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WO1998058521A1 - Haut-parleur - Google Patents

Haut-parleur Download PDF

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Publication number
WO1998058521A1
WO1998058521A1 PCT/US1998/012688 US9812688W WO9858521A1 WO 1998058521 A1 WO1998058521 A1 WO 1998058521A1 US 9812688 W US9812688 W US 9812688W WO 9858521 A1 WO9858521 A1 WO 9858521A1
Authority
WO
WIPO (PCT)
Prior art keywords
radiator
diaphragm
apex
piezoelectric
conical
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.)
Ceased
Application number
PCT/US1998/012688
Other languages
English (en)
Inventor
Clifford L. Blodget
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.)
ULTRA RESEARCH Inc
Original Assignee
ULTRA RESEARCH 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 ULTRA RESEARCH Inc filed Critical ULTRA RESEARCH Inc
Priority to AU79773/98A priority Critical patent/AU7977398A/en
Publication of WO1998058521A1 publication Critical patent/WO1998058521A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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
    • H04R17/00—Piezoelectric transducers; Electrostrictive transducers

Definitions

  • the invention concerns an improved loudspeaker design wherein a stiff vertical conical sound source is driven by a piezoelectric driver.
  • Walsh further added sound absorbing material positioned at the non-driven end of the diaphragm in order to absorb wave energy in the diaphragm and to avoid reflected waves returning into the diaphragm. Walsh believed that this feature caused vibratory waves to traverse the diaphragm substantially only once. Walsh also described the sound produced by his device as radiating only from the convex side of the diaphragm. He described the sound from a single radiator as omnidirectional, high quality, and as having a full frequency range.
  • One interesting feature of Walsh's speaker design was his use of the convex, or outside, surface of the diaphragm as the sound radiating surface. This is contrasted with the conventional speaker design in which the sound radiating surface is perceived as the concave or inner surface.
  • Walsh further described his concept of coherent sound embodied in his device as resulting from the diaphragm being completely effective due to all parts cooperating to deliver one "bit" of audio signal contained in the electrical input to the listener's ear in one instant.
  • Walsh contrasted this diaphragm behavior with that of conventional speaker diaphragms which he described as a completely disorganized vibrating surface at middle and high frequencies.
  • Walsh presented an unconventional design of a loudspeaker diaphragm, and several new and innovative ideas in his coherent sound concept, he continued to rely upon the traditional and conventional means of transferring electrical signals to acoustic signals.
  • Walsh relied upon an electro-magnetic voice coil mechanism to provide the vibratory force to his diaphragm.
  • This mechanism is well known to those practiced in the art and consists of a coil of wire carefully wound about a cylindrical tube to which the diaphragm is attached.
  • the cylindrical coil is placed in a specially designed magnetic structure, also well known to those practiced in the art, and the electrical signals fed to the voice coil interact with the surrounding magnetic field causing the coil and attached diaphragm to vibrate axially at frequencies and velocities determined by the alternations and strength of the electrical signal.
  • Walsh's diaphragm was held in place in the speaker frame by flexible attachments at the driven and the non-driven end of his diaphragm. These attachments are well known to those practiced in the art and generally referred to as a "surround” and a "spider".
  • the surround attaches to speaker frame and the non-driven end of the diaphragm and serves to maintain the axial orientation of the diaphragm as well as to assist the spider (which is attached at the driven end) in maintaining the centered, axial position of the voice coil and keeping it properly inserted in the magnetic structure.
  • Walsh's application despite his claim to have invented a mechanism for the production of coherent sound, he relies upon sound absorptive materials placed both at the non-driven end and about the driven end of his diaphragm and the damping effect of the surround and spider. It appears that Walsh preserved the coherence of the sound produced by his diaphragm by filtering and damping those frequencies and waves that would interfere with the desired response to the signal transmitted to the diaphragm by the voice coil.
