ZA200101978B - Loudspeakers. - Google Patents

Loudspeakers. Download PDF

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Publication number
ZA200101978B
ZA200101978B ZA200101978A ZA200101978A ZA200101978B ZA 200101978 B ZA200101978 B ZA 200101978B ZA 200101978 A ZA200101978 A ZA 200101978A ZA 200101978 A ZA200101978 A ZA 200101978A ZA 200101978 B ZA200101978 B ZA 200101978B
Authority
ZA
South Africa
Prior art keywords
panel
drive unit
form member
unit according
loudspeaker drive
Prior art date
Application number
ZA200101978A
Inventor
Henry Azima
Original Assignee
New Transducers Ltd
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 New Transducers Ltd filed Critical New Transducers Ltd
Publication of ZA200101978B publication Critical patent/ZA200101978B/en

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Classifications

    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04RLOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R9/00Transducers of moving-coil, moving-strip, or moving-wire type
    • H04R9/06Loudspeakers
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04RLOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R7/00Diaphragms for electromechanical transducers; Cones
    • H04R7/16Mounting or tensioning of diaphragms or cones
    • H04R7/18Mounting or tensioning of diaphragms or cones at the periphery
    • H04R7/20Securing diaphragm or cone resiliently to support by flexible material, springs, cords, or strands
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04RLOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R7/00Diaphragms for electromechanical transducers; Cones
    • H04R7/02Diaphragms for electromechanical transducers; Cones characterised by the construction
    • H04R7/04Plane diaphragms
    • H04R7/045Plane diaphragms using the distributed mode principle, i.e. whereby the acoustic radiation is emanated from uniformly distributed free bending wave vibration induced in a stiff panel and not from pistonic motion
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04RLOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R9/00Transducers of moving-coil, moving-strip, or moving-wire type
    • H04R9/02Details
    • H04R9/04Construction, mounting, or centering of coil

