An Improvised Speaker

Radio Record, Volume II, Issue 40, 19 April 1929, Page 29

An Improvised Speaker

A Correspondent’s Successful Adaptation

Me: PERCY BAYLEY, of Silverdale, North Auckland, has arrived upon an idea to successfully tide over periods when the speaker is inopérative. He writes :--

HE following may be of service to listeners, who, like myself, live in the country and suddenly experience. speaker breakdown. I have a good qualfty speaker, horn type, of 4000 ohms impedance. Naturally, the finely wound coils are liable to give trouble in this moist climate, and after a year or two -of u : may break down altogether. The cost of replacement is very small, but to send the unit away to the dealers takes time and perhaps deprives one of the use of the speake for a week or more. My speaker suddenly gave out after two years’ use and no sort of adjustment either external or internal would

put it right. I immediately posted away the unit for coils to be replaced-guess-ing the probable cause of the troubleretaining the horn..nd theu tried to think out some means of using the earpieces of my phones as a working unit. ‘)The result was a great success-was used for ten days. until my speaker unit wa: returned-and for the tone quality it was almost impossible to realise that the proper speaker was not in use,

The two rough sketches should show quite clearly how it can be done and. at no cost. Take a block of close-grained wood about 12 inches long, 6 inches wide, and 2 inches thick. Saw a V-shape 4 inches long. The length and width are of importance only to give weight, but.thickness is essential, The whole can be rigged up in half an hour. The holes in the V-shaped section at the end-of the block should be bored clearly and if necessary filed smooth They should be approximately 4 inch to 5-8 inch in size. Bore the holes on each side of the V in an upward direction to meet the downward: hole from the top of V and again smooth off all internal roughness. Horns have a different form of attachment to their units. Mine has a split clip bottom tightened up by one screw to grip the tube projecting from the unit. Into the hole bored downwards from the top of the V a small piece of brass tube of correct diameter externally to fit hole’and also to fit the bottom’ of the horn, is driven about 4 inch leaving. about 4 inch projecting on which the horn fits. The two headphone earpieces are removed from. their carriers (they can usually be sprung out easily) and are held in position over the two side holes of the V by a stout elastic band (a narrow section cut from a car tube answers admirably). The phone plug or pins are, of course, inserted in set instead of speaker plug or pins. To assist in making an airtight join for earphones; two 14 inch diameter rubber or felt washers are tacked around the two side holes in the V. They also assist in correctly registering the holes in the earphones with the holes bored in the sides of the V. The remainder of the block of wood acts only as a steadying for the horn when mounted. Those economically inclined (and who is not?) who are just investing in a set capable of running a speaker, may like to try this idea ‘out before purchasing a speaker! Various sizes o- cardboard horns can be made and tried out. If the horn is made straight the block of wood should be placed vertical as all horns are ‘ery directional. If the earphones are from a good pair of phones the arrangement will excel most of the,cheap speakers I have heard.