UPDATE 28 Nov 20: I have just uploaded Version V2.0 - a complete redesign using a 3.3" driver

UPDATE 18 Dec 20: I have just added a wiring diagram - Enjoy!

Just a super stylish, super cheap, fully printable and surprisingly good sounding back loaded horn Bluetooth speaker using a simple 2 1/2" driver and a USD 1 Bluetooth board and amplifier.

First 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.

It is like kissing the frog. You kiss that tiny loudspeaker and hope it turns into a prince. Well it did, kind of...

This enclosure is for a 2 1/2" (6.5 cm) driver I had lying around (working on something slightly bigger, slightly more expensive so stay tuned). You can use it as a Bluetooth (as I do), active, or passive speaker. I have added a small chamber at the back that can easily hold a small BT board + amplifier.

• I am using this MP3 Bluetooth Decoder Board (< USD 1)
• plus a small 2x3 W single chip amplifier board (< 50 Cents)
• plus a simple 5V/1A power supply (USD 1.5) - but any old USB charger will do
• The driver I use is a Visaton 4 Ohm 6.5 cm (2.5") full-range speaker (around $7)

However, basically any combination will do (as long as the driver is 2.5" or smaller so it fits the enclosure - you may have to adapt the mounting holes). It is amazing how much sound you can get out of these ultra cheap components, but of course the more you are willing to spend, the more you are going to get.

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 - looks really good!). Glue the side panels to the body. Attach the front and speaker with M3 screws. The feet (I print these in TPU) are optional.

HOPE YOU LIKE IT AND IF YOU LIKE IT, PLEASE LIKE IT! Thanks!

Enjoy!