Diy Stationary Bookshelf Bluetooth Speaker

Hello everybody, hope you're doing well

in this instructable, I'm going to show you how to make a stationary bookshelf Bluetooth speaker.

It's stationary because it's not intended to be moved, which is also why it's not battery powered but it's mains powered. It features a 100w amplifier and a 5.0 Bluetooth audio module which are both placed in a wooden box. To make the box, I used beech wood and fir wood, I had some scrap piece of fir wood and additionally, I got myself a piece of beech wood. I used those two because I thought that they are gonna contrast each other nicely. I will also share with you some tips and tricks on how to check if everything works properly and do some troubleshooting if you decide to give this project a go yourself.

Bluetooth audio module

Power supply 2x

Amplifier (here I used tpa3116 class D mono amplifier)

Speaker

Speaker grille (optional)

Tweeter

100Ω resistors 2x

Wooden planks

L profile wooden batten

Cable connectors

Screws

Nails

Wire

Switch

Capacitors and coils ( or a crossover)

Mains cable

Tools: Soldering iron as well as some solder, drill, hot glue gun, jigsaw (or a handsaw), belt sander (or files), screwdrivers, pliers, utility knife.

I know I wrote a list of materials, but here I'm gonna explain them a bit more. Ok, so speakers are limited by the electrical energy that they can convert into audio, which means that you need to make sure that the speaker that you are using can handle the energy that the amplifier produces,

so, for example, I used a tpa3116 class D mono amplifier which has a maximum output power of 100w into 2Ω load, since I used a 4Ω speaker I got a maximum of 50w output power.

In this step make two holes, one for a speaker, and one for a tweeter.

First, measure the speaker and a tweeter that you're using, and trace the outline on the board, then drill a hole for a jigsaw blade to fit through, and then cut out a circle that you traced out before. Repeat this for a tweeter as well.

Start by cutting out the front side (the one with speakers on it), and then a backside of the box, since those two are identical use dimensions of the first side (that you cut out from a wooden plank) to trace out the dimensions for the backside and then cut that side out as well.

I didn't show you any dimensions here because they are not critical and they may vary.

In this step make the top and bottom sides (and also at this point I changed the wood that I was using, simply for them to contrast each other). Start by measuring the length of one of the sides you made in the previous step, trace it out and then cut it out.

Repeat this for the top side as well.

At this point, you should have 4 sides of the box, and in this step assemble them so you could trace out the other two sides and then cut those out as well.

In this step put the box together but leave one side open so that you could install electronics in the box.

Drill pilot holes and then use screws to put the box together.

Ok, for this to work you need to power up both amplifier and a Bluetooth module but the thing is that you shouldn't power them from the same power supply, and ground loops are a reason for that. Ground loops are caused by the interconnection of electrical equipment that results in there being multiple paths to the ground, although you could solve this with one of those ground loop isolators but I didn't do that here. In order to solve this problem, I used two power supplies. One from an old laptop charger ( for an amplifier), and the other one for the Bluetooth module (5v).

Note that if you use one power supply with a ground loop isolator you should also use some kind of a step-down converter to power the Bluetooth module.

You could either take apart those power supplies to expose the wires inside, or you could use something like cable connectors to make proper circuit connections.

If you use premade amplifier then you should be able able to see some letters on it, and they tell you what goes where. VCC stands for power supply input OUT stands for output (this is where the speaker goes) + GND - (or something like IN) stands for input (signal from Bluetooth goes here). And on the Bluetooth module, you should see some letters as well, more precisely R, GND, and L. This is stereo output, and since this is a mono amplifier you need to mix them to mono. Simply use two 100 ohm resistors. One resistor goes to R, and then the other one goes to L and twist together the ends of those two resistors. And also solder a small piece of wire to GND (this is an output of a Bluetooth module).

Ok, so this is how it goes connect the output of the Bluetooth module to the input of an amplifier. Speaker and a tweeter go to the output of an amplifier, and lastly connect power supplies, one to the amplifier and one to the Bluetooth module.

And of course, to power up this whole situation make sure to drill a hole for the mains cable. And also hot glue all components down to secure them in place.

To get the best results you're gonna need to do some experimenting.

So the purpose of the crossover is to eliminate some frequencies that are going into the tweeter. Simple crossover is a combination of capacitors and inductors. In my case, I used two 10 uF capacitors connected in parallel (which is equivalent to one 20 uF capacitor) and I also used one hand-wound coil. Capacitors and coil are connected in series which means that one wire from the amplifier output goes to the one wire of a tweeter and the other wire from an amplifier output goes to the one wire of a coil, then from a coil to a capacitor, and then from a capacitor to a tweeter. To sum it up the output of an amplifier goes to the speaker and then over crossover to a tweeter.

With electronics in place close the last side of the box.

This L profile wooden batten has a 90-degree bend which is perfect for the edges of the box. Start by measuring out edge by edge and then cut out those pieces. After that use some nails to secure those pieces in place and that is it.

Lastly, add a switch, and to do that you should either cut the whole mains cable or just one wire, in my case I snipped one wire with wire cutters. With a switch in place, this build is over.

Thanks for reading and checking out my project :D.