This version is a complete redesign, still just as stylish, super cheap, fully printable BUT sounding MUCH better. This back loaded horn Bluetooth speaker uses a 3.3″ (as opposed to the original 2 1/2″) driver and a USD 1 Bluetooth board and USD 3.5 amplifier. Total cost should be around USD 20. The enclosure with the back loaded horn (please read below if you are not familiar with the concept) is also a complete redesign.
However, the concept remains the same. It is like kissing the frog. You kiss that tiny loudspeaker and hope it turns into a prince. And yes, it does… It is truly amazing how much sound you can get out of these ultra cheap components.
The enclosure is for a 3.3″ (6.5 cm) driver. You can use it as a Bluetooth (as I do), active, or passive speaker. There is a chamber at the back for the electronics (BT board + amplifier).
I am using this MP3 Bluetooth Decoder Board (approx. USD 1)
plus a cheap TPA3116 D2 Dual Channel 50Wx2 Amplifier Module (approx. USD 3.5) – this is stereo, so I only connect one channel from the BT board
plus any 12V/1A+ power supply (approx. USD 1.7)
plus a small LM1117 Step Down converter (approx. USD 0.2) – this one is for the Bluetooth module, which needs 5V
The driver I use is a Visaton FRS 8 M – 8 Ohm 8 cm (3.3″) full-range speaker (around USD 12)
However, basically any combination will do (as long as the driver is 3.3″ or smaller so it fits the enclosure – if you use a different driver you may have to slightly adapt the mounting holes).
PRINTING. This should be a simple print. You will notice that the body has a 1 mm cover on one side. This is to give it more stability and make it easier to print and remove from the printer. No support or attachments needed. Print in PLA (or ABS, PETG…) at 0.28 mm resolution and (around) 15% infill. The side panels can either be printed or cut (15 x 20 cm) from 6-8 mm plywood (I use beech). Glue the side panels to the body. Attach the front and speaker with M3 screws. and the back panel that covers the electronic compartment as well. The feet (I print these in TPU) are optional. I have included a 2:1 PDF drawing of the side panels if you prefer to cut them from wood (as I do).
Here a little theory: What is a back loaded horn speaker? Think of it as a reversed megaphone or gramophone. A (front) horn loudspeaker uses an acoustic horn to increase the overall efficiency of the driving element (i.e. the sound coming out at the front). A back loaded horn speaker does pretty much the same. However, here the horn is mounted at the back of the loudspeaker. So you get the direct output from the front of the driver PLUS the one from the horn at the back. Which frequencies are amplified and how well depends on the air chamber, throat (the narrow part), and on the length, design, and diameter of the horn. Particularly with small (and cheap) drivers this can very much improve the sound quality.
Credits:
guppyk
Download 3D models
| File | File size |
|---|---|
Back+Horn+Speaker+V2.0+BL2+-+Bluetooth,+Active,+Passive
|
827 KB |