Since getting my CNC router, I have wanted to really test its ability to produce accurate and high quality parts that would make up a finished product. Picture gallery at the end of this post 🙂
Designing and making a bluetooth speaker has been in my mind since seeing a video from DIYPerks who used a cheap amplifier/bluetooth combo circuit board. I ordered one and then a few weeks or so later saw another video where he sandwiched acrylic between wood and it was edge lit with LEDs:
This was the inspiration I needed and I set about making designs in my CAD program of choice: Autodesk Inventor.
After a few days I had a finalised design:
For me, white oak was the obvious choice. It is one of the most beautiful woods and has a particularly nice endgrain which will show on the sides of the speaker. I have a good local source of offcuts which I can use for this project. It is in fact the only hardwood I use in my workshop besides birch-ply!
I did’t have any acrylic at the time of making this but I did have a large stockpile of polycarbonate left over from some other work, I doesn’t quite have the optical properties that acrylic does but it works just as well for this application. Polycarbonate is much much tougher than acrylic but it is softer and scratches more easily, using rubber feet would therefore be essential to aviod the polycarbonate getting scratched on the bottom of the case. The edges of the plastic would be sanded down so they are frosted and will diffuse the light nicely.
From these designs I could easily load them into my CAM programs. For the front panel, which had pockets to mount the speakers themselves further forward in the case (see later photos), I used MeshCam as it does all the work for me and even calculates finishing offsets and a machining margin for better chip clearance. This all helps achieve a good edge finish. For the rings that make up the body I used CamBam as it is easier to work with when doing 2D contours. This can be seen in the video I apologise for speeding it up so much but it would be a very long video if I didn’t!
The machining of the oak rings went flawlessly, They cut cleanly and with a finishing pass they were almost 400 grit smooth straight off the CNC! I did have an issue with my machine with the last piece as I didn’t clean up the dust between jobs and so some built up on the rails and caused a slight jam but the machine recovered and it didn’t affect the overall finish so it was fine. I used a 3 flute 6mm carbide endmill which handled a 3mm DOC at 1500mm/min feed perfectly, by the end of all the parts the tool was still just as sharp as when I started so it seemed there was no rubbing of the tool.
The tabs that hold the piece in place during the finishing passes can be cut with a knife and then removed completely with a flush trim router bit.
The polycarbonate rings were machined in much the same way but with lower feeds and speeds. They came out smooth as with the oak and I left the burrs on as they could be sanded off once the case was assembled.
The layers of the case were held together with some high strength epoxy adhesive which holds very well.
After everything was glued together and the back panel screwed in place it was just a matter of sanding and scraping everything down until it was perfectly smooth and flush. The polycarb strips could then be frosted using fine sandpaper as well.
I used my 3D printer to make the air inlet which provides additional base to the speaker and gives the sound a bit more body than you would otherwise get from a sealed case.
It wasn’t the best quality print but unfortunately my Prusa was having a few weird issues!
I wanted it to be battery powered of course but I also thought it would be cool if it could be charged from a USB outlet. The battery is therefore a 3.7v 12000mah battery and is connected to a small charging circuit that does offer over discharge protection but unfortunately the output is limited to 2 amps or so and the amplifier draws more than this. The terminals of the battery are also connected to a dc-dc boost converter which steps the voltage up to 12v to power the amp. Again the particular one I used can not really handle the power very well and so does some weird stuff when turning the speaker on as their is an initial current spike. I will change this at some point for sure!
I 3D printed a little holder which I glued a micro USB breakout board into so that the whole speaker could be charged from a USB 5v adaptor. The charging circuit can only charge the battery at 1A max though so it does take 12 hours to charge the speaker from flat… oh well!
As you can see in the last picture, I also wired in some 12v LED strips (blue) which added to the current draw and means I really need to replace the DC converter. It was a complete rats nest inside but you can’t really see any of it, event through the polycarbonate so I was fine with it. Everything was stuck down inside with foam tape to dampen any vibrations and keep the electronics securely mounted.
The final touch was an ‘angel eye’ led switch which has a blue ring around the button.
Final Thoughts and What I Would Do Differently:
I am quite proud of how well this project progressed and the end result was well above my own expectation! The grain of the oak is extremely nice and gives the speaker a natural and elegant look coupled with the smooth glow of the LED rings.
The electronics need some work to increase their efficiency and function. The amp is really designed to run on 15-20v but I didn’t want to push the DC converter any more than it was already. I will replace it with a better one.
Once this is sorted the LEDs can be upgraded to give a more even glow as it is a tad patchy due to the lack of power to drive more diodes.
Futhermore, I believe that using some calculations to correctly size the air inlet and buy a pre-made plastic one would improve the sound quality as it still sounds a little too much on the high end. This could be down to the quality of the speakers which isn’t great so perhaps investing in some better speakers would play a bigger part in increasing sound quality. The ones I selected were the only ones I could find in the 4 inch size at a price I was prepared to pay, any bigger speakers would make the speaker a little too bulky in my opinion.
Anyway, thanks for reading/watching this project! I hope you liked it!