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
Bluetooth speaker 3D printing Audio Circular economy DIY Loudspeaker Recycling Speakers Sustainable development

Bluetooth loudspeaker without an internal battery

What’s wrong with having batteries in your portable boombox?

Wireless electronics, such as bluetooth speakers, are extremely popular nowadays. All such devices must have a power source and typically it is a lithium-ion battery. However, the demand for battery raw materials is rising at an alarming rate:

The supply of some of these [battery] materials, in particular cobalt, natural graphite and lithium, is of concern today and for the future in view of the large quantities needed and/or very concentrated supply sources.

European Battery Alliance (EU)

As we have discussed earlier, when launching our Circular Sound program, the best solution for reducing reliance on critical raw materials is to reduce their use. The RD Physics BB1 boombox enables you to do just that. It is designed to use existing external power sources and therefore no new batteries are needed. Battery service-life or battery replacement is no longer a concern.

Alternatives to dedicated batteries

The BB-project started by looking at how power tools are sold without accompanying batteries. The idea being that the user needs only one battery (plus spares) that fits all tools. While this approach reduces the amount of batteries needed, it is also used to tie the customer to a specific brand. We wanted a universal solution and therefore the USB-C standard was chosen. The BB1 and BB2 boomboxes use a USB-C port as an interface to feed power to the amplifier. The boombox can be connected to any USB port: power banks, phone chargers, laptops, extension cords, solar panels etc. Obviously, the input voltage and current draw is limited, which leads to limited sound pressure level (SPL).

The weather-proof USB-C port is located at the top.
Frequency responce of 3D printed bluetooth speaker.
Frequency response of BB1 at maximum drive level.
BB2 boombox with Dayton Audio RS100 drivers.
Frequency response of BB2 at arbitrary drive level.


What you will need to build your own batteryless boombox:

  • Geometry files for 3D printing (free under Creative Commons License at Thingiverse)
  • 3D printer big enough to fit a 235 mm diameter sphere
  • Slightly over 1 kg of filament depending on your settings
  • Two active drivers. Either Peerless 3″ (BB1) or Dayton Audio 4″ (BB2)
  • One 6½” Dayton Audio passive resonator
  • A Sure (Wondom) bluetooth board with additional cables set
  • USB-C panel mount plug (from eBay) and 6 mm DC plug
  • Wood screws (4.2 mm for the drivers and resonator, 3 mm for the BT board)
  • Drawer handle, IKEA Eneryda 703.475.16
  • Damping material (bitumen or similar automotive damping mat and fibrous wadding, for example pillow stuffing)
  • Optional: Wall mount bracket, Genelec 4000-410B
  • Minimal soldering capabilites

The enclosure for the BB1 and BB2 can be downloaded from the link above. Assembling everything takes 30 minutes.

3D printed boombox enclosure
3D printed enclosure ready for assembly.

How to build the BB1/BB2 bluetooth speaker

  1. Start by soldering the 6 mm DC plug to the USB connector. Red (+) goes to center pin and black (-) to outer shell.
  2. Connect DC power and speaker cables to bluetooth board and fasten the board inside the enclosure by tightening the screws via the driver openings.
  3. Mount the USB connector and handle.
  4. Line the inside of the enclosure with bitumen or similar visco-elastic damping material. Heat will aid in conforming to internal shapes. Make sure the damping material is fully bonded to the walls.
  5. Bring the speaker wires through the driver openings and solder them to the drivers. Make sure polarity is the same for both drivers. Then fasten the drivers using wood screws.
  6. Fill the enclosure with fibers (cotton, polyester, wool etc.) and fasten the passive resonator.
  7. Optional: Attach the wall mount bracket.
  8. Connect a USB port and the bluetooth board powers on automatically. Pair your signal source with the device (“WONDOM”). Enjoy!
BB1 portable bluetooth speaker with 3D printed enclosure.
BB1 ready to rock.

Assembly instructions

Concept and sound test

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

Circular Economy of Loudspeakers – Reducing Waste and Creating Value

Introduction to circular economy

Circular economy is a model of production and consumption that prioritizes resource efficiency and waste reduction. It involves designing products with durability and repairability in mind, reusing and refurbishing materials and products, and recycling materials at the end of their useful life. The goal is to keep resources in use for as long as possible and minimize environmental impacts. Currently, only 7.2% of the materials we use circulate back into the economy 1. This number needs to increase in all industries, including the loudspeaker industry, in order to reach the Sustainable Development Goals, more specifically SDG 12.5 2:

“By 2030, substantially reduce waste generation through prevention, reduction, recycling, and reuse”

The current linear model of loudspeaker production

The global loudspeaker market size is anticipated to reach USD 8.48 billion by 20253. Its effect on the circularity gap can not be ignored. Most manufacturers using virgin materials attempt to mitigate their environmental impact by focusing on long lifespans by:

  • Producing long-lasting products
  • Offering spare parts and warranty repairs
  • Facilitating a second-hand market for pre-owned loudspeakers.

