This is the main Instructable for the outie/reversible headphones project. A finished sub-Instructable on the parametric CAD bent wood lamination part can be found here.
Step 1: Cannibalize Ze Speakers (and Electrical Planning)
The X-Minis have several inputs/outputs for music:
- external 1/8" male audio input (white cable)
- mini-USB female jack input (for charging and audio through the provided cable)
- 1/8" female audio output (for daisy chaining the output of one speaker to the input of the next)
Each of the X-Minis normally act as their own speaker, with their own power switch, volume, and audio input. As headphones, it would be ideal at all times for each to share the same volume, audio input, and power switch. The cable that comes with the X-Minis connects a USB Type A and a 1/8" audio input to the X-Minis with a 2x USB-Mini male connectors through a volume knob (see the picture with the black X-Minis).
This configuration works well for a pair of headphones: a master volume switch, shared audio source. The downfalls are no shared power switch (I decided to just let that be) and the USB-Mini inputs for audio are a little bulky and unsightly. To fix this, I decided to eliminate the USB-Mini male plugs from the cable, and solder the internal wires directly to the inside of the speaker. Additionally, decided to remove the audio output jack to save space, and to remove the volume dial on the speakers themselves so only the volume knob on the cable is used.
Step 2: Replace the Volume Potentiometer, Remove Audio Jack
Remove the circular volume knob (I used a solder removal tool).
Then solder 2.2 Ohm and 20 kOhm resistors in the proper positions. Try playing music through the speakers to make sure you wired things correctly (if nothing plays you probably reversed the resistors and it thinks it's at minimum volume).
Remove the audio output jack using a solder removal tool as well.
Step 3: Splice in the Audio Cable
Cut the USB-Mini plugs from the cable. I tested continuity between each of the wires (gold, red, and green) and the USB pins to identify which cable goes to which pin (as show in the sketch).
Very carefully solder each of the wires from the cable harness to the appropriate pins on the USB-Mini female connector on the speaker board. Once done, test your work by playing music through the speakers. If it doesn't work, check continuity between the connections you made. The pins are so close that if you weren't careful enough, it's likely you inadvertently soldered 2 together.
NOTE: I actually had to undo this step and thread the cable through my 3D printed pieces, then resolder for the final headphone. Allowed me to have a cleaner cable routing scheme.
Step 4: Headphone CAD Creation
- Use the original screws and mounting holes for fixing the speaker to the 3D printed piece
- Make sure the screw pattern and headband connection location results in the proper speaker orientation
- Create an outlet from the speaker internals for the cable harness
- Rotating joint between headband and headphones to allow speakers to rotate from innie to outie
- Mechanical stops so the headphones rotate only to the proper positions
- Connection channel for the headphones (decided using hot glue in the end would be fairly robust and let me disassemble if necessary)
- Attempted to match the style of the speakers and headband
The headband CAD will be addressed in the next step.
Step 5: From CAD to Existence
The headband is enough of a project in itself I decided to make another Instructable for it. Made it by creating a bent wood lamination using CAD, a CNC router, and a laser cutter.
Headband parametric CAD bent wood lamination
Step 6: Assembly
Hot glued the headband to the headphones and wiped away excess glue.