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

• Current Assignee: Core Brands, LLC (Melrose Industries Plc)
• Original Assignee: Robert W. Carver
• Inventors: Carver, Robert W.
• Primary Examiner(s): Isen, Forester W.
• Assistant Examiner(s): Mei, Xu
• Application Number:
  US08/909,892
• Time in Patent Office: 728 Days
• Field of Search: 381/395, 381/87, 381/89, 381/332, 381/150, 381/345, 381/349, 381/386, 381/394, 181/199, 181/198, 181/148, 29/594, 29/609.1
• US Class Current: 381/395
• CPC Class Codes: H03F 1/0227 using supply converters
• CPC Class Codes: H03F 1/0238 using supply converters
• CPC Class Codes: H04R 1/021 incorporating only one transducer
• CPC Class Codes: H04R 1/227 using transducers reproducing the same frequency band
• CPC Class Codes: H04R 1/2803 for loudspeaker transducers
• CPC Class Codes: H04R 1/2834 for loudspeaker transducers
• CPC Class Codes: H04R 3/00 Circuits for transducers , loudspeakers or microphones
• CPC Class Codes: Y10T 29/49005 Acoustic transducer

Abstract

A small, compact subwoofer cabinet; openings in two cabinet walls; first and second cages mounted on respective ones of the walls in alignment with the openings; a voice coil driven driver including an annular magnet weighing approximately 225 oz. affixed to the first cage; a stationary pole piece extending through the magnet and defining a magnetic gap therebetween; a voice coil mounted on a cylindrical voice coil former positioned within the gap; a cone affixed to one end of the former; a first flexible surround secured to the outer end of the cone and to the first cage; a flexible spider secured to the former and to the first cage; a mass driven driver including a mass aggregating about 2 lbs.; a second flexible surround secured to the mass and to the second cage; a flexible spider attached to the second cage and to the mass; both surrounds having a thickness of about 0.1", an edgeroll having a diameter of about 1.5", and capable of standing off internal pressures up to about 3 lbs./in² ; a drive amplifier capable of delivering up to about 2,700 watts to a nominal 4 ohm resistive load and swinging up to about 104 volts for delivering (+)Δv and (-)Δv drive signals to the voice coil for driving the voice coil driven driver through a peak-to-peak stroke of about 2.5" while generating a large back emf sufficient to counter the applied emf and minimize current flow in the voice coil.

Claims

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.

2. The woofer apparatus of claim 1, wherein said woofer apparatus exhibits a nominal impedance value and said magnet comprises an annular magnet and a cylindrical pole piece that extends axially along an opening of said annular magnet to form an annular gap between said annular magnet and said pole piece with said annular magnet and said pole piece establishing a magnetic field that extends radially across said annular gap, said coil member being of the type that includes a cylindrical voice coil that is positioned for axial reciprocal movement through said annular gap in response to a time varying electrical potential that establishes current flow through a voice coil of said voice coil member, said axial reciprocal movement of said voice coil having a maximum peak-to-peak value, said woofer apparatus being characterized in that the density of said magnetic field, said maximum peak-to-peak excursions of said voice coil and the length of the conductive windings of said voice coil collectively establish a voice coil back-emf that limits said current through said voice coil to a value that is substantially less than the value of said electrical potential applied to said voice coil divided by said nominal impedance value.

3. The woofer apparatus of claim 2 wherein said annular magnet has a weight that substantially exceeds 40 ounces.

4. The loud speaker as recited in claim 3, wherein said annular magnet has a weight with an upper limit in the order of at least about 225 ounces.

5. The woofer apparatus of claim 2 wherein said maximum peak-to-peak excursion of said voice coil is within the range that extends from a value that is substantially in excess of 0.6 inches to a value on the order of about 2.5 inches.

6. The sub-woofer of claim 2 wherein said annular magnet has a weight that is within a weight range having a lower limit that substantially exceeds 40 ounces and an upper limit on the order of at least about 225 ounces and said maximum peak-to-peak value of said reciprocal movement of said voice coil is within the range that extends from a value that is substantially in excess of 0.6 inches to a value on the order of about 2.5 inches.

7. The woofer apparatus of claim 2 wherein said voice coil back-emf substantially exceeds 13 volts rms for said maximum peak-to-peak value of said axial reciprocal movement of said voice coil when said time-varying electrical potential is at a frequency of 25 Hertz.

