Exploring organic enclosure design through modern 3D printing and acoustic engineering.

Some projects take a little longer than expected. The Calabash Maker Edition is certainly one of them.

The original idea dates back to 2009, when I started exploring the possibility of using the organic shape of a calabash as the basis for a loudspeaker enclosure. At the time, my intention was to manufacture the enclosure from ceramic, but the complexity and cost of producing something like this made the project impractical.

Fast-forward more than fifteen years, and advances in desktop 3D printing have finally made it possible to revisit the original concept.

The result is the Calabash Maker Edition (ME), a compact two-way loudspeaker that combines unconventional enclosure geometry with carefully considered acoustic engineering.

Why the Calabash Shape?

Most loudspeakers are built around rectangular enclosures, and there’s nothing inherently wrong with that approach. Some of the world’s finest loudspeakers use conventional cabinets.

However, I wanted to investigate whether an organic enclosure could offer some practical acoustic advantages.

The Calabash’s curved surfaces provide a naturally rigid structure, reducing the reliance on extensive internal bracing. The continuously changing internal geometry also avoids large parallel surfaces, potentially reducing the influence of standing waves within the enclosure.

Another important consideration was the front baffle.

The narrow, smoothly curved profile avoids the sharp edges commonly found on rectangular loudspeakers, helping to minimise edge diffraction and contributing to a smoother frequency response.

Of course, none of these characteristics automatically guarantees better sound. The enclosure still needs to be properly engineered, measured and integrated with the drivers and crossover.

And that’s where much of the development work went.

From Concept to Finished Loudspeaker

The Calabash ME went through numerous revisions before arriving at the final design.

Driver combinations changed, different tweeter waveguides were investigated, and several enclosure configurations were tested.

One of the more interesting developments was the decision to abandon the tweeter waveguide altogether. Measurements showed that the additional complexity wasn’t providing sufficient benefit, particularly around the intended crossover frequency.

The final design uses a 5½-inch SB Acoustics woofer and a 1-inch dome tweeter, with a crossover frequency of approximately 1,700 Hz.

The bass-reflex enclosure also incorporates an integrated Venturi-style port, developed to minimise port noise at higher listening levels while maintaining the desired low-frequency performance.

Throughout development, measurements and listening tests guided the decisions rather than assumptions about what should work.

Designed for 3D Printing

One of the main objectives of the Maker Edition was to make the design accessible to DIY loudspeaker enthusiasts.

The enclosure is designed around a build volume of approximately 300 × 300 × 300 mm, making it compatible with many larger consumer-grade 3D printers.

The main enclosure consists of a printed body and base, joined using a two-part epoxy adhesive.

The base also accommodates a custom-designed, double-layer 3D printed crossover board. This provides a compact and organised layout for the crossover components while keeping the assembly relatively straightforward.

Brass threaded inserts and Allen-head fasteners are used throughout, providing secure mounting points for the drivers and removable bottom cover.

Both PLA and PETG were evaluated during development. Although PLA is perfectly suitable and generally easier to print, PETG offers some additional material advantages and would be my preferred choice where practical.

A pair of enclosures can be printed using less than 3 kg of filament with the settings used during development.

A Complete Loudspeaker Design

The appearance of the Calabash was always an important part of the project.

As a designer, I wanted the finished loudspeaker to look as considered as it was acoustically engineered.

To complement the enclosure, I also developed optional matching stands combining 3D printed components with stainless steel rods.

Magnetically attached speaker grilles complete the design, providing driver protection without permanently concealing the drivers.

The result is a loudspeaker that works equally well visually as a compact desktop speaker or as a dedicated standmount HiFi loudspeaker in a listening room.

How Does It Perform?

The final measurements have been particularly encouraging.

The Calabash ME achieves a smooth, well-controlled frequency response, with good horizontal and vertical directivity.

The crossover provides excellent integration between the woofer and tweeter, while the predicted in-room response follows the gradual downward trend generally associated with well-balanced loudspeaker designs.

The nominal impedance is approximately 4 ohms, presenting a manageable load for a suitable amplifier.

Perhaps most importantly, the measurements demonstrate that an unconventional enclosure manufactured using consumer 3D printing technology can deliver the performance expected from a properly engineered HiFi loudspeaker.

The Calabash ME isn’t intended to prove that organic enclosures are inherently superior to conventional boxes.

Instead, it demonstrates what’s possible when enclosure geometry, acoustic engineering and modern manufacturing techniques are considered together.

Build Your Own Calabash Maker Edition

One of the reasons for developing the Maker Edition was to make this design available to other DIY enthusiasts.

If you have access to a suitable 3D printer and enjoy building your own loudspeakers, you can now build a pair yourself.

The Calabash Maker Edition build plans are available to purchase and download from the SoundBlab webshop.

The build package provides the 3D printing files, crossover information and supporting documentation needed to complete the project.

Get the Calabash Maker Edition Build Plans

Final Thoughts

Looking back, it’s satisfying to finally see an idea from 2009 become a finished loudspeaker.

What was once difficult and expensive to manufacture is now achievable using equipment available to many hobbyists.

More importantly, the Calabash ME demonstrates that 3D printing has matured beyond simply producing prototypes or decorative objects. When properly applied, it is a capable manufacturing process for serious loudspeaker design.

For me, this project has been as much about exploring those possibilities as it has been about building the loudspeaker itself.

And after more than fifteen years, I’m very pleased with where the design has ended up.