door John Koster
BTH brengt vanaf 1926 elektrodynamische
luidsprekers op de markt. Dit type uit 1927 heeft een
diameter van circa 6 inch en is voorzien van een
ingebouwde versterker en voeding.
Since 1926 BTH manufacures
the moving coil loudspeaker. For use with either AC or
DC, the unit incorporates the output amplifier as well
as the mains equipment giving the necessary high anode
voltage, exceeding 400, while the grid bias is also
obtained from the mains. The electro-magnet is of large
diameter, the pole being about 1 5/8 inch across. A
supple centring device holds the coil in position, and
the diaphragm is about 6 inch in diameter. Plunger
operated contacts break all current supply circuits by
the act of removing the unit from its containing cabinet
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