Portable Boombox/Speaker With Bluetooth





Introduction: Portable Boombox/Speaker With Bluetooth

So, you have a Bluetooth speaker but its lacking in volume and bass, this project cost me under £40 ($60) and packs a VERY loud punch. the whole project took me a whole summer holiday so around 6 weeks. the battery life on this project has not been measured because i cannot have it playing constantly on max volume whilst i am awake, i have calculated that it will last around 3 days 24hrs

The products i used were bought from eBay:

Amplifier: lepai LP-168HA - http://www.ebay.com/itm/12V-LEPAI-LP-168HA-HI-FI-2...

Bluetooth module: Cheap one from china (any cheap one will do the trick as long as it takes 5v to power it) - http://www.ebay.com/itm/3-5mm-USB-Bluetooth-Wirele...

Ground loop Isolator: Yet again a cheap one from eBay (try spending a light bit more on this as it will decrease the hum that is created, that will be explained further on): http://www.ebay.com/itm/20-AMP-RCA-Noise-Filter-Gr...

3.5mm to RCA converter: Cheap one will do fine (if you can find/make one of your own you could save a few pennies) - http://www.ebay.com/itm/3-5mm-Stereo-Audio-Male-Ja...

Battery: i would strongly recommend anyone to do what i did and take some laptop batteries apart but if you have nowhere to get any laptop batteries then this is the expensive bit - http://www.ebay.com/itm/Protable-DC-12V-20000mAh-L...

Paint: I used spay paint that was bought from B&Q, this is an optional extra but if you want your project to stand out and look great, this is what you need to get (parents bought me this but it cost them around £20/)

The rest of this project was salvaged and obtained for free!

Step 1: Configuring the Setup

The amp that i used can pump out two 40w outputs (two for stereo instead of mono) this can be loud or quiet depending on the speakers but the ones i had were well under the 40w limit. I used two seas woofers that were unmarked but i measured around 15-20w and 8ohms of impedance, connected in series to that were a pair of speakers from an old Samsung radio that were rated at 5w and 3.2 ohms of impedance. in parallel to that were two tweeters that were from the same enclosure as the seas woofers i used. for this configuration i used an online calculator: http://www.speakerimpedance.co.uk/

the seas speakers had no information inline what so ever and i could not find any information of them at all, the speakers were inside a Sony speaker set that was rated at 50w and consisted of one 1" tweeter, one 3" woofer and one 8" sub-woofer (the sub-woofers have been modded into my permanent speaker system as i had to take a smaller sub-woofer from there that is designed for small enclosures and packs a fair punch for as small as it is.

If you are going to build one of these for yourself then i HIGHLY recommend that you do a LOT of research until you are a speaker genius.

Step 2: Building the Enclosure

This is the hardest part of the whole thing because this is the step that decides how the speaker looks on the outside, some people may not care about this if all they want is a speaker that sounds great and does not break the bank then those people don't need to bother with spray painting it. The most important bit of this whole build is if it will fit in the box that you make. The strength and durability will increase with the thicker wood that you use, dencer wood will also be more durabal, i used about 20mm thick plywood for the front, top and sides whereas for the bottom and the back i used weaker 12mm plywood as i had run out of the thicker wood and this was the only bit i had lying around. i used a circular saw to cut these with precision and i added about half an inch to all of the measurements just to make sure the measurements were not off by a small amount. after the wood was cut i used an electric plainer to take more off than sandpaper and then used sandpaper to smooth the sides off.

Step 3: Wiring the Whole Thing Up

before you put the speakers inside the wood that you have cut i highly recommenced to do a test to see if everything works when the whole setup is turned up to max just to make sure that the amp can power the system properly, also keep the setup on for at least 4 hours just to make sure because once the setup is all closed up it is extremely annoying to open the thing back up to fix something that could have easily be solved. i made my own 4 port USB hub (it does not work like the usual one that you plug into a computer and then you can plug memory sticks into, it is just for powering USB devices.

