Hello! this is my first real Instructable and a work in progress as well. I wanted to start writing this as i design and build my boombox as with previous projects i never got around at taking pictures and stuff for a instructions so now i will build my Boombox and update this as i go.

So, i am making a beach / off the grid boombox. the finished product should be able to play music at least 24 hours on modest volume without solar charge and be able to fully charge if left out in the sun. Box will also serve as a backup battery for smartphones and tablets. It must be able to put out 2A for charging Asus Padfone 2 and other demanding devices.

Currently i am designing the enclosure around the electronics i have ordered from china. i mainly use aliexpress and dealextreme for parts. Technical specifications so far are:

12000mah lithium polymer battery (actually some tablet battery, made by LG)
5v 4.5w solar panel (maybe two)
charge and discharge protection for the li-po by using a powerbank board with an lcd. Input 5v out 5v 2A x2
4 fullrange speakers 50mm or 2" (allmost) 5w each
2 bass speakers 50mm 4w each
passive radiator if i can find one somewhere ( tell me if you have found any international source for small passive radiators!!)
3 stereo amplifiers, based on PAM8403, 5v 2x3w sounds really nice with my vintage Salora ks-330 speakers :)
buttons and connectors from old electronic junk.
the case is 3mm acrylic that will be part covered with blackboard tape and part two way mirror

Here are the links for the parts. (most, don't remember where i got some of them)

battery : http://www.aliexpress.com/item/Size-9068135-3-7V-1...

solar panel : http://www.aliexpress.com/item/5V-4-5W-Portable-So...

Bluetooth board : http://www.aliexpress.com/item/Bluetooth-Stereo-Au...

power bank board (also makes a good power bank on its own ) :http://www.aliexpress.com/item/hotsale-DIY-5X18650...

full range speakers : http://eud.dx.com/product/50mm-3w-speaker-driver-u...

bass speakers : http://eud.dx.com/product/2-5w-bass-speaker-driver...

amplifiers : http://eud.dx.com/product/2-channel-3w-pam8403-aud...

Dealextreme links are for European site because shipping is much faster from this site than the international one, at least to Finland, although prices are a bit steeper.

So far i have tested the amplifiers and Bluetooth to be working fine, better than i expected. Just a real pain in the ass to solder. Next update will be probably when i get the last parts and lots of acrylic )

So if you got any suggestions or questions, please comment :)

and sorry for any grammar errors or anything, i haven't written in English for a long time.So stay tuned for Ultimate-Solar-Boombox U-S-B

Update 31.3.2015.

Note for anyone using these PAM8403 amplifiers. Do not try to put speaker output negative wires to common ground. I was messing around with one of these and a pair of headphones and connected the ground together from both channels as they are together on the headphones. End result was the magical smoke leaking out of the amplifier and it has moved on to a better place :) I knew it was a good idea to order a bulk box of these. You learn best when you mess things up.

update 4.4.2015

here is a short clip of the amplifier and Bluetooth playing my Salora ks-330 hifi speakers. They sound actually really nice, the video does not do them justice. i also tried playing my 12" home sub with it using a simple RC-lowpass filter and it made the doors vibrate :) it is really hard to believe this little thing can put out so much clean music. no distortion what so ever and enough power for party level volume. clean bass and treble all the way.

I also made some measurements and battery testing today. Got approximate amp draw of 150-300mA for one amplifier and the Bluetooth uses next to nothing. So the math is simple. 12000mah battery dived by 2x the draw of the amp plus lets say 30mA for the Bluetooth so it sums up to 12000/630 = ~19h of play time on near max volume which is really loud! so the the solar panel puts out 840ma and the draw is less than the panel output so battery is always charging when its sunny and it will easily last through the night. Half volume draw is approx half so good guess is 38h of playtime! happy with this. If at some point it would seem too low i am designing the box so that it will be easy to add two more batteries in the case so total battery power will be 36000ma = 36A and battery time 57-114 hours straight. Just bit overkill maybe. Please tell me if my math is wrong.

Step 1: FInished

25.4.2015

IT IS COMPELTED! finally. here isd a video clip of the box in action, i will add a complete re-written quide when i finish doing it. for now enjoy looking at this awesome eardrum-blasting-floor-shaking-awesome-looking Boombox. :D

will be back.

https://www.youtube.com/watch?v=4Bvo5v_TIn8

Step 2: First Prototype of the Box

Finally i had the time to start trying out my box design ideas. This is the first i am making. I don´t know how meany it will take to get to the final design.

I ended up using 3mm plywood and 5mm pine sticks for this box. there will also be a see-through back panel and two windows on the front panel, both made from 3mm clear acrylic. Inside will be painted white and have blue led´s to illuminate the box and give a cool effect (hopefully) But here are some pictures on my progress so far. Feel free to comment and suggest. Everything i do is made with manual hand tools and a Dremel.

I also got the solar panel in the mail finally and tested that it alone could play the amplifier without battery on moderate volume before nasty clipping started, and it was a quite rainy and cloudy day.

Step 3: Box Design Continues

Update 15.4.2015

Now i have the basic design of the box where i want it to be. Front and back of the box have holes cut for acrylic windows so you can see the speakers inside along with the cool blue leds. I used a piece of white foam to diffuse the leds because they gave a bit of a harsh spotlight without the foam. Also i included a simple wiring diagram for the pam8403 amplifier and will add a complete wiring guide once i have figured it all out. The box works as it is now, but i will make a few changes later.

I came a cross a problem with the amplifiers and the Bluetooth module while testing. There is a really significant buzzing noise coming from the speakers. First a thought i could maybe get it to go away with large filter capacitors but no luck there. Then finally i figured out that it was a ground loop problem. I decided to go the easy way of solving the problem by using a separate batter for the Bluetooth. You can remove ground loop noise with a 1:1 audio transformer but those are expensive or the cheaper ones affect the quality of sound really much, they cut off some frequency ranges all together. So with a second battery, problem solved. But now i need to figure out a system to charge the second battery separate from the primary system automatically. To be continued.. :)