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Show Change 'Phone to Loud-Speaker Use Way to Solve Problem That Has Confronted Many Radio Fans. One of the most baffling problems which has confronted the radio fan is that of the loud-speaker. He equips his receiver with an amplifier, Increases In-creases the plate voltage until it is well into the hundred volts, connects in his special loud-speaker 'phone, but only hears signals spoiled by rattling and scratching. Where Is the trouble? In the first place, it is impossible to use a loud-speaker with a set unless the signals aro already very Btrong at the output. In other words, one should not expect the loud-speaker to amplify the signals. That is the duty of the amplifying unit Itself. Improved Speakers. If the signals are already loud enough, It may be possible to use a loud-speaker. Any device which makes use of the receiving 'phones, so arranged ar-ranged that they may be fitted to a phonograph or other sound horn, is suitable, provided the user takes cer-tnln cer-tnln precautions, it must be remembered remem-bered that ordinary receiving 'phones are not made for loud-talker use and that they will handle only certain amount of current. If more than the rated amount Is used, the diaphragms will be shaken up violently against the pole pieces, and a grating noise will result If large amounts of plate current are used, it will be necessary to alter the adjustment of the diaphragms, so that they will not hit up against the pole pieces. This can best be done by unscrewing the cap, taking off the diaphragm and cutting a very thin washer of paper, as shown in the Illustration. Illus-tration. First, a very thin piece Is tised, and the thickness may be Increased In-creased by the uso of additional washers, wash-ers, until all noise of a metallic nature, clearly traceable to the diaphragm trouble, Is eliminated. The operator should be sure to screw How tne Cardboard Ring It Placed Betwien the Diaphragm and th Case to Prevent Noises. up the cap receiver on the dlnphragm very tightly, so that there will be no possibility of the latter rattling or becoming be-coming loose. This Is a very Important point, which is sometimes overlooked. Amplifying Unit If greater amplification is to be obtained ob-tained from an amplifying unit, it may be secured by Increasing the plate voltage volt-age to CO, or even 90 volts, Instead of the 45 volts usually employed. But If a greater amount la used, the separation separa-tion of the diaphragms from the pole pieces will have to be Increased proportionately. |
