Circular economy 3D printed 3D printing Audio DIY Eco-friendly Loudspeaker Recycling Speakers Sustainable development

Circular Sound – Recycling loudspeakers with the help of 3D printing

This article describes the Circular Sound loudspeaker models in detail. We will dive into the technical specifications and also go into detail on how you can build your own.

The Circular Sound Process

All Circular Sound products rely on a circular flow of materials. There are two paths to obtaining circularity, but they are not mutually exclusive:

  1. Biological cycle: Using bio-based and bio-degradable enclosure materials.
  2. Technical cycle: Remanufacturing from old components.

The biological cycle means using bio-materials such as UPM Formi 3D, BrightPlus BrightBio, and Sulapac Flow. Our mono-material design principle allows easy recycling of the bio-materials at end-of-life.

The technical cycle means we disassemble old loudspeakers, inspect and measure the components and use them in a new product. This is called remanufacturing. The components typically have a decade or more of life remaining, but the old product they were in was no longer wanted by users.

We take sound quality very seriously and often this means only woofers can be reused, while wideband transducers need to be of virgin origin. Nevertheless, the majority of the mass resides in the woofers and enclosure, and therefore the recycled fraction of Circular Sound loudspeakers is 70-80%. You can read more about the circular economy and environmental impact in our blog.

Circular Sound Eikosa

The Circular Sound Eikosa gets its name from the Greek word eikosáedron referring to the 20-faced polyhedron. It’s a Bluetooth loudspeaker that uses upcycled woofers for bass frequencies and a virgin wideband transducer for producing mids and highs. The enclosure is 3D printed from a PLA-based polymer. Each Eikosa is slightly different on the inside depending on the old components used, but thanks to our acoustic design, the low-frequency reproduction varies very little from unit to unit. Besides, the user can adjust the bass tuning and level of the bass frequencies based on personal preference and listening space. You can order an assembled Eikosa by backing our crowdfunding campaign.

Size240 mm diameter
Weight~4 kg
ShapeRegular icosahedron
MaterialModified PLA
Amplifier2×30 W
InputsBluetooth 5.0
Power supply19 V laptop charger
Wide-band driver3″ BMR
WoofersUpcycled dual 4-6″
Frequency response60-20000 Hz (+-3 dB)

Circular Sound Sfaira (Pair)

Sfaira means sphere in Greek and refers to the shape of the enclosure. The spherical shape has many benefits in loudspeakers. It is made by 3D printing Sulapac Flow material, which is a bio-based and bio-degradable wood-filled plastic. The Sfaira is intended to be used as a stereo pair and supported by a subwoofer, such as the CS-012, if required.

Circular Sound CS-012 Subwoofer

The Circular Sound CS-012 is the first loudspeaker design in the Circular Sound line-up. The donor components come from an old Yamaha YST-SW012 bass-reflex subwoofer, which you can find second-hand for about 50€. Additive manufacturing was used to produce a smaller, sealed enclosure loudspeaker. The material used in the prototype is a bio-based material produced by BrightPlus. It has a natural dye made from woad by Natural Indigo Finland.

The original Yamaha loudspeaker is designed to be used as a single subwoofer unit placed somewhere on the floor out of sight. The new product, on the other hand, is designed to be used in a stereo configuration (2 pcs) and placed under the main speakers. It serves a different function compared to the original product, but no new materials need to be consumed. We are not injecting a new product made from virgin materials into the economy. Instead, we are taking two old ones out and replacing them with one value-added product. This is what Circular Sound is about. You don’t have to wait for distributors to bring sustainable products to your local market. You can start making these today. The files are shared for free under a Creative Commons license on Thingiverse.

3D printing a bio-based loudspeaker enclosure
Audio 3D printed 3D printing Carbon fiber DIY Loudspeaker Speakers Technology

Six reasons 3D printed spherical loudspeaker enclosures are popular


It is striking how often 3D printed speakers take the shape of a sphere and that is also how RD Physics started with the FR1 full-range speaker. What are the benefits of spherical loudspeaker enclosures and why are they so popular?

  1. Rigid and void of panel vibrations
  2. Minimum material use for a given volume
  3. Potentially avoid edge diffraction
  4. Omnidirectional up to a relatively high frequency and controlled baffle “step”
  5. Aesthetically pleasing with a single circular driver
  6. Difficult to manufacture any other way than 3D printing

As RD Physics has extensive experience in these types of enclosures, we have decided to share our learning in one blog post. The models are presented in chronological order allowing the reader to understand the development that took place over the years of building and listening to various versions of the FR. Most of the designs are offered open-source to the community.

FR1 – Full-range bliss in a compact form

The FR1 is a spherical (180 mm diameter) full-range loudspeaker with a sealed enclosure. Internal wall stiffeners are used in order to maximize internal volume as opposed to simply increasing wall thickness, which robs internal volume. We use Noise Killer paint to both seal the enclosure and also to add mass and damping. The sound of the FR1 speakers is very unique and quite tricky to get the most out of. The full-range emitters are very directional and the listening distance also changes the sound markedly.

