We are four students and we have made stereo speakers for 'Creative Electronics', a Beng Electronics Engineering 4th year module at the University of Málaga, School of Telecommunications. (www.etsit.uma.es).

Each of us has made his own speaker so there are some differences between the four speakers. We will explain each option and you will be able to decide the best for you :)

Let’s begin!

Step 1: Materials

Speakers and amplifier

4x Speakers SQ-2504 4W
2x TDA 7266 2x7W
4x 4k7Ω Resistor
2x 470µF Capacitor
2x 100nF Capacitor
4x 0,22µF Capacitor
6x Screw terminal (optional)
2x Heat sink (optional)
1x Pcb board prototype

Control elements

4x Switches
1x Jack 3,5 ST
1x Potentiometer tand. 4k7

Voltage supply

1x 3.7V Li-ion Battery >2000mAh
1x tp4056 charger module
1x 12V 1A adapter
1x Power supply connector male
1x Power supply connector female

Bluetooth (optional)

1x Bluetooth receptor

Tools needed

Soldering Iron and soldering tin
Wires
Saber saw
Drill
Flat screwdriver
Fret saw
Jack to clamp
Screw terminals
Jack-Jack wire
Sandpaper

Step 2: Speakers

We wanted to make a powerful and good quality speakers, so we have decided to make a system formed by four 4W and 4Ω speakers.

The model chosen specifically was the SQ-2504 4W from Fonestar.

(http://www.fonestar.com/catalogo.php?id_prod=2578)

Step 3: Amplifier

We have chosen the tda7266, a 7W dual bridge amplifier. Since each amplifier has two outputs we will need two of them. We have get the block and application diagram from the datasheet.

As can be seen in the diagram, additional components are required.

Then there are two options: you can buy the amplifier and components and weld them together or you can buy the complete module witch it is found in some online shops.

Unfortunately we couldn't get this module because we had no time to wait for an international shipment.
So we did the first option, we welded the two amplifier and their components in a prototype board.

If you choose this option we recommend you to draw in a paper the components placement before beginning to weld.

In my case I used screw terminals to connect the outputs (speakers) and the voltage supply but they are not necessary, you can use wires directly as I did with the input signals.

You can see final result in the pictures.

Step 4: Electrical Scheme

1. The first option is the electrical scheme for a basic configuration. As you can see, R signal goes to two speakers (what are in the right side) and L signal goes to the others speakers (left side).The potentiometer at the image is only one tandem potentiometer.

2. A second possible configuration is thought for connecting two speakers systems so that the first one has four speakers with R signal and the second one has four speakers with L signal. In that way we achieve a full stereo system.

Switch let you to change the signal input.

You only need a jack female connector although there are two connectors in the scheme.

3. The third configuration consists of a wireless connection using Bluetooth. You can choose between jack input and Bluetooth input.Bluetooth module proposed use a jack connector so you don’t really need other switch, you can use the same jack female connector.

You can also see the schemes for potentiometer, jack and switches connections.

Step 5: Supply Voltage

Our amplifiers need around 11V for a good amplification.

Therefore we need a supply voltage near this value.

We have thought in a dual power system that uses batteries outside home and a power supply adapter for not to worry about battery autonomy.

Step 6: Power Suppy Adapter

12V 1A power adapter is easy to find in shops and gives a good amplification.

You need to get female and male connectors.

Hack your power adapter by cutting his connector and welding the connector that fits with your female connector.

Step 7: Batteries. (Under Revision)

Several batteries in series provide more voltage, but are more difficult to charge. Finally we have realised that only one 3.7V battery works very well and we get a good amplification. Anyway, the tda7266 minimum input value for voltage is 3V.
This is the easiest option, if we find other form to connect a battery with more voltage we will be editing this step with the new information.

I have used a 2100mA Li-Ion battery, in particular a battery from a Samsung smartphone (express 2). I have seen a lot of samsung batteries that are good options because they have a big capacity, a square form and lower dimensions than others batteries with similar capacity (battery must fit in the box and dimensions of central space are 7x7x7cm)

Tp4056 charger module only works with only one li-ion cell, so we can use it in this case.

You can see the battery connections on step 11.

Step 8: Wood Box

The choice of box material is fundamental to achieve a good acoustic. Dense woods are the best for avoid vibrations and interferences but it is also more expensive. Therefore medium density wood is maybe a good option due to the less price and good qualities it can offer.

Two of our boxes are made by a professional carpenter in red steamed beech wood and the others two are made by ourselves in less dense wood (pine wood).

You can see the plans in the pictures:

Pieces dimensions and quantities.
Plan view. The central hollow is empty for control panel and the others four hollows are for the speakers. In control panel we will put the switches, the potentiometer, the jack connector and the power connectors.
Detailed front view for speakers hollow.
Profile view. That’s how the pieces are joined.

Step 9: Wood Box. Process

Cut the pieces with a saber saw and sand down them.
Mark the dimension for hollows.
Mark the center of the speakers holes.
Make the holes with a drill.
Make the four smallers holes to attach each speaker to the wood with screws.
For control panel make holes with a drill and use a saber saw or fret saw to achieve the final form.
Due to the fact that jack connector doesn’t have a square form I use a plastic piece to cover the hole. Power connector hole also have this plastic piece. To cover the switch hole you can use wood putty.
You can join the small pieces with wood glue or screws and use silicone to isolate junctions well.
Join the other pieces after making the electrical connections (next step).
It’s the perfect moment for painting your box! The easier way is a spray paint.

Step 10: Electrical Connections

It’s time to make the assembly of the entire system!

Weld two enough long wires at each speaker and attach it at the box. You can put a metal mesh to protect the speaker.

Now, you only must follow the electrical scheme you have chosen and make the connections. I chose the first one.

Step 11: Battery Connection

I bought a samsung battery connector to avoid welding wires at the battery, so the wires are welded to the connector and battery is connected by pressure. You can extract the battery when you want.

If you don't want to open the box in order to connect the micro usb and charge the battery you can make a small hole in the back cover for the micro usb connector.