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Waiting on my new speakers and sub I have some how convinced my wife with the absolute perfect layout in our living room for 5.1 and even a future 7.1(atleast until testing)
Now I ordered a 75 ft rca cable from media bridge and I need to run it and my 2 surrounds under the floor into the finished basement whwre I will have them together and secured to the corner/ceiling. Is there any issue with interference or anything with such a long rca run? I actually think I can get away with a 50 ft rca but just wonderinf if my 75ft should work. Thanks again!
 

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RFI

All unshielded wires like most speaker wire act as radio antennas and are susceptible to Radio Frequency Interference (RFI). The longer the run and the closer you are to a radio wave transmitter, the more chance of picking up RFI. When the budget allows, use shielded speaker cable and ground the shielding at one end of the run to a screw on the equipment. If shielded cable is too expensive, then cable that has twisted conductors will reject more RFI than a cable where the conductors run parallel. A shielded twisted conductor cable from a reputable manufacturer like Belden would be the best and an unshielded parallel conductor cable like Home Depot 12 AWG Speaker Wire would be the worst. You can also run your Low Voltage cables inside metal conduit which accomplishes the same results. Metal conduit can be more cost economical if you pull multiple unshielded cable runs through the same conduit.


EMI

All unshielded wires like most speaker wire will pick up a current through Electro Magnetic Interference (EMI) when run too close to a high voltage electrical wire, low voltage transformer ballast or electrical motor (laundry, A/C fan etc) The closer you are to a high voltage electrical current, the more chance of picking up EMI. When the budget allows, use shielded speaker cable or any of the solutions suggested above. Wherever possible keep low voltage wires away from high voltage wires and recessed lights. If your LV wires have to cross paths with high voltage, then try to cross at right angles. Below are the recommended distances between high and low voltage wiring (note that the use of conduit allows closer separation):


NEC (National Electrical Code) guidelines for low voltage wire installations:

- 6-in. separation between low voltage conduit and power line conduit

- 12-in. separation between low voltage conduit and unshielded power lines or electrical equipment

- 24-in. separation between low voltage and unshielded power lines or electrical equipment

- 46-in. separation between low voltage and electrical motors and transformers


Lastly, for 75 ft, I wouldn't run anything less than 12 AWG. All LV wires have voltage drop over long runs (and 75 feet is a long run). See attached guidelines below.
 

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