Inmediately after finishing my first bluetooth speaker, I started thinking about the second version. The first time I used laser cut MDF and this time I wanted to try a different material. I have a 3D printer at hand, so I decided to use it. Although I have use the 3D printer many times, I thought I would spend most of my time designing the speaker and printing it would be easy. But I was wrong. I had to print the speaker like 3 times and I can say that post-processing took longer than the laser cut speaker sanding and painting process.
Design
My design is inspired by an old Braun speaker designed by Dieter Rams. The idea is the same, but I made some modifications to make it work with the electronics and to be 3D printed.
I wanted a very clean and minimalistic interface, so I put a lot of effort to reduce the process of turning on the speaker to one operation. In my previous speaker, first you need to turn on a switch to power it on and then you need to hold a button for 3 secs. to turn on the bluetooth module. And besides a little bip, it provides no feedback about the current state of the speaker. So now, using a rather simple and inexpensive circuit I was able to use only switch equipped with a LED inside to turn on the system. I also added volume buttons that are really useful.
You can find the STL files here.
3D printing
As mentioned earlier, 3D printing was the hardest part of this project. After finishing the design, I left the Makerbot Replicator printing the whole body while I was sleeping. The next morning I was really excited to see the result, but I found a warped piece, split in 3 parts.
In the second attempt I split the body in two halves, but the curling persisted. So, in the third (and last) attempt I divided the body into 6 slices. This approach meant that the printing was much slower (I had to print 6 raft layers instead of one) and the post-processing took much longer, because I had to sand and bond each of the slices. But, at that point, it was the only safe way to do it. It would be nice to try PLA instead of ABS. Maybe all these problems are solved by switching materials. Removing the support material also took much longer than I thought. There was plenty of it on the outer surface and I must remove it really carefully, trying not damage anything. Finally I applied some layers of white spray painting.
Electronics
The electronics are rather simple and similar to my previous post. The main difference is that I used a module that integrated the bluetooth receiver and the amplifier. This is really nice because it decreases the noise considerably. As I mentioned above I also included this circuit (the diagram on the right) to avoid waiting for 3 secs. and to turn on the module with the same switch that I used to power the whole system. To achieve the time needed I changed the 22 uF capacitor to a 100 uF capacitor.
Here is the list of materials. If you have any question about the specifics, don’t hesitate to ask!
- 3.7 V Lithium battery
- 2 x 3W speakers
- 1 battery charging module
- Bluetooth + amplifier module
- 1 555 timer
- 1 microswitch
- 2x push button
- 1 white led
- Resistors, diodes and capacitors.
Francisco Sahli 