The clear reason to use 70 volts:
On August 25, 2016 at 02:48, buzz said...
I am a bit concerned how you will balance the output levels of that 3-3 series/parallel string of speakers if it will be a stereo room. (Add a balance resistor in series with the parallel speaker?)
Because of the nature of the impedances of a speaker at different frequencies, a resistor in series with speakers will depress the bass a bit but depress the mids and highs much more. So that's not a good idea.
If the room is mono, consider how you will generate the mono speaker feed because "mono" switches disappeared generations ago.
True.
And what happens if you decide you need another speaker? Or three? 70 volt makes this possible without doing much of anything. Low impedance makes it a major hassle or impossible.
