Trunkrattler is right.
If you do not have RCA outputs from your head unit you need to have an amplifier that accecpts low level inputs (the wiring to your rear speakers are low level) so you can connect these to the amplifier to get your subs working. Your amplifier should also have a crossover built into it - some switches with something like all, hi or low on them or maybe a dial with a few freqencies on it like 60khz 125khz etc. (A crossover filters out some of the frequencies so that all the sub plays are the deep rumbling sounds you want.) If you dont have a cross over the sub will try and play all of the sound that your rear speakers play and it will sound shite and may damage the subs/amp. You need to ensure that the sub only plays the low frequencies. 60khz or lower would be a place to start with.
If you have RCA outlets on your radio unless they are labelled subwoofer out you will still need to filter out the unwanted frequencies - either on the amp itself or on a crossover. Some crossovers have low level imputs as well as rca inputs. I prefer crossovers because they usually let you muck around with the range of frequencies that the subs play so that you can get the subs souding how you want them (sort of like how you can adjust the amount of bass the speakers play in the car with the head unit). The lower the range of the freqencies the sub plays the better they sound.
I personally have a crossover connected to my head unit with rca cables and i have it sitting in the boot. I have then connected the crossover to the amplifier by RCA cables. The cross over is connected the same way that trunkrattler recommended.
A few other tips: use as big a diameter power cable as you can. Not as thick as your little finger unless you want to add other amps in the future.
Put a fuse on the power cable as close to the battery as possible.
Find a good eathing point in the boot and use a decent size cable for that.
When you get this all sorted out you will need to make sure that the amps sensitivity is set correctly. You can do this roughly by turning the head unit up to about 60% - 70% and then turning the sensitivity (on the amp itself)adjustment all the way down. Most amps have a dial and a small led for the sensitivity.
The subs will sound much quieter with the sensitivity turned down. Then slowly increase the sensitivity until the led starts flashing about half the time. (This adjustment tells the amp how quicky it should increase its volume when you turn up the volume on the head unit). You dont want the amp running at full power at moderate listening levels because it over time it will destroy the amp/subs.
Getting a bit more adventourous - if you have a 2 channel amp you can power both the rear speakers and the subs from the amp. Look at the documentation that came with the amp about how to do that. At one point I had a 2x45watt coustic amp wired this way. Each of the rear speakers was putting out somethin like 40 watts and the sub was putting out around 100watts. Doest sound like much but, boy, was it loud. The sound from the subs was ok but didnt really give me the sound I wanted. Hence the additional 4 channel amp and change to the crossover.
If you want to run the rears and the sub from the 2 channel amp you will also need to change the way that the subs filter out the higher frequencies ie you probably wont need the crossover. This is normally done by soldering a small filter onto one of the sub terminals. These filters are pretty cheap and readily available from most electronic stores (Jaycar is pretty good).
Hope this helps
Evets358
:drink:
