Acoustics – Anatomic or prosthetic relation – Ear and mouth
Patent
1973-06-21
1976-09-28
Stellar, George G.
Acoustics
Anatomic or prosthetic relation
Ear and mouth
1791155DV, 1791155ES, 1791155VC, 179180, 179181R, 181157, 181172, H04R 714, H04R 718, H04R 902, H04R 904
Patent
active
039833372
ABSTRACT:
A very small audio speaker is described which has a broad-band electrical-mechanical transducer, a broad-band mechanical-air-transducer, and a special suspension system which combine to produce a substantially flat frequency response over substantially the entire audio range from about 50 Hz to about 18,000 Hz.
The broad-band electrical-mechanical transducer has either a voice coil with two axially spaced subsections, or a magnetic field with two axially spaced subsections, with the other being continuous between two effective boundaries. Each subsection of the coil, for example, is generally centered on the boundary of the magnetic flux field so that as one subsection moves into the flux field, the other subsection moves out of the flux field at the same rate, thus maintaining a linear force as the coil reciprocates through a much longer distance than is possible using conventional continuous coil and magnetic structures. The increased travel of the coil enhances low frequency performance while simultaneously preventing distortion of high frequency superimposed on the lows. The split coil achieves the long travel without increasing the weight of the coil or the inductance of the coil so that high frequencies can also be efficiently transformed.
Both the high and low frequencies can also be efficiently coupled to the air by a broad-band radiating surface characterized by transmission ribs which transmit the motional energy through the plane of the radiating surface at substantially the velocity of sound in air. A membrane extends between the transmission ribs to couple the energy transmitted radially by the ribs to the air. The coil and radiating surface are guided through the long travel by an anti-friction bearing positioned between the voice coil form and the magnetic center pole of the voice coil which introduces no spring forces to distort or retard the movement of the reciprocating members. Additionally, the bearing permits the tolerance between the coil member and the magnetic structure to be significantly reduced, which permits either an increase in the number of turns in the coil, thus increasing the force for a given diameter coil, or a reduction in the size of the magnet to produce the same force. The outer edge of the radiating surface is connected to a peripheral mounting flange by an edge suspension system which seals the annular space, maintains the cone axially aligned, and also exerts a minimum spring biasing force which returns the coil to the center of the magnetic field in the quiescent state. The edge suspension system includes a plurality of non-creeping spring elements, preferably spring steel to maintain long-term stability which are attached to, and damped by, a flexible rolled edge of graduated stiffness. The mid-sized driver is mounted in an unusually small air suspension enclosure.
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patent: 1895071 (1933-01-01), Fanger
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patent: 2661412 (1953-12-01), Dreyfus
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patent: 3201529 (1965-08-01), Surh
patent: 3403235 (1968-09-01), Bishop
patent: R24141 (1956-04-01), Brennan
Babbco, Ltd.
Stellar George G.
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