DIY Bluetooth Speaker From Old Jeans and Pallet Wood

When creating this instructable, my main aim was to create such guide, which will allow everyone to receive final product, which will look like a factory made one – no rough edges, dangling wires and glue blobs around, and I have made it! People who see this speaker for the first time are asking – where you get it, how much does it costs? Moreover, when I show them photos of the making in the process, they feel quite shocked. Therefore, in this guide, I will explain how to make very cool looking (and sounding too) Bluetooth speaker using old jeans, pallet wood and other non-expensive materials. Note: While I have used a $10K CNC for making some parts, you do not need it at all, you will get exact same look and sound by just using simple hand drill, and I will show you how. No advanced woodworking or electronics skills are required. Everything is plain and simple. All you will need is A LOT OF PATIENCE, because wood glue dries slowly, and if you touch it before it is completely dry, you will ruin your project.

Below is the list of materials and consumables you will need. I am providing reference links to ebay, it is not necessarily to buy using these links; you can use them as a guide for finding same product in store you prefer, or you might even already have them available at hands. If you buy on ebay, estimated budget will be under $30. If you can buy from Taobao, then your budget will be under $15.

Parts:

3-5w 40mm 4 ohm speakers - 3 pcs https://www.ebay.com/itm/2pcs-4Ohm-3W-40mm-Loudspe...

3 inch passive radiator – 1 pc https://www.ebay.com/itm/2pcs-3-inch-79-79mm-Passi...

PAM8603 amplifier module – 2 pcs https://www.ebay.com/itm/2PCS-USB-Audio-Receiver-2...

TP4056 charger/protection module – 2 pcs https://www.ebay.com/itm/2-5-10PCS-TP4056-5V-1A-US...

3A 5V boost module – 1 pc https://www.ebay.com/itm/5V-3A-DC-DC-Step-up-Conve...

DC/DC 5V isolation module – 1 pc https://www.ebay.com/itm/B0505S-1W-DC-DC-5V-Power-...

Bluetooth audio receiver module - 1 pc https://www.ebay.com/itm/Wireless-USB-Bluetooth-Ad...

1000-1500uf 6.3V-10V LowESR capacitor – 2 pc https://www.ebay.com/itm/10pcs-1500uF-6-3V-8x20mm-...

0.1 uf and 0.01uf capacitor – 1 pc https://www.ebay.com/itm/30-Values-300pcs-Ceramic-...

2.2k resistor – 2 pcs https://www.ebay.com/itm/100PCS-1-4W-0-25W-Metal-F...

5mm milk white led (even non-working one) – 1 pcs

2.1mm round dc socket – 1 pc https://www.ebay.com/itm/10pcs-DC-Power-Supply-Jac...

USB to 2.1mm round plug – 1pc https://www.ebay.com/itm/USB-2-0-A-Male-To-DC-5-5m...

Rocker switch – 1 pc https://www.ebay.com/itm/3X-6A-250VAC-10A-125VAC-B...

Camera tripod mount holders – 2 pcs https://www.ebay.com/itm/1-4-inch-Screw-For-DSLR-S...

Vintage style camera strap – 1 pcs https://www.ebay.com/itm/Vintage-Camera-Shoulder-N...

Brass spikes – 4 pcs https://www.ebay.com/itm/10-X-Brass-Screw-Bucket-...

3 inch speaker grills – 2 pcs https://www.ebay.com/itm/1PC-3-4-5-6-5-8-10-inch-S...

18650 battery – 2 pcs https://www.ebay.com/itm/2pcs-4pcs-Samsung-INR1865...

Consumables:

Old jeans

Scrap wood, you can use pallet wood, plywood, OSB – any type you can obtain.

Wood glue (I’m using Elmer’s wood glue, but you can use any you prefer, just make sure it is wood glue, not universal glue or silicone glue or whatsoever)

2 part quick set epoxy glue (choose one with at least 10 minutes set time)

Soldering materials, such as flux and rosin

Silicone glue (any will work)

Hot melt glue – 1 stick

200,400,600 grit sandpaper – one sheet of each will be enough.

Acrylic spray lacquer – I’ve used “flat clear”

M4 Speaker screws (at least 14 pcs) https://www.ebay.com/itm/M4-18-Inner-hexagon-Self...

