Constant-voltage speaker system

Transformers with various taps allow the installer to adjust the sound pressure level up or down at an individual loudspeaker.

Special-purpose transformers can tailor the system design to the project's target power levels.

For instance, three 70-volt amplifiers have been used to make a 210-volt line by connecting them to a special-purpose external output transformer that has three primaries and a single secondary.

For example, in 1967 Crown International introduced the DC300 amplifier, which is capable of directly driving 70-volt lines, as well as traditional speaker loads, thanks to its overall power[5] of 500W.

Many manufacturers make amplifiers capable of direct connection to a high-impedance constant-voltage speaker line.

High-voltage constant-voltage systems can be designed to use 140-, 200- and 210-volt lines, depending on the transformers selected and the amplifier connection topology.

Such high voltage systems have been used in locations where small diameter wire is already in place, where long-distance wire runs are involved and at especially loud installations such as Daytona International Speedway[10] and the Indianapolis Motor Speedway prior to its redesign in 2003.

[11] Safety considerations in such high voltages require speaker line installation within conduit in most of the world.

600 watt transformers are widely available for contractors needing high power loudspeakers in constant-voltage installations.