This mod is a fairly easy mod to put a pair of speakers in your backpack. you will need to know how to solder, sew, and you will need some common sence

Step 1: Requirements

List of items:
a pair of computer speakers with input voltage of around 9 volts DC(check the output on the ac adapter)
Soldering station and solder
Wire
Backpack
Needle and thread
NiCD or NiMH battery pack to match voltage of speakers
battery charger
molex plug with input plug or plug set of your choice
3.5 mm headphone jack input
3.5 mm cable
Altoids tin
hot glue and hot glue gun
knife or other cutting tool

Optional:
bigger/better speakers to upgrade to ; )

Step 2: Taking It All Apart

first off your going to need to open up the computer speakers to reveal the control board along with two speakers and a headphone cord to plug into an ipod.
once this is all done your going to either cut the power wire or unsolder the power input checking to make sure your know positive from negative.
hold onto that as you will turn it into a power supply for it when our battery is dead.

next your will either cut or unsolder the wire's going to the speakers so they can be placed correctly and have the cables extended. again make noe of positive and negative.

Step 3: Headphone Jack

now from you headphone cable you will get 3 or 4 wires when it is cut and stripped, white will be left positive, red will be right positive, and black or no casing will be ground, if you have 2 grounds twist them together. now your will solder your headphone jack o these wires accordingly, 1 will be ground, 3 will be left and 2 will be right (number on the diagram). solder these to the correct points and leave that be.

Step 4: Your Backpack

i was luck and i have the perfect backpack for this it had to side pockets the the speakers could be placed in. In the case you don't plan on them being placed in the smaller pocket.
i suggest you plan on putting the controls in the farthest back pockter to keep them well maintained.
now from where ever you are wiring to and from you will need to make holes along the stitching to run wire this is done with a knife or other sharp tool. After the holes are ready you will take your speakers that have been removed of all previous wires and your will solder new wires back to them and run the through the holes that had been made after the speaker wires have been ran stitch the holes back together to stop any fraying.

Step 5: Altoid Tin

Now you will be placing the control panel and 3.5 jack in the tin. but first you must run the wires from the speakers on of the backpack and to the control panel and re solder them in place. Remember to run them through the tin through a previously cut hole.
once that is done you will cut your Altoids tin accordingly to the controls and jacks you've used, place them at your discretion. after it can sit safely in place you will attach electrical tape to the underside to stop it from shorting out on the tin. you can see from the pictures below hoe i have mine setup. once it is how you want it hot glue it in place.

Step 6: Battery

Now it is time to make it portable, you will wire your battery pack to the power plug so it can be easitly removed and recharged. i soldered the wires together and taped them together but feel free to use shrink wrap(i 'but i had none on hand)