Ammo Box Speakers





Introduction: Ammo Box Speakers

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Hi all! As the title suggests I'm doing this instructible on ammo box speakers!  I came across this instructible > a good few months ago now, and this gave me all the ideas/concepts/designs to give me courage to build my own. I suggest you check out that instructible first just in case i miss anything out (the comments were especially helpful!) :)

I thought I'd tell you a little bit about myself as this is my first instructible. 
Name :- William Roberts
Age :- 18
Bio:- I am a student currently studying Design and technology: graphics products, physics, maths and geology. I absolutely love DIY ideas and i am very appreciative of design influences. I love the great outdoors and i regularly participate in sports. I also love the occasional extreme sport (mountain boarding most notably). Live in the UK, you could probably guess that since i quote everything in £.

well now that introduction is out of the way i'll get on to the 'ible! 

Step 1: Parts and Tools

On this build i wanted to keep the costs as low as possible but without sacrificing quality. To get it as cheap as possible this meant shopping around on the internet (Ebay especially!). Due to keeping costs down i did buy some stuff from China so this greatly increased waiting time in order to build. so, on with the parts list!

1) Ammo box - £12.73 (Ebay, price has gone up)
2) Speakers - £28.99 (incarconnections)
3) Battery pack - £2
4) Mini 12v amp- cost me £2.50 in an auction from this seller 
5)Panel mount 3.5mm jack- £2.48
6)Rubber feet - £1.78
7)3.5mm to 3.5mm jack - £1.98
8)Batteries! (wouldn't get far without these!) bought at Cost-Co pack of 48 for about £5
9) on/off switch - £3.84
10) Panel mount Female DC connector - £1.38 (ebay)
11) DC connectors (ebay) £1.48 x2 -

Total= £65.64 (with loads of extra batteries!)

Additional items (improvements)
12v deep cycle battery 9Ah - (ebay) £17
12v battery charger
(just a cheap one) - £7.90 -
Some decent wire £1 (1m). 
spade connectors £1 for 10 (local store)

extra £26.90

(i could have reduced cost by using cheaper speakers or getting the right battery to start with)

Tools used

1) Cordless drill with appropriate drill bits (2,3,10mm metal drill bits)
2) Jigsaw
3) Round metal file
4) Scissors (wire strippers would be better!)
5) Electrical tape
6) Towel (not nessesary, just used to protect table)
7) Quick-grip bar clamp
8) Small flat head and Phillips screw drivers
9) Bit of wood (see later)
10)  Hand saw
11) EAR AND EYE PROTECTION. This is vital! I started cutting without these and i got hit around my eye multiple times from metal fragments. And the noise is deafening. You've been warned.
12) Compass (for marking out)
13) Pencil/marker pen (or even a nail, works just the same)
14) Dustpan and brush!
15)  rotary tool (Dremel) with grinding tool to remove some burrs

Things I should of used
1) Wire strippers
2) Soldering iron and solder
3) Spot light (or just better lighting in general)
4) 20mm metal hole borer (would have been a lot easier and neater)

Step 2: Preparation

Before i go into the main part of this instructible i'll just give you a rough time guide. All times will be slightly exaggerated ;)
1) Marking out - 10 min
2) Setting up - 20 min
3) Cutting and filing - 1hr 30 min (take your time on this!)
4) Circuitry - 30 min
5) Mounting - 15 min
6) Cleaning up - 20 min (I got metal filings EVERYWHERE! plus you need to put the tools away)
7) Testing - 999999999999 min (well maybe not, but you need to give plenty of time to admire your work :) )

Obviously some people will do this quicker than others so don't take these times as set guidelines. If you do it slower who cares, you'll still get there in the end!

So here we go!

Marking out

The way i did this was... placed the speaker grills where i wanted them, traced the outline in pencil, found the middle using the compass, center punched the middle, set the compass to 93mm (size of speaker mounting hole) then draw the 93mm circle. This will give you the hole you need to cut. For the on/off switch, 3.5mm jack and external power just draw the circles you need to cut out in the appropriate place.

Step 3: Wiring

My knowledge of electronics is very limited so i did refer to Google quite a few times!
I thought this would be the hardest part due to my lack of electrical knowledge but this was the easy part! As you can see from my parts list I've gone for easy connectors (screw terminals and crimp connectors) as my soldering iron broke and gave me a nasty electric shock last time i used it.

Parts needed 

Battery pack
on/off switch

Mini amp
Small amount of electrical cable (I just cut some off the battery pack)
Panel mount 3.5mm jack
3.5mm to 3.5mm jack

Just to be safe (to test the system)
Speakers and speaker cable 
mp3/phone for music

This part is best shown with pictures.

Step 4: Cutting

This is by far the longest process. Make sure you have all your tools ready for this step.
Make sure you wear eye and ear protection!
support the box with a bit of wood (see pictures).

