Ammo Box Speakers

This instructable will demonstrate how to turn a .50 caliber ammunition box into a sweet set of speakers that can be used with your mp3 player, laptop, or any other portable device.

This set of speakers is rugged, compact, easy to take on the go, and LOUD!  The whole project will cost about $50.00 usd. and can be completed in an afternoon.

Step 1: Materials

Most of these materials can be purchased locally, but I chose to get some of the items online to cut down on costs.

Heres what you need:

1.  One .50 caliber ammo box- http://www.joesarmynavyonline.com/servlet/Detail?no=5984
2.  Two 4" speakers- http://www.amazon.com/Pyle-PL42BL-4-Inch-Two-Way-Speakers/dp/B000230LBI/ref=sr_1_2?ie=UTF8&qid=1291250695&sr=8-2
3.  2 sets of speaker wires- these will come with your speakers typically
4.  12 volt amplifier-http://www.dealextreme.com/details.dx/sku.34406
5.  3.5mm panel mount plug- http://www.radioshack.com/product/index.jsp?productId=2062450
6.  12 volt illuminated toggle switch- http:// http://www.radioshack.com/product/index.jsp?productId=206249312
7.  Computer power supply- a broken one is ok for this, as you will just be using the plug and cord.
8.  Egg carton foam- I had this piece of foam from some type of packaging.
9.  1 3/4" desk grommet- these can be found in the hardware store or office supply store.
10.  12 volt power supply- this is the kind of power supply that a laptop would use.
11.  Two 4" computer fan grates.
12.  3.5mm male audio to rca audio
13.  3.5mm male to 3.5mm male audio cable
14.  cheap little tripod from the dollar store
15.  various hardware.

Comments

[Mason_Ernie]

If I got an amp with a USB input and a micro Bluetooth receiver, could I just stream my music?

[scotprice]

I loved this project, but I am having difficulty getting the LED on the toggle switch to light up. I dont use the same toggle as mentioned in the parts list, but it is an illuminated toggle switch with LED light. I have tried everything I can to get the light to work, but nothing seems to help. Does anybody have any idea what might be going on? I did the same exact build as the instructable, so I havent switched anything up.

[WillERoberts]

check out my instructable and see if that helps, i've used pictures rather than words so it should be fairly simple to understand.
http://www.instructables.com/id/Ammo-box-speakers-2/

[WillERoberts]

http://www.instructables.com/id/Ammo-box-speakers-2/
Link to my ammo box instructable. Runs for 75 hours easily from 1 charge, check it out! This instructable was my inspiration!

[jricharc]

With the Kinter MA-160 it has a USB port built in, would this charge an iPod?

[WillERoberts]

Yes it would, i've tried it. Your main problem will be battery life then though. it will half your battery life if not more.

[ctx1985]

Hey not sure about that, but I actually built this instructable and wired in/converted an old blackberry charger so I can charge my i
Pod as well.

[reddragon]

Nice one, like the amp u used could I use a 500 watt amp? Would it be possible to make this both battery powered and plug-in?

[ctx1985]

I wired mine both battery and plug-in via a 5 pin automotive relay with a switch. I basically made it so when the switch is off, the box runs on battery power (pin 87a, NC on most relays), then when you plug it in and flip the switch, the relay is energized and switched to pin 87. Pins 30 and 86 get B+ and pin 85 is ground I believe.

[IgnorantZebra]

do you know what relay you used?

[ctx1985]

I used a 5 pin, Bosch style automotive relay. If you go to an auto recyclers, you can pull one out of pretty much any car. You can usually find them under the dash near the fuse panel. The pins will be labelled 30, 85, 86, 87 and 87a. Here's a link to a picture of one that's pretty much identical to the one I used.
http://www.traderscity.com/board/products-1/offers-to-sell-and-export-1/automotive-relay-19224/

[ctx1985]

Except the one in the pic is just a 4 pin, but the 5 pin looks identical except it has pin 87a.

[ajensen13]

Battery and plug sounds awesome but I would need instructions cause I'm stupid :)

[reddragon]

That's what I'm trying to get cause I'm electrically challenged

[the701man]

Where did you get your helping hands?

[ctx1985]

This was a great instructable! Fantastic idea! I wanted mine to be able to run off of a plug and battery, so I wired in a 5 post automotive relay with a switch...works great for switching between power supplies. I also took an old cigar lighter socket from an old car and wired it in, which is great because I have a 12v solar panel that plugs into a lighter socket.

[erest]

Honestly @yaunclesam I dont believe that you truly need the bass port as long as you have good insulation. A lot of people will tell you to put one but mine sounds great without it. It really depends on what speakers you have personally I wouldnt change them, I just upgraded my amp.

[Yaunclesam]

What size bass port did you use? What would you have done differently would you change the speakers?

