when you install a power cable you usually route it through the door seal and under the carpet. If there are existing speaker wires that go to your rear speakers, will the power cable create an interference?
No, just run it through the middle of your car, not through the sides. My runs right under the cup holder area under the seats and right to the back. You cant even see it lol, my pros did a great job putting it in
General rule is to keep power wires and wires that run sound signals separte. I always run my power and remote wires on one side of the car and speaker and rca wires on the other side of the car.
The speakers are probably just being under-driven. Meaning they need more juice to operate efficiently (Like they were designed). Factory speaker wires tend to be small AWG, but I think you will find that larger wires wont make much of a difference in this case. However if you are going to add an amp, you should go ahead and run some aftermarket wires. I once changed out some speakers in a 97 taurus with the same results. Worse than stock.
I have my power wire and speaker wires touching each other under my carpet. no interference at all. I'll say that it may be possible, I have just never experienced it. So I would say that it won't interfere with your speaker wires. Actually I have my power wire, all speaker wires, and the Remote wire right next to each other. no problems at all.
