Abstract: A mechanical two way loudspeaker includes a low frequency diaphragm arranged coaxially with one another which are driven by the same voice coil. In order to flatten the sound pressure versus frequency characteristic of the loud speaker in the high frequency range, the low frequency diaphragm is provided with a flat sound wave radiation surface. The flat surface may be of a honey-comb configuration, or may be made of a low density synthetic foam.

Abstract: A honeycomb shaped diaphragm for use in acoustic instruments such as speakers is manufactured by kneading a mixture of flaky graphite powder and thermoplastic resin, preferably polyvinyl chloride, rolling the mixture into a plate, forming honeycomb recesses in the plate, and mating two recessed plates with each other so that the corresponding recesses form closed cavities. The formed plate may be carbonized before assembly. The resultant diaphragm shows a high Young's modulus, a low apparent density and a remarkably high specific modulus of elasticity ensuring improved acoustic characteristics.