MB, welcome to Axiom. Probably the best info available online discussing speaker wiring is the site of a veteran audio professional found here . There's a table of recommended gauges and lengths as well as plenty of helpful advice to avoid the wire scams that pollute our hobby.

You can shop at a local supplier of electrical wire(there's no such thing as "speaker cable" in reality)or deal with a low cost online supplier such as MonoPrice.

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Enjoy the music, not the equipment.