Step 4: Making the Battery Pack

So this is the bit where you can save loads of money, find any unused/dead laptop batteries, after opening them up you will see 3-9 cells, they can vary in color, shape and sise but as long as on the outside of the battery there will be a sticker that should have somewhere on it one of these: NiCd, NiMh, Li-ion and SLA. the type that you will need is Li-ion as these types of batteries have the most power per kg, this is perfect for portable electronics. i used 3x16 (48) laptop cells so it gives this speaker an insane playback time of around 3 days 24hrs (this is just an estimate). i wired up 16 laptop cells in parallel and had three of those in series to make 12v (the amps power). the overall capacity of this battery arrangment is 612Wh which is 12v 44,800mah. this is just an estimate as some batteries may be worse than others as they are used laptop cells.

Step 5: Putting It All Together

So half of it is put together but this is the bit where you need to make sure everything fits into the enclosure that you have build. i secured the batteries down with some wood and screws but i would highly recommend to use hot glue as well as it will make it just that little bit more secure. the strength of the wood and screws holding it down is strong enough for me to carry it upside down with no worries and walk around with it, but i would much rather hold it by the handle. i used silicone and help from my dad to get this together as silicone dries rather fast and i wanted a good seal on it. i used silicone because it creates an amazing seal and this is good for speaker acoustics as no bass escapes from the box as this harms the output sound. i left the bottom of the box unsealed without silicone as i may (and will) upgrade in the future.

Step 6: In Conclusion

So in conclusion, this is my first audio project i made and the first thing that i made that will benefit me. if i was to do this again i would defiantly buy a better Bluetooth audio receiver because for the music to sound decent i need to plug in an aux cable. i would also use a stronger handle as this feels like it may snap at any moment. Apart from all of that i think this project is amazing, it has been fun and stressfull to build but the outcome to it is exelent

Step 7: Update

I am planning to add a higher power 12v output as the chargin port acts as an input and output but gets rater warm when 12v 5a (around 60w) is running through it, so i will add an AWG output (the one that should be on the back of your computer) this is NOT ti be connected to a 230v outlet but I figured that if it can carry 230v at 13a max then it should be able to handle 12v 10a with relative ease.



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    I the concept, but be sure to organize and insulate those wires next time. Could be a hazard in the future, check out techflex and pair it with heat shrink for maximum protection. And also for sound quality purposes, if possible separate the chambers for each speaker and use crossovers to separate frequencies.

    1 reply

    Yes i did open this up again as the left side had stopped working (wire i forgot to solder) so i put electrical tape around it as i have no heat shrink because this was on a tiny budget
    And the crossover, i was going to use differant encousures but the drivers on the sides are crap anyway as when i plug it into my pc it starts to distort at around 110db so i dont mind if they get damaged and the rest of the speakers has plastic shrouding over them or didnt have anywhere for the sound to output on the back. The two bass speakers are acualy running off the same signal just on the amp there is two places to connect subwoofers (presumabaly for easier connection to the amp)

    Great tutorial (instructable), thanks!
    I want to ask one thing: how do yoy charge the 12v battery "pack", if i can call it so? I've always wanted to build smth powerful, but never figured it out what charger i need. Thanks in advance!

    2 replies

    Yeah about the battery pack, i bought a 6800mah 12v battery, it wasnt able to power the speakers at all so i took it apart and upon inspection i found out it was just 3 3.7 2550mah phone batteries in series, so i used the connecters out of there on the charging bit on the back and i just used a 12v psu to charge it up relitivly fast and then just used a 12v charger that came with the crappy batterys from ebay so i didnt overvolt the batteries

    Yeah i will do an instructabal on it, thanks for the idea keep a look out

    I like the industrial design. Great idea to repurpose the laptop batteries!

    Do you have an idea of how many decibels it pumps out?

    The amount of speakers looks like it would be deafening!

    Have a great day! :-)

    2 replies

    This is what bluetooth pumps out but my phones mic only seems to be able to go upto 100db as i turned down the volume and my phone still mesured 99db


    Yes i did mesure it and it pump out around 105db max through aux, but only 100 or so through b/t because the module canmot pump out high volatges for the amp