Unless you have ears that hear things that mere mortals can't, use THHN, Romex, barbed wire, SJOOW, or any other appropriatly sized conductors you have laying around. If the AVERAGE or RMS, but NOT PEAK power of the speaker is less than 300 Watts, I would use nothing larger than 14 or 12 AWG, especially if the run is less 100 feet round trip.
The 16 AWG is probably fine.
Larry
