High Quality Content by WIKIPEDIA articles! Constant voltage speaker systems refer to networks of loudspeakers which are connected to an audio amplifier using step-up and step-down transformers to simplify impedance calculations and to minimize power loss over the speaker cables. They are more appropriately called high-voltage audio distribution systems. The voltage is constant only in the sense that at full power the voltage in the system does not depend on the number of speakers driven (as long the amplifier`s maximum power isn`t exceeded). Constant voltage speaker systems are also commonly referred to as 25-, 70-, 70.7-, or 100-volt speaker systems; distributed speaker systems; or high-impedance speaker systems. In the US, they are most commonly referred to as 70-volt speaker systems. In Europe, the 100V system is the most widespread, with amplifier and speaker products being simply labeled with 100V.