[erest]

Ill let yall know about my build. I have a 12v SLA battery its a 5ah, i think its called a hanger 12 battery on amazon for about 30 bucks. Its wired to a lighted switch and runs my 100w amp (It doesnt run the true 100w because its only getting 12v but its much clearer than my 25w amp) I have a bluetooth module so that I can connect my phone to it wirelessly, it has a input switch as well so that I can swap inputs on the fly which I used the schematic from the instructable that I linked at the bottom, I have some boss 250w speakers I got at Frys for about 30 dollars, and I topped it off with some sound isolation foam that I have also linked. All in all, I have about 130 dollars into this, but it kicks! Ill post pictures later. If you have any questions how I wired anything please let me know I'm a electronics technician, and I am very obsessed with this speaker!



http://www.instructables.com/id/Curiously-Small-Audio-Switch/ http://www.amazon.com/gp/product/B006IJJH7O/ref=oh_details_o01_s00_i00 http://www.amazon.com/Hangar-12V-Battery-Charger-Combo/dp/B0006OBOFK/ref=sr_1_1?ie=UTF8&qid=1359437580&sr=8-1&keywords=hanger+12v+battery http://www.amazon.com/gp/product/B003XRK73W/ref=oh_details_o00_s00_i00 http://www.amazon.com/gp/product/B0007XFBE0/ref=oh_details_o00_s00_i01

[derrickcan]

got it to work! a journey man electrician got the dc plug wires mixed and now in business! yes! first 'able down!

[derrickcan]

@mstoner: so i wired as you said, i can get the light on my switch to turn on whether the amp is on or not, which seems odd to me. i am using the amps shipped plug and am using the black wire as negative and the wire with thin white lines as the positive. the switch is for a car, up to ten amps, the battery is 7a, i do not know what to do now.

[derrickcan]

@mstoner thanks man, i will give it a shot!

[mstoner]

@derrickcan
You need to use the negative terminal on the battery as the ground point for all your wiring. There is not enough mass in the metal can to make an effective ground.

[derrickcan]

hi, so i bought a ta 2024 board, a 12v hangar battery some low watt speakers a switch with a light. I have it wired - to ammo box to light to switch to amp and back to battery. the switch will turn on the light with the amp off, turn on amp no light from the amp and no sound....I am grounded to the ammo can and my light wire is attached to a screw off the speaker mount. Is it cause the speakers are part of the ground? i fried two boards figuring this stuff out. I really could use some expertise. It looks pretty cool so far as an anchor or paperweight. Thanks.

[nbeck4]

I used this instructable as a base design for my stereo. I used a .50 cal ammo can, cut out the power supply cage from an old server and used the twin supplies that come with it. it took some modification of the card the supplies plug in to, but I made it work. I JB welded it all together then got to work on the inside. I mounted the speakers internally and drilled holes in the side of the can instead of going the external mount, fan grille route. Here are the components I used:

Kinter MA-700 amp (includes USB, RCA, and FM modes with a remote for which I mounted the receiver in between the speakers)
8x D cell bettery box internally
12v computer power supply
DPDT "ON-OFF-ON" switch
Speakers from an old stereo my dad had laying around
external speaker hookup from the same stereo which will connect to a pair of 50W bookshelf speakers I already have.
5A in line fuse and holder
3.5mm - 1/4" - RCA adapter string to plug in cell phone/mp3 player
all the necessary wiring was scavenged from the server or speakers.

All in all I am about $55 into it as I was able to get some free parts like the power supplies and such. I posted pics of the outside here, the inside will take a bit more to make it photo quality.

Thanks for the idea, I really needed something like this for camping trips and such and now I have it.

[mstoner]

Here is my ammo can project. It was inspired by the Thodio A-Box, and I admit I copied it to a large degree. Mine runs on 24 volts, the amp board, that is rated for 100w per channel, needs a minimum of 22 volts to even turn on, so it is powered by two 12 volt 8ah SLA batteries wired in series. They are charged with a 24 volt electric scooter charger. The Ipod controller board and touch pad were from a cheap Ihome dock. That is powered from the batteries, but through an adjustable voltage regulator tuned to 7.3 volts. The can is lined with 1/4 inch MDF, it took a fair amount of hand fitting to get all the seams good and tight, because the can itself is not all that uniform on the inside, and has curved edges. The board is bonded to the metal with contact cement. The lid is lined with foam that came out of a hard side waterproof camera case. The drivers are 4 inch Polk Audio, marine rated car speakers, mounted with all stainless steel hardware. I chose car speakers because the amp is rated for 4 ohms. The bass port works well, I found a formula that you plug in the numbers for speaker size and specs, and the cabinet volume, and it gives you the optimal diameter and length of the tube. I can't recall at the moment where I found the formula, but it was on a DIY audio forum. The sound it puts out is impressive, and will run for 6-7 hours at medium to medium high volume. I built it to be portable, but it is not light, it weighs in at 22 lbs. But it's still very practical for camping, the beach and backyard parties. The amp board I used can be found here: http://www.ebay.com/itm/Hifimediy-T2-2-100W-TRIPATH-TK2050-TC2000-10000uf-/140646110153?pt=US_Home_Audio_Amplifiers_Preamps&hash=item20bf2953c9

[derrickcan]

WOOHOO! 12v 7a battery, 2024 amp and 4 inch speakers ordered! I can't wait to build my box! Thanks so much for this 'able!

