In collaboration with Matthew J Morgan, Elements Audio proudly released its first-ever free loudspeaker cabinet design, the 21 C2A Golden Formula Paraflex.
The 21 C2A Golden Formula is a high-performance Paraflex subwoofer that achieves exceptional low-frequency output through the use of a carefully engineered throat chamber combined with an increased rate of expansion within the low-tuned horn resonator section. This design approach delivers increased sensitivity, greater efficiency, and higher output throughout the enclosure's operating range, while maintaining the deep, authoritative bass response that Paraflex systems are renowned for.
21" C2A Golden Paraflex
Designed to provide extreme SPL and outstanding low-frequency extension, the 21 C2A offers a usable frequency range of approximately 30Hz to 90Hz, making it ideally suited for large-scale sound reinforcement, festival systems, and high-output bass applications.
The project took over twelve months of design, testing, and prototyping to complete. Throughout the development process, numerous revisions were evaluated to optimise performance, efficiency, and build practicality. The result is a design widely regarded as one of the highest-performing Paraflex subwoofers available as a free community-supported plan.
Comprehensive build plans are available in both Metric and Imperial formats and are accompanied by a large collection of detailed photographs documenting the construction process, assembly sequence, and key design features. Whether you're an experienced cabinet builder or embarking on your first Paraflex project, the documentation provides a clear and structured path from raw materials to a finished enclosure.
The 21 C2A Golden Formula represents Elements Audio's commitment to sharing innovative loudspeaker design with the wider audio community while pushing the boundaries of what can be achieved from a freely available subwoofer design.
21 C2a Golden Paraflex
The 21 C2A Golden Formula delivers exceptional low-frequency extension, remarkable clarity, and an impressive usable bandwidth. Despite its immense output capability, the enclosure remains clean, controlled, and highly musical, producing deep, powerful bass with outstanding definition even at extreme SPL levels.
Careful consideration was given to every aspect of the cabinet's construction. The enclosure has been engineered as a practical two-person lift, with the centre of gravity positioned low to improve handling and transportation. Extensive optimisation of the internal bracing structure helped reduce overall weight while maintaining exceptional strength and rigidity, minimising unwanted cabinet resonances and ensuring maximum acoustic performance. Even when driven at high power levels, the driver remains under precise control, contributing to the cabinet's accuracy and consistency.
A wealth of information, build logs, photographs, and demonstration videos can be found within the HOQWS Community on Facebook, where builders from around the world continue to share their experiences, completed projects, and performance results.
The 21 C2A Golden Formula is a challenging build that will test even experienced cabinet builders. However, by following the supplied plans and detailed build photographs, the assembly process becomes straightforward and highly rewarding. If you require assistance at any stage, both Matthew and I are active within the community and are always happy to answer questions and offer guidance.
We wish you every success with your build and hope you enjoy the process as much as we enjoyed developing the design. The plans are provided free of charge for personal, non-commercial use by the DIY loudspeaker community. Builders wishing to manufacture cabinets for resale, offer CNC-cut flat packs, or provide commercial build services based on this design should contact us to obtain the appropriate licence before doing so.
For optimum performance, we recommend constructing the enclosure from high-quality 18mm Baltic Birch plywood with a minimum 13-ply construction. While alternative materials may be used, they are unlikely to provide the same combination of strength, durability, weight, and acoustic performance as Baltic Birch plywood.
About the Author
Ben Wells is the founder and owner of Elements Audio. With a lifelong passion for sound and loudspeaker design, Ben combines his expertise as a master joiner with years of practical audio experience to oversee every stage of the design and manufacturing process. From concept development and acoustic design through to final assembly, Ben leads the Elements Audio design team and remains actively involved in every build, ensuring each product meets the company's exacting standards for performance, craftsmanship, and reliability.
