Bluetooth speakers are easy to make. But how about speakers that connect to each other? The days of running aux splitters and cords across the apartment are over! These speakers draw components and inspiration from my prior two instructables:

https://www.instructables.com/Best-CNC-Bluetooth-S...

https://www.instructables.com/The-Ultimate-CNC-Blu...

However, these speakers are different in that you connect to one, and it will broadcast to the rest. They use one motherboard from our old friend, the JBL Charge 3. You can pick these up on eBay for as little as $7. They fulfill multiple purposes, being the Bluetooth board, amplifier, AUX input, and rebroadcast unit. They also are designed to run off a 1s LiPo battery (3.3-4.2v). I utilize these speakers for movie nights at my apartment, with one connected via AUX to the TV, and the rest spaced throughout the living space. Alternatively having them paired on either side of the pickleball court, or for outdoor movies makes for some fun times.

Other components I will leave you to figure out. I use the below LiPo charger board, albeit it charges very slowly. LiPo's themselves are highly variable. I have used old portable chargers, 18650 batteries, and R/C batteries as well. So long as it's one cell and high capacity, you should be ok. Though two is doable in parallel if you know what you're doing.

Let's get started!

Supplies

Casing
- Wood casing
  - Wood
  - Glue
  - See "The Ultimate Bluetooth Speaker" for more
- 3D printed casing
  - Filament
  - 3D printer
  - Silicone (for sealing)
Electronics
- JBL Charge 3 Motherboard (eBay)
- JBL Charge 3 Button Board (eBay)
- FFC 12 pin 0.5mm pitch type B (Ribbon cables) https://www.amazon.com/gp/product/B07RVD1TT3/ref=...
- 1A 1s LiPo charging board https://www.amazon.com/Diymore-18650-Lithium-Batt...
- LiPo 1s of your choice (high capacity)
- Drivers (speakers) of your choice
  - 1.5-3.5" in diameter
  - 4-8 ohms
- Speaker wire
- Solid copper wire for Bluetooth antenna
Miscellaneous hardware depending on your case design

Step 1: Electronics

The casing is always a highly custom, and personal choice. But the electronics for this Surround-Sound speaker are pretty straight-forward. I will tell you how I did and, but realize that eBay electronics and old tech may not always function the way you want it to. One of my motherboards did not work with AUX input whatsoever.

First, the battery.

5 pins, the three pins closest to the outside of the board (follow the diagram) are connected to the negative terminal of your battery. The two pins closest to the middle of the board are positive. You can connect the battery to the board, but it will not turn on until you press the power button on the Button Board. Your battery should be a 1s (3.7v) LiPo battery. I use two identical cells in parallel, for higher capacity. Minimum 5000mAh recommended.

Button Board.

A very simple skinny board, connects to the motherboard in the tab indicated in the diagram. Make sure the metal contact is facing downward (the board) on both sides when plugging it in.

LiPo charging board.

Charges via a micro-USB cable. Connect the battery outputs to the battery. Very simple, and can be connected permanently to the battery. It outputs 4.2v, and charges at a maximum of 1A.

Drivers (speakers).

Connect these to the rear of the motherboard. If you don't have JST connectors for these ports, simply solder the wires to the prongs. Positive, negative, positive, negative. Two speakers. Recommended driver size is 1.5"-3.5". 4-8 ohms.

Bluetooth Antenna

This is super important, if you want the range to be more than 3 ft. You will need to solder a solid copper wire to the inner pin of the port indicated in the diagram. It is difficult, but you can do it. Just get it connected, and secure it further with epoxy to prevent it from ripping out. The length of this wire should be 28.8mm in order to have the best range.

And that's it! Super simple, thanks to JBL technology. But makes for a powerful and great speaker.

Step 2: 3D Printing

For the gray speaker, I got to use a few different technologies to make it. My work has an SLA resin printer, which requires the part to be cleaned in a supersonic IPA bath and cured in UV light. The gray body was printed at home using a traditional FDM desktop 3D printer.

The wood disc actually has purple heart inlaid by CNC, and it comes from my last instructable speaker.

Some tips to consider -

If printing buttons, be very careful with dimensions. PLA will expand and contract around holes in weird ways. Key your buttons so that they cannot rotate.

Don't print detail on large prints. Any small ports should be printed separately and attached.

Attaching with screws is highly recommended. If you want to take it apart repeatedly, make sure and use metal inserts to receive your screws. Simply design a hole slightly smaller than your insert, heat it up with a soldering iron, and let it cool inside the hole.

Files are attached for reference, but feel free to modify or design your own!

My personal settings:

PrusaSlicer:

0.15mm layer height

20% infill

60mm/s

3 horizontal shells

3 vertical shells

3 skirt loops

Autogenerated supports

215 degrees C for Overture PLA

Step 3: Additional Ideas

Adding an aux port is very easy. Simply look at the diagram, and experiment which pin goes where to get two-channel output. The center pin should be ground.

Having a USB charger is easy, so long as you don't want it to turn on and off with the rest of the speaker. Sometimes that's ok, though it may drain your battery. The JBL motherboard prevents over-discharge under normal circumstances but not for that.

The voltage meter on the wood speaker is connected directly to the battery, and toggled via the "V" button. It's good for checking the battery occasionally.

Passive radiators will increase your bass output considerably for these small speakers.

Sealing it completely makes it sound so much better. Use a lot of silicone.

These speakers alternatively can run under wall power, you would simply need a converter that puts out 4v at around 4A DC.

Step 4: IMPORTANT for 3+ Speakers

The original JBL Charge 3 operated off of the JBL Connect system. This only allowed for two speakers to be connected simultaneously. You need to upgrade the software via their app (JBL Connect) to JBL Connect +. In order to do so, the speaker needs to be plugged in and "charging". I faked this by tearing apart my existing JBL, plugging it in, and plugging the charging cord from that speaker into my updating motherboard. This is difficult to do without another JBL speaker, as the charging system goes through the second ribbon cable input. But let me know it you find a better way around it!

Step 5: Enjoy Your Surround Sound

These speakers work great! You may need to work on positioning to get them to connect properly. And you quickly learn how to minimize lag through trial and error.

But especially for social movie nights, or card games with music these have made my apartment the place to be!

Let me know of any questions or comments below.

-Peter