Introduction: A Great Sounding Bluetooth Speaker Build | Upcycled!
A while ago, my friend sent me a photo of an old speaker case lying on his rooftop. As you can see in the image (in the next step), it's in a horrible condition. Fortunately, when I asked him to give it to me, he agreed. I had been planning to build a loud Bluetooth speaker and this marked it's beginning! It's not going to be easy to turn junk to something neat, but I will not give up on this particular one because it involves recycling wood.
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. If you've seen my previous project (which was also a Bluetooth speaker by the way), you may realize that I'm pretty concerned about the aesthetic appearance of stuff, especially furniture. So even this build will have a pleasing appearance. And trust me, even after having all these properties, the speaker system 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. I will be writing the instructable simultaneously as I build the speaker, so sit back and experience my building process as you read ahead...
Materials and tools:
1x Woofer ~30-60w https://www.amazon.com/Dayton-Audio-PC105-8-Full-R...
1x Subwoofer ~30-60w https://www.amazon.com/BOSS-Audio-CXX8-Car-Subwoof...
Wood (or MDF board)
60w Audio amplifier board: https://www.amazon.com/Aideepen-TPA3118-Digital-Am...
Bluetooth audio receiver board:
Wood glue / Adhesive
Covering material (eg. Vaneer, fabric or chart) : Sample: https://www.amazon.com/Sauers-SCV-2X8-WLNT-FC-Waln...
Furniture legs (optional) https://www.amazon.com/Furniture-Glides-Straight-W...
Smps power supply (12-24v min 2A) https://www.amazon.com/TMEZON-Power-Adapter-Supply...
5v DC wall adapter https://www.amazon.com/Certified-Charger-Universal...
Self tapping screws and nails https://www.amazon.com/Parts-Express-Self-Tapping-...
Hammer, screwdriver, pliers, etc.
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Step 1: Restoration of the Old Speaker Case
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. Some expensive wood might make a better case but if you want to keep the cost low, just use MDF. 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 glueing 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. Tip: In case you don't have many clamps, use something hard and flat (like a CD or acrylic) below the clamp so that the force is distributed over a large surface area. This will also avoid too much pressure on the wood where you clamp it.
Now I will leave the box untouched for the night so that the glue can dry. Hopefully everything will be fine tomorrow morning.
Step 2: From Old to New...
After examining the speaker today, I was pretty happy seeing that the adhesive has done it's job well. The wood had become a little stronger. I only hope it will handle the vibrations of the subwoofer. Now it's time to hide the wood's old appearance and strengthen it a bit more.
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 a plier. Because of being rusted, they could be pulled out from a little amount of force. Although that face was still stuck on to the case pretty well, even after removing the nails, I nailed a few 1 inch nails around the corners, to avoid the face from being damaged due to a lot of vibration.
I then moved on to the bottom face and removed the nails that held the four rubber legs. At first my plan was to replace them with new ones, but the old ones look undamaged and clean. So I might use the same. Anyway that is to be done after covering the wooden surface.
To cover the surface, I'll be using 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.
Step 3: 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. They make very good quality drivers at decent prices. You can find the link in the 'materials and tools' section of the instructable. I've also provided the link to buy a subwoofer. While these could make very good drivers, neither of these brands can be found here in India. So I had to buy alternatives. 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.
Step 4: A Little Make-up
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 doing the same, I'll suggest using a thin piece of MDF or wood instead. 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 this 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 looks beautiful. This small touch can change the complete appearance of the final product.
Step 5: Wiring the Circuits
Now let's have a look at the amplifier. Mine is a Tpa3118 60w mono Amp. I would suggest using a stereo Amp. A good option would be a Tpa3116 50w x 2 stereo amplifier. You might say that I always suggest different materials than what I use. But this is because here in India, finding some stuff are difficult so it's actually me who is using alternatives. 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 I couldn't find the Tpa3116 Amp, I had to use the 3118 one. I shall connect the two drivers in parallel, although it's not preferred to connect a subwoofer and a mid range woofer in parallel. After a quick test, everything seems to work fine.
Here's the plan for the connections. 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. A 5v buck converter or a Lm7805 may be taken in parallel from the 12v supply to step it down to 5v and connect it to the input of the Bluetooth module.
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. So the only way was to either use an audio transformer or separate 5v power supply. I went with the second idea and made the final design. You can find the wiring diagram in the images above.
Step 6: The Final Assembly
I made all the connections as per the plan and fixed the amp inside the box, on the back face with self tapping screws. The Bluetooth module didn't have any holes, so I had to stick with double sided tape. The output of the Bluetooth module has three terminals while the input of the amp has just two. So I connected the ground of the Bluetooth to the ground of the amp, and then I soldered the left and right channels of the Bluetooth together and connected them to the positive input of the amp.
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 ready to finish it up. All I need to do is to stick the front piece I made earlier.
Step 7: Final Words...
This build required quite a lot of time and work, but when I look at the speaker and the box I started with, I realize the worth of my work. This project has come out to be beyond my expectation. The sound is very good, although not insanely loud, because of the 24w power supply instead of a 60w one. I'm pretty happy with the quality of the sound and the bass.
All I want to say is, before buying something new, especially to replace some existing product, please think a few times. You can upcycle the existing one, with a little hard work, to come out with something better than what you thought of buying for that money. Please recycle stuff like wood that can help tackle environmental problems. Doing so, you can be the part of a small change that can make a big difference!
Thank you for reading my instructable. I hope you will enjoy upcycling something as much as I did in making this one.
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