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WO1993007729A1 - Enceinte acoustique a depression - Google Patents

Enceinte acoustique a depression Download PDF

Info

Publication number
WO1993007729A1
WO1993007729A1 PCT/US1991/007324 US9107324W WO9307729A1 WO 1993007729 A1 WO1993007729 A1 WO 1993007729A1 US 9107324 W US9107324 W US 9107324W WO 9307729 A1 WO9307729 A1 WO 9307729A1
Authority
WO
WIPO (PCT)
Prior art keywords
diaphragm
force
loudspeaker
loudspeaker system
chamber
Prior art date
Application number
PCT/US1991/007324
Other languages
English (en)
Inventor
Andrew J. Langley
Michael J. Parrella
Jeffrey N. Denenberg
Original Assignee
Noise Cancellation Technologies, Inc.
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 Noise Cancellation Technologies, Inc. filed Critical Noise Cancellation Technologies, Inc.
Priority to PCT/US1991/007324 priority Critical patent/WO1993007729A1/fr
Priority to CA002120488A priority patent/CA2120488A1/fr
Priority claimed from CA002120488A external-priority patent/CA2120488A1/fr
Publication of WO1993007729A1 publication Critical patent/WO1993007729A1/fr

Links

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 
    • 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
    • H04R1/42—Combinations of transducers with fluid-pressure or other non-electrical amplifying means
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R9/00—Transducers of moving-coil, moving-strip, or moving-wire type
    • H04R9/02—Details

Definitions

  • This invention relates to a loudspeaker system having a rear chamber with a static pressure lower than that on the opposite side of the diaphragm.
  • Conventional loudspeaker systems for example, sealed box types, employ a large rear chamber to prevent sound from being radiated by the rear side of the loudspeaker diaphragm. This situation often results in inconveniently large enclosures being necessary
  • a still further object of this is to provide a lower static pressure in the rear chamber of a speaker system that reduces the resonance frequency of the enclosures thereby allowing for a small enclosure.
  • Another object of this invention is to provide a bellows or spring to counteract the static force on the front of the diaphragm produced by a low static pressure behind the diaphragm.
  • a "closed-box" sometimes called an infinite-baffle loudspeaker system
  • the back of the loudspeaker unit is sealed by a closed chamber of volume V in order to stop sound being radiated by the back of the loudspeaker's diaphragm.
  • Sr is the area of the loudspeaker diaphragm p s the density of the gas in the closed chamber behind the unit c is the speed of sound in the gas of the closed chamber
  • V is the closed chamber volume.
  • M M . is the total "moving mass" of the loudspeaker diaphragm assembly.
  • V is to reduce the value of p. This can be readily achieved by reducing the static pressure in the back-chamber to a value p x , say, that is less than the atmospheric pressure, p. If we assume that the temperature of the gas in the back chamber does not change as the pressure is reduced, then from the gas laws
  • K i (p ! /p ) K which is less than K.
  • V i ( P i /p ) V ,
  • Fig. 1 shows a cross section of a system where a spring is used to counterbalance the static pressure differential
  • Fig. 2 shows a cross-section of a system utilizing a second diaphragm to counterbalance the static pressure differential of the system
  • Fig. 3 shows an alternative bellows that can be used to counterbalance the static pressure differential.
  • One way of counterbalancing the static force on the diaphragm due to the reduction in pressure of the back-chamber is to use a spring.
  • the static straining of the spring provides the counterbalancing force, and the dynamic stiffness of the spring adds to the stiffness of the back-chamber at reduced pressure to give the desired overall suspension stiffness for the loudspeaker diaphragm.
  • the spring must be a type that is capable of large static strains whilst maintaining an acceptably small dynamic stiffness.
  • the loudspeaker diaphragm 1 is flat, and constructed of a honeycomb-cored laminated structure of a type well-known in the field of building loudspeakers.
  • a moving-coil loudspeaker unit such as voice-coil former 3, voice-coil 4, spider 5, top-plate 6, magnet 7, back plate and center pole 8, chassis 9, and surround 14.
  • the coil spring 2 adjustable plate 10, adjusting means 11, and diaphragm stops 12 and 13.
  • the spider, 5 keeps the voice-coil centered, but other arrangements, such as a linear bearing can also be used.
  • the cavity formed by the sealed chassis 9 (or by an alternative back-chamber if the chassis is not a sealed unit) is held at a pressure lower than atmospheric, and the
  • K s is the dynamic stiffness of the spring.
  • the spring can be designed so as to minimize its part of the overall moving mass and to avoid resonances that tend to make its dynamic stiffness different from its static stiffness.
  • FIG. 2 shows another embodiment of the invention.
  • the static counterbalancing force on the diaphragm is supplied by a second, smaller, back- chamber 17 that is pressurized above atmospheric pressure.
  • One wall of the second chamber is a diaphragm 18 that is flexible enough to deform under the dynamic displacements of the loudspeaker diaphragm, and yet strong enough to withstand the static forces on it due to the pressure differences.
  • the diaphragm 18 is connected to the loudspeaker diaphragm 1 through a lightweight link 19.
  • the diaphragm is shown as a cone of the normal type, although this construction is not fundamental to the operation - any diaphragm strong enough to withstand the static pressure forces would suffice.
  • the second chamber, 17 can be mounted as in the previous embodiment on a backplate that can be moved relative to the magnet assembly, 6, 7 and 8, to allow adjustment for diaphragm offsets due to changes in atmospheric pressure.
  • the pressure in the second chamber 17 can be adjusted by exchanging gas with a reservoir 20.
  • a control system comprising a sensor 15 that can be used to derive the average position of the diaphragm 1, and a control means 16 controlling a pump 21 to effect the change in pressure in the second chamber 17, is also shown.
  • the purpose of this control system is to maintain the average position of the diaphragm 1 in the presence of atmospheric pressure changes ( or other perturbing influences such as temperature differentials).
  • the pressure in the second chamber can also be controlled by regulating the temperature of the gas with, for example, an electrically heated coil. In this case, the pump and reservoir are not required, and the second chamber can be completely sealed.
  • the pressure in the back-chamber behind the diaphragm 1 can be adjusted to maintain the average diaphragm position by means that are essentially the same as those indicated for adjusting the second-chamber 17 pressure.
  • This embodiment relies upon the fact that whilst the static forces on a diaphragm bounding a closed volume are proportional to the area of the diaphragm, the dynamic stiffness of a cavity is proportional to the square of the area of the diaphragm.
  • the volume of the back-chamber behind the diaphragm 1 is V ⁇
  • the pressure is p i .
  • the second chamber 17 has a volume of V 2
  • its diaphragm 18 has an area of S s . In that case, the
  • the total dynamic stiffness of the suspension of the loudspeaker diaphragm (ignoring spider 5, surround 14, and diaphragm 18 stiffness) is
  • K T ( S D - S s ) 2 p c 1 2 /V 1 + S P 2 /V 2
  • p 2 and C 2 are the density and speed of sound of the gas in the second chamber 17.
  • the gas in both chambers is air with an external atmospheric pressure of 1.013xl0 5 N/m 2 •
  • the p2 must be 9.22xl0 5 N/m 2
  • K- 984.4 N/m. This is equivalent to a back-chamber at atmospheric pressure of volume 32 liters.
  • the diaphragm 18 must be designed to deform over the range of movement of the diaphragm (say + 6mm) whilst still being able to withstand the pressure difference P2"P1 across it.
  • a diaphragm with a high membrane strength and stiffness, with relatively low bending stiffness is appropriate.
  • a moulded fibre reinforced rubber component is suitable.
  • Rigid end cap 22 takes the place of flexible diaphragm 18 in Figure 2, and the axial displacement of the end cap 22 is accommodated by distortion of the bellow's wall 23.
  • Bellows units are well known for their ability to deform flexibility in the axial direction whilst containing gas at high pressure. The design requires low axial stiffness coupled with the ability to compress or stretch by a few millimeters as the loudspeaker diaphragm moves. At the same time, the bellows must withstand the pressure differential (p 2 ⁇ p 1 ) across its walls. A material that is not susceptible to fatigue (such as phosphor - bronze ) is preferred.

