Abstract: A speaker box for housing a radio speaker unit and intended for mounting within a vehicle door is formed of plastic by a monobloc molding method such as blow molding thus providing a seamless speaker box that is free from air leakage. The speaker box has an irregular configuration matching a space within the vehicle door, whereby it can be firmly secured in place maintaining maximum inner volume. The speaker box further has ribs extending across flat regions on the box thus improving its rigidity against vibration caused by sound pressure and the like.

Abstract: In machining a workpiece along a spiral line with a numerical control machine, an interpolation method is employed in which, in order to maintain the machining speed constant, the spiral line is divided into a number of segments, and a small movement in the direction of the rotational axis and a small movement in the linear axis direction are calculated for each of the segments.