If you can find high quality flexible (annealed?) copper then yes go for it. Solid wire does have some conductance advantages over stranded, but the lack of flexibility and the generally poor quality (re-cycled, repurposed) of industrial (ROMEX and MTW) would suggest not using building or machine tool, or distribution wire for audio. There are uses for flexible solid wire out there in the world. I purchased fine gauge silver instrument wire (my tonearm and cartridge lead supply) from a surplus dealer who in turn purchased from Gov't sources. In the pre internet days I was on his mailing list, and I think I remember seeing heavier single conductor wire. 11 gauge should not be needed for speakers. 12 gauge is overkill (the conductor operates most efficiently when sized correctly for the load). Unless exotic materials have superior numbers, inductance, capacitance, resistance, etc. stick with Silver, best condector by far, and copper, best compromise for cost performance and ease of fabrication. All mechanical connections with malleable wire can loosen over time. Aluminum wire, no longer popular had a terrible reputation in older homes, some loans and insurance companies wouldn't approve Al wire
Keep track of your results, I for one would be interested in what you find.