There are no RCA connections on the head unit.

The head unit has a built in DSP that adjusts output to each speaker dynamically. The louder you set the volume, the less bass is passed to the speakers. Typically, the rear speakers receive less bass than the fronts, so tapping into the fronts would provide better bass signal for the sub.

Many people tap the front door speakers, then run them into a DSP or LOC. I personally use an LC2i Pro LOC with accubass (Amazon Link #ad). What this LOC does is enhances the bass signal by dynamically adjusting the low frequencies that are being reduced by the head unit.

From the LOC, you’d run RCA cables to the amp.

Yes, an amp needs power directly from the battery. The best route is along the door jambs under the carpet. Where you go through the firewall is a good question there is a rubber grommet that can be cut to push the wire through, or you can remove the tape from another grommet where an existing cable is going through the firewall already.

In my case, I would have:

• Power cable from the battery to the amp (with a fuse on the positive cable near the battery)
• Ground cable from amp to existing ground bolt under rear seat
• RCAs, power, and remote wire from the LC2i LOC to the amp
• Power wire from a fuse tap on the accessories fuse to the remote on the LOC
• Speaker wire from the front speaker(s) to the LOC
• Speaker wire from the amp to the sub

I forgot to mention that if you have a factory amp, you’ll most likely tap the existing sub, but be aware it is already going through a DSP and may not give you the response you want for you aftermarket sub. The DSP is setting the crossover frequencies so you’ll be stuck with whatever Honda is giving you.

 

Hi
I would agree with most of the above for the power supply. I earthed on the rear seat mounting bolt. You can use a tap on the accessory fuse for the amp remote turn on. Pretty sure the factory sub is fed with speaker level out from factory amp. You can use this for new the amp input if it accepts speaker level input without the need for LOC. Then RCA from amp to sub.