Landscapes

  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Health & Medical Sciences (AREA)
  • Otolaryngology (AREA)
  • Diaphragms For Electromechanical Transducers (AREA)

Abstract

Une enceinte acoustique (9) comporte un panneau dorsal étanchéifié par l'intermédiaire d'une petite chambre close remplie d'un gaz agissant comme un ressort mécanique qui serait raccordé au diaphragme du haut-parleur (1). Ce système évite les problèmes inhérents aux chambres dorsales de grand volume en modifiant la pression statique qui y règne. On utilise un diaphragme souple monté sur ressorts (2) ou des soufflets (21) pour compenser les différences de pression.
PCT/US1991/007324 1991-10-02 1991-10-02 Enceinte acoustique a depression WO1993007729A1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
PCT/US1991/007324 WO1993007729A1 (fr) 1991-10-02 1991-10-02 Enceinte acoustique a depression
CA002120488A CA2120488A1 (fr) 1991-10-02 1991-10-02 Enceinte acoustique a vide

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
PCT/US1991/007324 WO1993007729A1 (fr) 1991-10-02 1991-10-02 Enceinte acoustique a depression
CA002120488A CA2120488A1 (fr) 1991-10-02 1991-10-02 Enceinte acoustique a vide

Publications (1)

Publication Number Publication Date
WO1993007729A1 true WO1993007729A1 (fr) 1993-04-15

Family

ID=25677162

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US1991/007324 WO1993007729A1 (fr) 1991-10-02 1991-10-02 Enceinte acoustique a depression

Country Status (1)

Country Link
WO (1) WO1993007729A1 (fr)

