It's been a long time since I built something cool. Now that it's Christmas holidays, I thought of doing it.
Bluetooth speakers aren't cheap. And if you want a branded/good sounding one, start collecting money from at least a month before. The cheapest I came across was Xiaomi's MI Compact speaker that costs Rs.799 ($11.4) at the time of writing. Definitely not cheap. Also, it has only one 2W speaker, so not even stereo. So I built a Bluetooth speaker from scratch which costed me less than Rs.300 (USD may vary depending on price of components but it should be around $5).The sound quality is great and yes, it is stereo. So let's get to it!
I am writing this instructable at the time of building(except the intro). So it is more like a live instructable with the build.
2x Speakers (2W to 6W each) with impedance 4-8 ohm.
Audio amplifier board. If you are in India buy here: https://robu.in/product/pam8403-mini-5v-digital-am...
Bluetooth audio receiver. Buy it here (India): https://www.amazon.in/Drumstone-Bluetooth-Receiver...
5v SMPS power supply (a 5v 1A mobile charger will work)
Hot glue gun (optional)
Step 1: The Speakers!
Now I could have bought good quality speakers too. The problem is, they are a bit expensive for our budget build. So I took apart my old cassette tape player with quite big 3W speakers only to find that both of them have their diaphragms torn horribly. Neither will they sound clear nor look good. I then realized that I have a piano keyboard (kinda like a toy) which is also quite old and works rarely. I took it apart and found the speakers in good condition, but were quite small. Nevertheless, I took them out and performed a quick test by connecting a 3.5mm audio jack to the speaker terminals and playing an audio directly from my phone at full volume. Seems to work good. Lets move on!
Step 2: The Front Wooden Frame
This is an important part if you're like me and want to make it aesthetically attractive. This is not exactly a frame, but adds to the beauty. What I am going to do is give it a nice wood finish from the front and the rest can be made of hard card board covered with a black hard paper. Cardboard sounds less sturdy than other materials like wood or plastic, but I want this build to be simple and cheap. In case you want to use wood or something else, you're free to do so.
For the front, I cut out an extremely thin wood layered with veneer in a rectangular shape with rounded corners. I didn't dimension it, but used the two speakers as a reference. I sanded the edges and corners to make it look smoother. Now the speaker holes need to be made. The problem is that I don't have a drill. So I am going to use a cutter. Hopefully it should work.
It was extremely hard cutting it with a cutter and I could not get a smooth circle. Now my idea is to cut two rings out of black hard paper and stick it around the holes to hide the uneven cuts. I did the same and now it looks a lot better. I cut a similar piece from a cardboard and pasted it to the back of the thin wood to make it look thicker.
Step 3: The Rest of the Case
Now there are some advantages of cardboard. It is quite strong and easy to cut and shape it. But there's a disadvantage especially in audio related stuff. Cardboard vibrates a lot and this can mess with the audio quality. I think that should not be a big difference and continued with cardboard. So I drew the shape and cut the cardboard as in the images.
I just ordered the audio amplifier circuit from Robu.in. There were many options to choose from but the one I have ordered costs Rs.99 ($1.4) and seems to have lower noise and a potentiometer. Its 11:00 AM right now and they say they will deliver it by tomorrow 8:00 pm. Pretty fast for the same delivery charges as that of Amazon. I have provided purchasing links in the components section of the instructable. If you are buying it from amazon or ebay, it would be better to order it a few days before you start with the build. I didn't order the bluetooth receiver because I had already bought it for a previous project (for Rs.170 / $2.4). Now you can also use an audio amplifier that has built in bluetooth receiver. The problem is, they are not very good sounding. A normal audio amp will have deeper bass and punchier sound.
I think I will wait for the circuit to arrive and then continue with the build.
Step 4: The Bottom Surface
So its 2:00 PM the next day and the shipment tracking website tells that there is some sort of delivery exception. This means it is going to be delivered one day later. I can't wait till tomorrow for the rest of the build, so I started with the case again.
The bottom of the case cannot be made of hard paper. It might have to sit on wet/dirty/oily surfaces. So I found a matte black soft cover from a stick file and cut it into a rectangular shape. I cut a slightly smaller rectangle out of cardboard and stuck the soft cover on it with adhesive. This will later on be pasted to the bottom face of the case.
Step 5: Mounting the Speakers and Some Soldering
Since the front part is wooden, we could just mount the speakers by making holes in the wood and using screws. The problem here is, my speakers don't have holes for screws. So I used some epoxy compound and stuck it on the front. This compound comes in the form of two bases, a resin and a hardener. We have to mix the two in equal amounts and apply it on the required surface. It will set in 30 to 45 minutes (as it says on the label). In my country, a brand called M-Seal is a famous epoxy compound manufacturer.
