The Double-Roll Speaker.

Radio Record, Volume II, Issue 9, 14 September 1928, Page 26

The Double-Roll Speaker.

[THIS speaker, built to the dimensions given, is the equivalent of a 26inch cone. The paper used for -the diaphragm should be rather heavier than that used for the cover of the Government telephone directory, which forms a handy standard of comparison. The omniphone unit for this speaker is also stocked by the Rodger Importing Company, 159 Manchester Street, Christchurch, at 30s. Field Current for Coil-Driven Speakers. PARAGRAPH in "Radio Broadcast" states that for the excitation of coil-driven speaker magnets requiring six volts, this can be adequately supplied by many. of the poyfular trickle chargers with a Tube A lock connected across its- output to eliminate hum. This combination, it is’ st ed, is altogether satisfactory, not \a trace of a.c. hum being perceptible in the speaker, which functions at full ' efficiency, referring specially to. the _ Jensen and Magnavox types. |