switchable voltage tap

can someone tell me what the heck the 70 volt switch thing is on these speakers, here is the link

http://www.outdoorspeakerdepot.com/apprspp.html

my dad bought them and i saw the back and dont know what it is.........

While the speakers themselves are 8 ohms, that 70 volt transformer allows them to be driven by Public Address type amplifers that output a standard 70 volt signal. This is quite common for PA use when many, many speakers are being driven by one amplifier.

so this should be set what voltage on that dial if im hooking them up to a stereo receiver,

thanks guys, now i see that there is a switch to set it at 8ohm or all of those other voltages, i got it now, just put the dial to 8ohms...thanks....................... learn something new everday