If your next project needs some sound, a bone conductor transducer will have you experimenting with all sorts of objects. If you've ever wired a speaker system before, you'll find this DIY electronics project is fun and easy!

This incredible speaker does not have a moving cone like most speakers you've seen, instead, a small metal rod is wrapped with the voice coil. When current is pulsed through the coil, the magnetic field causes a piece of metal to expand and contract - if pressed against a flat surface or cavity it turns it into a speaker!
PLA @230 
No Raft/Support
%15 infill
2 shells
0.2 layer height
Takes about 1.5 hours to print all pieces
The enclosure is a three piece design that snap-fit together. The bonebox-top.stl part houses the slide switch and audio input jack. The bonebox-case.stl part houses the amplifier and lithium polymer battery. The bonebox-bottom.stl part houses the bone conductor transducer exposing the vibrating metal piece but is secured in place with built in clips on the bottom part.

The parts are optimized to slice with MakerWare and printed using PLA with no raft or support material.
Follow the circuit diagram above to connect the components. If your new to electronics, use a bread-board to prototype the circuit before soldering any connections.

Stereo Jack

Connect the most far left and right terminals to the R+ and L+ pins on the TPA2016. The middle terminal will connect to the R- pin. You will need to jump the R- and L- pins with a separate wire. We aren't using both channels, so you can also tie R+ and L+ together to make a basic 'stereo mix'

Slide Switch Adapter

Use a JST extension cable to create a slide switch adapter. The positive cable will split a connection to the two terminals of the slide switch. You will need to shorten the length of the JST extensions as short as possible. To avoid soldering the JST extension that is connected to the switch, use another JST extension to solder into VDD and GND pins.

Bone Conductor

The bone conductor transducer can be soldered to either the right or left audio channels.
Please note: Bone conductor transducer wires are soldered from the bottom of the amplifier for positioning the circuit into the 3d printed enclosure.

Stereo Headphone Jack

Start by placing the audio input jack into the bonebox-top.stl part by lightly pushing apart the clips and pushing the input jack into the opening. The jack should snap into place with the tips of the clip holding the input jack in place.

Slide Switch Adapter

The slide switch is pressed into the bonebox-top.stl part by pushing it into the opening. Once it's secured, set it aside.

Bone Conductor

The bone conductor transducer is secured to the bonebox-bottom.stl part with clips built into the part, similar to the bonebox-top.stl part. The metal plate is exposed so that it can transfer audio more efficiently.
Pull the bone conductor transducer and bonebox-bottom.stl part through the bonebox-case.stl part with the inner lip positioned towards the bottom.

Amplifier + Lipo Battery

Push the amplifier down into the bonebox-case.stl part, it should stop from hitting the bone conductor with the inner lip holding it in place.
The lipo battery is placed on top of the amplifier. The slide switch adapter and battery wiring should tightly fit into the bonebox-case.stl part.
Gently arrange the wires of the battery and slide switch adapter into the bonebox-case.stl part and snap the bonebox-top.stl piece into place.

Closing it up

Coil up the excess wiring of the bone conductor transducer and press fit the bonebox-bottom.stl into the bonebox-case.stl part. Now your bone conductor transducer is packaged up and ready to turn surfaces into speakers!
Works on several different surfaces! Objects that are hollow perform much better than objects that are more dense. Below is a list of materials that it seems to work well with.
  • Acrylic
  • Wood
  • Plastic
  • Glass
The bone conductor transducer produces that best quality sound when it's pressed up against a surface. If the bone conductor box is loosely placed on a surface, it will cause the metal plate to vibrate the surface to much and cause clippy audio.

This guide was first published on Mar 20, 2014. It was last updated on Mar 20, 2014.