Connecting 4 Channel amp to Factory Speakers

[Neil1]

Hi, am looking to amp up the 4 factory speakers on my Seat Ibiza 2009 so have just purchased a Kenwood Kac-8405 4 channel amp, shown below, to amp up a new headunit I purchased. I have run the power cable, remote power on
wires down one side, the front and rear rca jacks and 'Flatflex' speaker cables down the other side. The Amp wiring kit was the Vibe Slick 1500w kit. Have attached the amp earth wire to the seat belt bolt as well.

The Headunit I have is an Alpine CDE-136 bt headunit. It has front and rear rca cables.

What I would like to know is how do I connect into the existing speaker cable without buchering my factory speaker harness. Do I run 8 sets of cables from the amp to the wire harness at the back of the headunit and tap into them their. I have done various searches on no one seems to go into this in much detail. From what I understand I have to disconnect the speaker harness from the headunit and tap into the factory speaker harness otherwise you will have power going to the speakers from the amp and headunit and this could cause damage, is that correct?

Also the speaker wire I received in the vibe wiring kit is flat and the wire seems a bit thicker than the factory speaker cables I will be splicing into is that ok?

Your Help is greatly appreciated!!

 

[BrettBlade]

The difference in wire size won't affect much, and to do what you are wanting to do then I would agree with your thoughts about splicing in to the speaker wires behind the HU. I would leave the existing connectors intact but change the wires on the HU side from the HU to the amp sourced ones. Don't connect the wires together, tape up the wires that come from the HU.

However, I hasten to add that you're likely to blow your factory speakers, and I would highly recommend changing your speakers and then wiring directly to each speaker.

 

[Neil1]

Thanks yeah i will need to be careful, just want it a bit louder than standard to start off with. If i just amp the front speakers to start off with is it okay to leave the rear speaker wires still connected and powered by the h/u. I will then connect the rear speakers at a later date.

 

[Neil1]

Bump!

 

[Neil1]

All done now and yes it does sound awsome!!
I do have a jbl subwoofer wo may look at connecting this in as well.
Just worried about the boot space lol
É

 

[SaxophoneMn]

Where did you make the cut? It would seem better to make all of the cuts in the harness or better yet connections into the harness so you don't have to do the work in a cramped space.