Some long M3 screws or just some metal rods

Some wires, not too thin or too thick, 20AWG will do just fine

Small piece of old PCB, protoboard or even hard enough cardboard

Tools:

Hand drill

Wood drilling drill bits

Utility knife

Scissors

Ruler

Hot glue gun

Screwdriver

Soldering iron

Caliper (optional)

3 Axis CNC (Optional)

Printer (Optional)

Here you can also download the PDF file which has all schematics and drawings included, which are required when making this speaker.

Here is schematics of complete speaker, nothing too hard or special, below I will explain how it works. (For some reason, preview gets cropped, so please click on it to see the full circuit)

We have 5.5mm round dc jack on the left; it is used to deliver 5V from standard USB charger to the speaker system. Next, there are two protection and charging boards, each of them protecting and charging single 18650 battery. Why two boards? – Two boards means twice faster charging, twice maximum current and more safety, in case of single battery has some issues. After these boards, battery output goes thru rocker switch, which is used to power speaker on and off to the 5V boost board. Why we need it? First, we need 5V for our Bluetooth receiver, and second, higher is output voltage, higher is output power, and since our speaker enclosure is relatively small, we will need to pump in it more power, to get good oomph. There are two electrolytic capacitors connected to both input and output of voltage booster board. They smooth out the current consumption spikes, which will happen when volume is set to high. Without them, booster protection might kick in, and shut down the music in the middle of the play. There is another DC/DC 5 volt module connected to output of main booster. Its purpose is to provide galvanic isolation of Bluetooth audio module power, so you will not get that nasty whine, which happens if you power such module directly. There are two PAM8603 amplifier boards connected to power supply, and they are connected to 3 pcs of 40mm speakers too. Why I used three speakers and two amplifiers and not say one larger speaker and one higher-powered amplifier? The answer is simple – to drive bigger speaker, we need higher output amplifier; higher output amplifier needs higher voltage to work – at least 12 volts. To step up from 3.6V provided by our battery to 12V, we need larger, bulkier and less effective step-up board, which will need much more current to work, and this also will require more complicated and expensive battery protection circuit. Therefore, I decided to get most watt per the buck, using such scheme. You might also ask, why three speakers and not four, since I have one channel left unused? Of course, I can add 4th speaker, but output power of my 5V booster board won’t be enough, so I’ll need to add another one, and also, 3 speakers perfectly fit into speaker grills I already have, and there’s no place for 4th one. So if you have larger grills and case, you can use as many speakers as you like, just equip them with enough number of booster boards and amplifiers. For example, if you add another 5v booster in parallel to existing one, you can also add an extra PAM8603 board, so now you can have 6 speakers working at same time. Now let us back to circuit description. Output of Bluetooth audio receiver being feed into simple T-filter, which rejects middle frequencies, so our speaker will have more bass and highs, and less Mids. That's all, quite simple, I think.

First, I have sourced an old pallet, which was dry, not bent and not been exposed to elements. I’ve cut it apart, and allocated relatively even parts, so I can use CNC to machine them out.

The speaker body consists from the following wooden parts. 3 pieces of middle parts, they have holes for battery housing too. Two end cap parts, which are used to seal battery chamber, Two “face” parts, one of which holds passive radiator, and another one is used as mounting surface for 3 speakers. Thickness (or length) of final speaker is 130mm. You can go longer, to have a slightly better bass, just try to not make it shorter. The diameter of speaker is 107mm and speaker grills, which I already had at hands, dictated it. The quantity of "layers" was dictated by the width of the available material, which in my case was about 17mm. If your material is thinner, say you're using 5mm or 10mm plywood or OSB, all you have to do is make extra "middle" parts, so final length will be the same.

Since there are many many CNC's, CAD software and standards, to make things less messy, I'm providing drawings in PDF format. They are 1:1 scale, so you can directly cut them out. To make things even easier, Depth information is provided via color - white color means hole thru, yellow color means partial cut out with 5mm depth, gray color signifies solid wood - no cut out required.

As you can see, construction is fairly complex and practically can’t be repeated without CNC. But do you have to repeat it? Not at all! Of course, if you have CNC, drawings are included and you are ready to go, but reason why I selected such complex shapes is due to my love of perfection. You do not have repeat them to get exactly same outlook and sound too (just maybe your speaker will be heavier by 50-100 grams, which is almost impossible to note).

