Laser Cut Bluetooth Speaker

I made a fully laser-cut bluetooth speaker. I suppose the electronics and speakers weren't laser cut.... but the entire casing is laser cut.

I am pretty new to audio circuits and wanted to learn more about speakers and amplifiers. Bluetooth was a pretty cool addition to the project as well. Basically, I used a bluetooth headphone set, fed through an amplifier and finally output through two speakers. The entirely laser cut frame is because laser cutting is fast, looks clean, and is easy to replicate for assembly. Let's dive in!

Supplies

A lot of these supplies I had from previous projects or from looking around the house, but I tried to add links for everything. I am sure you can source some of these cheaper by spending more than the 5 seconds I spent looking on the internet.

1. Superglue
2. 1x2 ft sheet of 1/8inch plywood (The link is for a 4ft x 8ft panel)
3. Cheap Bluetooth hphone
4. Amplifier
5. Tweeter (This is a 2-pack, If you only want one, there are other options)
6. Subwoofer
7. Wire
8. Push button (momentary)
9. Rocker switch
10. M2 x 6mm screws (these need to fit the amplifier and battery holder mounting holes)
11. 1/4 inch screws (these need to fit your speaker mounting holes)
12. 4 X 18650 batteries
13. 4 X 18650 battery holder
14. 18650 battery charger
15. Magnets

Tools

1. Laser Cutter
2. Soldering iron and solder
3. Crimping tool and connectors (optional)

Okay, so this diagram may look like a lot, but its really not that bad, so let's break it down:

1. There are two independent circuits that I am controlling with a DPST switch. A DPST, or "Double Pole Single Throw" switch, basically means that I want to turn on two different circuits with one switch.

2. I have the speaker circuit, which is a 12V powered circuit (the red-orange highlighted block) and the 4V Bluetooth circuit (the purple highlighted block).

3. The Bluetooth circuit is powered by one 18650 battery and is turned on by turning on the DPST switch and then holding the push button for 3 seconds. The Bluetooth circuit and single battery share a ground.

4. The speakers operate at about 12 V, so I power the amplifier with three 18650 batteries to get about 12 V. The amplifier is turned on by the DPST switch as well. The speakers, amp and 3 batteries all share a ground.

5. The Bluetooth circuit outputs an audio signal, which is on the scale of millivolts, into the amplifier, which then boosts it to the order of 12V.

6. There are a couple basic rules when selecting speakers and amps:

• Match the impedance rating of the amp to the speaker (8 ohms amp to 8 ohms speakers)
• The amp should be able to provide 1.5-2X the power the sum of all your speakers. 25W speaker + 10W speaker = 35W. 1.5* 35 = 52.5W. The amp can provide 50W which is pretty close to 52.5. As long as we don't kick the speakers up to full power for a long time, we'll be good. I don't see myself doing that anyways - I'm more of a chill listener.

7. I have one subwoofer and one tweeter speaker. They are supposed to operate at different frequencies - Subwoofer hits bass and midrange frequencies (60Hz to 4kHz). Tweeter hits midrange and brilliance frequencies (2kHz to 12kHz). Audio Spectrum reference

I did not do this, but if I wanted these to operate in their sound range I could (and may for a future iteration) feed the audio signal through low-pass and high-pass filters respectively rather than feeding into the speakers directly. This way, the bass only plays lower and the tweeter only plays higher frequencies - its more efficient this way.

I didn't bother because the sound quality was pretty good as it was.

This is the one hacky thing I had to do. Using a screwdriver, I pried open one of the earphones to remove the circuit. Luckily it was pretty well-labeled and easy to figure out.

1. I cut the two wires leading to the LiPo battery that was mounted on the circuit and peeled the battery off.

2. I soldered two wires to B+ and B- wires that I just cut (the red and blue wire pair in the picture to B+ and B- respectively)

3. Okay, feel free to skip the reading and just follow the soldering I did with the yellow and blue wires in the picture, but If you are curious:

• The earphone turns on by holding the middle button for 3 seconds. This means the battery is always powering the chip and the middle button is being read by a pin on the chip.
• To find which pin was being read by the middle button, I used a continuity tester on my multimeter to find which pin was connected to the switch. Note that I did this with the battery detached so I did not accidentally short anything.
• After I found the pin (pin 9, if it follows the normal DIP numbering scheme), I soldered the yellow wire to it, and the blue wire to B-, since that is what the middle button was connecting it to.
• With those two wires exposed, I could then wire in my own push button to turn the Bluetooth chip on and off

Basically for all the speakers, battery holders and Bluetooth chip, buttons and amplifier, I soldered wires to their leads so that I could place them more flexibly in the casing.

I also crimped JST connectors to the ends of those leads so that all of the electronics are modular and easily replaceable.

I used fusion360 to design the casing for the speaker. Fusion is cool because its really easy to add dynamic parameters that you can change easily and regenerate the entire drawing. For instance, the speakers I bought were 3 inches diameter. If I bought new ones that were 2 inches or 5 inches, it would be very easy to change that parameter and have the CAD scale automatically.

In the section view (the last picture), you can see how I added a back panel that sits on a thin rim. This is easy access to the inside of the speaker.

The pattern tool was my best friend in this endeavor - I made one joining piece in one corner of the speaker, and from that I was able to pattern it in such a way to get all four edges on the speaker.

I used the project tool and the same patterning to make the accompanying holes for these skeleton pieces.

I added holes for mounting the battery casings, the amp and the buttons. I also added one finger hole so that it is easy to pull out the back panel.

I exported all the bodies of the speaker as .DXF files so that I could import them into my favorite vector editor: Inkscape.

Luckily I did not have to change much - I made some small modifications.

I added some extra holes using the circle tool for magnets on the back panel, and I moved the finger hole to pry up the back panel to the top of the panel to get better leverage.

I then saved the Inkscape file as an SVG and sent it to a laser. This is what the laser cutter gave back to me.

Using the superglue and the smaller, top/bottom panels, glue the skeleton braces in each hole until you have all 20 glued into place.

Glue the side panels into place as well.

Glue the front and back panels into place

Note: I did not do this, but you can screw the speakers in place with the 1/4 inch screws to the front panel before gluing the front panel in place. It is much easier to screw to the speakers in this step. I screwed the speakers in after I had assembled the whole thing and it was quite difficult.

Glue the magnets into place using laser cut circles.

1. Glue the magnet to the circle

2. Glue the circle to the inside of the back panel rest such that the magnet fits into its hole.

3. Repeat with the back panel itself. BE SURE TO MATCH THE POLARITY OF THE MAGNETS

1. Screw the speakers into place using the 1/4 inch screws

2. Use the M2 screws to mount the battery cases and the amp on the back panel

3. Glue the switches into place

4. Connect all the electronics together and push all the wires into the casing

5 . Insert the charged batteries into their casing

6. Close up the back panel

Note: The switch hole cut near the bottom did not work because the rocker switch interfered with the speakers. Therefore, I recut the hole a bit higher so that it fit between the two speakers.

You now have a working laser cut Bluetooth speaker!

You can turn it on by flipping the rocker switch and holding the pushbutton for 3 seconds.

You can pair new devices to it by opening the back panel and pressing the down volume button on the actual chip for 3 seconds. It will enter a pairing mode at which point you can find it in your Bluetooth devices in your phone.

I've added the files to the build below: