Abstract: A stereophonic reproduction system which improves an unnatural sound image localization at an asymmetric position relative to right and left loudspeakers. Deterioration in tone quality incidental thereto is improved by filters providing right and left channels with selected phase characteristics.

Abstract: A constant-voltage power supply circuit having a light-emitting element and a photosensitive element optically coupled with each other and a driving power source for driving the light emitting element, the circuit using an output voltage of the photosensitive element as a reference voltage; and an amplifier circuit using a constant current converted from the reference voltage of the constant-voltage power supply circuit; and a DA converter adapted for delivering binary digital signals to the constant-voltage power supply circuit.

Abstract: A dome speaker comprising a dome-shaped diaphragm formed of a highly rigid material such as titanium or a titanium alloy, and having at least one elongated cut-out portion which varies the rigidity of the diaphragm and prevents a dip in the anti-resonance frequency range and a peak in the high resonance frequency range of the dome speaker. The speaker also includes a voice coil bobbin connected to the diaphragm. Preferably, the diaphragm includes two elongated cut-out portions in parallel relation to each other and with a center portion of the diaphragm interposed therebetween. A reinforcing rib may be integrally formed at an end of each cut-out portion. The cut-out portion may be covered either by a peripheral member made of a soft material or by a loss stopper formed of a viscoelastic material.

Abstract: A structure for a dome speaker includes a dome-shaped diaphragm formed of a high rigidity material and having an outer periphery, a voice coil bobbin secured at a top end thereof to the outer periphery of the diaphragm, a voice coil mounted about the bobbin, and a variation means in the bobbin for varying the resonance conditions of the diaphragm. The variation means includes at least one cut-out portion provided at the top end of the bobbin and a sheet which closes the cut-out portion. Preferably, the diaphragm is made of a nitrified titanium alloy and the sheet is made from a material softer than the bobbin. The cut-out portion may have a width from about 7 to about 50 percent of the total circumferential length of the bobbin.

Abstract: A DC power supply circuitry comprises an AC power source transformer with its secondary winding having a center tap; a rectifier circuit; a smoothing circuit; and a bidirectional switching circuit having predetermined threshold values, interposed in between the center tap and the smoothing circuit.

Abstract: A loudspeaker system with a plurality of direct loudspeakers mounted on an enclosure front for radiating in a forward direction and at least one compensation loudspeaker for each loudspeaker. The compensation speakers are mounted to direct sounds rearwardly so that both the sound pressure as a result of the direct sounds and the sound pressure as a sum of the direct and indirect sounds are substantially independent of frequency.

Abstract: A dome-shaped diaphragm for loudspeakers comprising a substrate fabric of synthetic fiber, a poly-urethane elastomer film for giving airtightness to the substrate fabric, and a viscoelastic resin adhesive adhering the fabric and the film together.

Abstract: A method and an apparatus for automatically establishing proper adjustment of recording bias current to obtain a flat reproduction frequency characteristic with a three-head type taperecorder in which sound recorded by a recorder head on a running magnetic tape may be immediately reproduced by a reproducer head immediately downstream of the recorder head.

Abstract: A circuitry has a calibration signal generator, a higher frequency range output level adjusting circuit and a recording bias current adjusting variable resistor. The signal generator continually alternately gives output two kinds of calibration signals of lower and higher frequencies. The higher range adjusting circuit is operatively connected with the variable resistor, and adjusts output sound level, as indicated at an indicator, only of the higher frequency signal of the two calibration signals.

Abstract: A horn speaker comprising a diaphragm positioned close to a throat and side walls forming sound passages for radiating the vibrations of the diaphragm effectively as sound waves from the mouth of the speaker.

Abstract: An apparatus for comparing frequency of an object signal with a given reference frequency, with a reference signal generator for developing a reference signal having the reference frequency. If the object signal is frequency-modulated, then its center frequency is compared with the reference frequency. A switching signal generator, switching circuitry actuated by the switching signal, a frequency discriminator, low-pass filters and a voltage comparator are also provided. Actuated by the switching signal, the discriminator alternately discriminates the frequencies of the object and reference signals, and the averaged discrimination output voltages are compared by the comparator to give the indication of comparison of the frequencies of the object and reference signals.

Abstract: A horn speaker comprising a diaphragm positioned close to a throat and side walls forming sound passages for radiating the vibrations of the diaphragm effectively as sound waves from the mouth of the speaker.

Abstract: A horn speaker comprising a diaphragm positioned close to a throat and side walls forming sound passages for radiating the vibrations of the diaphragm effectively as sound waves from the mouth of the speaker.