8. The woofer apparatus of claim 2 wherein said voice coil back-emf substantially exceeds 13 volts rms and ranges up to about 100 volts rms for said maximum peak-to-peak value of said axial reciprocal movement of said voice coil when said time-varying electrical potential is at a frequency of 25 Hertz.

9. The woofer apparatus of claim 1 wherein said surround of said driver has a thickness that is within a thickness range that extends from about 0.1 inch to at least 0.14 inch.

10. The woofer apparatus of claim 1 wherein said surround of said driver includes an edgeroll having a diameter of about 1.5 inches.

11. The woofer apparatus of claim 1 wherein said surround of said driver has a thickness that is between a value in excess of 0.02 inch and a value that is on the order of at least 0.14 inch and wherein said surround includes an edgeroll that has a diameter in excess of 1.0 inch and up to about 1.5 inches.

12. The woofer apparatus of claim 1 wherein said surround of said driver is formed of n laminations of surround foam having an initial aggregate thickness on the order of at least 23/16 inches compressed to a thickness on the order of about 0.1 inch.

13. The woofer apparatus of claim 12 wherein said n laminations of surround foam is equal to five laminations, each having an initial thickness on the order of about 7/16 inch.

14. The woofer apparatus of claim 12 wherein said n laminations of surround foam have an initial aggregate thickness on the order of about 31/16 inches compressed to a thickness on the order of about 0.14 inch.

15. The woofer apparatus of claim 12 wherein said n laminations of surround foam is equal to seven laminations, each having an initial thickness on the order of about 7/16 inch.

16. The woofer apparatus of claim 1 wherein the interior volume of said cabinet that is not occupied by said driver and said amplifier is less than one cubic foot.

17. The woofer apparatus of claim 1 wherein said power amplifier includes an input terminal for receiving a positive operating potential and an input terminal for receiving a negative operating potential and said power amplifier is a switching mode amplifier that supplies a signal representative of the low frequency components of said input audio signal as said current to cause said voice coil member and said cone to move in a reciprocating path in accordance with said input audio signal.

18. The woofer apparatus of claim 17 further comprising a power supply having an output terminal for supplying said positive operating potential and said negative operating potential to said power amplifier, said power supply having input terminals that are connectable to a source of alternating current, said power supply being made up of semiconductor devices and capacitors that are directly connected to said power supply input terminals without the use of one or more transformers.

19. The woofer apparatus of claim 18 wherein said power supply is a full-wave voltage doubler power supply.

20. The woofer apparatus of claim 18 wherein said input audio signal is a stereophonic signal having left and right channel signals and said woofer apparatus further comprises circuit means connected for receiving said left and right channel signals of said stereophonic signal and for supplying a composite audio signal as the input signal to said power amplifier;

said composite audio signal being selected from a group of composite signals that can be expressed as (L+R)+α

(L-R) and α

(L+R)+(L-R), where L and R respectively represent the left channel signal and right channel signal of said stereophonic signal and α

is a predetermined constant.

21. The woofer apparatus of claim 1 wherein said power amplifier includes a first input terminal for receiving a positive operating potential and a second input terminal for receiving a negative operating potential, and said woofer apparatus further comprises:

a) signal splitting means for receiving a signal representative of low frequency components of said input audio signal, said signal splitting means dividing said signal representative of low frequency components of said input audio signal into positive and negative signal portions; and

,

b) amplifier power supply means connected for receiving said positive and negative signal portions of said signal representative of low frequency components of said input audio signal, said amplifier power supply means having a first input terminal for receiving a pre-determined positive direct current operating potential, a second input terminal for receiving a predetermined negative direct current operating potential, a first output terminal for supplying a positive time-varying operating potential to said first input terminal of said amplifier for receiving said positive operating potential, and a second output terminal for supplying a negative time-varying operating potential to said second input terminal of said amplifier for receiving said negative operating potential, said amplifier power supply means including means for supplying said positive time-varying operating potential so that it substantially tracks said positive portion of said signal representative of low frequency components of said input audio signal and for supplying said negative time-varying operating potential so that it substantially tracks said negative portion of said signal representative of low frequency components of said input audio signal.

22. The woofer apparatus of claim 1 further comprises a mass driven driver having a frame for mounting said mass driven driver in a second opening of said cabinet and a resilient, semi-rigid surround that fills said second opening of said cabinet when said mass driven driver is mounted therein;

said mass driven driver also having a mass that is mounted to said surround and extends inwardly into said interior of said cabinet, said mass of said mass driven driver moving axially inward and outward of said second opening of said cabinet in response to variations in air pressure within said interior of said cabinet to deflect said surround caused when said voice coil member and said speaker cone of said driver are driven axially inward and outward of said cabinet;

said mass of said mass driven driver being selected for resonance at a selected low frequency that is within the frequency range of said woofer apparatus.

