Best CNC Bluetooth Speaker - the Sequel

A couple years later, I decided my original bluetooth speaker needed an upgrade. While I still use it (daily), I wanted to push the limits of 3 axis CNC design to their limits. Not only that, but the limits of hobby prototyping in general. This is my best CNC creation to date. And the best circuitry I could design. It beats my prior speaker by a mile, and competes with top brands. Enjoy!

(Keep in mind this is my first project using fusion360).

Some features:

· 360 degree sound

· IPx6 splashproof (self-tested)

· Two full-range 3" drivers

· One subwoofer and passive radiator

· 10 hr+ battery life

· Dual USB charging ports

· Aux and bluetooth connectivity

· LED battery indicator

Approximate 45 watt output.

I paid very little for parts, as I used most from my stockpile of saved components. However, I had to design some circuits to get these boards to... behave. If you intend to follow this instructable to the letter, you will need good knowledge of soldering and reading schematics. My protoboard is a mess. But it works. You can print your own board from my schematic, if you wish.

I carved all of the body with a single bit - a 1/4" shank x 1/4" cutting diameter x 1" cutting length endmill. Because of that, I designed each piece to have no trouble with that. It's amazing the amount of detail you can achieve with the right toolpaths. I have a 2'x4' CNC, Mach3 for controlling, and Fusion360 for 3D design. Toolpaths can be created through Fusion, though I was more comfortable using Vectric Aspire.

Anyone can make this, if they are creative. Some may use this just for the .stl files to 3d print it, others will copy the electronics. The speaker sounds amazing. I have yet to see any quirks with this either. It turns off at low-voltage, automatically. Auto connects with bluetooth. Charges devices at a 3A charge rate.

The main advantage you will learn from this instructable will be design process. I changed this probably hundreds of times, and you guys can follow along with these changes and why. And hopefully, maybe even inspire you to design your own speaker. One that isn't made from some sunglasses case or sprinkler supply parts.

Feedback is appreciated, questions, concerns. I designed this for my needs. What would you have added?

-P^2

Electronics:

• 12x 18650 Li-ion batteries
• 2x 2.5" (3" OD) full range speakers
• 2.5" Subwoofer
• 3" Passive radiator
• 12v-5v voltage converter
• Dual USB port
• 4s Li-poly balance charger
• Bluetooth module
• Aux port
• DC charger and port
• Wire
• Assorted passive components (explained in Schematic section)
• Protoboard
• Solder
• Electrical tape

Wood n stuff (interchangeable with any hardwood):

• Walnut
• Maple
• Purpleheart
• Type III wood glue (to be more water-resistant)
• Misc. screws
• Double-sided tape
• Poly finish
• Epoxy finish (optional)
• Vinyl tubing
• JB Weld
• Silicone
• Semi-gloss and gloss polyurethane
• Liquid electrical tape (or black silicone)
• sandpaper

Tools Used (Get creative! If you don't have it, do it another way!):

• CNC Router (3D printer would work too)
• Bandsaw
• Table saw
• PlanerJointer
• Impact drill
• Drill
• Clamps
• Soldering iron
• Hot glue gun
• Spindle sander
• Bluetooth Speaker (To listen as you work :)

Like previously stated, one can subtstitute anything. I highly encourage you to use what's on hand.

I used three very nice hardwoods, though 3d printing or even a softwood like pine might work. Just be willing to experiment. I generated probably an entire garbage can worth of sawdust, and as evidenced, dozens of prototype pieces.

I sourced all of my parts on amazon. I will not link them, as they are subject to change all the time. All I will say, is that the two amplifiers are 2x15w old-style amps with massive heatsinks. Batteries are from a yard tool battery pack that quit working, and speakers are from two decomissioned speakers in my house. In other words, this is unique, and yours should be too. Find what's cheapest that will work well, and go for it. Go to goodwill or DI and take stuff apart. (After buying it, preferably.)

As far as specs you want to look for, the bluetooth board has an important one. Find one that doesn't make dumb start up noises. Like the bad english "the bluetooth device is connected succesfully" voice.

Find amplifiers that function well within your battery packs' voltage range.

And a dc voltage converter that functions within your voltage range.

Create your list of specs that are permanent, and then base it all off of there. I will explain in the next step how I began with the batteries.

I knew that amplifiers typically operated better at higher voltages, so I went to the highest voltage I could that was still inexpensive to charge. I went with a 4s (four cell lithium) system. I had a balance charger that does 4s, so I connected the 12 batteries in strings of four, and put those three strings in parallel. I then added balance wires to make it charge correctly.

I wanted to be able to charge this speaker with USB, but I couldn't do it effectively at the wattage of typical USB ports. So, I decided to just charge with a "wall-wart" style dc brick. In this case, an old amazon echo brick. It made for faster charging anyway. This voltage is fed to the 4s charging board (which I removed from my old charger), and then given to the batteries as a balanced feed.

I have not attached basic hookup connections to the amps, as that should be self-explanatory. However, I have added a few things.

All of this was done on a single protoboard. Read the shematics for parts info.

There are two low pass filters. One helps prevent line noise for the bluetooth board. The other acts as a passive crossover for the second amplifier. (Makes it just play subwoofer frequencies.) Google "low pass filter calculator" to find something that works with components you already have.

Another is a voltage divider for the usb ports. This gives a signal voltage that tells modern devices how much current to draw. Mine is optimized to pull at least 1 amp for any device.

Another is a hacked circuit for an led battery level indicator. It uses the fixed voltage from the dc converter to measure. I highly recommend designing a new or better indicator, as this one is pretty hacked.

The final is my proudest. It is heavily modified from another website, using components I had on hand. You see, my first speaker used a latching push switch. I push it, and it locks in place. I wanted a momentary push button, similar to the power button on your phone. A one press on, one press off operation. Hence the "soft latch" switch circuit. It utilizes two transistors and a mosfet to connect/disconnect the negative lead from the circuit. The "low" side of the circuit simply provides a 5v signal to the mosfet when on, allowing current to flow. A "logic level" mosfet was used.

My protoboard looks awful. It was my first real protoboard circuit. Judge all you want, haha.

The entire switch circuit can be replaced with a latching push switch, for around $9 for a nice one. But I prefer my wooden button and flush operation.

The most difficult physical piece of this project was the middle section, that I dubbed the "sound castle". It is thin, and complicated, and makes a smooth transition between the cylindrical and rectangular halves of the speaker.

Because of these unique properties, I ended up having to carve into the end grain of a thick piece of walnut. I wanted to use the stripy blank that I had glued, but it chipped too badly every time. Could be the bit, but why fight it when something else works?

I glued two small blocks of hardwood to either corner, with holes drilled. These allowed me to screw the workpiece to the cnc bed, along with double sided tape. It needed to be extra secure.

I started out with a different, less complicated sound castle. But I needed to condense it, so that's how we ended up with this one. After 5 unsuccessful prototypes, that is.