DIY Portable Bluetooth Speaker 30W, BT4.0, Passive Radiators

by Barry_L

132K788109

Intro: DIY Portable Bluetooth Speaker 30W, BT4.0, Passive Radiators

Hey everybody! So in this tutorial I'm going to show you exactly how I built this (true) 30W RMS portable bluetooth speaker! Parts for this speaker can be obtained pretty easily and cheaply, and there will be links provided to everything needed. Everything in this project was built using only hand tools, meaning that anyone can build this project from home with ease. First off, here are some specs and features:

  • Bluetooth 4.0 with function keys
  • Real 30W RMS
  • 20 hour battery life
  • 18v power supply
  • 4 48mm Bose drivers
  • 1 5" Passive Radiator
  • Notifications LED

In this tutorial I won't go into a lot of detail about explaining how different parts work. I have already published a tutorial over here that explains different parts' functions in greater detail. I'd recommend reading both tutorials to really get the hang of it all :)

STEP 1: Parts List

Here's the parts list for everything you need. Aliexpress requires credit/debit card, and Etsy.com requires PayPal.

PCBs:

Speakers:

Miscellaneous:

STEP 2: Tools Needed:

You don't need any complicated tools for this build.

Useful Hand Tools:

  • Hacksaw
  • Files
  • Sandpaper
  • Snips
  • Scissors
  • Knives

Useful Power Tools/Electric Tools:

  • Drill
  • Soldering Iron
  • Hot Glue Gun
  • Multimeter

STEP 3: Making the Enclosure

In this build we will reusing an old lunch box or other container. It's important to measure the dimensions of all your parts and make sure that they'll all comfortably fit in your container. It's also important to use a material thick enough so that the enclosure doesn't flex from the air pressure from the speakers. If you're using plastic, I would recommend you use plastic at least 2.5 mm thick. It's good to choose a box that will comfortably fit in your hand, and will also be able to stand independently.

In my case, I used a lunchbox. I had to cut the top down 5 cm. If you need to cut down your box, make sure you leave a few mm of extra space at the front so that your front panel wont be flush with the box. You need the extra space for adding a front speaker cloth (more on that later on). I cut the box down using a hacksaw blade. After you get your box down to the right size, we then need to drill holes for buttons, LED, charging and power switch. Use a needle file and a small drill bit to get the holes perfectly neat.

Next up, we need to sand down the outer and inner surfaces of the box. This makes the box a little more rough so that paint and glue will stick to it easier. Make sure to sand down all branding on the back of the box too to give it a more authentic look. Now that our box is ready, its time to work on the front panel.

STEP 4: Making the Front Panel

On my speaker, the front panel is built out of 3 mm perspex. Perspex is great as its easy to work with and can be cut with a table saw. If you plan on cutting it with power tools, bare in mind that a tool with a rougher blade is better than tool with a finer blade. Finer blades may melt through the plastic rather than cut through it.

Mark out the size of your panel by laying it underneath your box, and trace a line around it. Then remove 2-3 mm depending on the thickness of your box.

Before cutting out the panel lay out all your parts and double check that everything fits. Next up mark it out and cut! I used a hole saw to drill out the driver holes, and then I cut out the passive radiator hole by drilling loads of small holes around the perimeter, and then filing them out to remove the centre piece. Be careful with your drill bit while drilling the holes, it can get quite hot!

STEP 5: Preparing the Bluetooth Module and Amp

To fit everything into the enclosure, we're going to do a small bit of editing to the amp which will allow us to mount our Bluetooth module directly on to free PCB space on the amp. To do so we're going to unsolder the 2 rca inputs for the amp. We will solder cables directly on to the board instead. This frees up some space. In its place, we're going to put a small square of breadboard (copper side faced down), slightly raised off the board using hot glue, to prevent shorts.

Before mounting the Bluetooth module, we will solder on all the cables we need first. I have labelled all the connections in one of the photos above^. If your bluetooth module is in quite a cramped place where there won't be a good connection, you can add some length to the antenna by soldering a wire on to it (see the images for where to solder it^). To keep all the cables neatly together, I used little rings of heat shrink tubing around several cables.