As you can see, I have soldered the wires on to the speakers before sticking it to the front. This is because it might be difficult to solder it later.
By the time it sets, I started soldering the wires on the Bluetooth module. First, remove the circuit board from the case. At the front, you will find the usb connector. The two contacts in the middle are for data, they are not useful for our project. The part where I have touched the soldering iron is the negative input and the last contact is the positive. You can see in the last image that I have soldered two wires, one on negative and the other on positive. Please ignore the color of the wires, I made a mistake and connected red for the negative and black for the positive.
Next for the audio output contacts. In the fourth image, you can see the two arrows. The arrow at the last shows the ground and the first arrow shows the left channel. The un-arrowed terminal is the right channel. We have to solder one wire to each channel. In the last image you can see I have soldered red wires to the left and right channels and a black wire to the common (ground) channel. Have a look at the fifth image for reference.
I just examined the epoxy compound and it still didn't set properly. It has been 90 minutes though. I shall stop here for today and let the compound to set overnight. By tomorrow the amplifier board should also arrive.
Step 6: The Star of the Show Is Here!
So it is 1:30PM the next day and the amplifier is finally here. I was having my lunch and the delivery man gave a call. I was super excited, so I left my lunch midway.
It is a really tiny board and I am skeptical about the sound. The board has a PAM8403 audio amp IC as ithe heart of the circuit. Almost none of these small circuits online have a potentiometer except this one. Anyway, I didn't have plans to use the pot though. But later I made a hole in the middle of the wooden frame for the pot.
I soldered all the wires to the terminals. The connections are straight forward. You can have a look at the last image for reference.
Step 7: Hooking Up the Electronics
I soldered all the wires that connect to the circuits and the speakers. The hole I made for the potentiometer at the front was too big and the whole circuit board could come out of it. I changed the plan and placed the amp to the bottom of the case keeping the pot at a little less than full volume. I then soldered the 5v input wires of the bluetooth and the amp in parallel which I then connected to a long wire that is further connected to a usb. Take much care about soldering positive and negative of the amp properly. Reverse polarity will burn the board. I connected the usb to a smartphone charger and touched the amplifier IC to find out if it is heating up. All cool and ready to be sealed!
Make sure to play a music to test the phase of the speakers. Speakers work by pushing and pulling the coils inside by alternating magnetic fields. If not connected in phase, one speaker will be pushed when the other is being pulled. This might mess up with the audio quality. I could connect them properly because the speakers had + and - mentioned in the terminals. If not, the only way is to hear some music and test by changing the polarity of one speaker for better audio quality. Finally, I sealed all the solder joints with electrical tape to avoid shorts.
I then stuck the two circuit boards in place with double sided tape and the wires with transparent cellophane tape to arrest any movement.
In the last image, you can see that I stuck a copper slab with double sided tape to the bottom of the case. This is to keep the center of gravity to the bottom or the system might fall to the front due to the weight of the speakers (this happens because I used cardboard which is quite lightweight).
Step 8: Final Assembly
Finally I cut a rectangular piece of cardboard and pasted black paper on it. I then stuck it to the back making sure to seal it properly. Any air gaps will mess with the audio quality. I used black electrical tape to seal the back because it is easy to remove in case I would want access to the internals.
I cut a small circular disc and painted it black. I then stuck it to the front to cover the hole I made for the potentiometer. To give the front wood a glossier look, I coated it with a mixture of olive oil and lemon juice at 1:1 ratio.
Step 9: Boom Boom!
The speaker sounds pretty good for the price spent. It is pretty loud and has decently deep bass. Now I am not saying it is the loudest or cleanest sounding speaker out there. No no. There are brands that do it better but demand premium prices. But for a budget DIY build that is so cheap, I don't think there can be any speaker that you can buy for this price that sound this good. And that too, our speaker is stereo! The speaker drivers I used aren't of good quality. A good driver will have better sound, loudness and deeper bass.
It is also very beautiful looking. Just leave it at your table and it should attract visitors. If I would have to change anything, I would make it smaller. I think it is a bit too big for my liking. Anyway, it looks good and I don't think I need to search for places to keep it. I can just leave it anywhere. I plan in upgrading the drivers and using a higher wattage amplifier.
Thank you for having a look at my instructable and I hope you enjoy building it as much as I did.