Audio Systems: Speakers under cars, mitsubishi galant, marine speakers

Question
Hey,
Whenever I'm driving my 2001 Mitsubishi Galant I want my music to play loud on the outside, even when my windows are up.  I hear that the only way I can do this is my putting speakers under the cars.  I want to install them myself, but I don't know how.  Do you know how I could install the speakers under the car, and run the wires to the head unit?  If you're not sure how, do you know of any websites that show how?  I would want it to end up looking similar to the car on this website, but I wouldn't use as many speakers.http://www.vroombox.com/  (When you go to the website go to F.A.Q. and scroll down)I could use any information that I can get, because right now I'm clueless on what to do, all I know is to use marine speakers.  Please help.  Thank you.

Answer
It is just like installing any other audio system except it is exposed to the envirionment all of the time.
Accordingly, you will have to deal with making the sub enclosure fit. One extreme option is to cut a hole in the car floorpan and use the interior of the vehicle for most of the enclosure, instead of putting it all outside the vehicle. This will help with ground clearance at the cost of some interior space (and probably not in a great location of the interior, considering the layout of a Galant). This is not easy and can be very tricky to accomplish without compromising the cars' integrity.

You need to decide how much of the frequencies you want to be loud. If you want 20-20kHz.. you probably will be let down.
If you want say..500hz and above, use a concert horn or two.
They only need 100 watts or so and they are ultra-effecient.
Then you could use a marine sub array for the lows if needed/desired. Remember, that if you have subs in the trunk, they are omni-directional and will fill in the lows even if you only use horns on the outside.

Perhaps you just need a louder interior system ??
My competition rig hit way loud even with windows up and all the Dynamat/lambswool I could put in it. You could not see any of the 17 drivers inside or outside of the vehicle including twin 18's. There is little shunting with a system of that caliber by closing the windows.

At anyrate, you are looking at a duplication of some or all of your interior system to accomplish this. If you do not know how, you will need a local pro to assist you. Many well intentioned novices have ended up with a car that was  reduced to ashes trying to upgrade its' audio.