I'm going to install my rear surround speakers. The speakers are to be bi-wired. Should I use a 12/4 cable or run 2 sets of wires 12/2 and join the cables at the amp.? Will I get better sound from the two sets of 12/2 or am I wasting money?
My 2 cents:
Wasting money would be using 12 AWG to begin with. Have never seen an installer or theatre designer use more than 14/2 AWG for rear in-wall/ceiling runs unless they are out to impress the owner with fancy cables that are visible in the rack. You can have peace of mind knowing that you used nice fat pipes in the walls, however it really isn't necessary.
Just run 2 14/2 runs and you are good to go, no need to bi-wire or use 12AWG. Just use a decent cable made in the US, not China (I've carried both and there's a major difference, it's not worth it just to save a few dollars), as you will get better insualtion and less kinking when pulling the wires through.