[L33T_h4x0r_d00d]

This project needs some work. There were no precautions taken to mitigate rearwave destructive interference. There are no indications that TSP's were taken into consideration when selecting drivers. The enclosure was insufficiently physically and sonically damped which should be a high priority given metals tendency to propagate vibrations. I'm not even sure that the amplifier impedance capabilities were compared to the drivers Re. Let me explain why these things matter and what you can do to mitigate their affects.


Speakers are motors. They move a diaphragm back and forth to produce sound. Sound is actually produced on both sides of diaphragm and they are the inverse of each other. That means that if the two waves were to meet at 0 degrees in time-space you wouldn't hear any sound at all since the two waves are canceling each other out. In all but dipole  (which are very specialized and not at all applicable here) the sound created by the front of the speaker must be isolated from the sound coming from the rear of the speaker. This is why speakers come in boxes. A speaker may have multiple drivers in it but if all those drivers are sharing the same internal box volume, they're all working from the same signal. That means that if you have a speaker that has 4 woofer drivers in it, and there is no division in separating each of the woofer drivers, they're all working from the same source signal. All 4 drivers are working together to act as one larger driver. 

In your box you've got two channels of sound (left and right) sharing one box volume. If you have two discrete channels they're going to, at some point since they're producing different sounds, be working against each other. This means you'll have significant dips in the sound produced because the speakers rearwave's are canceling each other out. What happens to the rearwave happens to the front wave as well. Here's what it looks like when you measure the spectrum.  http://modulatedlight.org/optical_comms/comb_filtered_audio_spectrum_1a.gif  That line should be relatively flat but it has severe dips.  Granted that pic was created by AC hum interference but rearwave combing looks the same.  

All driver's have what are called Thiele Small Parameters. They measure every aspect of how the driver reacts.  These parameters are used by the engineer designing the speaker to model the output.  If for instance you put a driver in a box that is too small, generally they lose a significant amount of low end.  Speaker engineering is a balancing act of finding the right driver, putting it in the right sized box and creating the best crossover you can that meets your requirements for overall size, output, cost etc. If you slap any speaker you find into any box you have it will most likely make some sound but there is very little chance it will do it with any efficiency for both accurate reproduction or power output. There is a very good chance you can damage components as well.  

You used an ammo can which is a very interesting speaker box.  They're light, easily portable and fairly weather resistant. The problem is, the only damping you used was some foam.  Most speaker boxes are built out of MDF or something very similar. MDF has a couple of key properties that make it useful for speakers. It's heavy which means it requires a lot of driver movement to make the speaker rock or move. It's very rigid.  When a driver moves inward, if a speaker is sealed, the driver is compressing the air inside. One of the TSP's specifically measures a drivers ability to do this.  If  your box is not rigid when the driver moves inward the box can swell causing indirect resonance.  Also when a driver moves inwards the rearwave moves away from the diaphragm and at some point will impact the rear wall of the box. If the box isn't rigid the rearwave will impart some of it's energy into the box which will resonate through the box to the outside. Again, it's bad when the rearwave gets out of the box.  Also, just to be thorough, MDF is highly machinable which is makes fabrication with it very easy but that has no bearing on your project. 

All speakers have a rated impedance. The TSP for it is Re. It's how many ohms of resistance a speaker provides.  Amplifiers are also rated  by how many ohms they can push a signal into. No matter what class amplifier you have (A,B,D,T) it will say somewhere in the documentation that it shouldn't be used with speakers rated less than X ohms. Generally home audio speakers are rated at 8 ohms and amplifiers are capable of driving a signal to 8 ohms without issue. On the other hand generally car audio speakers are rated at 4 ohms with matching car audio amplifier ratings. It appears that you're using a small home audio amplifier with a set of car audio coaxial drivers. It may not be the case but there's a very good chance you're powering those speakers with an amplifier that is not rated to do so. I'd imagine at some point you're going to have the amplifier fail. If you're lucky it will just stop working but it could do as much as cause a fire or shock someone touching any exposed metal. 

