High back emf, high pressure subwoofer having small volume cabinet, low frequency cutoff and pressure resistant surround

  • US 5,937,074 A
  • Filed: 08/12/1997
  • Issued: 08/10/1999
  • Est. Priority Date: 08/12/1996
  • Status: Expired due to Fees
First Claim
Patent Images

1. A woofer apparatus for processing an input audio signal, said sub-woofer having a small cabinet volume relative to air displacement volume of the woofer apparatus, comprising, in combination:

  • a. a cabinet defining an enclosure of predetermined cabinet air volume;

    b. a voice coil driven driver mounted in said cabinet, said driver comprises;

    i. a magnet which establishes a magnetic flux field B of predetermined flux density,ii. a voice coil member positioned for reciprocating motion in said flux field B with a maximum peak-to-peak excursion d that exceeds or equals a pre-determined value;

    iii. a speaker cone connected to said voice coil member for reciprocating motion therewith and connected in an opening in said cabinet, said cone having an effective bore surface of a pre-determined bore area which acts against ambient air in a PUSH/PULL pattern during reciprocating motion of said cone; and

    ,iv. a surround connecting said cone to said cabinet;

    c. a power amplifier operatively connected to said voice coil member for delivering to the voice coil member input current representative of the audio input signal to cause said voice coil member and said cone to move in a reciprocating path in accordance with the audio input signal;

    d. said woofer apparatus having the following operating characteristics and relationships;

    i. the pro-determined bore area and the predetermined length of the maximum peak-to-peak excursions being related to provide a maximum air displacement volume during a maximum peak-to-peak excursion of said voice coil member and said cone, said maximum air displacement volume being substantially equal to said predetermined bore area multiplied by the length of said maximum peak-to-peak excursion;

    ii. said predetermined cabinet air volume and said air maximum displacement volume being interrelated in that an increase in the ratio of the air maximum displacement volume to the cabinet air volume results in an increase in peak cabinet pressure and a decrease in said ratio results in a reduction in peak cabinet pressure;

    iii. back-emf generated in said voice coil member is proportional to dφ

    /dt so that the back-emf is, in turn, generally proportional to the strength of said magnetic flux field B of said magnet times the length of the peak-to-peak excursion d of said voice coil member at a given frequency; and

    ,e. said apparatus being structured and arranged so that;

    i. the maximum peak to peak excursion of and said cone is greater than 0.6 inches.ii. said cabinet air volume is sufficiently small relative to said maximum air displacement volume so that the peak cabinet pressure at maximum peak-to-peak excursions is substantially greater than 0.2 lbs/in2, and the cone area is sized relative to the maximum peak excursions to produce said maximum cabinet pressure, and,iii. the density of the magnetic flux field B produced by said magnet is sufficiently great and the maximum peak-to-peak excursion of said voice coil member is sufficiently long so that a) the resulting back-emf at maximum peak-to-peak excursion is at a level sufficiently high relative to maximum voltage output of said amplifier so as to limit the input current to a level to preclude overheating of the voice coil members and b) the maximum voltage output and maximum power output of said amplifier are sufficiently high so as to supply sufficient current at a sufficiently high voltage to drive said voice coil member through the magnetic flux field B at maximum peak-to-peak excursions, while maintaining tho level of current flow through said voice coil at a level sufficient to drive the voice coil member through the maximum peak-to-peak excursions and yet to preclude overheating of said voice coil member.

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