EP0256593A2 - Lautsprechersystem und Lautsprecher zur Umwandlung eines n-bit-digitalisierten, elektrischen Signals in ein akustisches Signal - Google Patents

Lautsprechersystem und Lautsprecher zur Umwandlung eines n-bit-digitalisierten, elektrischen Signals in ein akustisches Signal Download PDF

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Publication number
EP0256593A2
EP0256593A2 EP87201485A EP87201485A EP0256593A2 EP 0256593 A2 EP0256593 A2 EP 0256593A2 EP 87201485 A EP87201485 A EP 87201485A EP 87201485 A EP87201485 A EP 87201485A EP 0256593 A2 EP0256593 A2 EP 0256593A2
Authority
EP
European Patent Office
Prior art keywords
voice
coil
coil devices
transducer
conductors
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.)
Withdrawn
Application number
EP87201485A
Other languages
English (en)
French (fr)
Other versions
EP0256593A3 (de
Inventor
Jorus A. M. Nieuwendijk
Wilhelmus D. A. M. Van Gijsel
Georgius B. J. Sanders
Jacob M. Van Nieuwland
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.)
Koninklijke Philips NV
Original Assignee
Philips Gloeilampenfabrieken NV
Koninklijke Philips Electronics NV
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
Priority claimed from NL8303184A external-priority patent/NL8303184A/nl
Application filed by Philips Gloeilampenfabrieken NV, Koninklijke Philips Electronics NV filed Critical Philips Gloeilampenfabrieken NV
Priority to EP87201485A priority Critical patent/EP0256593A3/de
Publication of EP0256593A2 publication Critical patent/EP0256593A2/de
Publication of EP0256593A3 publication Critical patent/EP0256593A3/de
Withdrawn legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; ELECTRIC HEARING AIDS; PUBLIC ADDRESS SYSTEMS
    • H04R1/00—Details of transducers, loudspeakers or microphones
    • H04R1/005—Details of transducers, loudspeakers or microphones using digitally weighted transducing elements
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; ELECTRIC HEARING AIDS; PUBLIC ADDRESS SYSTEMS
    • H04R9/00—Transducers of moving-coil, moving-strip, or moving-wire type
    • H04R9/02—Details
    • H04R9/04—Construction, mounting, or centering of coil
    • H04R9/046—Construction
    • H04R9/047—Construction in which the windings of the moving coil lay in the same plane

