Cone – Poly Injection
A substance called “Polyurethane” and is categorized as a “Polymer." It is a resilient, flexible, and durable manufactured material that can take the place of paint, cotton, rubber, metal, or wood in thousands of applications across virtually all fields. It can be hard like fiberglass, squishy like upholstery foam, protective like varnish, bouncy like rubber, or sticky like glue.
In the specific case of Boss' cones, this material allows for maximum flexibility that produces great sounding speakers to last a long, long time.
Surround – Foam
The average life span of standard foam surrounds is about 8 to 16 years. New foam formulas last much longer than before and are a superior product for speaker drivers that need a large excursion (how much the cone needs to move back and forth). Foam keeps the cone centered and yields a high excursion. Foam is self-damping (the ability to control undesirable movement of the speaker cone) and reduces its own standing waves. It is also very light and has a minimal effect on the motion of the cone. Foam can be mixed with other substances to produce different flex and strength properties.
Tweeters – Mylar
For a modern edge, the best car speaker could be the high-tech Mylar tweeter, as it generally has more ability for a wider variance of sound modifications and channel handling. Unlike paper cones, the Mylar has a higher rate of durability, as the cone is made of a plastic poly material, which does not rip or tear easily under abnormal frequency changes.