  • Walsh describes in detail his interpretation of the action of the vibratory waves as they traveled through the diaphragm of his speaker. He presents mathematical formulas expressing a relationship between the wave or vibratory action and the angle of inclination of the diaphragm measured from a surface perpendicular to the diaphragm axis. Walsh contrasts the angle of his diaphragm, as steep as eighty degrees, with that of the conventional diaphragm, typically on the order of thirty degrees. In practice the Walsh loudspeaker design has not supplanted the conventional loudspeaker design and appears to have faded from use.
  • Hegeman employs a fixed acoustic load, described as a "solid fixed conical plug" which is placed inside the conical diaphragm so as to largely displace the inner air volume within the cone. Hegeman also describes a small inverted cone, secured to the driven-end of the conical radiator, which is used to reduce acoustic interference within the radiator. Hegeman's acoustic radiator is also attached to the speaker frame by means of one or two spider attachments at points near the driven-end of the radiator, which serve to maintain axial alignment and the position of the voice coil within the magnetic structure.
  • Hegeman's acoustic radiator does not use a surround to attach the non-driven end of the radiator cone to the speaker frame. Nor does Hegeman's acoustic radiator employ sound absorptive materials at the non-driven end of the radiator, though the above described "solid fixed conical plug" would seem to serve a similar purpose.
  • An additional difference is Hegeman's use of a conical radiator that is cut at the non-driven end on a plane that is not perpendicular to the axis of the radiator, essentially producing an unbalanced and flared cone.
  • Hegeman describes his acoustic radiator as an "infinite number of point sources, each out of phase with the other.” This is contrasted with Walsh's description of his similar device as being completely coordinated.
  • the third example of prior art important to this application is that of H. W. Schafft, U.S. Patent 3,786,20 1, Acoustic Transducer Including Piezoelectric Driving Element, issued January 15, 1974.
  • Schafft describes a piezoelectric element utilized as a driver of an acoustic transducer.
  • the piezoelectric element is a planar device specially designed to bend or warp in response to an electrical stimulation, such as would be used to carry an acoustical signal.
  • Schafft describes his piezoelectric driver as being attached to the truncated apex of a generally conical diaphragm, of the standard design.
  • the electrical signal excitation of the planar piezoelectric device serves to transmit vibrations to the diaphragm which produces sound.
  • the diaphragm is attached to a speaker frame and Schafft describes several damping mechanisms employed to reduce the uneven frequency response and produce a generally flat or even response to different frequency within a range.
  • the piezoelectric driver is quite different from the traditional or conventional electromagnetic voice coil driver most often used in loudspeaker devices.
  • the piezoelectric driver is attached to the truncated apex of a conical speaker diaphragm which, in turn, is attached to a frame or housing by a flexible surround.
  • the piezoelectric driver is comprised of a sandwich-like element, having a metallic centervane, oppositely poled ceramic wafers, a fine mesh conductive material, and electrodes for attaching the element to an electric signal source.
  • the ceramic components are attached to the centervane on opposite sides.
  • the fine mesh conductive material is then attached to each ceramic component as the outermost layer. This permits an electric current to be applied to the centervane and the fine mesh material which serves to permit an alternating current, or signal, to be applied to the ceramic components, thus producing a flexion or vibratory motion which is used to drive an attached speaker diaphragm and create sound.
  • the ceramic components are constructed so as to be uniform in thickness, generally circular, and imparted with a permanent electrical field orientation, or polarity, analogous to a magnet. As a result of the polarity, the diameter of the ceramic wafer will either expand or shrink when an electrical voltage is applied.
  • the electro-magnetic voice coil has a number of characteristics that are in contrast with the piezoelectric driver.
  • One of the most important for the present application is the lesser ability of the voice coil to respond accurately to transient signals and high frequency signals.
  • the electromagnetic induction action of the voice coil which is its basis of operation, is well known to those skilled in the art to have lessened response characteristics to higher frequencies and sharp transient signals. This is due to the susceptibility of the voice coil to impedance at higher frequencies.
  • the voice coil driver does have a wide range of travel, or excursion, which is especially useful in reproducing lower frequencies.
  • the piezoelectric driver has a relatively narrow excursion or range of travel and offers a very strong immediate response to high frequencies and transient signals.
  • Each of the three examples of prior art represents some degree of improvement in the art of reproducing audio signals and transmitting sound. However, each device fails to provide a significant improvement over conventional designs due to inefficiencies and inconsistencies in the design.
  • the coherent-sound device of Walsh relies upon a conical diaphragm that possesses a significantly stiff and rigid acoustic profile. Unlike conventional design loudspeaker diaphragms, the Walsh device does not provide flexion and resilience to the resistance of the air mass when driven by the electro-magnetic voice coil driver. The same may be said of the Hegeman acoustic resonator.
  • the diaphragm At the initial moment of thrust from the voice coil in response to a signal, resistance, or impedance, of the diaphragm provides sufficient opposition to the force of the voice coil to prevent a true and accurate reproduction of the sound conveyed by the electrical signal.
  • the Schafft piezoelectric transducer driver With respect to the Schafft piezoelectric transducer driver, it lacks the smooth or flat response to the frequencies within the range it is designed to reproduce.
  • the piezoelectric driver tends to have a spiked or noticeably stronger response to certain frequencies, and concomitantly a lower or noticeably weaker response to certain other frequencies.
  • the piezoelectric driver is used to drive a conventional type diaphragm for production of sound.
  • the resilience and flexion of the conventional diaphragm causes the sharp transient response of the piezoelectric driver to be lost at the initial thrust, and fails to take full advantage of the piezoelectric drivers ability to reproduce sharp and clear high frequency signals.
  • the truncated conical diaphragm attached to the center of the piezoelectric element is thus caused to vibrate axially, along a path that is perpendicular to the diameter of the piezoelectric element.
  • This vibratory path of the diaphragm causes the diaphragm to act as a piston, alternately pushing and pulling the air mass coupled to the concave or inner area of the diaphragm.
  • the diaphragm is very widely flared and made of a material that is significantly less rigid than the piezoelectric element, the diaphragm will flex or bend in response to both its own inertia and the inertia) force of the air.
  • the size of the diaphragm is greatly limited by the need to reduce this flexion action.
  • the practical limitation on the size of the diaphragm is such that its diameter rarely exceeds twice that of the piezoelectric element to which it is attached, and the mismatch between the characteristics of the piezoelectric element and standard loudspeaker diaphragms creates a severe limitation in the designs and sound reproduction possible with the piezoelectric element driven loudspeaker.
  • the piezoelectric driver In constant to the electromagnetic voice coil driver, the piezoelectric driver has a strong initial thrust to high frequency and transient electrical signals. Therefore, the driver is ideally suited to the reproduction of high-frequency transient signals, such as snare drum, percussion, instrument coloration, and consonants in speech. This ability is lost in the prior art and present practice due to use of an unmatched diaphragm as the means of transmitting the electrical signal to the surrounding air.
  • the present invention overcomes the shortcomings of the prior art and represents a significant advance in the art of loudspeaker design.
  • the present device combines the high quality sound reproduction possible with a sharply inclined conical diaphragm and the clear high frequency and sharp transient response possible with the piezoelectric driver.
  • the invention provides a loudspeaker reproducing audio signals comprising: a piezoelectric drive element, having a major surface, electrodes attached to said drive element for driving the element in a bending mode to reproduce an audio signal when the electrodes are properly energized, and a radiator having an enlarged open end and an apex, constructed of an acoustically stiff material such that an audio signal from the piezoelectric drive element propagates a wave form in the acoustically stiff material traveling form the apex to the enlarged open end at a speed greater than the speed of sound in air, the traveling propagated wave coupling the audio signal radially to the surrounding air, the radiator having the piezoelectric drive element fixedly connected to its apex end, the outer surface of said radiator being freely exposed for radiation generally radially of the flare axis.
