sub woofer cable

[najo49]

I have about 15 ft. of cable running to a sub thats between my speaks. It is Fed from the extra out on my fp3 extended.do es that affect the quality of my main out ,and the jena cables that go to main amp.,,also it's a powered sub.The sub goes all over the place in its sensitivity .

 

[Grainger49]

The input of subs is usually high.  So in parallel with your amp(s) it won't affect the sound.  Can you look up the input impedance for your sub's line level (RCA) inputs and post it?