ModelRD Physics FR1
DriverMark Audio Alpair 6M 2.5″
Enclosure3 liters sealed
MaterialUPM Formi3D
ConstructionInternal webbing with Noise Killer damping
TiltFixed at 15 degrees

FR2 – Exotic carbon fiber skin reduces resonances

Additive manufacturing (AM) has many benefits over traditional construction methods, such as design freedom, fast product development, and integration of functions into one part. There are drawbacks as well. The plastic AM parts tend to be low in mass and not very stiff. Air-tight walls are sometimes difficult to achieve, too.  Adding mass by increasing the fill density of the print is not a good solution, since it adds build-time and material cost. Stiffeners and bitumen paint were used in FR1. However, the stiffeners were cumbersome to paint with bitumen and it did not add significant weight. For FR2, we used the vent as a part of the mechanical structure and used a thicker wall. But some additional means were needed to bring 3D printed enclosures on par with traditional cabinet materials.

Carbon fiber in loudspeaker building

Dry carbon fiber tow was wound around the enclosure and then wetted with epoxy resin. The composite skin was sanded after curing and additional coats of epoxy were added. The result is a unique unidirectional carbon fiber surface finish. The composite shell adds mass and stiffness to the enclosure. The loudspeaker sits on four feet printed from TPU material, which allows rotation.

ModelRD Physics FR2
DriverMark Audio Alpair 7MS 3″
Enclosure5 liters vented
MaterialUPM Formi3D + CFRP
ConstructionStructural port and carbon fiber skin
TiltTPU feet allow tilt ~0-15 degrees

FR3 – Metal-filled filament for mass and rigidity

The FR1 used internal ribbing and Noise Killer paint to reduce enclosure resonance. The FR2 used an external carbon fiber shell. Both approaches were a bit cumbersome and laborious. For the third version, we wanted to fully use the capabilities of 3D-printing. Therefore, a high-density metal-filled filament was used an internal gyroid-shaped support was used even where overhanging surfaces would not have required it. In addition, height and tilt can be adjusted using three threaded rods that form a tripod. The finished enclosure with three 14 mm trapezoid-threaded nuts bonded to it weighs 1.2 kg. The RS100 drivers have a distinct on-axis peak at the upper treble, which actually works nicely for those who like a bright sound. Those who don’t should toe-in the speakers a bit.

ModelRD Physics FR3
DriverDayton Audio RS100 4″
Enclosure2 liters sealed
MaterialColorfabb steel fill
ConstructionGyroid infill as an internal stiffener
Tilt14 mm leadscrew tripod

FR4 – Refining the concept further

The metal-filled filament used in the FR3 was too brittle and difficult to post-process. The FR4 uses wood-filled filament, which is more ductile and easier to sand if needed. The surface is quite nice straight out of the printer thanks to the matte surface. A quick touch with an orbital sander gives a smooth finish. Leadscrew nuts are bonded into recesses in the enclosure and allow for adjustment of the legs. Small TPU feet can be printed and placed at the ends of the leadscrews in order to avoid scratching the desktop. These are satellite speakers and need a subwoofer to complement the lower frequency spectrum.

ModelRD Physics FR4
DriverTangband W3-1878 3″
Enclosure1 liter sealed
MaterialAddNorth Textura
ConstructionGyroid infill as an internal stiffener
Tilt12 mm leadscrew tripod

FR5 – Returning to square one

Reviewing the FR project so far, we came to the conclusion that all things considered, the original FR1 is the DIY project that was the most fun to build and listen to. It’s simple but rewarding once dialed in. For the FR5 we went back to basics by ditching the tripod and returning to a simple white spherical enclosure. The tilt adjustment is handled by a TPU mounting ring that allows a large adjustment range. The Scan Speak 10F driver is one of the best for voice reproduction, but our subjective view is that it needs a tweeter in addition to a subwoofer making it suitable for three-way builds only.

ModelRD Physics FR5
DriverScan Speak 10F 3″
Enclosure2 liters sealed
MaterialAddNorth Textura
ConstructionStiffeners and alu-butyl sound-deadening mat
TiltTPU ring +-30 degrees

3D files and components

In the table below you’ll find links to the drivers used in each version as well as the geometry files needed for slicing the toolpaths. Support us by clicking on the Soundimports affiliate links before buying anything from them (we get a small commission and it won’t cost you a dime). Thank you!

ModelComponents3D files
FR1Alpair6M at SoundimportsFR1 at Thingiverse
FR2Alpair7MS at SoundimportsFR2 at Thingiverse
FR3RS100 at SoundimportsFR3 at Thingiverse
FR4W3-1878 at SoundimportsFR4 at Etsy Shop
FR510F at SoundimportsFR5 at Thingiverse



We wish to thank UPM for the Formi3D materials and support. Photos taken by J-P Virtanen and Markus Markkanen. Erell Bodinier handled the carbon fiber skinning.