(11) EP 0 409 429 A3


(88) Date of publication A3:
18.03.1992 Bulletin 1992/12

(43) Date of publication A2:
23.01.1991 Bulletin 1991/04

(21) Application number: 90307020.9

(22) Date of filing: 27.06.1990
(51) International Patent Classification (IPC)5H04R 9/06, H04R 3/00
(84) Designated Contracting States:

(30) Priority: 19.07.1989 JP 186290/89
20.07.1989 JP 85489/89 U

(71) Applicant: SONY CORPORATION
Tokyo (JP)

(72) Inventors:
  • Inanaga, Kiyofumi
    Shinagawa-ku, Tokyo (JP)
  • Sogawa, Hiroyuki
    Shinagawa-ku, Tokyo (JP)

(74) Representative: Ayers, Martyn Lewis Stanley et al
J.A. KEMP & CO. 14 South Square Gray's Inn
London WC1R 5LX
London WC1R 5LX (GB)

(56) References cited: : 

    (54) Loudspeaker drive unit

    (57) The invention relates to a constant current drive speaker system in which a dynamic speaker is driven by a constant current amplifier. Generally, when the dynamic speaker is driven by a constant current, it is frequently observed that the vibrational system thereof cannot be damped satisfactorily near the low band resonance frequency. To remove this disadvantage, a damping coil (23) provided bodily with the vibrational system is terminated by a predetermined impedance and is provided within a magnetic gap of a magnetic circuit (25) provided independently of the magnetic circuit (15) of the vibrational system, thereby damping the vibration system. Alternatively, a voice coil bobbin is formed of a conductive material to form a short-circuited ring on which there is wound a voice coil. This speaker system is driven by a low frequency, whereby the vibrational system thereof is damped without electromagnetic coupling.

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