However, it does not matter if a product can be used forever if nobody wants it anymore. Our research shows that having a specific need is the main reason for loudspeaker buyers not using the second-hand market. This is confirmed by studying the thousands of near-zero-priced loudspeaker listings in online marketplaces. There is low demand and a high supply of old but fully functional loudspeakers. The current economy has no end-of-life solution.

Old loudspeakers with negligible market value.

The importance of loudspeaker magnets

Not having an end-of-life solution for old loudspeakers is especially problematic due to rare-earth elements found in the magnets of loudspeaker transducers. Rare-earth elements are essential for manufacturing permanent magnets. Permanent magnets are critical components in most decarbonisation technologies4 .

Lithium and rare earths will soon be more important than oil and gas. Our demand for rare earths alone will increase fivefold by 2030.

Ursula von der Leyen, President of the EU commission5

The EU imports 98% of its magnets from China and less than 1% is recycled6. Relying on China poses a geopolitical and supply chain risk. China has a history of export restrictions and weaponisation of REEs in trade wars7. Recycling is not commercially viable due to the high cost of manual separation of magnets and the relatively low price of the raw material itself8.

Loudspeaker transducers have large magnets containing precious materials.

The circular economy approaches to loudspeakers

The circular economy of loudspeakers can be described with the help of the 7Rs.

  1. Rethink: Use fewer components and eco-friendly materials, combine functions, or make the product easy to disassemble and recycle.
  2. Reduce: Spend less material and energy. Generate less waste.
  3. Reuse: Sell in the second-hand market.
  4. Repair: Fix broken loudspeakers by re-coning transducers, replacing components, and refurbishing the enclosure.
  5. Remanufacture: Disassemble old loudspeakers and use the materials to make a new product.
  6. Recycle: Use raw materials, such as plastic and metal, again.
  7. Recover: Burn the enclosure for energy.

All of the approaches are a step forward from the current linear economy. The first two (Rethink and Reduce) are effective since they occur already at the design stage. However, they still rely on virgin materials and do nothing about the current levels of waste. The last two (Recycle and Recover) are not recommended, because they do not preserve added value and hardly generate any jobs or social well-being. Reuse and Repair are great if there still is demand for that product. Remanufacturing allows for meeting new user needs using existing materials. An example of remanufacturing is the RD Physics Circular Sound loudspeakers.

Circular economy loudspeaker
A new loudspeaker using components from old loudspeakers.

Benefits of circular economy

The benefits of a circular economy include reducing the extraction of virgin materials, reducing greenhouse gas emissions, creating new job opportunities, and improving the resilience of the economy. It also has the potential to create a more sustainable and profitable industry, reduce resource costs, and improve social and environmental outcomes. By introducing a circular economy for the loudspeaker transducers specifically, we can achieve:

  • Independence of imported magnets
  • Reliable supply chains
  • Reduced need to mine rare-earth elements
  • Preservation of added value in existing products
  • Utilization of electronics waste

Life-cycle impact assessment of loudspeakers

Life-cycle analysis can be used to quantify the impact of the circular economy of loudspeakers. The majority of the impact comes from magnets and the chemical processing of the rare-earth elements in them. For example, the Circular Sound Eikosa loudspeaker contains approximately one kilogram of magnets in the upcycled transducers it uses. The life-cycle impact assessment of 1 kg of magnet reported here is an average of several sources reported in two studies 9,10.

Impact categoryQuantityUnit
Global warming69kg CO2 eq.
Acidification0.63mol H+ eq.
Eutrophication (freshwater)0.015kg P eq.
Eutrophication (marine)0.09kg N eq.
Eutrophication (terrestrial)1.26mol N eq.
Ecotoxicity (aquatic)331CTUe
Human toxicity (carcinogenic)3.4CTUh
Ozone depletion4.2*10-6 kg CFC-11 eq.
Particulate matter0.12kg PM2.5 eq.
Ionizing radiation4.19kBq U235 eq.
Water consumption0.63m3
Impact per kilogram of rare-earth permanent magnet


All industries need to transform into a circular economy in order to close the circularity gap and reach the Sustainable Development Goals. The current loudspeaker industry operates in a linear fashion and trusts that a long product life will mitigate environmental impact. However, there is no end-of-life solution available and precious raw materials found in the loudspeaker magnets end up in landfills.