Description

> ud © WO 00/22877 PCT/GB99/03209
TITLE: LOUDSPEAKERS
DESCRIPTION TECHNICAL FIELD
The invention relates to loudspeakers and more particularly to resonant panel loudspeakers, e.g. of the kind described in International patent application
W097/09842, i.e. so-called distributed mode loudspeakers. : BACKGROUND ART
In the past there has been great difficulty in providing a loudspeaker covering the mid and high frequency audio range at high quality. Directivity varies greatly in this range and extension to the highest frequencies is very difficult for mid driver alone. Typically two drivers are used with the expense and complication of a crossover network to divide the frequency range between them. The crossover frequency 1s generally around 3kHz which is the most sensitive in human hearing which adds to the difficulty.
The concept of the present invention is to devise a mid and high frequency driver which replaces the two convention drivers previously used, which does not crossover in the critical region and which has consistent, desirably wide directivity throughout its working range.
Distributed mode loudspeakers can be designed to operate over some B8-Octaves of the audio frequency band, although this may not always be the best solution, for instance in hi-fi applications. It is envisaged that it might sometimes be appropriate for a distributed mode loudspeaker to be used in association with a subwoofer for low frequencies, crossing over, say, at around 100 to 200
Hz. \
There is therefore a need for a loudspeaker or at least a loudspeaker drive unit that 1s not meant to necessarily work over B8-Octaves but perhaps over 6 to 7
Octaves of the audio band, which would allow a wide choice of material and various construction possibilities that would help optimise the loudspeaker fully over its operating range. An example c¢f this is a hi-fi midrange/tweeter drive unit working under the distributed mode loudspeaker principle. This can bring significant benefits to a conventional boxed loudspeaker system by allowing the cross-over point to be designed away from the critical 3kHz area down to 1kHz range, typically 300-500 Hz ad © WO 00/22877 PCT/GB99/03209 as well as benefiting from the superior radiation properties associated with a distributed mode loudspeaker.
There is also an expanding market in multimedia and computer peripherals for high performance compact speakers and ever increasing demand for better sound and more compact construction for conventional televisions, monitors and flat panel televisions.
Thus there is a need for a structure that can be very compact and which can allow numerous features to be added for performance enhancement, application versatility and cost saving.
The present invention provides a cost-effective vehicle for all such applications and allows a manufacturer to optimise on tooling outlay and its production processes.
The basic concept revolves around a simple construction of the loudspeaker “engine” or drive unit which would allow easy production assembly and provide consistency.
DISCLOSURE OF INVENTION
According to the invention there is provided a mid/high frequency loudspeaker drive unit comprising a stiff lightweight resonant panel-form member, a housing in which the panel-form member is mounted, a resilient suspensicn connected between the edges of the panel-form member and the housing, the arrangement being such that the housing and the panel-form member together define a sealed enclosure, and an electrodynamic vibration exciter for applying bending wave energy to the panel-form member to
© WO 00/22877 PCT/GBY9/03209 cause it to resonate to produce an acoustic output, the exciter comprising a magnet assembly rigidly fixed to the housing and defining an annular gap and a voice coil disposed in the annular gap and rigidly fixed to the panel- form member near to the geometric centre thereof, the location of the voice coil in the annular gap being provided by the said resilient suspension.
The bending stiffness of the panel-form member may be in the range 0.15Nm to 24Nm and is preferably in the range
ZNm to 9Nm.
The vibration exciter may be bonded to the panel-form member (herein after ‘panel’)and/or to the enclosure by way of injection moulding or by use of the adhesive. The vibration exciter voice coil may be bonded directly to a resonant panel during the injection moulding of the panel.
Alternatively the voice coil of an exciter may be bonded into a pre-formed aperture moulded in a resonant panel during assembly. The need for a separate voice coil carrier is thus removed.
The panel may be co-moulded with the suspension. The suspension may be of resilient a material, eg plastics.
The panel may be injection moulded as a monolith or using foaming techniques. The panel may be flat or curved and may vary in thickness or cross-section.
The enclosure may have embedded electrically conducting inserts for carrying electrical signals efficiently from connectors on the enclosure edge to the vibration exciter. The assembly and connectivity of the od © WO 00/22877 PCT/GB99/03209 drive unit may thus be automated.
The drive unit may be clad in other mouldings and structures to suit the application, e.g. for aesthetic reasons. For example an appropriate trim will make it 5 suitable for surface mounting onto a hi-fi speaker cabinet.
Conversely, a suitable outer moulding will turn the engine into a multimedia speaker. Further the engine may be mounted onto other structures such as television cabinets.
BRIEF DESCRIPTION OF DRAWINGS
The invention is diagrammatically illustrated, by way of example in the accompanying drawings, in which:
Figure 1 is a perspective view, partly cut-away to reveal hidden detail, of a loudspeaker drive unit;
Figure 2 1s a cross-sectional side view of the loudspeaker drive unit of Figure 1, and ] Figure 3 is a graph representing the frequency response of the drive unit of Figures 1 and 2.
BEST MODE FOR CARRYING QUT THE INVENTION
In the drawings there is shown a loudspeaker drive unit 1 intended as a mid/high frequency driver which may be used as a component in a loudspeaker system also comprising a low frequency driver, in which case the mid/high frequency and low frequency drivers may be assembled into a common cabinet, or as the sole driver in a compact loudspeaker, e.g. for multi-media or computer or automobile use.
The drive unit 1 comprises a generally rectangular enclosure 2 having a dish-like body 11 surrounded by an outwardly extending fixing flange 3 formed at intervals with holes 12 whereby the enclosure can be fixed in position by means of suitable fasteners (not shown) e.g. in the cabinet (not shown) of a loudspeaker. The enclosure 2 5S may be made from plastics, e.g. by injection moulding, and is formed internally with cross-bracing flanges 13 in the interests of adding stiffness to the enclosure while retaining its light-weight nature.
The enclesure 2 is formed at its base 14 with an internal generally circular shallow recess 4 having a central through hole 16, the recess being adapted snugly to receive a circular backing plate 6 on which is rigidly mounted the magnet assembly 7 of an electrodynamic vibration exciter 5 by means of a bolt 20. The exciter 5 comprises the said magnet assembly which defines an annular gap 19, and a voice coil and cylindrical former assembly 8 { disposed in the annular gap and moveable axially thereof in ; response to an electrical signal applied to the voice coil.
The backing plate 6 is fixed to the enclosure in any convenient manner. Thus it may be fixed by fasteners or by adhesive means or may be moulded integrally with the enclosure.
Adjacent to the edge flange 3, a generally rectangular stiff, lightweight resonant panel-form member 9 is resiliently mounted on the enclosure 2 by means of a flexible foam suspension 10 which extends round the periphery of the panel 9. The enclosure and the panel thus define a closed cavity 15. The suspension 10 may be fixed of © WO 0022877 PCT/GBY99/03209 to the panel 9 and to the enclosure 2 by adhesive means.
The panel 9 is a distributed mode panel in accordance with the teaching in W0S7/09842. The voice coil/former assembly 8 of the exciter 5 is rigidly fixed to the panel 9 at a suitable near-centre drive position as taught in W097/09842 to introduce bending wave energy into the panel toc cause it to resonate to produce an acoustic output. The voice coil and coil former assembly 8 has an annular mounting member or foot 21, e.g. of plastics, rigidly fixed to its end adjacent to the panel 9 to aid its fixing to the parel, which may be with the aid of an adhesive. It is to be noted that, unusually, the exciter 5 1s grounded to the enclosure 2 and does not comprise a suspension between the magnet assembly and the voice coil so that centring of the voice coil in the annular gap 19 of the magnet assembly is achieved only by the panel edge suspension 10. In this way the moving mass of the exciter is reduced to improve its high frequency response. The magnet assembly may be thermally coupled to the voice coil to improve its power capacity and heat may be radiated from the exposed rear face of the backing plate 6.
Selective locally positioned small masses 17, e.g. in the range from about 2 to 12 grams are bonded to the panel to optimally tune the coupled resonances such that the overall response is suitably tailored. This technique has the specific advantage of extending the low frequency range of the assembly. An aperture 18 through the panel 8 co- axial with the voice coil extends the high frequency
© WO 00122877 PCT/GB99/03209 L response. Some acoustic absorbent material (not shown) in the cavity 15 may be helpful in reducing the magnitude of higher order standing waves in the cavity, and may further refine the frequency response.
A drive unit as described above may have the following specification: -
Panel size = 210X148.5mm (A5 std. size)
Core = 3mm polycarbonate honeycomb, 3.5mm cell diameter
Skins = 100um woven glass reinforced polycarbonate faceskins (0°/90° skin orientation) 50wt% glass
Bending stiffness = 5.6Nm
Areal density, p = 0.7kg/m2
Zm = 16Ns/m
Voice coil diameter = 26mm
Coil is positioned at standard distributed mode ] position (4/9, 3/7 = ratio)
Large ferrite ring magnet to improve -BL and power handling.
As discussed, there is no suspension between the -magnet and the voice coil and the panel is held in position by the foam suspension around the edge. The panel may be aligned and located accurately using the hole in the panel within the voice coil to assist alignment of the voice «coil in the annular gap.
Locating pins might possibly be provided on the enclosure near to the panel edges to prevent sideways movement of the panel. The frequency response of this
» © WO 00/22877 PCT/GB%9/03209 panel is shown in Figure 3.
Smaller versions of the drive unit are envisioned with high quality piezo exciters which may extend the response into the ultrasonic range which could be useful in connection with new audio formats with a 50kHz or 100kHz sound bandwidth; this performance is beyond the compass of conventional pistonic technology.
INDUSTRIAL APPLICABILITY
The invention thus provides a novel loudspeaker drive unit for mid and high frequencies which solves significant problems in known arrangements both as concerns frequency cross-over problems and dispersion.