STEP 6: Building the 4S Battery Pack

This is the most dangerous part of the build. Lithium Ion batteries can be dangerous when mistreated, especially when you are dealing with multiple batteries. If you're new to DIY battery powered projects, I would recommend familiarising yourself with them first before undertaking projects like these.

First we need to connect all the batteries in series (ie. positive connected to negative). We'll connect them together by soldering a wire from one battery terminal to the other. You will also need another wire branching off from that wire to leave loose for connecting to the battery protection circuit board later on. Solder doesn't directly stick to the metal on 18650 batteries, so to make it stick, we will scratch the surface of the battery using a scribe and some sandpaper. Use a cloth to remove the metal dust afterwards instead of your fingers. The oils on your fingers can make the it more difficult to get a good contact to the metal. Now that its rougher, you should be able to solder on to the batteries more easily. Check out this guy's tutorial on it, he goes into the procedure a little bit more in depth.

Now that our batteries are all connected, we will tape them together into one handy compact battery pack. After that it's time to add the battery protection circuit. It will require battery positive and negative, as well as a wire coming from each of the cells. Battery protection circuits are important in order to keep the battery healthy and safe. After soldering up the protection circuit, you can also tape it in with the battery pack.

Lastly we will connect the switch and the charging port. Make sure not to connect the wires the wrong way around on the charging jack!! Always do tests with a multimeter first!

STEP 7: Adding in the Voltage Step Up/Step Down Conveters

Now that our battery is all connected and protected, its time to add our voltage converters. We need a higher voltage for the amp, and a lower voltage for the Bluetooth Module. For the Amp, we will use a boost step up module, and for the Bluetooth module we will use a buck step down module. Be sure to set the voltages before connecting the amp/bluetooth module! Connect the inputs, and then use a small screwdriver to adjust the metal screw to change to voltage (see photo above for screw location^). You can monitor the voltage using a multimeter. For the Bluetooth module 5v is ideal, and for the amp 18v is ideal.

Your Bluetooth module should come with a 10V 470uF capacitor. Once you have set the voltage, add the capacitor across the positive and negative output of the step down converter. You don't need to add any capacitors to the step up module, as the amp already has capacitors built on to the board.

Now that we have the converters sorted, we will connect up the wires and mount them on a piece of breadboard, along with the amp and Bluetooth module. This keeps everything nicely together and adds a little bit of structural rigidity.

Now everything should be working! Try plugging in the charger, turning it on/off etc. Connect up the wires from the amp to the speakers and give it a listen to make sure everything's working OK. If it is, then we will continue on to by painting the box and front panel, and install our electronics.

STEP 8: Finishing the Box

We're going to now spray paint the box and front panel. I decided to go with grey for the box, as I could then liven it up with a brightly coloured grille on the front. I used Montana Gold spray paint as well as a clear coat spray paint on top. Spray thin light layers in 5 minute intervals (depending on your type of paint) and wipe the surface in between sprays, until you have a solid coloured box. Then finish it off with several clear coats.

For the front I decided to use red paint. The colour of this panel really doesn't matter because there will be speaker cloth on top of it, but I wanted to paint it in some colour so that it would no longer be transparent. That way light leaks from the LEDs inside won't be visible.

Don't paint the inside of the enclosure! I did this first time round, and it just peals off when you have parts glued to it. You're best off leaving the surface unfinished.

STEP 9: Adding the Electronics

Now that the box and front panel are complete, its time to add the components! Rest the box on a soft material so it doesn't get scratched, and add in all the parts. When adding in the buttons and switches, make sure you glue it very well so that no air can leave or enter the enclosure through the holes. Hot glue is great for sealing holes. I went quite a bit overboard with hot glue on this project as you can probably see, you don't have to go to such extremes as I did :)

You may also want to add some extra glue bridging sides together to add some structural rigidity to the enclosure. You want it to be as solid and stiff as possible.

When mounting the speakers and passive radiators, I used 2 piece epoxy, followed by hot glue to make sure that it's 100% sealed. As you've probably noticed, there are 4 drivers but only 2 channels, that's because each channel gets 2 drivers in series. Each driver is 4 Ohms, which means that each channel is 8 ohms.

