This is the standard DIY job for running long sub cables using rg6 cable. http://www.partsexpress.com/pe/pshow...1-1060&ctab=14 Although fourteen feet isn't very far,you'll have to see if you need a more shielded cable. I used rg59 cable with bnc connectors and rca adapters from radio shack. my sub cable is about 50' and I don't have a problem with it.
For a powered sub, youll need coax. (for others who stumble on this post and are confused)
For your passive sub, then I'm assuming you are talking about the run from the sub amp to the sub, in which case speaker wire is what you need, and don't worry about shielding. I would go for higher gauge wire since 12 gauge is really cheap, and you're dealing with sub wiring which takes a lot of juice.