I have been a home theater enthusiast for decades. When it came to speaker cable I've always pretty much stuck to Ohm's law and ensured I simply used a low gauge speaker cable to ensure there wasn't any signal degradation.

Now as I build a new home theater I'm met with a new challenge. The design I currently have has the equipment in a closet outside the media room. I'm using Magnepan speakers which are 4 ohm speakers that probably dip down to 2 or 3 ohms at times. I'm also using a subwoofer at the front of the home theater but the amp for it will remain in the closet so this is yet another long run. Ultimately, the center, two fronts, and the subwoofer will each have 80-90 foot runs of speaker cable, all going directly from their respective amp to the speaker.

I am committed to using Belden 10 gauge speaker cable but I'm starting to have some reservations. I just worry that these runs are simply too long. I've read a few articles online and they seem to suggest 50 feet should really be the maximum for 4 ohm speakers but I can't tell whether that is for a higher gauge of speaker cable or not.

I'm sort of a purist and want to ensure I don't have any signal degradation. I won't be using wall plates with connectors and thus won't have to cut the cable at either end. It will simply connect directly from the amp to the speaker which I suspect will help but again, I just don't know if that is enough. Can anyone share any guidance in this area?

http://www.roger-russell.com/wire/wire.htm#wiretable

10GA at 4 Ohms nominal is likely OK from a resistance point, but there may be capacitance and inductance issues for 2 conductor wire at this length. I don't know much about these effects, but I recall something about multi-conductor wire perhaps being "better" for longer runs. My speakers are about 6 ohms average impedance with about a 50 foot max run length. I used 14ga x 4 CL3 wire (about 11 AWG) - I chose this wire for two reasons - slight overkill on AWG and in wall rating on the cable.

Another option is use long coax runs to an amp located near the speakers.

You could kick the resistance of the circuit up by putting a 4 ohm resister in series with the speaker.