I'm in the process of running all new wiring throughout my car for this system. Its a wagon and the amps are mounted in the far back corner walls. I'm running the power lines and remote turn-ons down the driver's side, as thats the side my battery is on; all patch cables down the passenger side.
Now, will noise resonate into 14ga. speaker wires? Obviously I have a front and rear driver's side doors that will have to be run, so somewhere along the lines those and the power cables are going to cross paths. If so, there may be a Plan B, but I'm curious none the less.
One of those things I didn't think of til I got there.
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Subtlety is EVERYTHING.
Just make sure the cables you are using are street wires zn3 or zn6 series cables (doesnt have to be streetwires but they seem to make the best cables, just make sure they are a twisted pair cable this is your best bet against noise)
they also make a twisted pair speaker wire, not cheap but very good.. see how you go with the speaker wires you have , but most of your noise is induced between the head unit and amp (as it gets amplified and then you can hear it ) cables will have to cross or get close at one point or another just try to minimise it i guess
see how you go ..
Signal wires (pre-amplification) that run parallel with power wires are apt to pick up interference which then becomes amplified, but crossing perpendicularly should not cause a problem. Speaker wires, on the other hand, should be fine to run any which way, because they are after the amplification stage.
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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.