JPS5545269A - Plate speaker - Google Patents

Abstract

PURPOSE:To make a cheap and good-quality acoustic reproducing possible by constituting a ring plane diaphragm so that the ratio of inside diameter b to outside diameter a may be 0.3<=b/a<=0.7 and the radius of a voice coil may be (a+b)/2. CONSTITUTION:For the purpose of preventing ring plane diaphragm 1 from generating division vibration in a used band, primary division resonance frequency f10 is prevented from being generated, and further, secondary division resonance frequency f20 is raised. Since lambdan rises by 15% at b/a=.03 in comparison with b/a=0 and rises by 33% approximately at the resonance frequency in characteristics curves indicating the change of inherent value lambdan of diaphragm 1 for the ratio of the inside diamter (radius b) to the outside diameter (radius a), f20 can be raised easily by making diaphragm 1 into a ring shape. Then, though lambda2 becomes large rapidly when b/a is larger furthermore, the reduction rate of an area becomes 50% approximately at b/a=.07, and this value is the limit considering efficiency, and consequently it is practical that b/a is within a range of 0.3-0.7.