Actually, I have 20 speakers and I want to divide them into four groups (for four floors in my building with five speakers in each floor). I need to activate the speakers according to their group, so I can select only one group, two groups or all of the groups (in this case, all of the speakers turned on together).
I use speakers with max. power rating 20W (and these speakers don't use 100v transformer in their configuration) with impedance 8 ohms. There are three terminals on the amplifer output: 4 ohm, 70V and 100V. I will use NYMHY cable for my configuration and the distance between two speaker is not less than 25 m.