23. The woofer apparatus of claim 1 further comprising a mass driven driver having a frame for mounting said mass driven driver in a second opening of said cabinet, said mass driven driver also having a mass which moves inward and outward of said second opening of said cabinet in response to variations in air pressure within said interior of said cabinet.

24. The woofer apparatus as recited in claim 1 wherein, said woofer apparatus comprises a resilient suspension system for supporting movable driver components of said woofer apparatus within stationary driver components of said woofer apparatus, said resilient suspension system comprising, in combination:

a) spider defining means including at least on annular flexible spider adapted to have its outer periphery coupled to the stationary driver components of said loudspeaker and its inner periphery coupled to the movable driver components of said loudspeaker; and

,

b) said surround comprising a circular surround formed of flexible, resilient, self-supporting material, said circular surround having an edgeroll adjacent its outer periphery, with the outer boundary of said edgeroll being adapted for attachment of said circular surround to the stationary driver components, said circular surround further having a region that is located inwardly of said edgeroll for attachment of said surround to the movable driver components, the thickness of said surround and the diameter of said edgeroll being selected to allow a maximum peak-to-peak excursion that substantially exceeds 0.6".

25. The woofer apparatus as recited in claim 1 wherein, said woofer apparatus comprises a resilient suspension system for supporting movable driver components of said woofer apparatus within stationary driver components of said woofer apparatus, said resilient suspension system comprising, in combination:

a) spider defining means including at least on annular flexible spider adapted to have its outer periphery coupled to the stationary driver components of said loudspeaker and its inner periphery coupled to the movable driver components of said loudspeaker; and

,

b) said surround comprising a circular surround formed of flexible, resilient, self-supporting material, said circular surround having an edgeroll adjacent its outer periphery, with the outer boundary of said edgeroll being adapted for attachment of said circular surround to the stationary driver components, said circular surround further having a region that is located inwardly of said edgeroll for attachment of said surround to the movable driver components, said surround being formed of a material and having a thickness that enables operation of said loudspeaker in a speaker cabinet in which the maximum internal cabinet pressure is substantially in excess of 0.2 lbs/in².

26. The woofer apparatus of claims 24 or 25 wherein said surround of said resilient suspension system has a thickness in a range that extends from about 0.1" to at least 0.14".

27. The woofer apparatus of claims 24 or 25 wherein said edgeroll of said surround has a diameter of about 1.5".

28. The woofer apparatus of claim 27 wherein said surround of said resilient suspension system has a thickness in a range that extends from about 0.1" to at least 0.14".

29. The woofer apparatus of claim 1, further comprising

said woofer apparatus including a basket-like frame fastened to one wall of said cabinet said magnet comprising annular magnet defining means and a cylindrical pole piece, said cylindrical pole piece extending coaxially through said annular magnet defining means in spaced apart relationship with said annular magnet defining means to form an annular gap, said annular magnet defining means and said pole piece establishing a magnetic field that extends radially across said annular gap, said voice coil member comprising at least one winding, connected to output terminals of said amplifier and mounted for axial reciprocal movement through said magnetic field that extends radially across said annular gap in response to current flow through said at least one winding of said voice coil member that is caused by said signal supplied by said amplifier, said axial reciprocal movement of said voice coil member having a maximum peak-to-peak value, said maximum peak-to peak value of said reciprocal movement of said voice coil and the length of the conductive windings of said voice coil collectively establishing a voice coil back-emf for limiting said current through said voice coil member to a value that is substantially less than the voltage of said signal supplied by said amplifier divided by said nominal impedance value.

30. The woofer apparatus of claim 29 wherein said surround is of a thickness that imparts rigidity and strength to said annular surround that enables said surround to withstand maximum internal box pressures within said cabinet that are substantially in excess of 0.2 lbs/in².

31. The woofer apparatus of claim 1 wherein said voice coil member exhibits a nominal impedance value and said voice coil member includes at least one conductive coil wound from a length of wire and wherein said maximum peak-to-peak value of said reciprocal movement of said coil and the length of the conductive windings of said coil collectively establish a voice coil back emf for limiting said current flow through said voice coil member to a value that is substantially less than the voltage of said signal supplied by said amplifier divided by said nominal impedance value.

