Pure Resonance AudioSD4 SuperDispersion Ceiling Speaker Array, Built-In 8 Ohm/70 V Transformer

In a 2000 sq ft lecture auditorium with 16 ft ceilings, how many would a person need for adequate coverage?

I understand "160 watts at 8 ohms". but what does "64 watts at 70 volts" mean?

I have about 480 sq feet in a DMV lobby, would 1 be able to cover it?

what about music??? Would these deliver in a dance studio? I have 2000+sf of open dance space.