Microphone
N° Inventaire : AP-18-3290
Collection : La Cinémathèque française
Catégorie d'appareil : Son
Nom du modèle : Western Electric Moving Coil Type Microphone n° 618 A
Numéro de fabrication : n° 448
Lieu de fabrication : New York, New York, Etats-Unis
Année de fabrication : 1931
Brevet : Patent 1 373 019, 1 456 538, 1 692 317, 1 707 544, 1 766 473
Copyright photo : Dabrowski Stéphane
Fiche détaillée
Type de l'appareil
microphone électromagnétique à bobine mobile ; diaphragme en duralumin ; ruban en aluminium ; aimant ; prise six broches
Auteurs
Informations non disponibles
Fabricants
Electrical Research Products Incorporated
[Chicago, Illinois, 1848 Larchmont Avenue]
Utilisateurs
Informations non disponibles
Distributeurs
Western Electric Co - Electrical Research Products Inc.
Philadelphia
Sujet du modèle
Informations non disponibles
Objectif
Informations non disponibles
Taille de l'objet
Ouvert :
Informations non disponibles
Fermé :
Longueur : 10 cm
Largeur : 8 cm
Hauteur : 8.5 cm
Diamètre :
Informations non disponibles
Taille de la boîte de transport
Informations non disponibles
Remarques
Marque : "Western Electric Reg. U.S. Pat. off, 618 A n° 448, Patent 1 373 019, 1 456 538, 1 692 317, 1 707 544, 1 766 473, pat. pend. Made in U.S.A.".
"This microphone has a low electrical impedance and may be connected to its amplifier by means of a suitable transformer ; it may be used at a considerable distance from an associated amplifier. The microphone may be mounted in a suspension, table, or floor type of mounting. The microphone has a thin duralumin diaphragm of low mechanical stiffness, which is clmaped around its outer edge. To this diaphragm is attached a coil of aluminium ribbon. Motion of the diaphragm causes the coil to move in the magnetic field in which it is located. The magnetic field is maintained by a permanent magnet made from a high grade colbalt steel alloy. The use of the permanent magnet eliminates the necessity for supplying a polarizing voltage to the microphone. Motion of the coil in the magnetic field, caused by sound pressures acting upon the diaphragl, induces a voltage in the coil that is proportional to the velocity with which it moves. A number of air chambers and slot openings connecting them have been associated with the diaphragm in order to obtain substantially uniform response over a frequency range from 35 to 9500 cycles per second. One of these acoustic elements, in addition to exerting a control on the motion of the diaphragm, allows air to be transferred from the front to the back of the diaphragm. This eliminates effects due to changes in barometric pressure. The design and principles of operation of the N° 618A Microphone are such that it is not affected appreciably by any chances in temperture likely to be encountered in its use. The electrical impedance of the N° 618A Microphone at low frequencies is approximately 28 ohms with a phase angle of nearly zero degrees. The impedance rises gradually to about 38 ohms with a phase angle of about 20 degrees at 10 000 cycles per second. The efficiency of this microphone is higher than that of the conventional form of condenser microphone" (http://www.coutant.org/we618a/)