32. The woofer apparatus of claim 31 wherein said annular flexible surround of said voice coil driven loudspeaker has a thickness that imparts sufficient rigidity and strength to said annular surround to enable said surround to withstand maximum internal box pressures within said cabinet that are within a pressure range that extends from a pressure value that is substantially in excess of 0.2 lbs/in² to a pressure value that is on the order of 3 lbs/in².

33. A woofer apparatus as in any one of claims 1, 24, 25, 29 and 31 inclusive wherein said magnet is an annular magnet having a weight that substantially exceeds 40 ounces.

34. A woofer apparatus as in any one of claims 1, 24, 25, 29 and 31 wherein said surround has a thickness that is between a value that is substantially in excess of 0.02".

35. A woofer apparatus as in any one of claims 1, 24, 25, 29 and 31 inclusive wherein said edgeroll of said surround has a diameter in excess of 1.0" and up to about 1.5".

36. A woofer apparatus as in any one of claims 1, 24, 25, 29 and 31 wherein the air volume of said cabinet is less than one cubic foot.

37. A woofer apparatus as in any one of claims 1, 24, 25, 29 and 31 wherein said amplifier includes a first input terminal for receiving a positive operating potential and a second input terminal for receiving a negative operating potential, and said woofer apparatus further comprises;

a) signal splitting means for receiving a signal portion representative of low frequency components of said audio input signal and dividing said signal portion representative of low frequency components of said audio input signal into positive and negative signal portions; and

,

b) amplifier power supply means connected for receiving said positive and negative signal portions of said signal portion said amplifier power supply means having a first input terminal for receiving a pro-determined positive direct current operating potential, a second input terminal for receiving a predetermined negative direct current operating potential, a first output terminal for receiving a predetermined negative direct current operating potential, a first output terminal for supplying a positive time-varying operating potential to said first input terminal of said amplifier for receiving said positive operating potential, and a second output terminal for supplying a negative time-varying operating potential to said second input terminal of said amplifier for receiving said negative operating potential, said amplifier power supply means including means for supplying said positive time-varying operating potential so that it substantially tracks said positive portion of said signal portion representative of low frequency components of said audio input signal and for supplying said negative time-varying operating potential so that it substantially tracks said negative portion of said signal representative of low frequency components of said audio input signal.

38. The woofer apparatus of claim 37, further comprising a protection circuit connected for receiving an audio input signal and for supplying said signal representative of low frequency components of said audio input signal to said signal splitting means, said protection circuit including excursion limiter circuit means and low frequency auto-throttle circuit means, said excursion limiter circuit means for processing said audio signal and for decreasing the amplitude of said signal representative of low frequency components of said audio input signal when said output signal supplied by said amplifier is at a level that potentially overdrives said driver;

said excursion limiter circuit means connected for receiving said audio input signal and including filtering means having a passband that extends over a desired subwoofer frequency range and includes a low frequency cutoff that is substantially equal to a desired low frequency limit of said subwoofer speaker assembly;

said low frequency auto-throttle circuit means being connected for receiving said audio input signal and being connected to said excursion limiter circuit means, said low frequency auto-throttle circuit means including means for supplying a signal representative of low frequency components of said audio signal and means for increasing the low frequency cutoff of said excursion limiter circuit when said signal representative of said amplitude of said low frequency components of said audio input signal reaches a predetermined level to thereby decrease the amplitude of said signal representative of low frequency components of said audio input signal that is supplied to said signal splitting means and thereby prevent overdriving of said loudspeaker.

39. A woofer apparatus as in any one of claims 1, 24, 25, 29 and 31 wherein said cabinet includes a second opening for the mounting of a mass driven driver having a frame for mounting said mass driven driver in said second opening and a resilient, semi-rigid surround that fills said second opening when said mass driven driver is mounted therein;

said mass driven driver also having a mass that is mounted to said surround, said mass of said mass driven driver being mounted for movement axially inward and outward of said second opening of said enclosure in response to variations in air pressure within said cabinet.

40. The woofer apparatus of claim 39 wherein the air volume of said cabinet that is not occupied by said voice coil driven loudspeaker, said mass driven loudspeaker and said amplifier is less that one cubic foot.

41. The woofer apparatus of claim 39 further comprising a dc power supply having a first output terminal for supplying a predetermined positive direct current operating potential to a first input terminal of an amplifier power supply means and a second output terminal for supplying a predetermined negative direct current operating potential to said second input terminal of said amplifier power supply means said dc power supply having input terminals that are connectable to a source of alternating current and being made up of semiconductor means and capacitors that are directly connected to said power supply input terminals without the use of one or more transformers.

