Some (Updated) Thoughts on Plastics for Speaker Enclosures
For the March 2022 edition of Voice Coil Magazine, Mike Klasco provided an updated overview about speaker enclosures and more specifically the use of plastics and derivatives for that key application. Here is an extract:
I have observed that no matter how much effort is spent on the loudspeaker driver design, the speaker enclosure characteristics are still a significant factor in achieving smooth response, controlled bass, and well-defined stereo image. At the most basic acoustic level and to state the obvious — the purpose of the speaker enclosure is to hold everything together, isolate the back-wave of the woofer from the front to avoid cancellation, and provide a rigid structure to support the drivers with minimum panel resonances, all the while looking pretty.
Wood and wood particle board cabinets were traditionally used for speaker enclosures, but that is mostly in the rearview mirror. Back in the 1970s, plastics were relegated to table radios, “transistor” radios, “shoe box” cassette recorders, and other inexpensive electronics. That has changed in a big way for various reasons, one being that back then plastic tooling costs for upscale audio products could not be amortized by the product sales numbers. Now, consumer audio electronics are mainstream and global, and the quantities are huge.
The days of the US union machine shops and hand tooling on lathes are history. Today, tooling for injection molds for plastic parts are done on computer numerical control (CNC) machines directly from 3D CADs in China from very efficient specialists, and the costs are reasonable.
Over the years, there has been great interest in finding alternatives to wood enclosures. The ideal material to replace wood construction should be as strong, light, and thin as plywood and for these reasons injection-molded plastics dominate audio these days. Simplified construction is another consideration as moldable material eliminate most joint assembly and enable rounded edges and shaped front baffles minimizing edge diffraction, time alignment, waveguides, as well as esthetic flexibility.
This article examines all the different options for plastic applications in speaker enclosures and the implications for loudspeaker driver design in general. Enclosure characteristics, construction features, advantage comparisons between wood and wood particle board cabinets, and production techniques are some of the topics explored.
Topics discussed include:
- Injection-Molded Plastics
- Supply Chain
- Design to Manufacture (D2M)
- Recent testing performed by Warkwyn (MISCO) to evaluate performance of a half-dozen resins used in soundbars.
- Alpine HX5 — Injection-Molding Nanocomposite
- Covestro Maezio
- TLC Products' PET Graphene injection-molding thermoplastic composites.