Various circular economy solutions exist. Minimizing material use and swapping one material for another is an incremental improvement, but still involves virgin materials. Repairing and relying on a second-hand market assumes there is still a demand for the old product. Recycling the raw materials destroys the added value of the product and is not economically viable due to manual disassembly steps. Remanufacturing, on the other hand, offers a way to meet new customer needs using components and materials from old products.

Sustainable loudspeaker
A remanufactured loudspeaker 3D printed from bio-based materials and using components from an old subwoofer.

Upcycling old loudspeaker transducers and using them in a new product keeps the magnets in our economy and reduce the need to produce virgin magnets. This has quantifiable environmental impacts, such as avoiding 70 kg of CO2 equivalent in greenhouse gas emission per one kilogram of magnet.

Appendix A: Life-cycle impact assessment categories

Life cycle impact assessment (LCIA) is a tool used to evaluate the environmental impact of products or services across their entire life cycle. To measure these impacts, a variety of impact categories and units can be used. Here are some examples:

  1. Global warming: This impact category measures the amount of greenhouse gases (primarily carbon dioxide) that are emitted over the life cycle of a product or service. The unit used is typically kilograms of carbon dioxide equivalent (kg CO2e).
  2. Acidification: This impact category measures the amount of acidifying substances (such as sulfur dioxide and nitrogen oxides) that are emitted over the life cycle of a product or service. The unit used is typically moles of hydrogen ions (mol H+).
  3. Eutrophication: This impact category measures the amount of nutrients (primarily nitrogen and phosphorus) that are released into the environment and contribute to the growth of algae and other aquatic plants. The unit used is typically moles of phosphate (mol PO43-).
  4. Particulate matter (PM): This impact category measures the amount of fine particulate matter (PM2.5) that is emitted over the life cycle of a product or service. The unit used is typically micrograms of particulate matter per cubic meter (μg/m3).
  5. Ecotoxicity (aquatic): This impact category measures the potential harm that a product or service may cause to ecosystems and their inhabitants. The CTUe (Characterization Factor Toxicity Unit – ecotoxicity) unit is based on converting the amount of a substance emitted during a product’s life cycle into a standardized ecotoxicity value. The ecotoxicity value is expressed in CTUe per kilogram (kg) of the emitted substance. The characterization factor takes into account various parameters such as the chemical properties of the substance, its persistence in the environment, its toxicity to aquatic organisms, and the extent of the area affected by the emissions.
  6. Human toxicity (cancer): This impact category measures the potential harm that a product or service may cause to human health. The human toxicity value is expressed in CTUh per kilogram (kg) of the emitted substance. The characterization factor takes into account various parameters such as the chemical properties of the substance, its toxicity to humans, and the extent and duration of exposure. When the CTUh unit is used to assess cancer risk, it is often expressed as cancer cases per million people per year (cases/million/year), rather than CTUh/kg. The cancer risk is calculated by multiplying the amount of the substance emitted by its cancer potency factor, which represents the likelihood that the substance will cause cancer in humans. The resulting value is then converted into cancer cases using demographic and exposure data.
  7. Ozone depletion potential: The ODP of a substance is determined by comparing its potential to deplete ozone to that of CFC-11. Many ozone-depleting substances, including CFCs, are banned. The use of CFC-11 as a reference substance is only relevant for historical analysis or for assessing the impact of new substances that may have similar properties to CFCs.
  8. Ionizing radiation: It is used to represent the potential harm a substance can cause to human health through exposure to ionizing radiation. The unit kBq U235 represents the activity of uranium-235, which is a measure of the rate at which the material emits ionizing radiation. The unit kBq stands for kiloBecquerel, which is a unit of radioactivity. One kBq corresponds to 1,000 disintegrations per second.
  9. Water consumption: This impact category measures the amount of water used over the life cycle of a product or service. The unit used is typically cubic meters (m3) of water.
  10. Land use: This impact category measures the amount of land required over the life cycle of a product or service. The unit used is typically square meters (m2) of land.

There are many other impact categories that can be used in life cycle assessment, depending on the specific environmental and social impacts of interest.