42. Woofer apparatus as set for the in claim 1 wherein said amplifier employs switching mode techniques for generating an amplified signal having essentially the same or similar waveshape as the audio input signal and for supplying said amplified signal to said voice coil member in the form of a time varying current, said amplifier including a first input terminal for receiving a positive operating potential and a second input terminal for receiving a negative operating potential;

and, further including a power supply having first and second output terminals for supplying (+)Δ

v and (-)Δ

v output signals alternately to respective ones of said first and second power amplifier input terminals, said power supply having input terminals that are connectable to a source of alternating current and being made up of semiconductor means and capacitors that are directly coupled to said power supply input terminals;

said amplifier and said power supply being devoid of transformers.

43. A woofer apparatus for processing an audio signal and comprising, in combination:

a) a cabinet having a chamber of a predetermined air volume and an opening formed in the cabinet;

b) a magnet which is mounted to said cabinet and which establishes a magnetic field of a predetermined flux density;

c) a voice coil member positioned to reciprocate in said magnetic field through maximum peak-to-peak excursion strokes substantially in excess of 0.6 inches;

d) a speaker cone connected to said voice coil member for reciprocating motion therewith through maximum peak-to-peak excursion stokes substantially in excess of 0.6 inches;

e) a flexible resilient suspension for supporting said speaker cone and said voice coil member from said cabinet for reciprocation relative to said stationary magnet through peak-to-peak excursion strokes substantially in excess of 0.6 inch and capable of withstanding cabinet pressures of said air volume substantially in excess of 0.2 PSI;

f) a power amplifier operatively connected to said voice coil member;

g) said apparatus being structured and configured so that;

i. the air volume of the chamber of said cabinet is sufficiently small relative to volume of air displaced by said speaker cone so that as said speaker cone reciprocates through its maximum peak-to-peak excursions, the maximum pressure in said cabinet is substantially greater than 0.2 lbs/in² ;

ii. the density of the magnetic flux field produced by said magnet is sufficiently great and the maximum peak-to-peak excursion of said voice coil member is sufficiently long so that the resulting back-emf at maximum peak-to-peak excursions is at a level sufficiently high relative to the maximum voltage output of said amplifier so as to limit current to the voice coil member to preclude overheating the coil member and,

iii. said amplifier having a maximum voltage output and maximum power output that are sufficiently high so as to supply sufficient current at a sufficiently high voltage to drive said voice coil through the magnetic flux field established by said magnet.

44. The woofer apparatus of claim 43 wherein there is a surround connecting the speaker cone to the cabinet.

45. The woofer apparatus of claim 44 wherein said surround of said driver has a thickness that is within a thickness range that extends from about 0.1 inch to at least 0.14 inch.

46. The woofer apparatus of claim 44 wherein said surround of said driver includes an edgeroll having a diameter of about 1.5 inches.

47. The woofer apparatus of claim 44 wherein said surround of said driver has a thickness that is between a value in excess of 0.02 inch and a value that is on the order of at least 0.14 inch and wherein said surround includes an edgeroll that has a diameter in excess of 1.0 inch and up to about 1.5 inches.

48. The woofer apparatus of claim 44 wherein said surround of said driver is formed of n laminations of surround foam having an initial aggregate thickness on the order of at least 23/16 inches compressed to a thickness on the order of about 0.1 inch.

49. The woofer apparatus of claim 48 wherein said n laminations of surround foam is equal to five laminations, each having an initial thickness on the order of about 7/16 inch.

50. The woofer apparatus of claim 48 wherein said n laminations of surround foam have an initial aggregate thickness on the order of about 31/16 inches compressed to a thickness on the order of about 0.14 inch.

51. The woofer apparatus of claim 44 further comprises a mass driven driver having a frame for mounting said mass driven driver in a second opening of said cabinet and a resilient, semi-rigid surround that fills said second opening of said cabinet when said mass driven driver is mounted therein;

said mass driven driver also having a mass that is mounted to said surround and extends inwardly into said interior of said cabinet, said mass of said mass driven driver moving axially inward and outward of said second opening of said cabinet in response to variations in air pressure within said interior of said cabinet to deflect said surround caused when said voice coil member and said speaker cone of said driver are driven axially inward and outward of said cabinet;

said mass of said mass driven driver being selected for resonance at a selected low frequency that is within the frequency range of said woofer apparatus.