So how you should able to get same shaped body for your speaker? There are several possible ways, let me show some of them.

1. Get the 3” plastic sewer pipe of appropriate length and equip it with wooden end caps. This is the simplest way, but plastic pipe might have unwanted resonance at some frequencies, so you will need to dampen it with some kind of anti-vibration coating.

2. Get piece of bamboo of required diameter and length. This will be the best choices for areas, where bamboo is available, it is lightweight, has good sound absorbing properties and easy to work.

3. Use lathe. Well, if you have access to lathe, you probably already know how-to, so no need from me to explain anything about it.

4. Still want to make solid monocoque speaker unibody like I did, from the wood, but have no CNC? No problem, all you will need is hole saw kit. I will show some reference pictures – sizes are not matched, just these are two hole saws which I have at hands now. First, cut out piece of wood with desired outer diameter, using large hole saw. Then, fix cut out chunk to some surface with at least two screws, and using smaller hole saw, cut out center from it. Repeat these steps until you have desired number of wooden pieces. Of course, in this case you have to mount 18650 batteries and electronics a bit differently, but that also is not a big issue.

For the speaker mounting plate, which has a bit complex shape, the secret is, you actually don’t need it! I just made it because I was able to do it. All you need to do is to cut holes using hole saw and glue in speakers, like one shown on the picture.

Making top panel can be tricky, a much more trickier than any other parts of the speaker, but it is also doable, just it requires a lot of hand job. Assume you already have saw of some kind (hacksaw, bandsaw, oscillating saw), cut the piece of wood according to stencil provided, mark all the holes on it, again using that stencil and now you have to shave wood down to proper size using 200 grit sandpaper. Since pallet wood is usually on the softer side, you will need approximately 15-20 minutes in doing that. Since cutting out square holes without CNC needs steady hand and good woodworking skills, I suggest you to simply drill a round hole, and use round rocker switch. After you finished, take 400 grit sandpaper and smooth out rough areas left with previous sanding pass, and finally, smooth out all details with 600 grit sandpaper. Apply lacquer, let it dry for 24 hours, smooth out again with 600 grit sandpaper and apply final coat of lacquer.

After all parts are ready, I’ve started assembly process. First, I will assemble the middle part, where batteries go, and then will add end caps. Using M3 screws as guides, I’ve glued parts to each other using wood glue. After parts are connected, put on some weight and let it dry. After you put on weight, wipe glue, which leaked outside with some cloth, do not allow it to dry, or it will be very hard to remove if after that.

After 24 hours, check all areas, there should be no holes from where air should leak, because if such holes will exist, you will get no low frequencies at all. This is very important. Therefore, for additional air proofing, I’ve applied wooden glue to internal surfaces of the assembled block. Drill two small holes, which will go into battery department and connect it to “outside world”. This is required, because when in use, Lithium batteries do release some gases, and since we are going to put them into sealed chamber, we do not need elevated pressure there, gases should have place to go.

The top part cover, where power switch, charging socket and strap clips are mounted, is also made from same piece of pallet wood, as main speaker itself. I’ve made it using CNC, but it is quite easy to make it using saw, sandpaper and drill. All plans are included here. To get it “untreated” wood finish, I’ve covered it with matte lacquer, allowed it to completely dry, finished surface with 600 grit sandpaper, and applied another cover. That’s it. Please note, it has a 5mm hole, where LED is inserted, led has no connections, it is just placed right above the blue led on the Bluetooth audio receiver, so it simply acts as a light guide.

Now it is time to install batteries. You have to solder wires to battery, before installing it. This is most dangerous task you will have to do. I strongly suggest you to buy 18650 batteries with tabs, and solder to them. Remember, no more than 3 seconds per each solder point. If you see that, you cannot fit into that time, put battery away, allow it to completely cool down and retry only then.

After batteries have been installed, you can glue their chamber top and bottom parts to main body. At this stage, you can also glue passive radiator holder part to main body, to save time on glue drying. I suggest you to use silicone glue for that, instead of epoxy or wood glue, because it has several advantages – it is more vibration-proof, and in case you need access to internals, you can remove it.

