Power Management is the key word here. Most if not all auto outputs comming from your reciever are "line level" which means they are very low decebles aka dB's. You reciever normally "amplifies" the other lines going to your speakers using small transistors. However, subwoofers require more power than the tiny power supply build in your reciever, henceforth why you only have "line level" output. So as you may know, you need an external amplifier capible of amplifying the line level output to a suggnificant enough level to boom your subs.
Unfortunatly with large amplification comes problems. Now you can just slap in any old amp and boost your speakers and yeah they will bumb. But they will also raddle, pop, fizz, much like rice crispies, and also wine to the sound of your engine if not properly set up.
Your alternater generates power through centrifical motion. Though it is efficent in keeping your car running, it however acts like a giant pickup much like a pickup on a electric guitar. To your car, spark plugs, sencors, headlights, etc... power is power regardless of the amount of "resonence" in the line. You engine hums, gergles, cuh-thuds, and perse sending out vibrations. Your altinator like a giant pickup has a magnatic field which these vibrations disturb. Those vibrations are then reproduced in the electricity produced by the alitinator. Much like throwing a rock in a pond and seeing the waves... That now "resonating" power is going into your reciever where a CD, or radio takes that power and "resonates" it even more with audio. For the most part it goes un-noticed in the normal speakers, however take that line level sub out amp it up 1000watts with that "resonating" power and those tiny litte resonating peaks become mountains and vallies. Booom Pat Tap Sizzle, Hummmm fizzz WAAAAAAAHHHHHHNNNN, Booooooom Booom pat - goes the sub.
So how do you fix this? Simple... a Capacitor. A capacitor is a device with two leads that actually never touch. But how does electrons flow you ask? Magic... research it yourself.. its too complicated to get in to. Non the less... You put power to the capacitor before you amp. Those peaks and valleys become smooth like buttuh. So now you have clean power going into your amp. And the better the amp, the less noise you get.
As far as what kind of amp. I don't know much about amps. But I would seek to use "Monster Cable" for everything, the capacitor, wires... etc. They specialize in eliminating and protecting your clean power.
After this your subs will sound like : Boom Boom Boom..... BOoooooooooooooom boom...... Boooooooooooooom boom. And be sure to have a method in place to eleminate Hi Freq signals, usually a good reciever can do this through a Hi Pass Filter, and even some Amps have it. And Equalizer will let you effectively ajust this. Because who wants to hear some guy's voice Boomming "WAAHAHA WAAAHHA wooo WAHAHA WAA WHAA" comming from the sub. There is alot to know... research it.
Hopefully in the futuer reciever and recording artist will work hand in hand in producing multi-channel lines that support clean bass, and clean highs. As off now your getting a single stereo line that you have to try to decifer to clean up, and all music is different, with different levels... maybe one day... maybe....
PS... excuss my spelling.... i don't care.
