of the associated loudspeaker.
  • the reaction of the air in the apertures overcomes that of the air in the box. There then occurs considerable compression in the interior of the box, and a limited flow of air from the apertures.
  • the movement of air in the apertures is in opposite direction with respect to that in the interior of the cone such that, for example, if the cone moves inwards air is sucked into the interior through the apertures, or vice versa.
  • the apertures behave like a second source of sound reinforcing the loudspeaker.
  • the movement of air in'the apertures reverses the phase and opposes the sound-effect of the loudspeaker.
  • the main defect of that system is the considerable distance between the apertures and cone, so that the movement of air in the apertures is no longer in phase with the external face of the cone. Moreover, sound is radiated in part by the apertures and in part by the loudspeaker; the two parts must compound with each other in external space to yield the complete and entire sound. The reproduction obtained is very poor.
  • the loudspeaker is assembled in a completely closed box which leaves only the front face of the cone free.
  • the cone of the loudspeaker itself there are provided one or more apertures which permit communication of the air enclosed in the box with the external space.
  • the number of those apertures and their area are chosen preferably in such way as to tune the box approximately with the resonant frequency of the loudspeaker itself and to avoid weakening the cone too much which latter advantage may be achieved by using a great number of small apertures in lieu of few large apertures.
  • FIGURES l and 2 illustrate a section and front view of a device provided with a magnetodynamic loudspeaker.
  • FIG. 3 is a variant of the preceding figures.
  • FIGS. 1 and 2 is illustrated an electroacoustical device comprising a conical membrane 3 including a peripheral portion 3a and a central portion 31;.
  • This device further includes in the central portion 13b means "4 responsive to magnetic variations for being vibrated.
  • magnetic means 5 are operatively positioned with respect to means 4 to produce the magnetic variations necessary to vibrate the latter.
  • a support or casing 1 is provided to support the membrane 3 by means of the peripheral portion 3a thereof.
  • the membrane defines at least one aperture 4' for the passage of air through said membrane. The aperture is spaced from 0 the means 4 by a distance which is less than one-half of there are thus two sources which enhance each other,
  • the membrane 3 divides the casing 1 into two chambers 6 and 7 which chambers are connected through the apertures '4'.
  • the mechanical reactance due to the inertia of the air in the apertures is higher than that due to the rigidity of v the air in the box.
  • the air contained therein is compressed. This pressure acts upon the walls of the box, including the loudspeaker cone and, therefore, also upon the air in the apertures, and tries to expel it.
  • Due to the inertia of the air in the apertures this air assumes such a movement that its acceleration is directed towards the exterior. For an oscillatory movement as is verified in acoustics, this corresponds to a movement of direction opposed to acceleration and is directed towards the interior.
  • the cone moves towards the interior of the box, the air in the holes is sucked towards the interior, and
  • the air is blown 3 from the holes towards the outside.
  • the air passing through the holes assists and enhances, therefore, the sound-action of the loudspeaker.
  • the reactance of the air in the apertures is equal to the reactance of the air in the box, with the result that the least movement of the cone causes a flow of air in the apertures, together with a strong pressure upon the cone that opposes its movement.
  • the overall result is that the cone remains nearly motionless, while the role of a source of sound is assumed by the air in the apertures.
  • the reactance of the air in the apertures is smaller than that of the air in the box.
  • the air in the box is slightly compressed, but leaves from the apertures with a movement opposite that of the air displaced by said cone.
  • the volume of air leaving the apertures is greater than that of the air displaced by the cone.
  • the apertures are more effective as a source of sound than is the cone.
  • the particular effectiveness of the apertures in the cone according to the invention lies in that the two sources of sound, that is, the cone itself and the apertures, cooperate positively, and in that the air emitted by the apertures joins immediately that displaced by the cone to form in practice a single source of sound to the end of optimum sound-radiation. All the obnoxious effects of non-uniformity of the sound-field are prevented, as might otherwise occur in the case of multiple sources.
  • the apertures may be advantageously arranged at approximately equal distance between the apex of the cone and its border, said distance being that measured along a generating line.
  • the arrangement indicated in FIG. 3 may be useful, where 4 indicates the apertures.
  • An electro-acoustical device comprising a conical membrane for reproducing a range of audio frequencies including peripheral and central portions and further including, in the central portion, means responsive to magnetic variations for being vibrated, magnetic means operatively positioned with respect to the first said means and adapted for producing the magnetic variations, and a support supporting the membrane by means of said peripheral portion, said support defining a chamber in which said conical membrane is mounted and having a single opening substantially closed by said membrane, said membrane defining apertures for the passage of air from said chamber, said apertures having an area whercby the resonant frequency of the chamber is matched to that of said membrane, said membrane and magnetic means being supported on said support adjacent said opening.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Multimedia (AREA)
  • Health & Medical Sciences (AREA)
  • Otolaryngology (AREA)
  • Audible-Bandwidth Dynamoelectric Transducers Other Than Pickups (AREA)
US672832A 1956-07-24 1957-07-18 Electro-acoustical device for reproducing low pitch notes Expired - Lifetime US3009528A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
IT556921 1956-07-24

