Welcome to my second Instructable:)

A few months ago my dad told me he had a couple of old headphones lying around. I thought, I have an old backpack lying around. Do you see the connection already? Well, you can see the finished product above.

Step 1: Materials and Tools

Here is a list of materials you'll need:
- 1x old backpack. Do not pick your new backpack your so proud of, because if might go wrong, and then you ruined your beautiful backpack, so pick an old one.
- 2x speaker. Could be from headphones, could be from some other thing which makes sounds.
- 2x potentiometer
- 1x stereo mini jack plug
- some wire
- some cloth in the same colour of your backpack.
- thread
- solder
- soldering and sewing skills

And here is a list of tools you'll need:
- soldering iron
- drill
- saw
- scissors
- screwdriver
- needle
- pliers
- knife
- sewing-machine is pretty handy, but not necessary.

Step 2: Disarming the Speakers

My dad's headphones were really old and they had volume regulators at both sides, so I was pretty lucky.
I don't think you guys will be that lucky, so I'll explain what to do in your case.

Well, first of course you use the screwdriver to open up the headphones/speakers and get the speakers out of it. Be sure you do not open the working part of the speaker, only the housing! Then take out your soldering gear and disconnect all wires. This seems to be a bit weird to do, but this makes the part of placing the speakers in your backpack much easier.

Step 3: Preparing the Backpack

Now we need to prepare the backpack. There are a couple of things you'll want to do with your backpack.
First you make a little gap at the front of the shoulder straps on exactly the place you want your speakers to be. Then you make a little gap in the back of the shoulder straps really close to the point the shoulder straps are connected to the backpack. Through these gaps you can lead the wire.

Then you'll want to make one little gap at the backside of your backpack. The easiest way to do this, is by making a buttonhole with your sewing machine, if you have one. If you do not, you'll make a little incision and affix the sides of the gap with some thread. This is because you want the wires coming from your speakers to get inside your backpack. You do not want to lead these wires through the connection point of the shoulder straps and the backpack. If you do, the wires wont be visible anymore and yes, this will look better, but this will weaken your backpack really bad.

Last you'll want to make a little pocket inside your backpack for your Ipod or MP 3 player. For this use a piece of cloth which is the same colour as the inside of your backpack and sew it to the backside of the inside of your backpack, just beneath the gap through which the wires will get to the inside of the backpack, with only 3 sides (do not sew the upper side). This way you have a nice little pocket to secure your audio player.

Step 4: Preparing the Housing of the Speakers

You need to make a housing for your speakers, so first take the housing of the original speakers/headphones and drill a little hole in it, just under the speaker itself, so the potentiometer can fit through. Also saw the housing in a nice shape, so it does not look strange on your backpack.

Step 5: Guide the Wires Through the Backpack

This part is really tricky but also real easy to explain. The thing is, you need to get a wire through the shoulder straps of your backpack. This wire actually needs to be two wires, so the best thing to do is use that kind of wire which contains two wires (no idea how that's called). I think the easiest way to get the wire through is to take some iron wire and put this through the shoulder straps. Then make a little hook at it's tip and put the wire through this hook. Then pull the iron wire back and your wire will be through.

Step 6: Soldering the Speakers

Now here is the part of soldering the speakers and making the volume regulators (potentiometers) functional. You will have two wires from your backpack, a speaker with two connection points (an input and an output) and a potentiometer with three connection points (see picture). Also you'll need some lose wires to solder the potentiometer to the speaker.

First take a lose wire (not to long) and solder is to the first connection point of the potentiometer. Then solder the other end of the wire to the input of the speaker. Then take an other lose wire (also not to long) and solder one end to the second connection point of the potentiometer and the other end to the output of the speaker. Next your going to solder the speaker and the potentiometer to the wires which are already in your backpack. Solder one of the wires which comes out of the shoulder strap of the backpack to the output of the speaker (this will be the output wire, so remember that). Then solder the other wire from your backpack to the third connection point of the potentiometer (this wire will be the input wire).
Do not forget to do this twice, ones with the right speaker and ones with the left.

Step 7: Placing the Speakers and Housing

When the speakers are soldered to the volume regulator and the backpack it's time to make the speakers look nice. First be sure the wire coming from your backpack is not to long. If it is, just pull at the wire at the inside of your backpack. Do not pull to hard! When you do, you might break a wire or a soldered point.

When the wires are short enough, it's sewing time. Take a piece of cloth which is the same colour as your backpack. You'll have to make a housing for your speakers. They only things you need to make sure with this part are: you need to make two, the speaker with costumed housing needs to fit in, you need to make sure you can place them over the shoulder straps of your backpack (or sew them while they are), the housing needs to have a gap for the volume regulator and a gap for the speaker, otherwise the sound will be dimmed.

After the speakers are in place and have a nice housing, you might want to place some kind of hood over the volume regulators to make them look nicer and cover up the gap in the housing.

Step 8: Solder the Mini Jack

Now it's time to solder the connection to your Ipod or MP 3 player, the mini jack. First you need to take off the housing of the mini jack and pull it over the wires. If you don't, your won't have any housing on your mini jack, so the wires won't be save and will not stay on there places. Then you need to solder both output wires to the ground point (the big one) of the mini jack. This is the way the electrons will be going back to your audio device. Then take the wire which comes from the right speaker's input and solder it to the right point of the mini jack. Then take the last not connected wire and solder it to the last not connected point of the mini jack. This is the way the music will leave your audio device and go to the speakers. Be sure the wires do not touch each other or make contact, because that way you won't have any music from your backpack. Now close up the mini jack by pulling the housing over the soldered parts.

Step 9: Enjoy

Now enjoy your music while carrying your stuff around:)

Step 10: Possible Improvements

Amplifier
You could easily turn your backpack into a boombox by making an amplifier on batteries (there are lots of instructables about that) and place it inside your backpack. Before you do so, check the maximum wattage your speakers can take, because when you put a to strong amplifier to it, your speakers might blow. The maximum wattage of my speakers is 0,2 Watt, so I'll have to use other speakers if I'd want to add an amplifier.
Extra volume regulation
Apple has earplugs with a volume regulator somewhere half way to the plugs. The mini jack of these earplugs has 4 connection points in stead of 3. With this volume regulator you can adjust the output volume of your Ipod/Iphone. You could use this mini jack and volume regulator to add the possibility to turn your music to silence. This could become handy when you walk in a store or library or some other place where your music could irritate others. The best place to put this volume regulator would be on the back of one of the speakers. If you do so, you should make a little kind of pocket to secure the volume regulator. Also you will need to guide an other wire through one of the shoulder straps of your backpack.