Definitions

  • the invention relates to a loudspeaker system for converting an n-bit digitized electric signal ( n be­ing an integer and ⁇ 2) into an acoustic signal, which system includes an electrodynamic transducer comprising a diaphragm, a magnet system and n voice-coil devices which cooperate with the magnet system, means being pro­vided for driving each of the n voice-coil devices in ac­cordance with the value of a respective one of the n bits of the digitized electric signal.
  • the invention also re­lates to an electrodynamic transducer for use in a loud­speaker system in accordance with the invention.
  • a loud­speaker system of the type specified in the opening sen­tence is known from the publication "The acoustic characteristics of Moving-Coil type PCM digital loud­speaker (I)" by K. Inanaga and M. Nishimura, from the Proceedings of the Spring Conference of the Acoustical Society of Japan, pages 649 and 650, May 1981.
  • the known loudspeaker system includes an elec­trodynamic transducer in the form of a moving-coil loud­speaker, the voice-coil devices being arranged on a voice-coil former as separate voice coils.
  • the transducer described in the afore mention­ed publication comprises a plurality of voice-coil de­vices each having 48 turns.
  • the means for driving the voice-coil devices are constructed so that the voice-coil devices are driv­en with switched voltages whose magnitudes vary (increase) in conformity with the significance of the bits associat­ed with the voice-coil devices.
  • the known loudspeaker system requires as many sup­ply voltages as there are voice-coil devices. Providing so many different supply voltages is very intricate, may render the system expensive, and is therefore a disadvan­tage. More-over, the known loudspeaker system does not have an optimum efficiency at maximum drive.
  • Japanese Kokai no. 58-31699 a step is proposed which is such that the means for driving the voice-coil devices require only one supply voltage so that a substantially optimum efficiency is obtained at maximum drive.
  • the voice-coil devices each comprise a conductor whose length is the same for all the voice-coil devices, the conductors being made of a material whose specific mass and specific resistance are at least substantially the same for all the voice-coil devices, and being such that when an index m (m being an integer and ⁇ n) is assigned to each said voice-coil device in such manner that the in­dex 1 is assigned to the voice-coil device corresponding to the most significant bit of the n bits of the digitiz­ed electric signal, consecutive indices to voice-coil de­vice corresponding to consecutive less significant bits of the n bits of the digitized electric signal, and the highest index to the voice-coil device corresponding to the least significant bit of the n bits of the digitized electrical signal, the ratio between the area A m of a per­pendicular cross-section of the conductor of the m th voice-coil device and the area A1 of the perpendicular cross-section of the conductor of the first voice
  • the step proposed in Japanese Kokai No. 58-31699 is based on the recognition of the fact that it is possible to drive the various voice-coil devices cor­rectly ( i . e . with the appropriate level or amplitude) even in the case of a single supply voltage, whilst more-­over a substantially optimum efficiency can be achieved.
  • each conductor comprises only one more, the core diameters of the conductors cor­responding to consecutively more significant bits in­creasing by a factor of ⁇ 2. Manufacturing such a transducer is comparatively intricate and therefore ex­pensive.
  • a loudspeaker sys­tem according to the invention is characterized in that the electrodynamic transducer is in the form of a rib­bon-type loudspeaker, the diaphragm comprises a plurality of superimposed foils, adjoining foils being attached to one another over their entire surface areas and at least one voice-coil device being arranged on each foil.
  • either the thickness of the con­ductive layers may be equal for all the conductors - in which case the ratios between the widths of the conductors must be such that the afore-mentioned equation is satis­fied - or the width of the conductive layers may be equal for all the conductors - in which case the ratios between the thicknesses of the conductors must be such that the aforementioned equation is satisfied.
  • the first mentioned possibility is preferred because the transducer is preferred can be constructed very simple be local etching of a conductive layer provided on a foil. This also enables several voice-coil devices to be arranged on one foil in a very simple manner.
  • electrodynamic loud­ speakers for reproducing a pulse-code-modulated electric signal are known from Japanese Kokai no. 52.121.316 and Japanese Kokai no. 57.185.798.
  • the ratio between the perpen­dicular cross-sections is not selected in conformity with the above equation.
  • the loudspeaker system of Japanese Kokai no. 51.121.316 employs a current drive for the excitation of the voice-coil devices. This results in a higher electric power dissipation.
  • the other ends of the coils of the voice-coil devices 4.1 to 4.n are connected to a point 17 of constant potential (earth).
  • the most significant bit of the digitiz­ed electric signal is applied to the switch 14.1 via the line 13.1 and thus controls the drive of the voice-coil device 14.1.
  • Consecutive less significant bits are applied to the switches 14.2, 14.3, ... via the lines 13.2, 13.3, ... (in this sequence) and thus control the drives of the voice-coil devices 4.2, 4.3, ...
  • the least significant bit is applied to the switch 14.n via the line 13.n and controls the drive of the voice-coil device 4.n.
  • the means 10 for driving the voice-coil-device sections operate so that if a bit of a high value (logic "one") is applied to the switch 14.1 via the line 13.1, this switch is closed. Conversely, if a low value (lofic zero) is applied via the line 13.1, this switch 14.1 is opened. It is obvious that the same applies to the control of the other switches 14.2 to 14.n via the lines 13.2 to 13.n.
  • Fig. 2 shows the voice-coil former 5 on which four voice-­coil devices 24.1 to 24.4 are arranged.
  • the voice-coil device 24.1 is driven in accordance with the value of the most significant bit and the voice-coil device 24.4 in accordance with the value of the least significant bit.
  • the voice-coil devices comprise conductors 25.1 to 25.4 respectively with only one core. In total each voice-coil device therefore comprises four turns. It is clearly visible that the areas of the perpendicular cross-sections of the cores, starting from the core 25.1, decrease for successive cores 25.2, 25.3 and 25.4 (each time by a fac­tor of two).
  • Fig. 2 also shows schematically a part of the electrical conductors from the switches 14.1 to 14.4.
  • Fig. 2 The construction shown in Fig. 2 is not very convenient because it requires four different cores for four different cross-sectional areas. Moreover, the ratios between the diameters vary in accordance with the incon­venient factor ⁇ 2.
