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Hello. This is my first Instructable, so please rate, comment, and make suggestions. In this 'ible, I will show you how I wired and installed some cheap speakers into my backpack.
They produce fairly good quality sound indoors, but seem rather muffled when outdoors. I found this to be a great idea when it came upon me, as it would be convenient to bee able to carry my books in the bag and be able to listen to music "hassle free".

Step 1: Supplies

Tools:
Hot Glue Gun
soldering Iron
solder
soldering flux?
damp sponge
pocket/utility knife
scissors
lighter
electrical tape

Materials:
book bag/backpack 
cheap cassette/radio or speakers
a 3.5mm AUX cord (or old headphones/earbuds)
MP3 player 
old bags with mesh pockets/store-bought mesh material 

Step 2: Speaker Extraction

Take the radio into your hands. Examine it for all screws. If the screws are easily accessible, then unscrew them and open the radio up and remove the speakers from the body/boards. If not, go outside and throw the radio around until the speakers come out.
*IF YOU CAN UNDERSTAND YOUR RADIO'S CIRCUIT BOARD, AND NOTICE AN AMPLIFIER ON IT, THEN KEEP THE SPEAKERS CONNECTED AND USE THE AUDIO INPUT TERMINALS OFR WIRING INSTEAD!*IF YOU DO THIS, THEN FORGET THE COPPER WIRES IN THE COMING STEPS AND SOLDER A 9 VOLT BATTERY AND CLIP TO THE POWER TERMINALS.* 

Step 3: Wire Prep

I thought it would be best to get done with the wiring in the beginning. I used an AUX cord instead of headphones, as i didn't have any old headphones lying around.

First cut the cord into two. Put one of the halves away for later use (or repairs).

*I didn't think of this, but it would have made the project better if i had:
Know how much length you need between the speakers: if you need for one speaker to be on each side, then make sure that you have +1/2 of the backpack's width's worth of cord ready. You may want to cut the same length of cord off of the spare half, as this will be useful for easily getting power "lines" to both speakers at once.

Strip the cord (to the needed length), and examine you wires. You should have one copper colored wire, and two wires of other colors (in my case, green and red). Take your lighter and burn the stripped part of the wires - this removes the insulation that covers them.
*Make sure that you leave a bit of the insulation unburned towards the end that you will not use, as you will need to know which wire is which. 

Step 4: ACTUAL Wiring

Plug in the soldering iron.

We will sort things through as we wait for it to heat.
1. You have speakers with two wire terminals. One is positive, and one is negative.
2. In order to give these speakers stereo function, you will have to give each speaker one audio channel.
3. The audio should go to the "+" terminal, and the power should go to the "-" terminal.

If you need help with soldering, then use this great Instructable: https://www.instructables.com/id/How-to-solder/step3/Soldering-wire/

Tin the iron's tip: Apply solder to the iron's tip until all of the TIP looks nice and shiny. Wipe excess solder off onto the sponge. This step keeps your iron's tip from oxidizing. 

A1. Take the first speaker. choose one of the audio wires, and solder it to the terminal with the "+" on it. (If the terminals on your speaker are not labeled, then I would just guess - I don't think that the side matters as much.)

*Put the wire up to/ inside the terminal's "loop", if provided, and heat it up. Wen hot enough, put the solder up to the wires and melt onto the terminal.

A2. *If your speakers have red and black wires attached, then solder the audio wire to the red speaker wire. 

B1. Solder the copper wire to the "-" terminal/black wire.

B2. Take the second, extra copper wire and solder it to the "-" terminal also (or to the copper wire on the AUX cord). Solder the other end to the negative terminal on the other speaker (speaker 2).

*Now you have audio coming through one speaker and power going to both.

B3. Solder the left over audio wire and solder it to the "+" terminal on speaker 2.


Step 5: Power?

If you have an MP3 player like an iPod Classic, the you don't necessarily need to wire batteries to the speakers, as they supply sufficient power. Some of you may find this necessary, but personally, I would suggest buying a headphone amp from amazon or ebay (ex: http://www.amazon.com/Fiio-E3-BK-E3-Headphone-Amp/dp/B001MPWMDA/ref=cm_cr_pr_product_top )

Step 6: Preparation/Installation 1

This step is just for looks.
Mesh Covering:
Take the knife (or scissors), and cut mesh (off of old bags/backpacks) into appropriate size squares / circles. The pieces should be larger than the speakers. Put each speaker on top of a mesh piece, upside-down. Apply hot glue to the back edges of the speakers, and pull the mesh edges around the front ends so that the edges of the pieces are glued to the back of the speakers. Your speakers should have mesh over their fronts, acting as an attractive covering.

Step 7: Preparation/Installation 2

Measure your speakers' diameters. Draw two circles with diameters that are just a centimeter less than the actual speakers' diameters on strategically selected areas of your backpack. Take your knife and carefully cut the circles out, leaving nice gaping holes through which we will (gently) push our speakers. 
Gently push your speakers through the holes, careful not to disconnect the wires. The aux cord should be on the inside, and the speakers' front ends should be on the outside. If you are adept at stitching/sewing, then develop a clever way to secure your speakers. If you are like me, and lack such skills, then apply hot glue to the backs if the speakers so that they are secured to the backpacks in such a manner that the glue is not visible.

Step 8: HIDE/PROTECT THE WIRES!!!

Apply electrical tape to the wires so that they will not get disconnected by any jostling of the bag's contents. Make sure that the AUX cord will not rip out if you drop your MP3 player. If you suspect that it may, then be sure to secure the wires' end with more electrical tape. *MAKE SURE THAT THE WIRES WILL NOT CAUSE ELECTRICAL DAMAGE TO ANYTHING/SINGE THE BACKPACK*

Step 9: Chill

You're done! Clean up your backpack and work area. Connect your iPod to the speakers, choose your favorite song, and turn the volume up!

(Dont forget the benefits of an amp!)
<p>I have an amp and 2 4 inch Fusion subwoofers. All that's left is the power source. I have a 12v powersport battery, normally used for boats, bikes and all that. Would that work and how would I hook it up?</p>
<p>If the amp is also a 12v, you can just hook it up directly. If it runs lower than 12v, use a regulator that can handle the current. Now if it's higher (although uncommon), you can use a voltage booster or add batteries to match the input voltage on your amp. Or you just may be running an amp that runs off AC current, if so, you need a power inverter or to modify the amp by connecting directly to the secondary output on the power supply (basically modifying the amp). I don't know what you're using for an amp, so i just gave a basic rundown of what you may need to do.</p>
You get cheap amps will work best for this. i made the same backpack but i connected a small radio and the speakers were soldered to the loud speaker of the radio. and i controlled the songs from my Nokia phone. with a Nokia transmitted. it worked out gr8. i made this in 2010 for some school fun. <br>
Ahh, so you used a little amp from a pocket radio... I have tried before, but failed when I got to dealing with the input. How did you arrange the input on the pcb? how could you tell where to disconnect the radio's outputs?
<p>check the ic number mostly used low voltage amp ic's are tda2822m, lm386 check the shematics online they are really simple to wire up.</p>
This looks cool. Now I wanna make a system with a 5&quot; subwoofer.
Lol, nice! Tell me how it goes if you choose to make one.
I would need an amp through.
I don't know if the amp in the link has enough power to drive a subwoofer, but there are plenty of small amps for sale on the internet that would be sufficient (and small enough). You could buy one if you are willing to pay the price. (You probably already know that.)
Yep, I was thinking of making a small amp, like in an altoids tin. I've seen a few on Instructables I believe.

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