Abstract: A speaker which is thin but which is capable of providing high-fidelity reproduction and ensuring a suitable level of sound pressure even when it is brought close to a wall. A closed chamber is formed behind one part of a disphragm mounted in an enclosure, and an open chamber is formed behind another part of the diaphragm. At least one voice coil driver unit is connected to the diaphragm. The phase difference between sounds radiated from the front and rear surfaces of the diaphragm is increased as large as possible by using an acoustic duct for the sound radiated through the open chamber, thereby minimizing cancellation of sounds and improving the sound pressure level.

Abstract: A speaker system has an acoustic diaphragm and an image projection screen provided on a surface of the diaphragm integrally therewith so as to enable the user to enjoy both realistic image on the screen and powerful sound reproduced through the diaphragm. The rear surface of the diaphragm is closed at a peripheral portion thereof while the central portion of the rear surface of the diaphragm is opened to the exterior, so that the speaker system can provide a high level of reproduced sound pressure in low-pitched region, while the thickness of the speaker is reduced remarkably. The diaphgram can be driven by a plurality of driving units so that the speaker system can operate only with an ordinary stereophonic amplifier.

Abstract: A sound reproducing apparatus for use in a vehicle having a speaker system constituted by at least one acoustic duct and a speaker unit disposed at a throat of the acoustic duct, an opening formed at the other end of the acoustic duct facing the passenger compartment of a vehicle. The apparatus is arranged such that, F0 and Fs are substantially equal to each other. Where Fs is the lowest frequency in a frequency range within which the imaginary part of the acoustic impedance at the sound radiating surface of the speaker system in the direction of the space within the passsenger compartment is zero and F0 is the low-range resonance frequency of the speaker system itself in the free space.

Abstract: A speaker which is thin but which is capable of providing high-fidelity reproduction and ensuring a suitable level of sound pressure even when it is brought close to a wall. A closed chamber is formed behind one part of a diaphragm mounted in an enclosure, and an open chamber is formed behind another part of the diaphragm. At least one voice coil drive unit is connected to the diaphragm. The phase difference between sounds radiated from the front and rear surfaces of the diaphragm is increased as large as possible by using an acoustic duct for the sound radiated through the open chamber, thereby minimizing cancellation of sounds and improving the sound pressure level.

Abstract: A pickup arm device comprising a rotary bearing having a mounting bed rotatable about both the vertical and horizontal axes, and an arm assembly consisting of an arm, a cartridge mounting head shell at one end thereof, a rider weight at the other end thereof and a mount or saddle which is formed between the ends thereof and adapted to be slidably mounted on the mounting bed of the rotary bearing, whereby the arm assembly including a cartridge may be easily replaced.

Abstract: A rotational speed signal sensor for a motor having a rotating permanent magnet as a rotor. One cylindrical surface of a hollow cylindrical rotating magnet has a series of magnetic poles which coact with the stator windings so as to produce the torque while the other cylindrical surface of the rotating magnet has a series of magnetic poles which coact with a sensor coil so as to derive the rotational speed signal.

Abstract: A pickup cartridge and a pickup cartridge mounting device therefor wherein a plug protrusion of tetragonal sectional area is formed at the rear end of a pickup cartridge, a recess of tetragonal sectional area with at least three walls for receiving the plug protrusion is formed at the front end of a tone arm or the like, and after the plug protrusion is inserted into the recess, the protrusion is strongly clamped between two walls of the recess by a mounting screw. Thus, replacement of pickup cartridges is made easy and reliable.

Abstract: A pick-up assembly carried by a tone arm itself or a cartridge adapted to be connected to the tone arm includes a vibrating section and a magnetic circuit section. The vibrating section has a cantilever having one end carrying a stylus and the other end mounted in a support ring. A pair of ring-shaped moving coils are mounted on the support ring in such a manner that the longitudinal axes of the coils are in parallel and equidistantly spaced relation to the longitudinal axis of the support ring so that the coils are angularly spaced at right angles to each other about the longitudinal axis of the support ring. The magnetic circuit section has a permanent magnet sandwiched between front and rear yokes of magnetic material.

Abstract: One end of an arm main body is formed integral with a head shell for mounting a cartridge while the other end thereof supports a balance weight. A mounting portion is formed integral with the arm main body between the ends thereof and close to the other end thereof. The mounting portion of the arm main body may be detachably mounted on an inner gimbal which in turn is mounted with pivot bearings to an outer gimbal for rotation about a horizontal axis so as to permit the arm main body to nod up and down. The outer gimbal in turn is mounted with pivot bearings to a yoke for rotation about a vertical axis so as to permit the arm main body to rotate in a horizontal plane. The yoke in turn is securely attached to the base of the pickup arm device.

Abstract: In a stereophonic pickup cartridge which derives two or more than two electric signals from a stereophonic sound recording disk of so-called 45.degree. -- 45.degree. type, there is provided a displacement-type pickup cartridge having an improved vibration transmission structure.