  • FIG. 3 An electrodynamic transducer in accordance with the invention is shown in Fig. 3 .
  • the transducer shown in Fig. 3 is an electrodynamic transducer of the ribbon type. Such a transducer is known from, for example, Netherlands Patent Application 79.03.908, which has been laid open to public inspection.
  • Fig. 3 shows an improved version of the transducer as described in the Applicants' previously filed Netherlands Patent Application 81.02.572 (PHN 10.062), which has been laid open to public inspec­tion.
  • the transducer may have a circular or rectangular shape.
  • Fig. 3 is a sectional view of a rectangular trans­ducer taken in a direction perpendicular to the longitu­dinal direction of the conductors in an air gap.
  • the mag­net system of the transducer comprises a centre pole 51, an upper plate 52, 53, a lower plate 54, and the parts 55 and 56.
  • the magnetic field in the magnet system can be obtained by constructing the parts 55 and 56 as per­manent magnets.
  • the direction of magnetization is indicat­ed by the arrows 64 and 65.
  • the directions of magnetiza­tion may also be reversed.
  • the other parts of the magnet system are made of a soft-magnetic material, for example soft iron.
  • the rectangular version 55 and 56 denote the cross-section of two rod-shaped magnets which extend pa­rallel to one another. It is alternatively possible that the parts 55 and 56 be made of soft-magnetic material and the centre pole, at least its shaded portion 51 ⁇ , be constructed as a permanent magnet. Air gaps 58 are formed between the upper plate 52 and the centre pole 51 and be­tween the upper plate 53 and the centre pole 51, which gaps extend parallel to one another. A diaphragm 57 is ar­ranged in the air gas 58. The construction of the dia­phragm 57 will be described hereinafter with reference to Fig. 4.
  • the upper plates 52 and 53 each comprise two plate-shaped parts 52 ⁇ , 52 ⁇ and 53 ⁇ , 53 ⁇ .
  • the two plate shaped parts of each pair 52 ⁇ , 52 ⁇ and 53 ⁇ , 53 ⁇ about against each other over part of their facing major surfaces, which major surfaces are disposed substantially in and parallel to the plane of the diaphragm.
  • Another part of said major surface of one of each pair of plate-shaped parts recedes slightly as indicted by 60, so that a space 61 is formed.
  • the diaphragm 57 is arranged between the plate-shaped parts 52 ⁇ , 52 ⁇ and 53 ⁇ , 53 ⁇ in such a manner than an edge portion of the diaphragm is disposed in the said spaces 61.
  • the diaphragm 57 may be tensioned on or in a frame 62 which is mounted between the two plate-shaped parts of each pair. However, alternatively the diaphragm may be clamped between the parts 52 ⁇ , 52 ⁇ and 53 ⁇ , 53 ⁇ themselves. Moreover, a damping material may be provided in the spaces 61.
  • the Figure shows a damping material 63 which is present only on the upper side of the diaphragm and is in mechanical contact with this dia­phragm. Preferably, the damping material will be provided on both sides of the diaphragm. This damping material damps the higher natural resonances of the diaphragm ( i . e .
  • the centre pole 51 also extends to the other side of the diaphragm.
  • the part 51 ⁇ disposed on this side of the diaphragm is in­dicated by a broken line.
  • the part of the dia­phragm which is disposed between the two parts 51 and 51 ⁇ of the centre pole is freely movable. The part 51 ⁇ is kept in the position shown by means of a support, not shown.
  • the end faces of the parts 51 ⁇ , 52 ⁇ and 53 ⁇ which face the air gap 58 are rounded. This means that these end faces diverge further from each another in a direction parallel to the diaphragm surface as the distance from the dia­phragm surface increases, so that a horn-like radiation aperture is formed.
  • Fig. 4a is a perspective view of the diaphragm 57 and Fig. 4b is a sectional view of the left half of the diaphragm 57 taken on the line B-B in Fig. 4a.
  • the left half of the diaphragm shown in Fig. 4a i . e . the part shown in Fig. 4b
  • the right-hand half of the diaphragm is disposed at the location of the air gap 58 between the part 53 and the centre pole 51.
  • the direction of the magnetic field in the two air gaps 58 and the di­rection of the signal currents in the conductors in these air gaps are such that the excursion of the diaphragm is oriented in the same direction over the entire diaphragm area.
  • Such a transducer is sometimes referred to as an isophase transducer.
  • the diaphragm 57 comprises a plurality (in the present case four) of superimposed foils 67.1, 67.2, 67.3, 67.4. Adjoining foils are attached to each other over their entire areas. At least one voice-coil device is ar­ranged on each foil. In Fig. 4a only the voice-coil de­vice 68.4 on foil 67.4 is visible.
  • the foils 67.1, 67.2, and 67.3 are provided with voice-coil devices 68.1, 68.2 and 68.3 respectively.
  • the voice-coil device take the form of conduc­tors which are arranged on the foils as electrically con­ductive layers.
  • the conductors of the voice-coil devices again have the same length. Each conductor comprises three turns.
  • Fig. 4b shows an example in which the thick­ness of the conductive layer is the same for all the con­ductors.
  • Fig. 4a also shows the electrical connections from the switch 14.4 for the drive in accordance with the value of the least significant bit.
  • the voice-coil de­vices 68.3 and 68.2 (in this order) are driven in accord­ance with the values of successive more significant bits.
  • the voice-coil device 68.1 is driven in accordance with the value of the most significant bit.
  • the width of the conductors corresponding to successivelysive more significant bits should always increase by a factor of two when the conductors have the same thickness. This is shown in Fig. 4b.
  • Another possibility is to make the conductive layer equally wide for all the conductors. In that case the ratio between the thicknesses of the con­ductors should always increase by a factor of two.
  • the diaphragm 57 comprises only three foils, namely 67.1, 67.2, 67.3, the voice-coil devices 68.1 and 68.2 being arranged on the foils 67.1 and 67.2 respectively and the voice-coil devic­es 68.3 and 68.4 being both arranged on the foil 67.3.
  • Fig. 4c shows an example of this. It is to be noted that the invention is not limited to the embodiments shown. The invention is equally applicable to constructions which differ from the embodiments shown with respect to points which are not relevant to the inventive idea.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Audible-Bandwidth Dynamoelectric Transducers Other Than Pickups (AREA)
  • Circuit For Audible Band Transducer (AREA)
EP87201485A 1983-09-15 1984-09-12 Lautsprechersystem und Lautsprecher zur Umwandlung eines n-bit-digitalisierten, elektrischen Signals in ein akustisches Signal Withdrawn EP0256593A3 (de)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP87201485A EP0256593A3 (de) 1983-09-15 1984-09-12 Lautsprechersystem und Lautsprecher zur Umwandlung eines n-bit-digitalisierten, elektrischen Signals in ein akustisches Signal

