Hi i just installed an aftermarket HU and now looking to run new speakers and a amp. my question is can i hook up the new speakers to the factory speaker harness and then just tap into the HU harness for the speakers and run the wiring to the amp? seems it would be less painful to do that then to run the wires through the doors.

 

Thats what I do and it works just fine.
I was going to ask the same question for those who has really high powered systems.
I was going to get some better components speakers for up front and wondering if its really worth it to wire through the doors.
From what I read how hard it is to get the wires through the grommets, I will leave mine wired through the harnness but I like to know what others think.

 

there are two issues with using small wires -
1) thinner wires have greater resistance, so if they are not large enough, some of the
power will be dissipated on the way to the speaker. In the relatively short run from the
headunit harness to the speaker, that loss is probably not significant.
2) the power lost to resistance is converted to heat, and every wire has a finite current
carrying capacity before it heats up and melts/sets something on fire. That's how a
fuse works - it carries power fine until you exceed its current capacity, at which point it
melts in a controlled fashion. The question is, what is the current carrying capacity of
the stock speaker wires, and alas I don't know. If you know the gauge, you can figure
it out, but a quick google is met with claims from 16 to 22 ga, which is a huge difference.
In any event, it's not actually that difficult to run wire into the door. There are
numerous posts - here's one.

 

I did the original writeup that's in the FAQ about removing the grommets and snaking the wires through (man, what was a few years ago)...
https://www.s2ki.com/forums/index.php?showtopic=84505

Several people have posted that they had success taping their wire to a coathanger, lubing it up, and pushing it through the grommets without removing anything.

For small amplifiers, I have no problem using the factory wiring. For higher power speakers, it's a good idea to run a heavier guage speaker wire. If you're using components and want to keep your crossovers dry inside the car, you'll need to run 2 sets of speaker wire into each door (that's what I did).

 

I agree with both oth and jeffbrig on all the concerns listed, and the main reason I ran new signal wires was to due to the location of the crossovers under the seats. Getting the wires through the grommet is not as hard as it might seem. I used a coat hanger to lead my wires through (without wire lube) and it took only half an hour to run the wires for both sides. Just be patient to avoid accidentally puncturing the grommet and exiting the sleeve midway.

Step 1: Cut a wire hanger section at least 1.5 ft long. Fold back the tip of one end and flatten to avoid tearing the grommet. Begin feeding the hanger wire into the grommet from the door to the car. Feel for the tip of the hanger wire along the length of the sleeve to track your progress and check for snags.


Step 2: Once the other end of the grommet is reached, back the hanger wire up as much as possible and begin taping the signal wires to the trailing end of the hanger wire. Tape one wire to the hanger wire first with at least two inches of overlap, then tape the second wire about four inches down from the tip of the first wire. This taper will prevent you from having to pull the thickness of the hanger and two wires into the grommet all at once.


Step 3: Finally, pull at the head of the hanger wire while feeding signal wire in from the other end until the wires make it all the way through!