Publications (1)

Publication Number Publication Date
US3009528A true US3009528A (en) 1961-11-21

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ID=11120284

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US672832A Expired - Lifetime US3009528A (en) 1956-07-24 1957-07-18 Electro-acoustical device for reproducing low pitch notes

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US (1) US3009528A (en))
BE (1) BE559436A (en))
CH (1) CH355813A (en))
DE (1) DE1109736B (en))
FR (1) FR1183056A (en))
GB (1) GB854851A (en))
NL (2) NL219278A (en))

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2546022A1 (fr) * 1983-05-10 1984-11-16 Philips Nv Transducteur electro-acoustique muni d'une membrane permeable a l'air

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3929266C1 (en)) * 1989-09-02 1991-01-03 Mercedes-Benz Aktiengesellschaft, 7000 Stuttgart, De
US5159139A (en) * 1990-06-13 1992-10-27 Evans Products, Inc. Drumhead with overtone suppression
DE102015106240A1 (de) * 2015-04-23 2016-10-27 Valeo Schalter Und Sensoren Gmbh Ultraschallsensor für ein Kraftfahrzeug mit einer Durchgangsöffnungen aufweisenden Membran, Verkleidungsanordnung sowie Kraftfahrzeug

Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB256395A (en) * 1925-07-29 1926-08-12 Charles Mahe De Chenal De La B Improvements in, or relating to, loud-speakers, gramophones, and other sound-recording or reproducing apparatus
US1869178A (en) * 1930-08-15 1932-07-26 Bell Telephone Labor Inc Sound translating device
US1997790A (en) * 1931-03-07 1935-04-16 Stephen L Heidrich Acoustic diaphragm
US2022060A (en) * 1934-08-29 1935-11-26 Bell Telephone Labor Inc Acoustic device
US2122587A (en) * 1925-07-20 1938-07-05 Rca Corp Acoustic device
US2712360A (en) * 1954-05-06 1955-07-05 Reisz Eugene Membrane for sound reproducing devices
US2732908A (en) * 1951-12-05 1956-01-31 brittain
US2766839A (en) * 1953-03-16 1956-10-16 Research Corp Loudspeaker system
US2845135A (en) * 1955-09-26 1958-07-29 Arthur Blumenfeld Auxiliary wave propagating and directing attachment for loudspeaker diaphragms

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB248497A (en) * 1924-12-12 1926-03-11 John Sydney Robert James Improvements in and relating to diaphragms for sound boxes
DE463900C (de) * 1925-05-05 1928-08-04 Kallistophon G M B H Elektromagnetischer Lautsprecher mit einer als Faecher ausgebildeten Schallmembran
GB301638A (en) * 1927-11-24 1928-12-06 Sidney George Brown Improvements in or relating to loud speakers
DE557850C (de) * 1929-06-12 1932-09-01 Cantora Soc Tonwiedergabevorrichtung, Schalldose fuer Sprechmaschinen, elektrischer Lautsprecher o. dgl.
DE593201C (de) * 1931-04-15 1934-02-23 I M K Syndicate Ltd Vorrichtung zur Bildzerlegung und Bildzusammensetzung beim Fernsehen
DE667495C (de) * 1935-07-09 1938-11-12 Telefunken Gmbh Verfahren zur Herabsetzung der Eigenschwingungszahl auf einen festgelegten Sollwert von nach dem Pappenguss- bzw. Schoepfverfahren hergestellten Lautsprechermembranen

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2122587A (en) * 1925-07-20 1938-07-05 Rca Corp Acoustic device
GB256395A (en) * 1925-07-29 1926-08-12 Charles Mahe De Chenal De La B Improvements in, or relating to, loud-speakers, gramophones, and other sound-recording or reproducing apparatus
US1869178A (en) * 1930-08-15 1932-07-26 Bell Telephone Labor Inc Sound translating device
US1997790A (en) * 1931-03-07 1935-04-16 Stephen L Heidrich Acoustic diaphragm
US2022060A (en) * 1934-08-29 1935-11-26 Bell Telephone Labor Inc Acoustic device
US2732908A (en) * 1951-12-05 1956-01-31 brittain
US2766839A (en) * 1953-03-16 1956-10-16 Research Corp Loudspeaker system
US2712360A (en) * 1954-05-06 1955-07-05 Reisz Eugene Membrane for sound reproducing devices
US2845135A (en) * 1955-09-26 1958-07-29 Arthur Blumenfeld Auxiliary wave propagating and directing attachment for loudspeaker diaphragms

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2546022A1 (fr) * 1983-05-10 1984-11-16 Philips Nv Transducteur electro-acoustique muni d'une membrane permeable a l'air

Also Published As

Publication number Publication date
GB854851A (en) 1960-11-23
CH355813A (fr) 1961-07-31
BE559436A (en))
NL109829C (en))
FR1183056A (fr) 1959-07-02
DE1109736B (de) 1961-06-29
NL219278A (en))

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