Abstract: In a loudspeaker system having an adjustable balance between two speakers having different low frequency reproduction characteristics, the attenuation of low frequency signals applied to the loudspeaker with the better low frequency reproduction characteristics is selectively inhibited even when the balance is adjusted toward the other loudspeaker, so that an adequate low frequency sound will be produced at all times.

Abstract: An audio processing circuit that is adapted for operation in a partial distortion mode of operation particularly when transitioning from partial distortion to clean signal operation and including a gain control circuit for sensing the level of the audio signal to control gain so as to increase output signal gain as the volume control is decreased in volume. The circuit also includes a sensing circuit for sensing the audio level to boost high end signal content as the volume control is decreased so as to maintain high end or treble signal content at low volume.

Abstract: A signal control apparatus includes a circuit (26) for bearing a first characteristic to an original signal and outputting it as a first signal; a circuit (28) for bearing a second characteristic to the original signal and outputting it as a second signal; an adder circuit (30; 50) for adding the first and second signal with a variable proportion therebetween; and a control circuit (38) for controlling the variable proportion in accordance with the original signal in order to vary the output signal characteristic continuously.

Abstract: An automatic graphic equalizer for a sound system has circuitry for measuring the effect of the physical environment receiving a sound on the frequency characteristics of the sound, and for adjusting the characteristics of a graphic equalizer to compensate for distortions in the desired flat frequency response caused by the physical environment. The circuitry includes a pink noise generator supplying pink noise to the graphic equalizer during an initialization operation, the graphic equalizer being controlled by a controller to present a flat frequency characteristic. The equalizer output is sent to a speaker which supplies the pink noise as a sound signal to the selected environment. A microphone picks up the sound in the selected environment and converts it to an electrical signal which is supplied through an ALC amplifier to a frequency-variable band-pass filter to detect the signal level in each of the equalizer frequency bands.

Abstract: A sound field correcting device for use in a stereophonic system intended for vehicular use. Speakers are installed on opposite sides of both the front and rear seats of the vehicle. The number of persons seated in the vehicle is determined and applied to a correcting unit. When plural persons are seated in the vehicle, the sound pressure levels in the high-frequency range of loudspeakers is increased. Also, the sound pressure levels of the speakers can be corrected in accordance with the positions at which persons are seated in the vehicle.

Abstract: A multiple band automatic gain control circuit having a band splitter which is responsive to an input audio signal for separating the audio signal into plural components of different frequencies. Plural gain adjustment circuits each control the gain of an associated one of the components, wherein each of the gain adjustment circuits includes a voltage controlled amplifier, and feed forward control elements for controlling the voltage controlled amplifier as a function of the amplitude of the associated component. A signal combiner combines the gain adjusted components to thereby form a gain adjusted audio signal. A limiter circuit prevents the combined signal from exceeding predetermined amplitude constraints by simultaneously reducing the gain of all of the variable gain circuits whenever the combined signals exceed the predetermined constraints.

Abstract: A device for generating a variable and adjustable control signal is provided. The device is of the type in which the control signal is generated in response to the manipulation of the device by an operator and is applied to suitable controlled amplifiers such as voltage controlled amplifiers or filters. The device comprises variable voltage generating member and a holding circuit coupled thereto. The voltage generating member is capable of delivering a voltage corresponding to the location where the operator touches or presses and when the voltage generating member is not touched the voltage generating member is inhibited from delivering a voltage. The holding circuit delivers a first signal corresponding to the voltage delivered under the manipulation of the voltage generating member, and holds a voltage corresponding to the previously manipulated location and delivers a second signal corresponding to the held voltage during the time the voltage generating member is not manipulated.

Abstract: An automatic dynamic equalization circuit has a potentiometer having a tap shunted by an active resonator circuit including a capacitor shunted by an active circuit presenting a high Q inductive reactance that is resonant at substantially 50 Hz and provides essentially no boost in the middle range of frequencies above 150 Hz with roll-off below about 45 Hz.

Abstract: An electronic amplifier control switch for controlled operation of a power amplifier connected to the output of an audio signal generating device and having an associated electronic equalizer/attentuator switching circuit that is switchable between its two modes by a manually settable switch.

Abstract: A circuit providing a known change in a parameter of a function without interfering with the basic operation of the function is utilized in an audio circuit "loudness contour" control. Bass and treble controls function independently of the volume setting while desired contours are obtained at each volume control setting.