Best CNC Bluetooth Speaker - the Sequel

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About: I'm a college student with a passion for engineering, high voltage, and cool projects in general. I have made a 5ft Tesla Coil, 8.5 ft. floating arm trebuchet, a bluetooth speaker, racing drone, and many oth...

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

Supplies:

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 :)

Teacher Notes

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Step 1: Supplies

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.

Step 2: Design Process - First Spec

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.

Step 3: Schematics

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.

Step 4: The Sound Castle

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.

Step 5: Designing Around Hardware

With my first speaker, I gave myself loads of room in the interior and didn’t worry about condensing the design.
I wanted to make a powerful, yet compact speaker this go around. It gives 3x the power of the other one, with larger drivers, and yet is roughly the same size. How? With tight tolerances. The bottom half was designed with less than 1/64” of tolerance. I actually had to sand the speaker magnet a hair for it to fit better. The top half was going to be a larger cylinder. But it wanted the dimensions to be roughly equal to the bottom half. So I created my “core” of electronics for that half, and put them in the center of a block of wood. I could push other 90 degree pieces in the mitered slots, and measure the furthest line away from center. This worked perfectly as my core was rectangular. So while the diameter (diagonal of the rectangle) is larger than the bottom, the thickness is roughly equal. I now have 1/16” of tolerance, without any large 3/8” gaps on the faces had I made a larger cylinder.
Hopefully that made sense. The pictures explain better than I do. I rearranged the “core” many times to put the electronics together as compact as I could.
The point is if you want a slim design, design with the hardware in mind.

Step 6: All Things in Time

The only point of this step is to stress that this was put together in a very specific order.
Because it is composed of two airtight halves, I needed a way to carry wires between the two. Hence the vinyl tubing. It connects the air pressures and the electronics at once. But, it needs to travel through three plates of wood, and in between the sound castle. Keep that in mind and don’t glue stuff up out of order. Clamps were heavily used, along with gorilla glue and wood filler in some cases (oops haha).
Permanent seals were made with wood glue, and removable pieces (the top crown and subwoofer plate) were attached with screws and liquid electrical tape. Keep it airtight, but don’t make it impossible to fix and improve.
I sprayed the paper speaker cones with three coats of polyurethane to make them weatherproof.
Also, note on glueing up wood blanks - use a lot of clamps. Especially if you used thin strips of wood.

Step 7: Finishing Up

Once it was all glued together, I filled in all cracks and slight divots with wood filler. Another half hour later, came 3 hours of sanding. I sanded the whole thing, then put on 5 coats of satin polyurethane.
The top disc is one of the most distinguished features on this build. I did a vcarve inlay, putting purple heart in a maple disc. That is a process in and of itself, but a familiar one as inlays is what my small business specializes in. The disc received high gloss poly, to make it stand out. It is attached to the passive radiator, and vibrates with the music.

Step 8: CNC Tips

Just a few quick things.
Be wary of feeds and speeds for your materials. Don’t chip or burn it. Make sure you secure each piece completely unless you want to remake stuff. (I had to.) Zero each piece every time. Even when just flipping it over. This carving requires at least 1/32” of precision to fit together properly.
And finally, know what side to carve first. You can’t secure a curved edge to a flat table.
Be safe!
Side note:
I can’t just give you toolpaths because every machine, bit, and blank is different. I used Vectrics Aspire, though fusion360 does great too.

Step 9: Good Luck!

This is not a perfect speaker, nor is it a perfect instructable. This is here mostly to get you guys to think, as duplicating it 100% is literally impossible.
But, anyone can make something just as good, or better.
I taught myself fusion360 to make this. This is my first model on this software, and my first model in nearly two years. Nearly all of the skills used here were self taught, or things you learn in a basic wood shop class. Just make something!
Ask me for help, question etc. I’ll do what I can. But I hope you all have enjoyed following along, and learning the design process I went through to make this.
-P^2

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    hardwiredman

    6 weeks ago

    So amazing what was accomplished here with just an x y and z axis!