Now here comes the tricky part – installing speakers into their chambers. Here you should use very precise amount of hot melt glue, to provide good seal, and to not allow glue to touch speaker-moving parts. I highly suggest trying this first on unneeded speaker and wooden part, as I did, to get idea how to do it properly. Please note, you should solder wires to speakers BEFORE you glue them in, because after gluing, you will have very limited access to contacts. There of course will be some glue leaking; you can cut it off with sharp knife. Be very careful not to damage speaker itself!

Check the top opening, where you have to place Bluetooth receiver and dc jack and power switch. As you can see from the picture, I've made error, and made hole in top cover at a wrong place, so it does not fits above the led on the audio module. You have to check this by yourself, because all modules appear to have LEDs at different places. Also, you will need to drill holes for top cover fixing. As you can see, I've made an error there too, and drilled holes at wrong places. If it happens to you too, you can use hot melt glue to fill the unneeded holes. This is necessary, because we don't want air leaking from any holes.

Time to assemble electronics. We should start with the Bluetooth audio receiver. Take it apart with a knife, unsolder 3.5mm audio jack and solder wires as shown. Channels are connected in parallel, so there will be no stereo, but this is OK, considering speaker overall dimensions. In addition, you should remove USB connector and solder power wires there. Mind the polarity, you can check "USB connector pinout" on the internet. Because if you will do it in reverse way, receiver will be permanently damaged! I have used small piece of PCB, left over from another project as a “chassis” for my electronics. Sanded it a bit with rough sandpaper, and glued all my components here using 2 part epoxy glue. I also drilled small holes between top and inner part – there will go wires, which connect Bluetooth module, charging socket and power switch to “mainboard”. Before gluing them, of course I have applied power and checked everything to be working – battery delivering power, charger charging and boost converter and amplifiers working. You can already try to play music at this stage; it will sound very thin and hollow, but do not worry, because sound quality will be much better after assembly is completed.

After you ensured that everything is working properly, you can assemble the speaker main body (without the top cover), but be very cautious, double check everything, because after you glue all parts together, it will be super hard to reach inside, In case of something was wrong. You will also need to make your speaker case as airtight as possible at this stage. This is because if there’s any air leak, there will be no bass. So for that, I’ve used hot melt glue to seal the place, where wires from internal chamber connect to top part, and also applied wood glue to any possible openings and holes. At this step, speaker should be already working and delivering the proper sound.

Now it is time to cut the jeans apart. I have used most solid looking part from the old jeans. Before cutting it apart, wrap it around your speaker and make sure it fits and you have 2-3cm of spare denim at all sizes. After you had ensured in dimensions, cut denim in a straight line, and glue it with wood glue to the edge of the speaker, as shown below. Let it completely dry, at least 24 hours, this is important! After it dried, stretch it to another side, and apply glue to another edge. Again, let it dry completely for 24 hours and now you can process with the sides. Using small scissors, cut the denim as shown on photos above, and using wood glue, glue it to the speaker main body. Denim might overlap speakers and passive radiator at this stage, but this is OK for now, just make sure no glue goes into speakers or radiator. After drying, use small scissors to cut away the leftover denim.

Installing speaker legs. There are several ways, initially, I was thinking making some wooden support, as shown on the picture, but speaker looked too bulky with them, so I have used some brass legs bought at craft store. To drill holes properly and at even distances, I am including a paper stencil, which you can hold firmly to bottom part of the speaker, and mark areas required for drilling with nail or something sharp (check the last page of included PDF file for stencil). However, before you drill thru denim, you have to check two very important things: 1 – make sure that you won’t hit the battery or speakers when drilling, this will cause fire and explosion, if you puncture the lithium battery. In addition, you should apply small drop of wood glue to the drilling area, so denim is glued to main body. Do not over apply glue here, as I did (check the picture), it will look ugly. Just use one tiny drop. The aim of this is to glue denim to the wood, so when you start drilling, it will not be damaged by drill. Let it dry, drill, and screw in the pins.

Now you can install top part and grills and finish the assembly. But before you go, check screw length carefully, to avoid them going thru the main body and damaging speakers or PCB.

Done, speaker is now complete and you can enjoy it!