You've also ported the box with a "bass tube". Ports are wonderful things but they must be calculated and the correct length, diameter and end correction chosen based on the TSP's of your drivers and the size of the enclosure. Doing anything else is just letting rearwaves out, which we already know isn't good. 

I'd suggest you head over to the DIY section of www.AVSForum.com and take a peak around. Also, download WinISD pro which is a free tool that will help you model your drivers in different enclosures as well as garner an understanding of how the TSP's affect speaker performance. 

[jimmydean602]

Ive had a need for a loud portable durable speaker for a few years and never could find one to buy that satisfied my needs and wasnt outrageously priced. Did a lot of research into making my own before stumbling across some ammo can speaker projects like this one and decided to make my own.

Used a 50 cal ammo can which I applied a butyl sound deadening material to, some kicker 4" speakers, Lepai t-class amp and a 7ah 12vdc sla battery that is most commonly used in home alarm systems with quick connects for a battery tender for recharging. Audio is connected to a 3.5mm plug with my ipod. I also did some subtle customization to keep the military feel with the blacked out nut washer combo and the graphic i made and trimming the speaker grills in flat white.

The 7ah battery is a little overkill since this amp and speaker combo is very loud and efficient. Future mods in the next few weeks will include:

-port tube hidden under the latch
-lighter battery pack (prob a 3ah li-ion)
-speaker feet
-bluetooth connectivity

[alarcon1573]

How did you wire the battery into the amp. I have fried two amps now. I have a switch with an LED in it, From the battery the positive goes to the positive the ground to the ground. I cut the cable supplied with the amp and ran it to the switch directly. The all black wire ran to the ground on the switch, the black and white wire runs to the switched power on the switch itself. Am I missing something here.

[alarcon1573]

Ok. I think I figured it out. I had the wires going to the amp backwards. I checked on a laptop 12 volt power supply with my multimeter and found that the inside of the plug was the "hot" side, and the outside was the ground, which is the opposite of the way I had my power unit wired.

[capeman29]

Have you come up with a way of doing internal bluetooth? I've been kicking around that idea for months and cant get around the notion that a bluetooth receiver inside a sealed steel box would have a range of about 14 inches, haha.

I have found lots of simple solutions on bluetooth receivers, some even run off of 12v so they could be wired to the battery... but the range problem still eludes me.

[mucusboy]

Ive contemplated the idea for my next one as well, and the only solution ive come across is taking a bluetooth reciever apart, finding where its internal antenna is and mounting/ attaching a wire or other antenna to it to run to the outside.

My idea was to make a tiny hole directly next to the speaker and have a tiny wire (antenna) go around the outside of the speaker to hide it inbetween the speaker body and the ammo box. That way you have an external antenna for the reviever thats partly hidden, maybe completely hidden by the speaker mounting body.

[jimmydean602]

I have had the same feeling, especially given that mine is lined in sound deadening material. Ultimately I decided that I will be using:
http://www.amazon.com/Britelink-Bluetooth-Audio-Receiver-Portable/dp/B0059M4G9K/ref=sr_1_3?ie=UTF8&qid=1346078657&sr=8-3&keywords=bluetooth+receiver
although I have yet to order it. Small, good battery life, rechargeable, great reviews. The only reason I am even attempting this is because I am porting my box and will be mounting the receiver directly above the port. Hoping this will allow adequate signal transmission but who knows. I will definitely post an update once it is all finished and let you know about the range.

[dtwoods]

I REALLY like your project and want to build one of my own... I was wondering your ideas on adding a IR remote for the volume... etc... I'm thinking that to maintain the durability I would need some type of IR "extender" so I can access the IR receiver on the amp. It would be sweet to have this strapped to the tractor while streaming Pandora or listening to NPR on a Saturday.... Just curious to your thoughts. THANKS!

[capeman29]

If anybody is looking for a great AMP/Battery combo for this project, i have had wonderful luck this setup.

Battery
http://www.amazon.com/Hangar-12V-Battery-Charger-Combo/dp/B0006OBOFK

Amp
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=320-304

The 7ah battery runs the amp easily over 48 hours without needing a charge... could be longer, i still haven't run it out. The battery weights about 7 pounds, making the box a nice and heavy manly man's stereo! haha.

Im no expert on electronics - was wondering if the batter wired straight to an amp like this needed any sort of regulation or protection - can you damage an amp by running the battery down to voltage below amp-spec?

[capeman29]

Picture of my box - i use it at the beach and camping

[cswett]

For the battery you used. Do you have to take it out and plug it in to the wall or can you leave it in the can and charge through a port?
Trying to find a battery that I can charge through an AC port on the can.

[dog digger]

Did you know that the computer power supply can power the amp?
it does provide enough power and it has 12v and -12v and 0v, 5v and the list goes on.

[dustinbikes]

yea, the reason I did it this way is that you want the power going to the amp to be DC