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
NL8303184A NL8303184A (nl) 1983-09-15 1983-09-15 Luidsprekersysteem en een luidspreker te gebruiken in een luidsprekersysteem voor het omzetten van een in n bits gedigitaliseerd elektrisch signaal in een akoestisch signaal.
NL8303184 1983-09-15
EP87201485A EP0256593A3 (de) 1983-09-15 1984-09-12 Lautsprechersystem und Lautsprecher zur Umwandlung eines n-bit-digitalisierten, elektrischen Signals in ein akustisches Signal

Related Parent Applications (2)

Application Number Title Priority Date Filing Date
EP84201316A Division EP0141447B1 (de) 1983-09-15 1984-09-12 Lautsprechersystem und Lautsprecher zur Umwandlung eines n-bit digitalisierten elektrischen Signals in ein akustisches Signal
EP84201316.1 Division 1984-09-12

Publications (2)

Publication Number Publication Date
EP0256593A2 true EP0256593A2 (de) 1988-02-24
EP0256593A3 EP0256593A3 (de) 1988-06-08

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EP87201485A Withdrawn EP0256593A3 (de) 1983-09-15 1984-09-12 Lautsprechersystem und Lautsprecher zur Umwandlung eines n-bit-digitalisierten, elektrischen Signals in ein akustisches Signal

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2421140A (en) * 2004-12-09 2006-06-14 Citizen Electronics Stereo speakers combined in a single unit

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3674946A (en) * 1970-12-23 1972-07-04 Magnepan Inc Electromagnetic transducer
US4242541A (en) * 1977-12-22 1980-12-30 Olympus Optical Co., Ltd. Composite type acoustic transducer

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2421140A (en) * 2004-12-09 2006-06-14 Citizen Electronics Stereo speakers combined in a single unit
GB2421140B (en) * 2004-12-09 2008-04-02 Citizen Electronics Stereo speaker system

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Publication number Publication date
EP0256593A3 (de) 1988-06-08

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