| 摘要 |
PURPOSE:To obtain a nodal circle and to improve performance by sticking surface materials to both surfaces of a unidirectionally expanded honeycomb core and providing a light-mass area which has a long diameter in the expansion direction of the honeycomb core in the center. CONSTITUTION:For example, an elliptic hole 32 having a 45mm. long diameter in the core expansion direction as shown by an arrow and a 31mm. short diameter is provided at the center part of the unidirectionally expanded honeycomb core 31 made of aluminum foil having 20mum thickness to obtain an annular core material. In said elliptic hole 32, a packing material 33 of styrene resin for foamed by 40-times is charged and surface materials 34 of aluminum foil with 50mum thickness are stuck to both surfaces of the material 33 to obtain a plane diaphragm having a 19cm diameter and 6mm. thickness. The mass in the core expansion direction is less than in a direction perpendicular to the core expansion direction, so the diameter of a nodal circle in the core expansion direction is increased to correct the elliptic nodal circle of the honeycomb core 31 into a complete nodal circle 35. |