Drill a starter hole, then jigsaw your way around the markings.

Step 5: Mounting

There's not much to say with this really, just follow the instructions on the speakers and use your common sense!
I still haven't secured my amp to anything because i don't know where to put it but it seems to be fine loose in the box.

Step 6: Turning Up the Volume!

The fun part! Just don't do this late at night ;) Pick out your favourite song, plug the mp3 player in, turn speaker on (make sure lid is closed) and press play! Don't put it on full volume straight away! gradually increase... Enjoy! :)

Easily fills a sports hall with music! I even use it instead of my home stereo system!

Step 7: Overview

Ok so I've thoroughly tested this and these are my findings.
Firstly, i never needed to buy the AA battery pack. The 12V sealed battery i replaced these with lasts 75 hours (being played at 60% volume)! For all the people who think that is a crazy amount of time, it is. Your standard electrical equations do not work with this system because of the deep cycle battery. Using some basic formulae (V=IR , P=VI etc...) i worked out that they should only run about 15 hours when being played at 25% volume. After doing some research into this I found out about the Peukert effect. Honestly i still don't fully understand it (not even my physics lecturer could), but if anyone could explain it well then let me know!
Charge time is roughly 8 hours.

Secondly, this weighs a tonne ( well not quite). So don't drop it ( i have on multiple occasions and there is a few dents to show for it) the battery itself weighs about 2.7kg.

Thirdly, there seems to be some feedback in the system (but only when i plug a 3.5mm in) I think it could be that the cable is cheap but i'm open to suggestions!

lastly, don't bother screwing around with a bass port. It sounds SO much better closed.

If you want any more detail or if i have any mistakes just comment below! Thanks for looking! and if you wouldn't mind voting for me i wouldn't say no ;)

I did try a Lepai amp in this set up but it drew too much power. It would only last around 18 hours on a full charge! the Lepai is a lovely amp but not for me.
The paracord handle makes it nice to carry and i think it makes it look better.
I have considered painting it, but i love the original look too much!
I have also considered a folding solar panel (in the process of testing it on a smaller scale (only 5v)). So depending on how that goes, i may end up charging from solar!
I did use this system with the AA battery pack i bought but the battery life was only 2 hours when being played at 50% volume. Pretty disappointing considering the deep cycle battery lasts 75 hours easily.



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I'd say it weighs close to 20 lbs. Maybe a little less. Not sure how many kgs that is. If you look at my wiring diagram, I've worked in a jack on the case that goes to the batteries. I then replaced the tip on the battery charger cord with a male connector that fits the jack. It's the panel mounted jack below the switch in the pictures if that helps.

Here are some finalized shots.

13, 12:29 AM.jpg13, 12:29 AM.jpg13, 12:29 AM.jpg

I know it has been a while since you made this, but I was wondering if you have any pictures/diagrams of how you wired the switch together? I saw your wiring diagram, but I can figure out how you wired the six post of the switch together so that it switches between battery power, and wall power.

i love the way you wrapped the handle, might do something similar on mine!
underneath the 2 handles is that just a bumper to stop the handles getting hit? or is it a port?

The two handles hold my iPhone and the bumper is so that the phone doesn't fall through. There's probably a better way to do this. If I could do it again I would probably use metal handles and distance them far enough apart so that you can still work the phone while its in there. So basically on the very top and very bottom of the phone.

ah ok! can you lift the box by those handles?

I probably could but I wouldn't expect it to hold. They're just cheapo plastic cabinet handles with a screw on each end. I much prefer the para cord wrapped handle as u recommended ; )

Finito! Mostly... I still haven't tried adding USB to the mix, but I'm kind of hesitant since the little charging module I got was only $.99 at Target. But other than that... Finito!

I ended up adding a place to put my Iphone while it's playing. I conveniently found some plastic drawer handles that fit my phone perfectly at a local hardware store for $1 each. Then glued a little rubber foot at the bottom so the phone doesn't fall through. It looks decent. If I could do it again though, I'd probably spend the extra $3 and get metal handles. The spray paint on these comes off easily when I bump the box on anything.

I also cannibalized a pillow that I wasn't using for it's polyfill (polyester fiber fill). As WillERoberts mentioned, the largish batteries I used took up a lot of the space in the box. The theory behind the polyfill is that it can trick your speaker into thinking the box is up to 40% bigger by slowing the air movement down. Not sure the specifics, but I think even with an empty 50 cal ammo box, you'd probably want this stuff. The calculations I did (see comments below) seemed as though you'd want a larger airspace for two 4.5" speakers.

At first when I installed the polyfill, it actually sounded worse. The key to this is that if you pack the polyfill too tightly, it can actually have the opposite effect. So I took some of it out, and whala. A lot more bass, noticeable instantly.

