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I built a PA system into my car to talk to other drivers, people on the street, and to mess around with my friends.  When I got the idea to put the PA in my car I found that the systems you can purchase are of low quality and are extremely expensive.  I then researched making my own and found that there really are no good instructions on how to make your own PA.  I messed around with a few different options and finally created my system.  I installed a CB radio and 5 ft antenna to accompany my PA.  I also installed a new head unit that has Bluetooth and HD radio as well as two 12 inch subwoofers and accompanying Amp.  Everything on my car I did myself.  I hope you enjoy my first instructable! 

Step 1: How to Build a PA System

I have drawn a basic setup of a PA system(one of the pictures).  You will have a CB radio, which you will talk into(must be a CB radio with PA capabilities).  The CB has a PA output on the back, which uses the came port as a headphone jack on an iPod.   You will connect this to the input on the amp(basically the CB doesn’t put out enough power for the speaker to be really loud, so the amp takes the sound output and amplifies it so it is really loud).  The input on all amps is a standard RCA plug(same as the red and white sound plugs you use to connect your vcr to your tv) .  The necessary cable can be purchased here: http://www.newegg.com/Product/Product.aspx?Item=N82E16882196069
Once the Amp has received your signal it will amplify it and supply the signal to your external speaker on your car.  You will use regular speaker wire to connect the two. http://www.newegg.com/Product/Product.aspx?Item=N82E16882125183 the speaker I bought is a radio shack speaker.  They have them online and at most stores. http://www.radioshack.com/product/index.jsp?productId=2103339 I only used one speaker because my van only had room for one.  If you have room for more beneath your car I highly suggest it.  I would get at least two.  Most amps have room on them for you to plug in more than one speaker.  I put four of those speakers on my friends land cruiser and its pretty awesome.  You can buy an amp for a hundred bucks at bestbuy, but I got one offline, I don’t really need a high quality amp for this sort of use. http://www.newegg.com/Product/Product.aspx?Item=N82E16882184347

Ok, so that was all audio, but a big portion of a PA system is getting power to everything and doing it right,  When you do anything with power on your car the first thing you will always want to do is disconnect the negative battery terminal from your car.  All of the electronics in your car connect their positive wires to your battery, and their negative wires to the metal frame(also called ground) of the car.  Then the negative on the battery is also connected to the frame of your car.  Thus completing the circuit.  When you disconnect the negative from your battery you are breaking the circuit.  This is the equivalent of flipping off the circuit breaker in your house before you do wiring.  You don’t really want to shock this shit out of yourself. 

Ok, so everything needs power, the most convenient way to power everything is to do it through the AMP, because it has power posts in which you can connect wires.  You will need power wire, ten gauge(thickness of the wire) will be more than enough.   A amp power kit normally comes with three cables, a long red or blue power wire, a short grey or black wire, and some of them cone with a really really long thing of super thin remote wire.  The long thick wire is to connect the positive on your amp to the positive terminal on your car battery.  You will want to sever this long wire and put the fuse box in, it should come with one(the fuse protects your car and keeps you from melting your wires in the event of a short circuit, which happens when you touch a live power wire against the negative or ground.  It can be odd to explain why you need a fuse through righting, but just have one and you’ll be good.  Ok, now you will use the short thick darker cable that came with you power kit to connect the negative on your amp to any non painted metal surface on your car(since the negative terminal on the battery is also connected to the frame of your car the circuit will be complete.  If you look from the footwell up toward your dash you will probably see a bunch of bolts and such, you can remove one, and put the cable on to bolt it to the frame.  
Ok, now that you have powered your amp you will need a switch to turn it on and off.  Since amps connect directly to your battery, they need to be turned on and off, because having the car off will not turn them off.  All amps have a remote port on them (some just say “rem”) when this terminal receives any amount of power it will tell the amp to turn on.  Normally this is connected to your cars head unit
(stereo system)  This way when your stereo turns on, so does your amp(since most amps are used as part of a cars internal speaker system) your amp however is not part of your cars internal speaker system, so you will want to use a switch(you can buy one at radio shack for probable $2 (they sell really cool looking ones at pep boys) you will run that really long thin wire from the positive post on your amp, to one of the ports on your switch(obviously cut it to size) then use some of what is left of that long thin wire to run from the other post on your switch, to the remote(
rem) port on your amp.  This way when you flip the switch the remote port on your amp receives a signal, and will turn on. 
This is probably the most obvious step, but connect your speaker to the speaker ports on your amp with speaker wire.
Alright, so your CB radio will also need to get power, you can connect the red wire on the CB radio to the positive terminal on the amp, and the black wire on your cb to the negative port on your amp.  You can turn you amp on and off with the dial located on the front of the CB. 
Then remember to reconnect the negative  terminal on your car battery when your finished.
Your amp and cb radio will not use much power.  I often leave mine on over night and my car always starts up no problem.  You don’t need to turn everything off every time you get out of your car.
When you set everything up the first thing that your going to want to do is place your amp and find where you are doing to connect the negative wire to the car chassis as the wire is rather short.  I put my amp up underneath the dash on the passenger side.  There were good places to attach the negative up there.  
Also, since your amp plugs into your CB with a headphone jack, you can always unplug it from your CB and plug it into your iPod if you want to share your music with the world.
<p>Old post but I'm doing something similar. On your amp for the speaker, you dont have power posts, just the 12v dc plug slot. Did you use the power supply cord and splice it into another cable that runs to your battery?</p>
Looks great. I need one.

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