Bluetooth Speaker - Quarter Wave Transmission Line

thingiverse

After seeing a post on the CR10 Facebook group by Jason Bach, I decided to design my own "quarter wave transmission line" Bluetooth Speaker - inspired by his work. This thing is incredibly loud for its size and the audio appears to be very nicely balanced considering this is made of plastic. It doesn't rattle or vibrate in any unwanted ways. See video: https://youtu.be/2t4e5r67g8a I had originally planned to sand and finish this, but the print came out so good, I just left it as it is. This project requires 2x 3" speakers and a Bluetooth dual channel 50w Amp - Total cost about £30. All of the parts mentioned in this project can be bought from eBay. Full Bill of Materials below. Firstly, I am not an audiophile. Nor do I know a huge amount about speakers and sound systems. I used some basic math to work out the required dimensions for the enclosure and the transmission line. The math revealed I needed a transmission line (or port/resonator) length of approx 777mm and its dimensions needed to be approx 90mmx33mm. It's essential to use the same speaker drivers as me (listed below), as the enclosure was designed specifically for their respective 'free air resonant frequency' and 'effective cone area'. You can find out more about 'Quarter Wave Transmission Line' speakers and the math involved in a video link I posted in the comments section of this thing. It's similar to the wave technology Bose use. From watching the video, you could design your own enclosure for your own specific speakers. Be advised - This is a large print! It takes approx 90 hours to print in total, and requires a build area of around 300x300x200 - so the CR10 is perfect for this project. The side cover attaches with 6mm x 3mm magnets. 32 pairs of them. I glued them into position, triple checking the polarity of them each time. The side cover also has two little 'locator notches' to ensure it snaps on in the correct position easily. I am thinking about adding a self-adhesive sheet of felt to the side cover, as it 'snaps' on quite violently with the pull of the magnets. I added some self-adhesive foam sheet inside the transmission line because something about absorbing unwanted resonant frequencies. I also added polyester pillow filling (polyfil) to the majority of the transmission line, which improved the bass sound so much. I might even experiment by adding more. There are 4 recesses on the base of the speaker to allow you to fit 4x 1" self-adhesive furniture felt feet so the speaker doesn't vibrate when placed on hard surfaces.. There are 2 holes on the back to allow fitment of a 20mm round on/off toggle switch and wireable 2.1 DC jack input. There is an additional version with no holes on the back too, if you want to incorporate your own ideas. You could easily run this off of some batteries for portability - just connect a 12vdc AC adapter with a 2.1 plug (I had a spare 5A one lying around - I think 2A should work fine too, but not tested yet). I would love to see someone print this in a wood filament!!