  • the angle of flare of the radiator is between 5 and 45 degrees measured from the longitudinal axis.
  • the enlarged open end of the radiator may be free floating.
  • two or more generally conical acoustic radiators having different flare angles from the longitudinal axis are fixedly connected to the piezoelectric drive.
  • the wider flared of said acoustic radiators has a shorter height than the narrower flared.
  • the drive element comprises a plurality of piezoelectric drive elements arranged parallel to each other and perpendicular to the vertical axis, each connected by means permitting the plurality of piezoelectric drive elements to vibrate in unison, and having rigid means to maintain the parallel orientation and spacing of said plurality of said drive elements.
  • the speaker has flexible means to provide damping of the plurality of the piezoelectric drive elements wherein the radiator is conical.
  • the radiator may be cut at the enlarged end.
  • a circularly or elliptically symmetrical conical acoustical radiator may be cut at its wide end along a line appearing in two dimensions as a parabola formed by the intersection of said conical diaphragm and a Plane surface directed angularly through said conical diaphragm and intersecting the longitudinal axis of said conical diaphragm at a point opposite the apex at or beyond the centroid of the interior of said conical diaphragm.
  • the invention Provides an acoustic transducer comprising a substantially conical diaphragm having attached at its apex a piezoelectric driver whereby electricity conducted signals are reproduced as sound, the improvement which comprises using a stiff narrow cone wherein the angle between the centerline of the cone and the surface of the cone is 5° to 45° and the sound radiates due to waves propagated in the cone the sound being propagated radially substantially perpendicular to the axis of the cone.
  • An acoustic transducer comprising: a plurality of concentric conical diaphragms each attached near the apex to a piezoelectric driver whereby electrically conducted signals in the driver are reproduced as sound.
  • the radiator 1 is constructed of a thin, acoustically stiff material so as to be lightweight and to conduct the vibratory force imparted by the piezoelectric driver directly with as little alteration as possible from flexion, elasticity, or other properties of the radiator material.
  • the radiator is attached at its apex to the piezoelectric drive element 2 at its center, preferably by means of a strong, non conductive adhesive.
  • a suitable adhesive possesses sufficient elasticity to avoid brittleness, and permanently affixes the radiator to the piezoelectric drive element.
  • the vibratory force of the drive element is conducted to the radiator as a wave, where the wave travels up the radiator from its apex and couples with the surrounding air producing sound that is radiated outward in a circular directional area, having a dispersion pattern that includes the area approximately 35 degrees above and below the horizontal axis.
  • the radiator does not act as a piston on its longitudinal axis, the size and material limitations applicable to diaphragms inherent in standard speaker designs such as tweeter designs do not apply. Instead, the design is oriented to producing the most pleasing and accurate emission of sound from the radiator.
  • the radiator may be constructed by cutting the appropriate shape from a flat sheet of the suitable material and forming it into a cone, with a seam.
  • the radiator may be any shape, having an apex and an enlarged end, however a cone is preferred.
  • the acoustic properties of the radiator may be modified by cutting the material for example, cutting the radiator in such a fashion as to produce a shape, being similar to a conic section produced by passing a planar surface through the cone at a non-normal angle to the longitudinal axis.
  • FIG. 3 depicts four piezoelectric elements in series-parallel combination to which the acoustic radiator is attached.
  • the centers of each drive element are connected by a column of rigid material, so that the vibratory force of the elements is combined to form a more powerful and acoustically efficient unit.
  • the acoustical properties of the device may be further altered by damping the piezoelectric driver with a suitable material placed 3 so as to physically damp its vibratory response to the electrical signal, thereby smoothing its response characteristics and removing response spikes at certain frequencies.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Piezo-Electric Transducers For Audible Bands (AREA)