Claims (9)

© WO 00/22877 PCT/GB99/03209 CLAIMS
1. A mid/high frequency loudspeaker drive unit comprising a stiff lightweight resonant panel form member, a housing 5S in which the panel form member is mounted, a resilient suspension connected between the edges of the panel form member and the housing, the arrangement being such that the housing and the panel form member together define a sealed enclosure, and an electrodynamic exciter for applying 10 bending wave energy to the panel form member to cause it to resonate to produce an acoustic output, the exciter comprising a magnet assembly rigidly fixed to the housing and defining an annular gap and a voice coil disposed in the annular gap and rigidly fixed to the panel form member near to the geometric centre thereof, the location of the voice coil in the annular gap being provided by the said ¢ resilient suspension.
2. A loudspeaker drive unit according to claim 1, wherein the enclosure comprises a dished body surrounded by a fixing flange.
3. A loudspeaker drive unit according to claim 2, wherein the dished body comprises a through aperture and wherein the magnet assembly of the vibration exciter is rigidly mounted on the dished body whereby a part of its surface closes the through aperture in the body.
4. A loudspeaker drive unit according to claim 3, comprising a recess in the dished body, and wherein the magnet assembly comprises a back plate mounted in the
. ‘ WG 00/22877 PCT/GB99/03205 11 recess in the dished body, the recess being formed with the through aperture.
5. A loudspeaker according to any proceeding claim wherein the resilient suspension is of foam material.
6. A loudspeaker drive unit according to any proceeding claim wherein the panel-form member comprises a core of honeycomb material sandwiched between skin layers and has a bending stiffness in the range 0.15 to 24Nm.
7. A loudspeaker drive unit according to claim 6, wherein the bending stiffness is in the range 2 to 9Nm.
8. A loudspeaker drive unit according to any proceeding claim, comprising an aperture through the panel-form member and co-axial with and smaller than the diameter of the vcice coil.
9. A loudspeaker drive unit according to any preceding claim, comprising at least one discrete mass mounted on the ' panel-form member and positioned tc damp the low frequency response thereof.
ZA200101978A 1998-10-13 2001-03-09 Loudspeakers. ZA200101978B (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GBGB9822246.6A GB9822246D0 (en) 1998-10-13 1998-10-13 Loudspeakers

Publications (1)

Publication Number Publication Date
ZA200101978B true ZA200101978B (en) 2001-09-11

Family

ID=10840427

Family Applications (1)

Application Number Title Priority Date Filing Date
ZA200101978A ZA200101978B (en) 1998-10-13 2001-03-09 Loudspeakers.

