Categories
Bluetooth speaker 3D printing Audio Circular economy DIY Loudspeaker Recycling Speakers Sustainability

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.

Components

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

Categories
Circular economy 3D printing Audio Loudspeaker Recycling Speakers Sustainability

Circular Sound – Disrupting the industry with 100% recycled loudspeakers

Introduction

The loudspeaker industry, like all other industries, needs to transform into a circular economy model. Why? because only 8.6% of the materials we use circulate back into the economy, according to the Circularity Gap Report 2021. We need to increase this number in order to reach the Sustainability Development Goal 12.5 set by the United Nations:

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

United Nations Sustainability Development Goal SDG 12.5

Circular Economy of Loudspeakers

Some loudspeaker manufacturers use recycled or renewable enclosure materials, but the biggest problem is circulating the electronics and loudspeaker drivers back into the economy. There is an abundance of old loudspeakers being discarded or sold very cheap every year, because demand for old models has diminished. Buying new loudspeakers made from virgin materials is not sustainable, especially due to the rare-earth elements (REE) used in loudspeaker magnets.

Rare earth elements (REEs) are essential for manufacturing permanent magnets. Permanent magnets are critical components in most decarbonisation technologies.

European Union EIT Raw Materials

The European Union is dependent on imported magnets and REEs. A circular economy model would not only be good for the environment, but also for the reliability of supply chains.

Additive manufacturing enables circular economy

Additive manufacturing offers many opportunities for a circular economy, where repair and remanufacturing are some of the best options to reduce the consumption of mass-produced products made in far-away lands. Circular economy can be described by the 6 REs:

  1. REduce – Don’t buy anything
  2. REuse – Buy second-hand
  3. REpair – Fix it, if it’s broken
  4. REmanufacture – Make something new using old components
  5. REcycle – Cycle the raw material back into the economy
  6. REcover – Burn for energy

As far as loudspeakers are concerned, the best option is of course not to buy anything. The second and third best options are to buy used loudspeakers or fix broken loudspeakers. These two options, however, do not consider the fact that the user may want something different compared to their current product or what is available second-hand. In other words, it does not help if a product can be used forever if nobody wants it anymore. Circular Sound tackles this issue by relying on remanufacturing with the help of 3D printing. In this context, remanufacturing means using the drivers and electronics from old loudspeakers and 3D printing a new enclosure. Obviously, the material of the new enclosure needs to be sustainable, too. Recycled and bio-based plastics are promising, but require special design considerations to obtain the necessary acoustic properties from the enclosure.

3D printing a bio-based loudspeaker enclosure

RD Physics CS-012 proof-of-concept prototype

The RD Physics 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. 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 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.

Near-field and far-field magnitude response.