Heya! So you want to build a speaker system? Well in this post you will find out how to do exactly that. Except, this is more of an up-cycling rather than building from scratch.
A while ago, my friend sent me a photo of an old speaker case lying on his rooftop. It was in a horrible condition. Fortunately, when I asked him to give it to me, he agreed. I had been planning to build a Bluetooth speaker and this marked it's beginning! It's not going to be easy to turn junk to something neat, but recycling wood is a great thing!
So the plan is to build a Bluetooth speaker that can push a whopping 60w of power to the drivers! The amp I've chosen for this is an inexpensive 60w mono amp with a clear sound signature even at high volume. The speaker will also include a subwoofer for good amount of bass. Not forgetting to keep the appearance attractive. And trust me, even after having all these properties, the project will be quite inexpensive to build.
I will be providing international purchasing links to most of the materials, so that you don't have to wander around different online stores to find similar stuff that I've used. So for now, sit back and experience my building process as you read ahead...
Materials and tools:
Tpa3118 amplifier: Purchase on amazon.com
1X Woofer: Purchase
1X subwoofer: Purchase
Wood/MDF(Fiberboard)
Bluetooth audio receiver module
12v 2A DC power supply Purchase
5v DC power supply Purchase
Self tapping screws
Hammer, Screw driver, Pliers...
Making the outer body:
If you're going to build the outer case from scratch, I would recommend fiber board (MDF) over wood since it is more dense. Being dense means good amount of rigidity which provide good damping. In other words, the sound would be clearer and have better quality on MDF compared to wood. Anyway, in this case, I'm going to restore the old wooden speaker box instead of building a new one.
As I mentioned earlier, the case is in a pretty bad condition. It, being left on the roof, had to go through different weather conditions, under sunshine, rain and what not. The wood has gone quite weak. Restoring it to a new speaker will take a lot of work. Since it is a budget build, this is probably the best way to cut down on the total cost of the project. So let's get to work...
I began by cleaning the inside of the speaker, which had a lot of dust and twigs. After that, I removed the black wooden covering all around the box. Some parts were stuck too hard to the wood and required a lot of force to remove. If you're doing the same, I'll suggest wearing gloves to avoid tiny pieces of wood getting inside your skin. Trust me it hurts.
I later used a sandpaper to remove any rough surfaces, but then the wood started showing it's age. On the front part of the box, the top layer of wood started peeling off. At first I thought I can just remove that layer off, anyway removing one layer will not weaken the wood. But then I realized that I underestimated the wood's age. After removing the first layer, the second started coming out.
This time I couldn't remove it because that would really weaken the wood. So instead, I thought of sticking it to the wood underneath. I used adhesive wherever the wood was peeling off and clamped the wood well, especially around the holes where most of the wood was peeling off.
Fix this, Make that…
After twenty four hours, I was pretty happy seeing that the adhesive had done it's job well. The wood had become a little stronger. Now let’s give the box a good look.
First of all, I removed all the rusty nails from the front face. It wasn't a hard job. Since I had removed a layer of wood earlier, the heads of the nails protruded out from the layer underneath. It was just a matter of pulling them out using pliers. Because of being rusted, they could be pulled out from a little amount of force. I nailed new 1 inch nails around the corners, to avoid the face from being damaged due to a lot of vibration.
To cover the surface, I’ve used black chart. This is quite a hard material and has a nice matte look, perfect for our build. The only problem though, is that it is not waterproof. Nevertheless, it's fine, considering it's low cost.
First, I cut the chart according to the dimensions of my box. I scored along the folding lines using a screw driver (any blunt object will work). I then stuck it on the wooden box using adhesive, making sure to apply lots of it, especially at the edges. I didn't stick all the faces at once. First, I covered two opposite faces and placed the box in such a way that one of the covered faces was facing up. Obviously the other will be at the bottom. In this way, I can place weights on the top face and let it dry for a while, allowing the two faces to stick well to the wood.
After covering all the faces, we need to work on the front of the box, where the speakers will be fixed.
