my hu only have 2 outputs and I want to put 2 amps(1 for sub and a 4channel). So I use the rear output for subwoofer. but how to use the front output to power 4 channels?

 

If you do not have the amps yet, find a 4 channel amp that has a pass through RCA, then a sub amp that comes with a remote level control. This will give you full capabilities in the system with the head unit that you have presently.

 

And if you already have the 4 channel you can use RCA splitters for the front RCA's to split them in to two sets. Plug both sets in to the 4 channel. You will not have fader control however so if you do have the option of getting a 4 channel with a pass thru it would be best.

 

Agree with the above, get an amp with pass-through or else just use a set of y-splits.

 

I already have a 4 channel. I just want to add a subwoofer. So I'll split the rcas before my amp (so I can control gain and hpf seperately front and rear but not fader). Where to find this splitter?

 

The Source, Most any audio/video place, Walmart electronic???, sure theirs many others.

 

And for power wire... can I use a fused 4 gauge wire and split it in 2 8 gauge wires in my trunk? Is there an adaptor I can use to split my power wire (same for ground) or just tape them togheter is ok? Do I need a distribution block or to fuse the 2 8 gauge wires?

for your information my 4 channel amp is a clarion 60watts rms at 4 ohms (400 watts max) and the mono amp would be a kenwood 500 watts rms.

 

Lets find you a sub amp that might have a pass through and a built in level control for the sub. I'll do some digging to see what I can find and get you a deal on it.

Use a basic distro block to split the 4 gauge at the back. It does not need to be fused. You do not need to use a distro block on the grounds. A basic distro block is fairly cheap.

 

so do i better use 2 grounds or split a 4 gauge ground in two? and how to split it is there an adaptor?

Is the distribution block necessary or splitting the power wire like the ground do the job? I don't want anything crazy just want a little more bass in my system.

And the amp I chose is not good? It's 500watts rms at 2 ohms (I want to put a kenwood sub of 500 wrms) and has the low pass filter gain control and bass boost, not all I need? I want to stay under 400$ for this upgrade.

 

I would think for $400, Rob (MR2NR) can get you into what your looking for. He's a good guy.

The distribution block is what splits you 4ga into 2-8ga.