Search Case Studies

  • Reset

End-Use Case Study

  • RTP Sheet Division Provides Specialty Solutions for Speaker Cones

Speaker ConeThe first loudspeaker may have been created when Thomas Edison attached a flexible diaphragm to the throat of an acoustic horn. Although this early invention later evolved dramatically into an electrical device, the basic concept of sound generation remained unchanged.

Today, modern loudspeaker designs involve a variety of intricate techniques, high performance materials, and often incorporate specialty thermoplastic sheet. Several of the industry’s leading manufacturers recently faced challenges with their supplies of specialty sheet materials ultimately used in audio loudspeakers, and RTP Company’s Sheet Division stepped in to alleviate the problem.

“RTP Company fulfilled an urgent need for sheet materials by utilizing their extensive research capabilities, coupled with our ability to test the sheet for sound velocity, to find a solution,” said Neil Kirschbaum, President of Loudspeaker Components, LLC. “Since RTP Company can compound its own resin used for sheet extrusion, they were able to quickly develop a formula that would work for us.”

Rapid Die, another speaker component manufacturer, also benefited from RTP Company’s specialty sheet solutions. “RTP Company offers consistent quality sheet products, technical compounding experience, ongoing R&D assistance for new materials, and a willingness to work through issues as they arise,” said Todd Yocum, President of Rapid Die. “We are looking forward to working with RTP Company on new materials to increase our market share and material usage.”

Material selection for speakers differs depending on end-use application such as home audio or automotive sound systems, on up to very large speaker networks used in concert halls or by musicians on tour. Each of these applications requires loudspeakers that meet demanding specifications for sound performance, durability, and appearance.

One component of the loudspeaker that can use a variety of materials is called the speaker cone. In designs requiring plastic, processing methods include either thin-wall injection molding or thermoforming. When thermoforming has been used, a custom sheet stock made from RTP Series 100 Polypropylene has met all the requirements.

Material compounding and the sheet processing both play into to the solution.

For example, proper stiffness that allows for the piston-like movement, and precisely controlled thickness, that yields the proper high frequency response, are functions of not only material but processing as well.

“Since we are a thin wall plastic molder in the acoustic field, we need materials that flow well, have high modulus at light weight, and are not brittle,” said Kirschbaum. “Previously, RTP supplied custom compounded materials for our injection molded cones and developed a special thermoplastic elastomer for an overmold on the thin wall cones that performed acoustically superior to previous materials. Because of the relationship we developed with RTP, it was a natural lead into working with them on sheet goods.”

There are additional aesthetic requirements as well. Materials must be black, textured, and free from any visual defects. “RTP Company’s Sheet Division has specifically processed its RTP Series 100 Polypropylene compound to meet all of the aesthetic requirements in the finished sheet goods,” said Bret Bjerken, RTP Business Development Specialist.

“Because our Sheet Division is relatively new, we are very energetic and willing to try most anything,” continued Bjerken. “It helps to have customers who will work with you proactively, not only in the compounding phase but also in the processing phase.”

For sound solutions to your specialty sheet needs, contact RTP Sheet Division for sound ideas!

JL Audio, award-winning manufacture of auto sound components, utilizes their patented speaker cone technology to produce a lightweight, stiff and critically aligned moving assembly that enhances sound quality. By incorporating specialty sheet materials from RTP Company, the assembly delivers astonishing cone stiffness with minimal mass.

Loudspeaker Components, LLC of Lancaster, WI is one of the largest U.S. manufacturers of speaker cone assemblies, they can be found on the web at