70 Volt vs 8 Ohm Audio
A Standard Stereo Receiver (8ohm)
A standard home stereo receiver and a few pairs of speakers could provide a small business with adequate background music — but that might not work well in a system with a lot of speakers and long wire runs. Standard stereo amplifiers put out low-voltage, high-current signals that require thick (and relatively expensive) speaker wires to power distant speakers. The more speakers you add to a stereo system, the more difficult it becomes to safely connect them. You may find that you need multiple amplifiers, driving costs up considerably.
The Benefits of a 70-volt system
Because the voltage is high, the current running through a 70-volt system is low. You can use thinner, less expensive speaker wires. The amplifiers in these systems don’t have "load impedance" issues. It doesn’t matter how many speakers you connect.
Speakers with adjustable power levels
The speakers in a 70-volt system are like houses connected to an electric power transmission line. Each speaker incorporates a transformer that steps down the high voltage to a level that the speaker can handle. The transformer has multiple taps to achieve different wattage levels for the speaker. The higher the wattage tap, the louder the speaker will play.