Door-ble Bass – turn any door into a single string double bass!

I’ve been teaching kids music for years now and one of my favourite things to do is creating instruments out of nothing to illustrate the principles of acoustics. And of those, putting strings on random surfaces at hand to turn them into basses must be the most satisfying. I decided to turn that idea into a printable design anyone can use with ease.

Instructions (consult the photos):

1. Print all the parts. Keep the orientation of the models for strength. A lot of perimeters, a lot of solid top and bottom layers. I used PLA for its rigidity. Wide brim for the peg and a bit of supports for the headstock.
2. Insert the tuning peg into the headstock hole. It requires some force. Try twisting motions.
3. Get a piece of string. I prefer thin 2 mm sailing rope for its dimensional stability. Use something prone to stretching and you’ll never be able to tune it. Put your string into the tiny hole in the peg. Twist the peg a few times to get a good length of the string on it. 
4. Put the headstock on top of a door frame (use shims if it doesn’t fit neatly). The less solid the door, the better. Ideally, it should be a thin sheet of plywood, or a hollow structure.
5. Measure the length of the string corresponding to the door’s height. Tie the end to the tailpiece. Put the tailpiece underneath the door.
6. Give the peg a few twists until the string is tensioned a bit.
7. Put the bridge underneath wherever it suits you – for me it’s about 1/3 of the door’s height.
8. Give it more tension, you can even tune it to E, A, D, or G – just like a real double bass!
9. Play. Experiment. Have fun. Tinker. Enjoy!

Here's a little demo:
https://youtube.com/shorts/eFaTKkFxLI0