For the connections on the outside, I pretty much followed my wiring diagram. I've got a DPDT switch with an On-Off-On configuration. I read that the 12V battery chargers can actually harm components if plugged while you're running off the batteries. The reason for this is that batteries are fine at higher voltages when being charged, where electronics are usually not. So when the battery is dead, the charger might spike at 14-15V. So the DPDT switch has 3 positions:
- On-1: Battery is connected to the amp.
- On-2: 12v power supply is connected to the amp
- Off: All power to the amp is cut off. This is the ideal position for the charger to be plugged in (and is my fail safe. I don't technically NEED this position. You could charge the batter in On-2 position, but I didn't want to risk forgetting which side was which).

So, on the side of the box you've got your switch, your headphone female panel mount connector, and two dc adapter connectors, one for the charger and one for the amp power supply. Note that I had to replace the tip on the end of my Battery Tender Junior so I could mount the jack on the side of the box. If you're ok with opening the lid to plug stuff in, you could easily forget this step.

In order to achieve a rattle-free design, I bought a cheap roll of door/window weatherstripping. It's not really it's intended design, but it works like a charm. I also glued in some metal L brackets to keep the amp and the batteries in place. Theoretically, after you put in the polyfill, these things shouldn't move around too much, but the batteries are heavy and I didn't want to chance it.

And speaking of rattling, I wrapped the handle in paracord like WillERoberts instructed. This makes it comfortable holding this thing (especially with the weight) but it also prevents the handle from rattling like crazy, which is will be prone to do.

Thanks for the 'Ible WillERoberts! I had a lot of fun doing this and it came out great!!!


Looks great! how much does it weigh? with 2 batteries i guess it's close to 5 kg?
when you charge your battery do you connect the charger straight to the battery terminals or have i missed something?

Another update. I might be taking this a little far... but it's certainly fun. So I made a wiring diagram that might help if anyone else wants to do this.

I decided not to go with a bluetooth module. Didn't want to add the complexity of switching back and forth between headphone in and bluetooth.

I did add a 7 amp fuse (I upgraded the power supply on my lepai 2020 to a 6 amp model, which was recommended in many forums). If you decide to add a fuse, make sure you get the right amperage. The volt rating on the fuse doesn't matter. You can't even really find fuses rated at 12v (I don't think). So using 125v fuse is fine.

I wanted this to be a nice clean build, with everything you need on the outside of the box. This adds a lot of complexity, but it's not too expensive.

The DPDT power switch is called an on-off-on type. Which means when I'm all said and done, it will switch from battery power to wall power and have a totally off position in between.

The usb  that I'm thinking of getting isn't exactly panel mount, but it will do, and it's really cheap. I'm just going to wire the power to the two leads, and it will convert the 12v to 5v for the usb. It looks like if you take off the cover, too, you could drill a large hole in your box and essentially panel mount it. For about 10, you can get something more legit, but I thought this would save a few bucks. Click here to see the one I'm using.

In addition to the usb and rocker switch, on the outside of the box will be:
    - a panel mounted DC jack for the Battery Tender Junior 12v charger
    - a panel mounted DC jack for the amp power supply
    - a panel mounted 3.5mm headphone jack

I was originally going to try to squeeze two 9 amp hour batteries into this little box, but after some research, it looks like 10 amp hours is going to be more than sufficient. If you want to do your own calculations, consider that 4-6 watts per speaker is actually a lot of sound. So if we assume 5 watts per speaker, 10 total, with a 12v battery the equation looks like Watts=amps x voltage so we get about .833 amps. That roughly equates to about 12 hours on a single charge, which was more than enough for my purposes. Click here to see the batteries I'm going to get.

In terms of the mounting in the box, I could just glue everything down. Totally fine way to go. I am OCD though and wanted to have the "option" to remove thing if I needed to. So here's what I was thinking. I'm going to get some little simple steel angles. The orange ones I will drill and attach to the bottom of the box, since the bolts will be hidden. The others (pink) I will glue on with some J&B weld. That stuff is seriously amazing. In theory, if you remove the bolt on the centermost angle on the batteries (assuming that the amp is removed first) you can slide it out far enough from the far angle to remove it. Kind of confusing but if you look at my photo you can probably make sense of it.

Two more angles will mount the amp. They'll glue on the box and then will bolt to the amp mounts. On the other side I will just glue on some sort of metal rod to the case (green). This will only work for the Lepai 2020a+ amp though. If yours is smaller you probably won't have any problems putting it anywhere.

Hope that helps. I'll post final images once I get the batteries and get everything mounted.

AmmoBoxWiring Model (1).jpgAutoSave_AmmoSpeakers.jpg
You will need to enter a value between 1.3 and 1.4 for the Peukert number becasue you are using lead acid batteries. If your amp is taking 6A then your speakers should last less than an hour.