Dynamic Speakers

Radio Record, Volume II, Issue 8, 7 September 1928, Page 12

Dynamic Speakers

Identical with Moving Coil Type [OVING coil loud-speakers are known in the country of their origin, U.S.A., as dynamic speakers. Dynamic is the name applied by the patentees, the Magnavox Company of Oakland, California, who own and control the master patents. Little has been heard here of the dynamie speaker, but it has been inanufactured and sold in huge quauntities in the United States for the past two years by the Magnavox Company, Company are catching up on their orders and are able to supply for export. Owing to the fact that the Magnavox Company are producing to the maximum of their capacity, ie., 1,000 units per day, they have just licensed

several manufacturers to use their patents for sale on the U.S.A. market only, and have decided to handle the Australasian market themselves. The construction of a dynamic speaker in quantity on a commercial basis requires a considerable amount of knowledge and experience. This is the reason why the present Magnavox speakers are the highest quality moving coil speakers produced anywhere. The Magnavox Compiuny are supply‘ing the largest manufacturers who produce the highest quality of radio sets in U.S.A. For instance: Stromberg: Carlson, Zenith, Splitdorf, Bosch. Freshman, Amrad, Gilfillan, Mohawk. De Forest Crosley, ‘Federal. One of the above manufacturers placed a contract With the Magnavox Company at the radio exhibition held in Chicago in June for 80,000 units. Those who have not had the pleasure of listening to a dynamic speaker ¢cannot very well realise what a revolution in sound production has taken place by this discovery. The great feature is that there are no parts in the dynamic speaker which can rattle. and providing the in-put is undistorted the Magnavox speaker will give perfect reproduction with unlimited volume.

Magnavox dynamic speakers are produced in types to suit all classes otf electrical current. There is one type operating with 280 volts A.C, which operates direct from the lighting mains. Another type which will take 110 to 220 volts of D.C. current. This type can be operated from any D.C. current available, but is primarily constructed for the purpose of operating from an amplifier of the Sampson type, from which it can be tapped off the required D.C. current. Those who have the ordinary electric light installed in their homes with the 230 volt A.C. current merely plug into the lighting socket and take the other two connections to the radio set in the ordinary way. Those who wish to operate their dynamic speaker from the accumulator may do so by using the 6 volt type. A very effective demonstration of the perfection to which sound reproduction can be brought was given at the American Radio Exhibition in Chicago. A dynamic unit operating from 230 volts A.C. current was installed in the centre of a 8ft. square panel. This large baffle increased the "ange of the musical scale tremendously, and the result was that it would be practically impossible to distinguish a band selection reproduced by a gramophone from the actual performance Manutacturers claim that the most perfect results from dynamic speakers would be secured if the speaker were mounted in the wall of a room so that the sound emitted from the front of the speaker was prevented from reaching .the back of it.