When everything is all glued in place, solder wires from the speakers to the amp, and the slot the front panel into the enclosure. Test the speaker on final time before glueing on the front. To glue on the front, run a line of hot glue around the gap created between the front panel and the rest of the enclosure. Make sure that the glue doesn't reach above 1.5mm from the top of the enclosure, as we need that space clear for mounting the speaker cloth/grille.

STEP 10: Adding the Speaker Cloth

To finish things off, we're going to add speaker cloth to the front. The 'speaker cloth' is actually just a piece of fabric from an old t-shirt. To keep it in place we're going to need some metal mesh glued in behind it. It needs to be clear enough for plenty of sound to pass through, but the holes shouldn't be too big either or else the pattern of the holes will come through the cloth. Add a small line of glue along the inner side of the metal and fold the fabric over it. Repeat for all 4 sides.

Now lastly to glue the panel on, we'll just add a few dabs of hot glue to the speaker panel and slot on the cloth panel and we're done!

STEP 11: Final Thoughts

Overall I think this is a great speaker. By using a pre made enclosure (lunch box) you save time and internal space. The shape also looks very professionally done and people often ask me about how on earth I made those perfect curves! It's also a very practical speaker. It fits great in the hand and can resist water quite well compared to some of my other creations.

In terms of sound quality, I think its quite good. It has an insane power output of 30 watts, and the passive radiator really helps extend the lower frequencies. On the other hand, the bass often isn't boomy enough for my liking. An equaliser on your phone helps greatly with this issue. Playing around with different sized lunch boxes would change the sound significantly, so I may have a few more shots at it at a later stage.

If you have any questions, or would like to see some of my more recent designs and keep up to date on the latest Instructable tutorials, you can follow me here on my Facebook design page: https://www.facebook.com/BL.car.design.and.renderi...

I'm selling lots of exotic speaker parts and passive radiators over on Etsy if you're interested: https://www.etsy.com/shop/SirBarryToTheMax

If you've made anything else similar, I'd love to see it, post below! :D

STEP 12: What I'm Working on Now

Just finishing off this speaker at the moment. Making a clear perspex cover for the front with holes in it as well as finishing off the clear coat on top of the wood. Don't be fooled by the crazy amount of speakers on it, its actually just as small as the blue speaker in this Instructable!

If you'd like to see more of this speaker, and be informed when the Instructable goes up, be sure to visit the Facebook page, https://www.facebook.com/BL.car.design.and.renderi...

Thanks for reading, see you shortly! :D

107 Comments

DanielB228 6 years ago

is the passive bass also wired in series?

LenaJ4 7 years ago

Hello :)
Ive bought a lot of different stuff to build a speaker. And i could reeeally use someones help to just simpely tell me how to connect it all. Ive been looking at speaker build for several days in a row now, and im still confused. Also... ive never tried something line this before ? Would you maybe help me?

ottotunz 8 years ago

may I know for how much time will the battery power last at full power?

(i apologize for my poor english)

tomtomlo187 7 years ago

How did you calculate how long the batteries will last? I'm trying to build something bigger but I'm not sure how many more batteries i will need.

Kandrix 7 years ago

Very basic math. First, take your 18650s. They're nominal 3.7 volts, 4.2volts at full charge and 3v fully discharged. Most of them are 2.2Ah-2.6Ah. Don't be fooled by those "5000mAh" ones on ebay. Best you can get (and also very expensive) are panasonics 3200mAh. They used to make 3400mAh as well, but stopped then. Anything bigger in capacity and I would be extremly suspicious. Just google for measured and empiric values for each model. That gives us for example for single 18650

3.7v * 2.2Ah = 8,14 watt-hours

That means single 18650 could run 1w speaker for 8,14hours, or 8,14w speaker for an hour.

I suppose this gives you all the math neccessary for your project. Happy building :)

(last word: Don't get scared if your big project needs alot of juice, I've even used 15x 18650 batteries in my handheld floodlight, which you could find with detailed guide on my instructables profile.)

АлексейЦ1 7 years ago

I can't figure it out: with your way of calculation 4 cells 3.1 A-h 3.7v should give us 45,9 w-h, which for a 30w system should give 1,5 hours of operation. While Barry is talking about 20 hours of operation. What am I missing or what is the right way to calculate power supply?

