Introduction: Reclaimed Bamboo Box Bluetooth Speaker
Second Prize in the
Audio Contest 2017
Because i do not really like the design of plastic portable speakers i decided to try build one from parts i have at home. I had a bamboo box that suited the project and from that box i started the work. I am quite happy with the final result even if i think i would make some changes to improve bass quality.
Step 1: Things Needed for the Build
1. Wood box (i had this box at home)
2. AMP: 2x15 W PAM8610 HD
3. Battery management system (BMS): 3S BMS
4. BATT: 18650 SAMSUNG 18650-15Q SDI 096 (saved from broken cordless drill)
6. Speakers (saved from old tv)
7. Passive radiator
8. Battery holders (i printed at home)
9. FM Antenna
10. 12v Battery meter led
11. External 2500mAH battery (optional)
Step 2: Prepare Front Panel and Other Woodwork
1 First cut a piece of plywood with the mini table saw to fit the box
2. Cut the holes for the speakers with the scroll saw
3. Paint the panel black and apply glue for the cloth
4. Apply the cloth on the panel and check if the panel fits the wood box
5. Use some screws to attach the speakers to the panel.
6. Cut the holes for antenna, bluetooth module, power switch, passive radiators etc.
Step 3: Prepare for Wiring
Because i had some space i decided to put an external battery totally independent from the speaker circuit for charging the phone or other things. I cut the battery case to fit the design and mounted the battery in the corner.
Try to design the place for every piece from the beginning and make simulation to be sure they fit, after you cut the wood is very hard to fix. Also keep in mind that things may get warm or hot, keep the design clean to avoid overheat and shorts. Insulate every wire and be careful not to leave any scrap or lose wire that could short a li-ion battery. This may cause a fire. Ensure every piece is fixed before wiring.
Step 4: Wiring
The system is powered by 3x18650 li-ion cells wired in series to result 12v (10.8v optimum). The 18650 cells are wired to the 3s BMS(Battery management system) that prevents over charge and over discharge. After first wiring the BMS will only start when you apply 12v to out terminals. When wiring the cells take great care at polarity. The cells can be charged thru the BMS with a 12v power source, but charging will not be balanced. BMS will cut off charging when first cell hits 4.2 volts. This also applies to discharge. With this method will have in time an unbalanced pack. I wired the cells so i can check and charge every cell individually to balance the pack. I added notes to the picture with the back of the speaker.
I used 4x8ohm speakers (2/channel) wired in parallel that makes 4ohm resistance/channel.
The result is a very loud system for its size.
Also i need to buy a "ground loop filter" to remove some bad noise when i use bluetooth.
This is my first instructable and i hope i could help you.
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