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).
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.
How to build the BB1/BB2 bluetooth speaker
- Start by soldering the 6 mm DC plug to the USB connector. Red (+) goes to center pin and black (-) to outer shell.
- Connect DC power and speaker cables to bluetooth board and fasten the board inside the enclosure by tightening the screws via the driver openings.
- Mount the USB connector and handle.
- 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.
- 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.
- Fill the enclosure with fibers (cotton, polyester, wool etc.) and fasten the passive resonator.
- Optional: Attach the wall mount bracket.
- Connect a USB port and the bluetooth board powers on automatically. Pair your signal source with the device (“WONDOM”). Enjoy!
