The Calico-Cone Speaker

Radio Record, Volume II, Issue 45, 24 May 1929, Page 34

The Calico-Cone Speaker

A CORRESPONDENT, "Sapiensis" (Lower Hutt), writes: It may be of interest to some of your readers -particularly those who delight iu making up various parts for them-selves-that upon completing the "ealico coné-speaker," details for which were published in your paper some time ago, I was astonished to find that it was possible to make for oneself an instrument considerably superior in tone to a great many expensive conesperkers at present on the market Driven by a 4-valve Browning-Drake set, also made up from details published in the "Radio Record"; volume and tone leave nothing to be wished for. I may say that I have departed slightly from the original design, for instance, I have fitted the small cone at ‘back upon an independent frame, which is adjustable, a decided improvement. I discovered that several coats of very thin shellac varnish was a much better job than a few thick coats. The two -cones were pulled together by means of an ordinary small socket,

such as are sold for use with shortwave coil fittings. This gives a good grip, and being hollow is easy to adjust. The small cone I made of thin silk, finding after making several from different materials, that this gave a much purer high note. The largopdiaphragm I made ef thin linen, alfl its reproduction of the very deep notes is a revelation. ‘The unit I used at first was a small one taken from a small heru speaker, but coming across a 3in. diaphragm old type Amplion cheap, I thought I could not get a reed to fit it, so I simply fitted the bar to the diaphragm, which works admirably. Incidentally, it is a:. well to pack the rod that passes through the cones with cotton, as there is liable to be a little burr otherwise.