Development of New Diaphragm Materials for Loudspeakers

1989 Fiscal Year Final Research Report Summary

• Project/Area Number: 63850064
• Research Category: Grant-in-Aid for Developmental Scientific Research
• Allocation Type: Single-year Grants
• Research Field: 電子通信系統工学
• Research Institution: Miyagi National College of Technology
• Principal Investigator: ONO Takayuki Miyagi National College of Technology, Department of General Education, Professor, 一般科目, 教授 (30005342)
• Co-Investigator(Kenkyū-buntansha): MATSUURA Makoto Miyagi National College of Technology, Department of Basic and Specialized Educa, 基礎専門科目, 教授 (40042262) ; TANNO Choichi Miyagi National College of Technology, Department of Materials Science and Engin, 材料工学科, 教授 (50042247)
• Project Period (FY): 1988 – 1989
• Keywords: Diaphragm for loudspeaker / Composite materials / Electrostatic attraction / Anode oxidation of aluminum / Expanded graphite / Mica / Specific modulus / Loss tangent

Research Abstract

Acoustic characteristics of loudspeakers are largely influenced by physical properties of diaphragm materials. The frequency band is in proportion to specific modulus E/rho and the harmonic distortion decrease with increasing loss tangent eta value. Acoustic reproduction characteristics of loudspeaker is improved by enlargement of E/rho and eta value.
The purpose of this investigation is development of new diaphragm materials for loudspeakers made of polymer-inorganic substance or polymer-metal composite materials. These composites were prepared by means of polymerization method, polymer emulsion method and anode oxidation method of light metal. Polymerization of vinyl monomers was carried out in the presence of inorganic, metal or organic powders in aqueous medium using various initiators, and powders encapsulated with polymer were readily obtained. Furthermore, polymethyl methacrylate emulsion particles was tightly deposited onto various fillers such as mica, graphites, carbon fiber, wood powder etc. by considering electrostatic attraction between filler surface and terminal ionic groups of polymer. These composite materials could be directly molded and accurately formed into any shape. On the other hand, aluminum thin plate was oxidized by the electrolytic oxidation and oxide film on anode was combined with various polymers. These composite materials showed a high E/rho and eta value, especially in mica, expanded graphite and oxide film of aluminum. Frequency response characteristics of speakers using a diaphragm made of the expanded graphite polymethyl methacrylate composite film was flat and harmonic distortion was lower in the high frequency range.
From results, these composite materials were found out to be excellent new diaphragm materials for Hi-Fi loudspeakers.