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RADIO AGE for February, 1927
The Magazine of the Hour
Building a 36 Inch Cone
at Home
BUILDING a thirty-six inch cone speaker at first blush appeared to our staff to be a very difficult job and one that the average experimenter or handyman would not tackle. But Columbus took a chance. So we figured if that venerable gentleman could discover this country the worst we could do would be to wreck about fifteen dollars worth of parts, and with that alibi in mind we tackled the task. Much to our surprise the matter was comparatively simple, requiring only a little patience and a careful adherence to instructions.
Two diagrams are shown with this article which will give a great deal of the detail necessary. Parts for the construction of such a cone may be secured from a number of manufacturers who supply the integral parts in kit form.
Material for the cone comes in 38 by 38 inch sheets, two being required. This is a special product which leading cone speaker manufacturers are using. One sheet is used for the front of the cone and the other for the back. The upper diagram on page 12 shows the manner of cutting the front cone. To properly scribe the 36 inch circle it is suggested the builder make up a beam compass, consisting of a ruler, or slat about 24 inches in length, with a tack driven through at one end and two small holes drilled 18 and I714 inches from the tack, the holes being for a pencil to mark the circle. The end of the ruler with the tack in it is placed in the center of the sheet (after you have marked into quarters the 38 by 38 sheetand found its center) a pencil inserted in the hole 18 inches from the tack, and the circle drawn. For the second cone, B, the hole 17^ inches from the tack is used since the diameter of disc B is only 35 inches compared to the first one, disc A.
Consult the top drawing on
page 12. Line 1 is now cut from the lower edge of the cone to the exact center. Measure 51/2 inches (at the bottom edge) to the dotted line 3. Place a ruler at this point inward to the exact center and draw a dotted line. Be careful not to use too much pressure on the pencil or you will tear the material. Then measure off three-quarters of an inch to the left of the dotted line
at the bottom edge and at the center. Here draw a full line which will be the line you cut, line 2. The dotted line, 3, is the three-quarters of an inch lap which the cone will have when its bottom edges are pulled together. A quarter inch hole should be punched out at the exact center.
The back cone, disc B, is made in the same manner except its diameter is 35 inches instead of
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