Amplifiers – Signal feedback – Combined with control of bias voltage of signal amplifier
Patent
1976-04-20
1978-09-12
Claffy, Kathleen H.
Amplifiers
Signal feedback
Combined with control of bias voltage of signal amplifier
330301, 179 1D, 179 1P, H04B 164
Patent
active
041139836
ABSTRACT:
Improved input filtering apparatus for loudspeaker systems, and loudspeaker systems including such apparatus. The bass roll-off point of input filtering apparatus for loudspeakers is automatically adjusted to an optimum in accordance with the amplitude and spectral content of the audio signal being received at the time, thereby attenuating components in the signal liable to cause "bottoming" of the loudspeaker. The input filter apparatus comprises a first high-pass filter having a breakpoint frequency at or near the lower threshold of the audio frequency range, a second variable bandwidth, high-pass filter connected to receive the first high-pass filter output, a feedback circuit responsive to the second filter output to provide a feedback signal as a linear function thereof with a gain which is substantially inversely proportional to the square of the frequency, and circuit means including threshold means connected with the second filter and responsive to the said feedback signal to relatively rapidly increase the breakpoint frequency of the second filter in response to values of the feedback signal which exceed a threshold and to relatively showly reduce that breakpoint frequency in response to values of the feedback signal which do not exceed the said threshold. Bass equalization circuit means having a frequency response at the low end of the audio spectrum which is substantiallythe inverse of the frequency response of said loudspeaker means are provided between the output of the second filter and the loudspeaker drive circuit.
REFERENCES:
patent: 2606970 (1952-08-01), Scott
patent: 3497621 (1970-02-01), Erath
patent: 3805091 (1974-04-01), Colin
patent: 3934190 (1976-01-01), Dolby
Claffy Kathleen H.
Kemeny E. S.
Teledyne Acoustic Research
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