Portable sound speaker system and driving circuit therefor

A speaker system comprising:

• a vertically oriented elongated tube supported on a ground surface and having an axial direction, said tube being open at upper and lower ends thereof;
• a first speaker mounted at a lower end of said vertically oriented elongated tube such that said first speaker is positioned substantially closer to the ground surface than to the upper end of said tube when said tube is supported vertically on the ground surface, said first speaker having a front driving face with an effective driving area and a rear face, said first speaker providing an in-phase audio signal directed upwardly through said elongated tube and an out-of-phase ground wave audio signal directed in an opposite direction therefrom, said first speaker being a woofer;
• a second speaker mounted at said lower end of said elongated tube such that said second speaker is positioned substantially closer to the ground surface than to the upper end of said tube when said tube is supported vertically on the ground surface, said second speaker providing an in-phase audio signal directed upwardly through said elongated tube, said second speaker being a tweeter;
• a mounting assembly for mounting said second speaker at substantially a same vertical level as the first speaker so as to avoid delays between different frequency sounds from the first and second speakers;
• and
• an arrangement for providing resistive loading at a lower portion to a rear of said first speaker when said tube is supported vertically on the ground surface, said arrangement comprising a restricted open area formed between said rear face of said first speaker and the ground surface when said tube is supported vertically on the ground surface, said restricted open area being less than said effective driving area and being arranged to transmit said out-of-phase ground wave audio signal from said first speaker in a direction substantially at right angles to said axial direction.

A speaker system comprising:

• a vertically oriented elongated tube supported on a ground surface, said tube being open at upper and lower ends thereof;
• a speaker mounted at a lower end of said vertically oriented elongated tube such that said first speaker is positioned substantially closer to the ground surface than to the upper end of said tube when said tube is supported vertically on the ground surface, said speaker providing an in-phase audio signal directed upwardly through said elongated tube and an out-of-phase ground wave audio signal directed in an opposite direction therefrom, said speaker having an impedance;
• a driving circuit for driving said speaker in accordance with an input signal thereto, said driving circuit including:
• a first power amplifier for amplifying said input signal with a variable gain and supplying a first amplified input signal to a first input of said speaker;
• a circuit for measuring the impedance of said speaker;
• a gain varying circuit for varying the gain of said first power amplifier in dependence upon the measured impedance of said speaker;
• and
• a second power amplifier for amplifying the amplified input signal from said first power amplifier and for supplying a second amplified signal to a second input of said speaker out of phase with the first amplified input signal, said circuit for measuring connected to an output of said second power amplifier;
• and
• a resistive feedback circuit connected only between one terminal of said speaker and an input of said second power amplifier for varying the gain of said second power amplifier in dependence upon the measured impedance of said speaker for all frequency components of said input signal and being unconnected with said first power amplifier.

A speaker system comprising:

• a vertically oriented elongated tube supported on a ground surface, said tube being open at upper and lower ends thereof;
• a speaker mounted at a lower end of said vertically oriented elongated tube, said speaker providing an in-phase audio signal directed upwardly through said elongated tube and an out-of-phase ground wave audio signal directed in an opposite direction therefrom, said speaker having an impedance;
• and
• a driving circuit for driving said speaker in accordance with an input signal thereto, said driving circuit including:
• a first power amplifier for amplifying said input signal with a variable gain and supplying an amplified input signal to said speaker;
• an impedance measuring circuit for measuring the impedance of said speaker, said impedance measuring circuit including a current monitoring circuit for monitoring a current supplied to said speaker;
• and
• a gain varying circuit for varying the gain of said first power amplifier in dependence upon the measured impedance of said speaker, said gain varying circuit including a gain adjustment circuit for increasing the gain of said first power amplifier primarily for low frequency components of said input signal in response to the monitored current by said current monitoring circuit, and said gain adjustment circuit includes:
• an amplifier for amplifying a signal corresponding to said monitored current with a variable gain and for supplying said amplified signal corresponding to said monitored current to the first power amplifier;
• and
• a frequency selective feedback circuit for feeding back an output signal of said amplifier to an input thereof with a level dependent on the frequency of said output signal so as to vary the gain of said amplifier, said frequency selective feedback circuit including a parallel circuit of a resistor and a capacitor supplied with said output signal and connected to said input of said amplifier, wherein high frequency components of said output signal pass primarily through said capacitor and low frequency components of said output signal pass primarily through said resistor.

A driving circuit for a speaker, comprising:

• a first power amplifier for amplifying an input signal with a variable gain and supplying a first amplified input signal to a first input of said speaker;
• a circuit for measuring the impedance of said speaker;
• a gain varying circuit for varying the gain of said first power amplifier in dependence upon the measured impedance of said speaker;
• a second power amplifier for amplifying the amplified input signal from said first power amplifier and for supplying a second amplified signal to a second input of said speaker out of phase with the first amplified input signal, said circuit for measuring connected to an output of said second power amplifier;
• and
• a resistive feedback circuit connected only between one terminal of said speaker and an input of said second power amplifier for varying the gain of said second power amplifier in dependence upon the measured impedance of said speaker for all frequency components of said input signal and being unconnected with said first power amplifier.

A driving circuit for a speaker, comprising:

• a first power amplifier for amplifying an input signal with a variable gain and supplying an amplified input signal to said speaker;
• an impedance measuring circuit for measuring the impedance of said speaker, said impedance measuring circuit including a current monitoring circuit for monitoring a current supplied to said speaker;
• a gain varying circuit for varying the gain of said power amplifier in dependence upon the measured impedance of said speaker, said gain varying circuit including a gain adjustment circuit for increasing the gain of said first power amplifier primarily for low frequency components of said input signal in response to the monitored current by said current monitoring circuit, said gain adjustment circuit including:
• an amplifier for amplifying a signal corresponding to said monitored current with a variable gain and for supplying said amplified signal corresponding to said monitored current to the first power amplifier;
• and
• a frequency selective feedback circuit for feeding back an output signal of said amplifier to an input thereof with a level dependent on the frequency of said output signal so as to vary the gain of said amplifier, said frequency selective feedback circuit including a parallel circuit of a resistor and a capacitor supplied with said output signal and connected to said input of said amplifier, wherein high frequency components of said output signal pass primarily through said capacitor and low frequency components of said output signal pass primarily through said resistor.

A speaker system comprising:

• a vertically oriented elongated tube supported on a ground surface and having an axial direction, said tube being open at upper and lower ends thereof;
• a first speaker mounted at a lower end of said vertically oriented elongated tube and having a front driving face with an effective driving area, said first speaker providing an in-phase audio signal directed upwardly through said elongated tube and an out-of-phase ground wave audio signal directed in an opposite direction therefrom;
• an enclosure for at least partially enclosing said first speaker;
• an arrangement for providing resistive loading at a lower portion of said first speaker, said arrangement for providing resistive loading comprising a restricted open area formed by said enclosure adjacent to said ground surface, said restricted open area being less than said effective driving area and being arranged to transmit said out-of-phase ground wave audio signal from said first speaker in a direction substantially at right angles to said axial direction;
• and
• a driving circuit for driving said speaker in accordance with an input signal thereto, said driving circuit including:
• a first power amplifier for amplifying said input signal with a variable gain and supplying a first amplified input signal to a first input of said speaker;
• a circuit for measuring the impedance of said speaker, said impedance measuring circuit including a current monitoring circuit for monitoring a current supplied to said speaker;
• a gain varying circuit for varying the gain of said first power amplifier in dependence upon the measured impedance of said speaker, said gain varying circuit including a gain adjustment circuit for increasing the gain of said first power amplifier primarily for low frequency components of said input signal in response to the monitored current by said current monitoring circuit, and said gain adjustment circuit includes:
• an amplifier for amplifying a signal corresponding to said monitored current with a variable gain and for supplying said amplified signal corresponding to said monitored current to the first power amplifier;
• a frequency selective feedback circuit for feeding back an output signal of said amplifier to an input thereof with a level dependent on the frequency of said output signal so as to vary the gain of said amplifier;
• and
• said output signal from said amplifier of said gain adjustment circuit is supplied as a positive feedback signal to said first power amplifier;
• and
• a second power amplifier for amplifying the first amplified input signal from said first power amplifier and for supplying a second amplified signal to a second input of said speaker out of phase with the first amplified input signal, said circuit for measuring connected to an output of said second power amplifier.