Materials the woofer is made of. To operate efficiently, a woofer cone should be made of material that is stiff, yet lightweight. Poly cones provide excellent sound, and stand up to the heat, cold and moisture that car speakers face daily. Paper cones treated for moisture resistance also do an excellent job, and are usually very efficient.
"Poly" refers to Polypropylene, thermoplastic plastics or fibers that are polymers of propylene. "IMPP" is Injection Molded Polypropylene, a common material and process used in car speaker cone manufacture.
"Pulp" refers to processed wood products, or paper.