2 Qs....Line level and Amp

[wired_af]

I want to add an amp to my system for a sub or two. My head unit doesnt have a sub out, but it has right (front and rear) and left (front and rear) line out plugs. Which would I connect to the to amp, front, or rear output?

Also, when I have the sub, would I adjust the bass from the head unit from the bass adjustment? Im asking because I dont want the four door speakers recieving full bass, only the sub. If I had to turn the bass up all the way for loud bass on the sub, the door speakers would be recieving full bass also, and on a lot of song a lot of bass isn't good on the door speakers.

Thanks

 

[Alec]

Use the rear outs.

Set the HU bass level about about 30-40% and set the amp for the sub for how you like it. Then leave the amp alone and use the HU for small adjustments.

 

[88vert]

You could add a crossover too

 

[M.Scott]

Just remember that the fader controls front to rear balance and will effectively be a volume control for your sub. Meaning if you set up everything using the rear RCA outputs and then fade to the front the sub volumed will decrease.

You can also buy yourself some flexibility by getting an amp that has remote gain control (s/a volume). You can then tweak from your seat while driving.