MINERAL REINFORCED PLASTIC FRAME Vented reinforced plastic chassis. Proprietary cone material with natural fibers made in-house. Butyl rubber surround for smooth frequency response. Vented motor system for low compression. Long stroke linear suspension for improved dynamics. Non-resonant long life lead wires. Vented reinforced plastic chassis Proprietary cone material with natural fibers made in-house Butyl rubber surround for smooth frequency response Vented motor system for low compression Long stroke linear suspension for improved dynamics Non-resonant long life lead wires