Tech Tip #13

In determining the watts of amplifier power required for a 70V sound system, it is necessary to consider that most line transformers are very reactive at higher and, especially, lower frequencies. As a result, the impedance of the system can vary widely as program content changes. (From 1 ohm at 63 hertz to 24 ohms at 1000 hertz). This is another reason why good system design will always allow at least 25-percent reserve between the calculated speaker load and the power available from an amplifier.