Country Status (12)

Country Link
EP (1) EP1121833A1 (en)
JP (1) JP2002528019A (en)
KR (1) KR20010075442A (en)
CN (1) CN1319320A (en)
AU (1) AU6213999A (en)
BR (1) BR9914147A (en)
CA (1) CA2345749A1 (en)
GB (2) GB9822246D0 (en)
IL (1) IL141966A0 (en)
TW (1) TW462206B (en)
WO (1) WO2000022877A1 (en)
ZA (1) ZA200101978B (en)

Families Citing this family (19)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2001008447A2 (en) 1999-07-23 2001-02-01 Digital Sonics, Llc Flat panel speaker
US6751329B2 (en) 2000-09-21 2004-06-15 New Transducers Limited Loudspeaker driver
GB0023134D0 (en) * 2000-09-21 2000-11-01 New Transducers Ltd Loudspeaker driver
GB2386790B (en) * 2001-03-23 2004-08-18 New Transducers Ltd Bending wave acoustic radiator
US7120263B2 (en) 2001-03-23 2006-10-10 New Transducers Limited Bending wave acoustic radiator
US7002070B2 (en) 2001-06-22 2006-02-21 Shelley Katz Electronic piano
US7062051B2 (en) 2001-08-17 2006-06-13 New Transducers Limited Acoustic device
AU2003202084A1 (en) * 2003-01-22 2004-08-13 Shelley Katz Apparatus and method for producing sound
DE10326761A1 (en) * 2003-06-13 2005-01-27 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. speaker
JP2006279284A (en) * 2005-03-28 2006-10-12 Kenwood Corp Screen speaker
JP2007322606A (en) * 2006-05-31 2007-12-13 Kawai Musical Instr Mfg Co Ltd Musical sound device and production method for musical sound device
JP2009260763A (en) * 2008-04-18 2009-11-05 Panasonic Corp Flat speaker
GB0811015D0 (en) 2008-06-17 2008-07-23 Deben Acoustics Improved acoustic device
US8494208B2 (en) 2008-07-17 2013-07-23 New Transducers Limited Inertial vibration exciter
CN101674517B (en) * 2009-09-25 2012-08-29 广东长虹电子有限公司 Acoustic generating device
JP5909169B2 (en) * 2012-09-25 2016-04-26 京セラ株式会社 SOUND GENERATOR, SOUND GENERATOR, AND ELECTRONIC DEVICE
GB2568282B (en) * 2017-11-10 2020-11-25 Amina Tech Limited Flat panel loudspeaker
KR102625724B1 (en) 2018-10-05 2024-01-15 엘지디스플레이 주식회사 Display apparatus
FR3110162B1 (en) * 2020-05-13 2022-05-27 Saint Gobain Glazing with audio exciter

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US3247925A (en) * 1962-03-08 1966-04-26 Lord Corp Loudspeaker
US4284167A (en) * 1979-06-04 1981-08-18 Electronic Research Assoc., Inc. Sound reproducing device
US4928312A (en) * 1988-10-17 1990-05-22 Amel Hill Acoustic transducer
FI94203C (en) * 1991-11-25 1995-07-25 Anturilaakso Oy Speaker
UA51671C2 (en) * 1995-09-02 2002-12-16 Нью Транзд'Юсез Лімітед Acoustic device
GB9701983D0 (en) * 1997-01-31 1997-03-19 New Transducers Ltd Electro-dynamic exciter
PL334440A1 (en) * 1997-01-09 2000-02-28 New Transducers Ltd Loudspeaker
WO1999037118A1 (en) * 1998-01-16 1999-07-22 Sony Corporation Speaker and electronic apparatus using speaker

Also Published As

Publication number Publication date
CA2345749A1 (en) 2000-04-20
CN1319320A (en) 2001-10-24
AU6213999A (en) 2000-05-01
EP1121833A1 (en) 2001-08-08
WO2000022877A1 (en) 2000-04-20
GB2357215A (en) 2001-06-13
WO2000022877A8 (en) 2000-05-25
GB0105807D0 (en) 2001-04-25
KR20010075442A (en) 2001-08-09
BR9914147A (en) 2001-06-26
JP2002528019A (en) 2002-08-27
IL141966A0 (en) 2002-03-10
GB9822246D0 (en) 1998-12-09
TW462206B (en) 2001-11-01

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