There are a lot of instructions about DIY Bluetooth speakers. I made my instruction because I followed some of these instructions and my first try was a disaster. I thought I share what was the solution for me. First of all my goal was to build a Bluetooth speaker, that has a good sound quality but still portable, cheap as possible. It should look cool. It should show the battery voltage to know when it is time to charge.
My mistakes at first try:
1. My first priority was that it should look cool. So I choose a metal house. I saw a lot of instruction how to turn an ammo box into a speaker. I modified my box according to these instructions. The result was an irritating, vibrating, creaking noise during music listening. I tried to seal the housing and used rubber and corkwood to reduce this noise, but I was not able to rid of it.
2. I bought some beautiful metal speaker protectors and I ordered small speakers (2”) to match to the size of the box and to the protector. The result was very bad bass performance.
I did not finish this metal box, voltage meter, charger, and cabling is still missing. You can see the green metal box picture attached.
Step 1: Speaker Disassembling
After my failure, I realized I should have to focus more on the sound quality instead of the outlook. I found on the internet an used SH-M10 Pioneer speaker for 5$, so I decided to give another shot.
The walls of the speaker are made of thick wood and it has a 4” speaker with 15W. I know that is still light years from studio quality, but for me it was fine.
I removed the protective frame. I broke one plastic part during this process, it was glued too well. Without this one part, the frame is still usable. Careful with this process, I used mobile phone repair plastic tools.
Step 2: BOM List, Schematic
Here is the BOM list
1 pc 25W amplifier + Bluetooth 4.0 Audio Receiver
2 pcs Terminal block 3 wire connector
1 pcs Terminal block 2 wire connector
1 pc DC voltage meter
1 pc 12VDC Lipo Battery 4800mAh
1 pc Power socket connector
1 pc power plug connector
1 pc switch
I connected all component on the table without housing to try out the circuit. A schematic is attached.
Step 3: Cabeling
I soldered every PIN on the surface mount component (power socket, switch, display) to a 20 cm long cable. The cable can enter through holes on the speaker housing, the component can be fixed, and then the only the end of the wires need to be connected together inside of the box with help of terminal blocks. This method will help to install quicker, and if something is wrong with the cabling, it is easier to repair.
Step 4: Mechanical Modification
I used a drill, multi-tools, rasp and abrasive to have holes suitable for the DC meter, battery charger socket and for the main switch. I made a very tight opening because I wanted to avoid any empty spaces between the component and the wall. It could cause vibration.
I used glue to fix all components. It was a hard task because I had to do it through the hole of the 4” speaker.
I recommend testing the complete system (operation, and charging), before gluing.
Step 5: Epilogue
I built this unit two days ago. I am running now some tests: I want to know how long can I use it with one charge? Is there any noise, or quality issue at low Voltage or at higher power? The amplifier power can be changed with a DIP switch (see picture attached).
I am satisfied with the speaker. It is not looking as cool as I planed, but small elegant black box always in fashion:)
Have a nice day!