Choosing the right drivers.
Please note that I shall be referring to the speakers as drivers, to avoid confusion. My build will have one mid range driver (woofer) and a low frequency driver (subwoofer). I didn't want to order them online because they'll take a lot of time to arrive. So, I bought them from a local audio store.
For the mid range driver, I would suggest speakers by Dayton Audio, if you can find them. They make very good quality drivers at decent prices. You can find the link in the 'materials and tools' section. I've also provided the link to buy a subwoofer.
The holes in my box measure 6 inch and 4 inch, and I've bought the drivers accordingly to avoid any sort of carpentry. Make sure that your drivers are rated according to the wattage your amplifier can supply.
Design the front.
If the whole speaker is made black, it will become boring to look at. So we need to make the front attractive. Most high end speakers like Amazon's echo or Google Home Max are covered with a nice looking fabric. So I'm going to make something similar. After searching for a while, I found an old T shirt of mine which had the exact fabric which I was looking for. After washing it well and drying, it was good as new.
I took a stiff piece of cardboard and cut the required shape for the front. After cutting out the speaker holes, I cut another similar piece and stuck them together for rigidity. If you're wondering why there's a little hole in the left side, it's called as a 'port'. It allows passage of air into and out of the box so that the subwoofer can function properly. Generally, ports contain a small pipe whose diameter and length is precisely chosen for resonance with the bass frequency for, obviously, good bass. But I didn't want to complicate it too much. In case you want to add a pipe, you can use an online calculator.
After sanding the edges and curving the corners, I cut a piece from the t-shirt and stuck the fabric on the cardboard. It rook quite a lot of time to stick the fabric around the curved corners and the speaker holes, but the final outcome is beautiful. This small touch can change the complete appearance of the final product.
The heart of the project!
Let's have a look at the amplifier. Mine is a Tpa3118 60w mono Amp. I would suggest using a stereo Amp, if you can find a decent one. A good option would be a Tpa3116 50w x 2 stereo amplifier. A stereo amplifier would be better because you'll have full control on your subwoofer independently. You may add a low pass filter or a crossover. Since the Tpa3116 Amp ships from china and would take a long time to arrive, I had to use the Tpa3118. I connected the two drivers in parallel, after a quick test everything seems to work fine.
Here's how the connections may be made. First, the 12v power supply goes to the power terminals of the Amp. The input of the amp goes to the output of the Bluetooth module. Then the output of the amp goes to the woofer and subwoofer in parallel.
But there's a problem. If the amp and the Bluetooth module is powered from the same supply, a weird sound appears in the drivers, even when there's no music playing. This is because of something called ground loop. It's due to the two audio devices sharing the same ground. This can be fixed by adding n inexpensive 5v DC-DC isolating converter.
While this is the best plan for the connections, I couldn't find the isolating converter in India. So the only way was to either use an audio transformer or separate 5v power supply. I went with the latter and made the final design. You can find the wiring diagram in the image below.
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| Wiring Diagram |
After another quick test, I realized that the inductors of the amp were getting hot. So, I stuck a heatsink on them. Then finally I made a hole in the back to pass the two power cords, stuck some epoxy compound to seal the hole and made the remaining connections. I then fixed the two drivers on the respective holes with self tapping screws. Again a successful quick test, and we,re almost done. All that is left, is to stick the front cover we made earlier.
Level up the volume!
Great! We have finally finished building our very own 24w bluetooth speaker! Why 24w and not 60w? Well, the power supply can only provide 24w. If a 60w supply is given, it will surely provide sound of 60w! Well, for me 60w would become an overkill, 24w being loud enough.
Now for the golden question: How's the sound quality? It's very good. It can provide very pleasing sound even at higher volume, thanks to the Tpa3118 chip.
So all in all, this up-cycling project looks like a success. Not to mention how beautiful the speaker looks. Hope I could inspire you to make stuff on your own. If you are confused on what to make for your next diy project, head to the maker's corner! Thank you and see you in the next one!
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