Just an observation and question from a noob. Everyone seems to recommend shielded wire for microphones/intercomms. However, speaker wire has no such recommendation. Speaker wire is larger to accomodate the wattage of the amplified signal but other than being amplified, the speaker wire carries the same exact signal as the microphone isn't it? Just going the opposite direction down the wire. So why does microphone wire need to be shielded? Is it just because the speaker signal is amplified so overcomes interference? Or is it something else? Also, what awg wire should I use for microphone wire for a 100'+ run? 18/4? Thanks for any explanations.