After I came across some awesome boomboxes on instructables I wanted to make one on my own. I had the idea to use a beer crate as a case. This keeps the whole thing portable and affordable. After doing some research I decided to use a powerbank instead of a lead-acid battery because it´s a lot lighter and smaller. I used a small chinese amp which is surprisingly loud and has quite a good quality. My battery (14ah) lasts about 8-12 hours at high volume but a better battery with 12v output could last even longer. The boombox supports 3.5mm audio cable (e.g. for mobiles), USB stick and radio. All in all this project cost me about 50$ because I already had some of the parts at home. If you have to buy everything, about 100$ for the more powerful 12v amp option are realistic. The 5v option should be about 40-50$. I have to say that this was my first bigger project so maybe not everything is perfect. But that also means that basically everyone else should be able to do this!

Step 1: Parts List/ Tools

Parts List

-beer crate (I used a 11x 0.5l Carlsberg beer crate because it seemed to be the best for this project but you can basically use everyone you want to)

-amp (I got a Kinter MA-700 for 15€ here in Germany but every class-D amp with 5-12v and up to 5a should be okay)

If you want to make it inexpensive, I recommend using a 5v amp board with a PAM8403 chip (just search for it on the Internet). You can power this one with 3 normal AA-batteries or a normal USB-powerbank.

-speakers (I used some old home audio speakers, full-range speakers would be the best but car speakers or just some old ones you already have are okay, too)

-powerbank/battery (if you have the possibility get one with a 12v output, I already got one with a 5v USB output at home so I needed a voltage transformer - I don´t recommend that version but it seems to work.)
UPDATE: I have purchased a 12v powerbank, that increases the sound quality and especially the maximum volume a lot.

-audio cable (3.5mm to RCA), speaker cable and power cable (depending on the output of your powerbank)

-some wood (I just used some old wood that was lying around)

-spring loaded latches (I hope this is the right word for what I mean :D)

-screws, nails, nuts

-spray paint

[-optional: bass reflex tube or an old plastic tube]

Tools

-drill and drill bits

-screwdrivers

-saw

-hammer

-grinding machine or sandpaper

-maybe a chisel

Step 2: Preparing the Crate

I removed the inside of the crate using multiple small saws, a knife and a hammer. Someone told me it could be easier with a chisel and a hammer but I haven´t tried that.

I also drilled some holes for the amp and cut a hole to get the powerbank in and out. If you aren´t really shure where exactly the amp will be leave this step out and do that later on. I also cut in a small hole for the bass reflex tube because I made the speaker housing a bit too large.

I took the picture at a later date and because of that the amp is already built in and the latches are already mounted.

Step 3: The Amp and the Battery

After I had prepared the crate I built in the amp and the battery. For that I attached a wooden plate to the bottom of the crate using a few screws. Then I mounted the amp on the plate (mine already has some tiny holes in it to mount it). I just put the battery in, it´s not mounted yet because I plan to use a battery with 12v output soon but all the stuff around it keeps it in place. If you haven´t drilled the holes for the amplifier in step 2 you can do that now when you have the amp in place.

My amp, the Kinter MA-700 has quite a good sound and is quite loud, too. If you need more volume you could use a better class-D amp but that will shorten the battery lifetime and it will get the boombox a lot more expensive, too.

Step 4: Speakers and Speaker Housing

The housing of my speakers was not only too big for the beer crate but also broken. I decided to make a new housing using some old wood. I measured the inside of the crate and built a housing which should fit the crate. But it went a bit wrong and my housing was too high. I solved that problem by building a different lid but I´ll mention that later on.

I could use some parts of the original housing so I didn´t have to cut the holes for the speakers. I just took my saw to make all parts I needed (4 sides, top and bottom). I built in the speakers on the smaller sides of the housing because my crate had holes in the smaller sides and I wanted the speakers to fit behind them. After I had mounted the speakers with a few screws I took some nails to put the parts together and then put screws in the corners to make it more stable.

I drilled a hole at the bottom of the housing where the speaker cables come out because the amp is under the speaker housing in the crate.

Last but not least I made a hole in the side of the housing for the bass reflex tube (which is a normal PVC tube in my case :D) and painted it all black with some spray paint.

I´m no expert in this and I´m sure there is a better solution for this but I´m quite satisfied with the sound so I´ll just leave it as it is. But there are already some instructables on how to build speakers so you should find something there if you´re interested in this.

Step 5: The Lid

Originally I planned to make an easy lid which just lays on top of the crate but due to a measuring mistake on the speaker housing I then built this lid. I needed it to be a bit higher so I screwed pieces of wood to the lid which had to be quite thin so that the speaker housing still fit in. Because it looked really bad after that I painted it black with spray paint and made a pattern of a custom logo I made with Photoshop. Now the boombox is called "Carli".

Step 6: Putting It All Together

After the amp was mounted and I had built the speaker housing and the lid I put all the parts together.
I found out that the speaker housing fit right into the crate on the 4 sides and was lying straight on the amp. To make it a bit more stable I screwed some blocks of wood on the wooden plate, a bit higher than the amp. Because some of the were a bit too short I put some coasters on the wood. Now the speaker housing lay right on the wood and the coasters, a few millimeters over the amp.

I then mounted the latches on the lid and the crate. And the final step was to mount the cap for the hole to put the battery in and out using a screw on the outside and a nut on the inside of the crate.

And then Carli was finished :)

Step 7: Further Thoughts

There are some things that I plan to change in the future:

- I want to add LED lighting to the crate with a USB ledstrip

- I want to add a bluetooth receiver so you don't need to plug your phone directly into the boombox