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1997009849A1 (fr) * 1995-09-02 1997-03-13 New Transducers Limited Haut-parleurs dotes d'elements radiants acoustiques en forme de panneau
US6320967B1 (en) 1995-09-02 2001-11-20 New Tranducers Limited Passenger vehicles incorporating loudspeakers comprising panel-form acoustic radiating elements
GB2379827A (en) * 2002-01-23 2003-03-19 Eugenie Sergeyevich Aleshin Loudspeaker enclosure at reduced pressure
US6739425B1 (en) * 2000-07-18 2004-05-25 The United States Of America As Represented By The Secretary Of The Air Force Evacuated enclosure mounted acoustic actuator and passive attenuator
US6904154B2 (en) 1995-09-02 2005-06-07 New Transducers Limited Acoustic device
GB2408890A (en) * 2003-09-22 2005-06-08 Eugenie Sergeyevich Aleshin Vacuum loudspeaker system
US7068806B2 (en) * 2003-01-14 2006-06-27 Walsh Casey P Condensed speaker system
US8042647B1 (en) 2009-03-16 2011-10-25 Robert Layton, Jr. Speaker side air supply
US20150281814A1 (en) * 2013-10-08 2015-10-01 Wistron Corporation Speaker module
WO2020033892A1 (fr) 2018-08-09 2020-02-13 Fallon James J Production de sons à l'aide d'une enceinte de haut-parleur à pression interne réduite
US10750261B2 (en) 2017-08-07 2020-08-18 James J. Fallon Recording high output power levels of sound at low sound pressure levels

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3772466A (en) * 1970-11-25 1973-11-13 Romen Kg Kdt Loud speaker system
US4547631A (en) * 1982-06-23 1985-10-15 U.S. Philips Corporation Large-excursion electroacoustic transducer
US4595801A (en) * 1983-10-27 1986-06-17 Ronald Coffin Coupled dual cone velocity driver speaker
US4607382A (en) * 1983-04-26 1986-08-19 U.S. Philips Corporation Electroacoustic transducer unit with reduced resonant frequency and mechanical spring with negative spring stiffness, preferably used in such a transducer unit
US5060274A (en) * 1988-06-10 1991-10-22 Ishikawajima-Harima Heavy Industries Co., Ltd. Hydrostatic speaker and speaker driver

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3772466A (en) * 1970-11-25 1973-11-13 Romen Kg Kdt Loud speaker system
US4547631A (en) * 1982-06-23 1985-10-15 U.S. Philips Corporation Large-excursion electroacoustic transducer
US4607382A (en) * 1983-04-26 1986-08-19 U.S. Philips Corporation Electroacoustic transducer unit with reduced resonant frequency and mechanical spring with negative spring stiffness, preferably used in such a transducer unit
US4595801A (en) * 1983-10-27 1986-06-17 Ronald Coffin Coupled dual cone velocity driver speaker
US5060274A (en) * 1988-06-10 1991-10-22 Ishikawajima-Harima Heavy Industries Co., Ltd. Hydrostatic speaker and speaker driver

Cited By (18)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6904154B2 (en) 1995-09-02 2005-06-07 New Transducers Limited Acoustic device
US6320967B1 (en) 1995-09-02 2001-11-20 New Tranducers Limited Passenger vehicles incorporating loudspeakers comprising panel-form acoustic radiating elements
US7194098B2 (en) 1995-09-02 2007-03-20 New Transducers Limited Acoustic device
US7158647B2 (en) 1995-09-02 2007-01-02 New Transducers Limited Acoustic device
WO1997009849A1 (fr) * 1995-09-02 1997-03-13 New Transducers Limited Haut-parleurs dotes d'elements radiants acoustiques en forme de panneau
US6739425B1 (en) * 2000-07-18 2004-05-25 The United States Of America As Represented By The Secretary Of The Air Force Evacuated enclosure mounted acoustic actuator and passive attenuator
GB2379827B (en) * 2002-01-23 2003-07-30 Eugenie Sergeyevich Aleshin Loudspeaker of closed type
GB2379827A (en) * 2002-01-23 2003-03-19 Eugenie Sergeyevich Aleshin Loudspeaker enclosure at reduced pressure
US7068806B2 (en) * 2003-01-14 2006-06-27 Walsh Casey P Condensed speaker system
GB2408890A (en) * 2003-09-22 2005-06-08 Eugenie Sergeyevich Aleshin Vacuum loudspeaker system
US8042647B1 (en) 2009-03-16 2011-10-25 Robert Layton, Jr. Speaker side air supply
US20150281814A1 (en) * 2013-10-08 2015-10-01 Wistron Corporation Speaker module
US10750261B2 (en) 2017-08-07 2020-08-18 James J. Fallon Recording high output power levels of sound at low sound pressure levels
US11425477B2 (en) 2017-08-07 2022-08-23 James J. Fallon Recording high output power levels of sound at low sound pressure levels
WO2020033892A1 (fr) 2018-08-09 2020-02-13 Fallon James J Production de sons à l'aide d'une enceinte de haut-parleur à pression interne réduite
US10979801B2 (en) 2018-08-09 2021-04-13 James J. Fallon Sound production using speaker enclosure with reduced internal pressure
US11595753B2 (en) 2018-08-09 2023-02-28 James J. Fallon Sound production using speaker enclosure with reduced internal pressure
US12225345B2 (en) 2018-08-09 2025-02-11 Monophase Llc Sound production using speaker enclosure with reduced internal pressure

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