In this project, I will take you through the process of creating a mini portable speaker that can be built for under 10 USD in under one hour. It provides great volume at an acceptable level of audio quality (as can be heard above). It is a great build if you are looking for a small, fun and useful project to work on.

Supplies

Hardware BOM

Future Kit Casing
2x Loudspeakers
Audio Jack
2m Multi-Core Wiring
Heat Shrink Tubing
Li-Ion 2x Battery Holder
8x M4 Phillips Head Bolts
8x M4 Washers
8x M4 Hex Nuts
Perf Board

Electronics BOM

7805 5V Regulator
5V 2-Channel 3W Audio Amplifier
2x 3.7V 4000mAh Li-Ion Batteries
SPDT Switch

Step 1: Electronics: Circuitry Part 1

In this step, we will complete the first part of the circuit which includes the Li-Ion batteries, the switch and the 5V regulator (on a perf board). The reason why we need a 5V regulator is because the amplifier board can only handle 5V, however, the output of the 2 Li-Ion batteries in series is 7.2V making it necessary to step down the voltage.

The positive terminal of the Li-Ion battery holder should be soldered to the common pin of the SPDT switch. While the negative terminal should be soldered directly to the GND pin of the 7805 regulator. When soldering remember to be careful while keeping the area you work in well ventilated.

One of the other terminals from the SPDT switch should then be soldered to the positive input pin of the 7805 regulator via jumper wire.

Step 2: Electronics: Circuitry Part 2

For the second part of the circuit, we will add in the other components such as the headphone jack, the audio amplifier and the speakers.

First take the positive 5V output and GND from the 5V regulator and solder it to the audio amplifier board via jumper wires.

Next, take apart the headphone jack until the pins are visible. Then using the pin out diagram above, use jumper wires to connect the correct pins to the audio amplifier board and solder them in place. For aesthetic and organisational purposes, heat shrink tubing can be placed over the wires leading up-to the headphone jack.

As for the speakers, we won't solder those just yet....

Step 3: The Housing

Now its time to create the necessary cut outs that are required in the Future Kit Box. Two circular holes in the front for the speakers and accompanying holes for screws. And one hole in the back for the jack cord and another slot for the switch.

Starting with the front of the box, take the speaker and place it over the box to create an outline for the speaker hole as well as the hole placements for the screws. Use a pencil and create the necessary markings. For the screw holes, use a centre punch to create an indent over each hole and then using a 5mm drill bit and a hand drill, drill out each of the 8 necessary holes.

For the speaker holes, there are many ways it can be done, yet in most cases it can get a bit messy. The method that I recommend is to drill 4 holes each at the outer edges of the circle, and then using a coping saw to cut out the rough shape of the circle. After which, we can take a file and sand down the rough edges.

Finally in the back, a 5mm hole should be drilled for the headphone jack cord and a slot for the switch should be cut out using the similar method of drilling and sawing stated above.

After this is done, make sure the speakers and the switch all fit into their required spots and make any adjustments necessary.

Step 4: Securing Components in Place

After all the cut outs have been made, secure the speakers to the front of the case by inserting the M4 screws from the front and securing them from the back using M4 washers and hex nuts.

Make sure the the headphone jack cable can fit through the hole in the back and pop the switch into place.

Step 5: Solder the Speakers to the Amplifier and Seal the Box

Make the final connections by soldering the speaker inputs to the correct pins on the amplifier board via jumper wire. As a precaution, heat shrink can be used to prevent shorts from occurring between exposed wiring when the box is shut.

Run a final test of the system and make sure everything works alright. Secure any loose screws and fix any dry solder joints. Align up all the components so that the box can close properly and to finish it off, seal the box by screwing it shut.