A Portable Speaker

Radio Record, Volume III, Issue 22, 13 December 1929, Page 31

A Portable Speaker

Use with "Tramper’s Two" OWING to. the * dmallness -0f; the Tramper’s Two and the desirability of having a light, efficient speaker which can be used with both portable and ordinary receivers, there is a demand for a portable cabinet speaker. No doubt there are. a number of enthusiasts who would rather use the small cabinet speakérs, e.g., the Am-

plion Cabinet, but those who wish to make only a small expenditure yet get quality will do-well to construct a speaker like the one to be described,. A speaker that will accompany the tramper and the picnicker must be light but strong; it must, however, be able to take a fair amount of volume, especially if there. are more than one ’ to be amused. Dynamic cones are out of the question: where there ‘is.not a ear to supply the | power for the field windings and as a means of transport. The speaker then must be a horn or a and hetween these. the enthusiast t decide. A-horn is very sensitive, but. in very few cases robust, so that there is little else to choose from except the home-made and the purchased cabinet cone, In an article in last week’s issue -"Megohm" outlines the essentials of

cone speaker construction, and his remarks need little adaptatiGn in order that the builder may construct a portable. speaker: .. A robust cabinet is of primary necessity and the accomhpanying diagram shows a suitable form this may take. Reference to the section vf _"Megohm’s" article dealing; apyith baffie board speakers discloses ‘the fact that the ‘cone should be about 8 inches in™ diameter and should be attached to the baffle by thin chamois or other suitable material. These remarks can be applied to the construction of, a suitable cabinet speaker. To accommodate a suitable speaker the dimensions of the ease: Should not be less than 14 x 14‘x 1042). The first task is the construction of the cone, for which.a circle of 9 inchés‘*diameter should be inscribed on a piece of suitable material. Cut out thefcircle ard cut a wedge-shaped section of 50 degrees or one-seventh. of the circumference. Join with seccotine. The size of the cone will be about.72 inches diameter, so that the ‘opening’ should be about 8 inches, The front piece witl be 14 x 14. ‘The cone shoyld-be attached as described by "Megohm" in last week’s article. The sides, top and bottom should now he ‘fitted: These are respectively 14 x 103, and the sides are made to fit, their dimensions depending on the size of.timber’ used. Dressed }-inch is suitable, three-ply is a little too light for portable speakers. Assemble the front with the. cone, the top and’ the sides. ° Place the’ back in position and find where the adjusting screw is .to be placed, .,Remove. and drill and’ complete the Care must be exercised to seé that the inner dimension for depth is,not less than 104, otherwise the cone will. not. fit.

These dimensions have been given for the blue spot 66K units, thoygh-others are suitable. It may be. ‘necessary in cases such as these to alter’ the dimensions. ;