Kandrix 7 years ago

No, the math is correct. What I'm suspecting is that first - the amplifier board is capable of nowhere near 30 watt output. The "2*15w" way they call amps on ebay means most of the time nothing else that the amplifier is 15w total, not for two channels. According to the data speadsheet for the amplifier chip used (MAX9736A), it is capable of maximum output of 15 watts into 8ohm load with source voltage of 24volts. This output is when THD+N=10% (sh*tton of distortion). At 12 volts, with THD+N=1%, the maximum output for the chip is 8 watts into 8 ohm load. Those 8 watts are RMS, not continuous power. This means that this "30 watt speaker" is actually only 8 watts at best total, and I am not surprised by this value. These days, everyone is marketing their speakers as much higher wattage than their output really is (yes I blame JBL and similiar manufacturers). At best they market it with peak power being actual power of the device, which is not. If you saw a real 30 watt continous output from a speaker, it would definitely not look like this. This does by no means mean that it is not loud, damn my speaker (real continous 8W Yamaha PDX-B11) gets way louder than my friend's JBL Charge 3 which is marketed as "20W speaker"! You cannot cram such an wattage into so small speakers, thats just not how electronics and particularly speakers work. Again, judging by its battery, which is total of 22.2Wh, and marketed "20+ hour playtime" rating, this cannot last this time with more than a watt of power, with 100% efficient amplifier. You see now the bait? The company simply lies to people. Same with this speaker, which is by no means bad project, but "30w" is not something that this is.

АлексейЦ1 7 years ago

Hi! Thanx for such a quick and detailed answer, it really helps. Now I faced another question: if an amp gives for example 8 W into 8ohm and the system consists of 4 speakers let's say 10 W at 4 ohm, does it mean it won't play at it's maximum power? By power I mean loudness which is described by spl graph.

Kandrix 7 years ago

The amount of speakers doesn't matter at all. All what the amp sees is load resistance. If you put in 2x8ohm speakers in parallel, it sees it as one 4 ohm load. Also, putting them in series means 8+8ohm=16ohms. You can get a bit more output on lower ohm speaker, yet the quality depends highly on the amplifier, as 4 ohms are much more prone to interferences and hiss from low quality amps and wires. The total output wattage gets higher, but again, if the amp distorts at 10w and clipping occurs, it doesn't matter what the load is. If it can cleanly play 8w max, then its going to play 8w clean on both 4ohm( from parallel 8ohm) and 8ohm single driver, if you use proper wires to support the larger current that 4ohm might draw. Also amps that are designed for 8ohm do not always support 4ohm, or at least it might not be reccomended for them by manufacturer of the board.

Alex345 7 years ago

How do I wire the battery pack.where to connect the wires on the batteries

JerryM59 7 years ago

I'm a total noob at using 18650 batteries, can I use the battery protection board you used in this tutorial or something similar to charge 6 18650 4.2 batteries. I mean I'll have 3 pairs so the total voltage is around 12.6v. I think it would be a 3S3P setup. Sorry I'm totally new to this.

VincentK16 8 years ago

Hey Barry,

Your instructables and YT videos really inspired me to build my own. But i'm not sure if I should use four of those k.tone (LG) speakers in 1L nett volume with 2 7x8cm passieve radiators OR two of those 'bose' drivers, 1L, 2x 7x8cm PR's. Since those bose speakers are double the price, is it worth it? Does it really add that punch that you're missing? By the way, any idea what the volume of your box is, with(out) components?

I hope that you'll respond!

Cheers, from the Netherlands, Vince

VincentK16 8 years ago

**** Bose SL mini speakers, not the ones you used in this build!

Palt3ch 8 years ago

what's a BEC if I may ask I'm new to making stuff and DIYs and I'm looking to make this for fun please help

christian.koder 8 years ago

I like this Tutorial so much.

But there is one thing I would like to change.

Is the any possibility to charge the batteries over an USB Port.

Do I habe to add a USB charging Board to the battery protection board. Or do I need to use a USB charging board instead of the protection board?

Thx for your help.

Barry_L 8 years ago

Hey sorry for the slow response. This speaker draws quite a lot of power, USB only puts out 5V, which simply wouldn't be enough. For this speaker you need about 16V input, so you're basically stuck to using this method for power source, or just build a far less powerful speaker that runs off 5V. Hope that helps.

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