In reply to:
In other words, does my 25 ft two-conductor cable count as 50 ft?
No, your 25 ft. two-conductor cable counts as a 25 ft. run.
I'm not sure why Mr Russel phrased it quite that way. I'm guessing he did so, because if you run 4-conductor cable and connect 2 of the conductors to the "+" terminal, and the other 2 conductors to the "-" terminal, the impedance of the wire is changed.
For example, if you have 4 conductor, 16 gauge cable, and connect as stated above, what you have is equivalent, I believe, to 13 gauge wire.
So he justed wanted to be clear that his chart refers to your basic 2 conductor speaker wire.
So, your 25 ft. runs of 16 gauge into 8 ohm speakers is just fine. However, using 12 gauge won't hurt. I use 12 gauge for all my runs, some as short as 6 ft. No biggie.