Abstract

On décrit un haut-parleur combinant les caractéristiques suivantes: des constituants peu coûteux, une fabrication simple et une reproduction précise et efficace des signaux sonores haute fréquence y compris une reproduction exceptionnellement nette et précise des signaux transitoires. Le dispositif représente une combinaison des améliorations apportées à des hauts-parleurs actuels, dans une nouvelle configuration jamais utilisée auparavant dans cette technique. Cette invention concerne un haut-parleur reproduisant des signaux sonores et qui comprend: un élément d'excitation piézoélectrique (2) comportant une surface principale, des électrodes qui sont fixées à l'élément pour exciter celui-ci dans un mode de flexion pour reproduire un signal sonore lorsque les électrodes sont excitées correctement, et un cône de rayonnement (1) comportant une extrémité ouverte élargie et un sommet et construit dans un matériau rigide du point de vue acoustique, de telle sorte qu'un signal sonore partant de l'élément d'excitation piézoélectrique propage une onde dans ledit matériau, laquelle se déplace du sommet jusqu'à l'extrémité ouverte élargie à une vitesse supérieure à la vitesse du son dans l'air, l'onde propagée en déplacement couplant le signal sonore, de manière radiale, à l'air environnant, l'élément d'excitation piézoélectrique étant fixé à demeure sur l'extrémité du sommet du cône de rayonnement, la surface externe de ce dernier étant librement exposée pour émettre des rayonnements globalement radialement par rapport à l'axe d'évasement du cône.
PCT/US1998/012688 1997-06-17 1998-06-17 Haut-parleur Ceased WO1998058521A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU79773/98A AU7977398A (en) 1997-06-17 1998-06-17 Loudspeaker

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
US4980697P 1997-06-17 1997-06-17
US60/049,806 1997-06-17
US9869098A 1998-06-17 1998-06-17
US09/098,690 1998-06-17

Publications (1)

Publication Number Publication Date
WO1998058521A1 true WO1998058521A1 (fr) 1998-12-23

Family

ID=26727556

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US1998/012688 Ceased WO1998058521A1 (fr) 1997-06-17 1998-06-17 Haut-parleur

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Country Link
AU (1) AU7977398A (fr)
WO (1) WO1998058521A1 (fr)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2001054450A3 (fr) * 2000-01-24 2002-04-25 New Transducers Ltd Transducteur
US6865277B2 (en) 2000-01-27 2005-03-08 New Transducers Limited Passenger vehicle
US6885753B2 (en) 2000-01-27 2005-04-26 New Transducers Limited Communication device using bone conduction
US6965678B2 (en) 2000-01-27 2005-11-15 New Transducers Limited Electronic article comprising loudspeaker and touch pad
US7151837B2 (en) 2000-01-27 2006-12-19 New Transducers Limited Loudspeaker

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3032136A (en) * 1956-09-27 1962-05-01 Jr Andrew Stewart Hegeman Loudspeaker
US3749855A (en) * 1969-01-09 1973-07-31 Motorola Inc Resistive electrode for an electrostrictive transducer
US4330729A (en) * 1980-07-30 1982-05-18 General Electric Company Locking support arrangement for a flexible sound-generating diaphragm
US4401857A (en) * 1981-11-19 1983-08-30 Sanyo Electric Co., Ltd. Multiple speaker
US5652801A (en) * 1994-05-02 1997-07-29 Aura Systems, Inc. Resonance damper for piezoelectric transducer

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3032136A (en) * 1956-09-27 1962-05-01 Jr Andrew Stewart Hegeman Loudspeaker
US3749855A (en) * 1969-01-09 1973-07-31 Motorola Inc Resistive electrode for an electrostrictive transducer
US4330729A (en) * 1980-07-30 1982-05-18 General Electric Company Locking support arrangement for a flexible sound-generating diaphragm
US4401857A (en) * 1981-11-19 1983-08-30 Sanyo Electric Co., Ltd. Multiple speaker
US5652801A (en) * 1994-05-02 1997-07-29 Aura Systems, Inc. Resonance damper for piezoelectric transducer

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2001054450A3 (fr) * 2000-01-24 2002-04-25 New Transducers Ltd Transducteur
US7149318B2 (en) 2000-01-24 2006-12-12 New Transducers Limited Resonant element transducer
US7684576B2 (en) 2000-01-24 2010-03-23 New Transducers Limited Resonant element transducer
US6865277B2 (en) 2000-01-27 2005-03-08 New Transducers Limited Passenger vehicle
US6885753B2 (en) 2000-01-27 2005-04-26 New Transducers Limited Communication device using bone conduction
US6965678B2 (en) 2000-01-27 2005-11-15 New Transducers Limited Electronic article comprising loudspeaker and touch pad
US7151837B2 (en) 2000-01-27 2006-12-19 New Transducers Limited Loudspeaker

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Publication number Publication date
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