Some years ago I was presented with an Amplion AR 114 horn speaker which was in a rather deplorable condition. There was no driver and the petals had almost rotted away but fortunately the metal work was A OK even the rubber seal though perished was still intact. Amazingly the 3 special thumb screws that secures the gooseneck to the flare were present. After a futile shopping around for a driver I concluded that if I want one I would have to make one.
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I eventually was able to borrow a driver so I could now make a
complete working drawing. As I could not make aluminium castings I
decided to turn them out of solid aluminium. Next down to Alcan to pick
up a piece of aluminium rod 100 mm in diameter. I then put it in the
lathe and out came two halves of the shell of an AR114 driver. Dead easy
to say, not so easy to do. A bit more machining and I have an adjusting
screw, knurled adjusting nut, polepiece mounting plate, terminals. Then wind
coils with much fine wire, photo engrave the name plate etc. The diaphragm was made from .3mm Grain Oriented electrical steel carefully cut to not cause any bending or creases in the metal which would hinder vibration. Strips of this steel was also used to make the polepieces. Ferrite magnets were used as they fitted perfectly into the space available. |
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After spraying with black crackle it was ready to assemble, test and
mount on the goose neck. The adjusting knob was smooth in operation and the sensitivity is probably at least as good as when the speaker was new with its original driver. All petals had to be replaced but when done and the speaker assembled it sits well into my collection and works well with my favourite old radios. The working drawing is a large file so if you only have a dialup connection it will take about 5 minutes to download. AR114 drawing Note: Correct drawing temporarily unavailable |