Volunteering to set up an audio system for a church can lead to unexpected challenges, especially when dealing with 70V speakers like the JBL Control 28T-60. This scenario is common for individuals stepping into the realm of commercial audio systems, where the principles of operation and equipment requirements can vastly differ from home audio setups.
The Basics of 70V Systems
70V audio systems are designed for distributed sound applications, such as in churches, retail spaces, and large buildings. The key advantage of a 70V system is its ability to run multiple speakers over long distances with minimal loss of audio quality and without the need for thick, expensive cabling. This is achieved through the use of transformers attached to each speaker, which step down the high voltage to a level the speaker can handle.
Understanding Speaker Compatibility
A common question arises when individuals attempt to use home audio amplifiers, like a Yamaha 2-channel 100W+100W amp, with 70V speakers. Surprisingly, these speakers can indeed operate with such an amp, albeit inefficiently. The reason lies in the transformer technology of the 70V speakers, which allows them to adjust the impedance to match the output of a standard low-impedance amplifier. However, this setup is far from optimal, as it does not utilize the speakers or the amplifier to their full potential and can lead to increased power consumption without delivering the best sound output.
Choosing the Right Amplifier
For a proper 70V system setup, a dedicated 70V amplifier is recommended. These amplifiers are designed to handle the high impedance of a daisy-chained speaker configuration, ensuring efficient power distribution and optimal sound quality across all speakers. The Rockville Commercial Amplifier with Matrix Routing, for example, is a product designed for such applications, offering the flexibility to connect an audio mixer and manage multiple input sources effectively.
Calculating Total Impedance
The total impedance of a 70V line, assuming all speakers are tapped at the same wattage and wired in parallel, can be calculated using the formula 70.7V² / wattage per speaker. This calculation helps determine the total load on the amplifier and ensures that the system is within the operational limits of the equipment. It’s crucial to measure the actual impedance with an impedance meter to avoid overloading the amplifier.
Installation Tips
- Speaker Selection: Ensure that the transformer tap settings on each speaker are correctly set to match the desired volume and power distribution.
- Amplifier Compatibility: Use a 70V amplifier to ensure efficient power use and to accommodate the high impedance of the speaker line.
- Wiring Considerations: Understand that 70V systems simplify wiring, allowing for long runs without significant signal loss. This makes it ideal for distributed audio systems in large or complex buildings.
Conclusion
Setting up a 70V audio system in a church or any other large venue requires a fundamental understanding of how these systems work and the differences from standard home audio setups. By choosing the right amplifier, understanding the transformer tap settings on speakers, and calculating the total impedance of the system, volunteers and professionals alike can ensure a successful installation that delivers clear, consistent sound to every corner of the venue.
