The Simplest to Build But Very Robust Bluetooth Speaker

The BT speaker is very easy to build from the electronics point of view. It contains in the simplest version only four devices: BT module, speakers, LiIon battery and power switch. All other additions are optional. This project uses 3D printed housing, but more simple wooden or cardboard can be used instead. The solution to use strong PLA case was taken to make the device strong, compact and comfortable to use.

The Bluetooth speaker is based on the CT14 module ,which has embedded BT receiver, two power audio amplifiers and simple battery charger. All cables with corresponding connectors are included in the kit . As speakers I used two 40mm 3W 8Ohm ones. The LiIon battery was taken from old MP3 Player. The power switch can be whatever you have. I used also additional speakers protection grids and one passive bass diaphragm.

Because the charging circuit in the CT14 module for the LiIon battery is very simple (only limiting resistor and diode) may shorten battery life, I decided to use TP4056 module instead the embedded one. For that purpose I removed the limiting resistor and the diode and I connected the charging module positive input in the place of the resistor (its left terminal - see the picture). The charging module I glued with hot glue over the battery. Its USB connector I removed, but It can be left without problems.

The housing body I have printed using PLA filament. The whole housing consist of two parts - the main corps and the bottom cover. The thickness of the bodies walls is enough to make the body very strong. I used sandpaper to clean up the 3D printing artefacts. I did a hole on the side wall for the power switch and for the micro USB connector of the BT module. To make the surface glossy after sanding I use the following trick - with a hot air gun I heat it up for some time until I see that is starts to melt and after that I stop the heating and leave it to cool down. You have to be careful performing this because you can overheat and melt the whole wall and distort the shape.

Firstly I inserted the power switch. After that I fixed the speakers rings using super glue. I mounted the speakers together with their grids using hot glue. The battery and the BT module were fixed in the same way.

I had to increase the opening for the passive diaphragm to adjust their sizes. After that I attached the diaphragm on the cover using universal glue. Finally the bottom cover I glued with super glue.

As can be seen in the video the speaker is small in form but powerful enough to sound a medium-sized room. If more power is desired there can be added an DC/DC converter, which can boost the 3.7V battery voltage to 5V (5V is the maximum allowed supply voltage for this module) or lower impedance speakers can be used (min 2 Ohm), but take in mind the maximum power delivered by the module is 2x5W.

Good like in your designs!