52. The woofer apparatus of claim 43 wherein the interior volume of said cabinet that is not occupied by said driver and said amplifier is less than one cubic foot.

53. The woofer apparatus of claim 43 wherein said power amplifier includes an input terminal for receiving a positive operating potential and input terminal for receiving a negative operating potential and said power amplifier is a switching mode amplifier that supplies a signal representative of the low frequency components of said input audio signal as said current to cause said voice coil member and said cone to move in a reciprocating path in accordance with said input audio signal.

54. The woofer apparatus of claim 53 further comprising a power supply having an output terminal for supplying said positive operating potential and said negative operating potential to said power amplifier, said power supply having input terminals that are connectable to a source of alternating current, said power supply being made up of semiconductor devices and capacitors that are directly connected to said power supply input terminals without the use of one or more transformers.

55. The woofer apparatus of claim 54 wherein said power supply is a full-wave voltage doubler power supply.

56. The woofer apparatus of claim 43 wherein said power amplifier includes a first input terminal for receiving a positive operating potential and a second input terminal for receiving a negative operating potential, and said woofer apparatus further comprises:

a) signal splitting means for receiving a signal representative of low frequency components of said input audio signal, said signal splitting means dividing said signal representative of low frequency components of said input audio signal into positive and negative signal portions; and

,

b) amplifier power supply means connected for receiving said positive and negative signal portions of said signal representative of low frequency components of said input audio signal, said amplifier power supply means having a first input terminal for receiving a pre-determined positive direct current operating potential, a second input terminal for receiving a predetermined negative direct current operating potential, a first output terminal for supplying a positive time-varying operating potential to said first input terminal of said amplifier for receiving said positive operating potential, and a second output terminal for supplying a negative time-varying operating potential to said second input terminal of said amplifier for receiving said negative operating potential, said amplifier power supply means including means for supplying said positive time-varying operating potential so that it substantially tracks said positive portion of said signal representative of low frequency components of said input audio signal and for supplying said negative time-varying operating potential so that it substantially tracks said negative portion of said signal representative of low frequency components of said input audio signal.

57. The woofer apparatus of claim 43 wherein the woofer apparatus of claim 43 further comprising a mass driven driver having a frame for mounting said mass driven driver in a second opening of said cabinet, said mass driven driver also having a mass which moves inward and outward of said second opening of said cabinet in response to variations in air pressure within said interior of said cabinet.

58. The woofer apparatus of claim 43 wherein said input audio signal is a stereophonic signal having left and right channel signals and said woofer apparatus further comprises circuit means connected for receiving said left and right channel signals of said stereophonic signal and for supplying a composite audio signal as the input signal to said power amplifier;

said composite audio signal being selected from a group of composite signals that can be expressed as (L+R)+α

(L-R) and α

(L+R)+(L-R), where L and R respectively represent the left channel signal and right channel signal of said stereophonic signal and α

is a predetermined constant.

59. A woofer apparatus for processing an input audio signal, said subwoofer 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 with a maximum peak-to-peak excursion that exceeds or equals a pre-determined value;

iii. a speaker cone having an effective cone area and connected to said voice coil member for reciprocating motion therewith and connected in a first opening in said cabinet; and

,

iv. a surround connecting said cone to said cabinet;

c) a mass driven driver mounted in said cabinet, said mass driven driver comprising;

i. a mass

ii. a speaker cone having an effective cone area and connected to said mass and

iii. a surround by which said mass driven driver is connected to said cabinet, said speaker cone and said mass of said mass driven driver being mounted in a second opening in said cabinet for reciprocating motion in response to variations in air pressure in said cabinet, said cone and mass having a peak-to-peak excursion;

d) 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 connected thereto to move in a reciprocating path in accordance with the audio input signal, and in turn to cause reciprocating motion of the mass and cone of the mass driven driver;

e) said woofer apparatus having the following operating characteristics and relationships;

i. the effective cone areas and the maximum peak-to-peak excursions of the cones being related to provide a maximum air displacement volume;

ii. said predetermined cabinet air volume and said maximum air displacement volume being interrelated in that an increase in the ratio of the maximum air 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

,

f) said apparatus being structured and arranged so that;

i. the maximum peak-to-peak excursion of at least the cone of the voice coil driven driver 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

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 member, 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 filed B at maximum peak-to-peak excursions, while maintaining the level of current flow through said voice coil member 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.