Surge Protection for Public Address Systems

Surge Protection for Public Address Systems

Created by: Glen Zhu | Updated Date: December 05th, 2023

Public Address Systems and Surge Protection

A public address system, or a PA system, is an electronic ensemble comprising microphones, amplifiers, loudspeakers, and related equipment, used to project sound in public spaces, enabling clear and widespread audio communication for announcements, music, or speeches in various settings such as schools, events, and businesses.

Within this intricate electrical network, whether they are public address systems in buildings or installed outdoors, wired through cables or public address systems with wireless microphones, surge protection is indispensable for all types of systems.

Voltage surges, often caused by lightning strikes, equipment switching on and off or improper wiring, can potentially damage or degrade the performance of these sensitive devices or even cause irreparable damage. Surge protectors act as a barrier against voltage spikes, diverting excess energy away from the connected devices and preventing potential damage.

It’s worth noting that in the case of portable public address systems, where mobility is a key feature, the risk of encountering varying electrical environments is increased. Without adequate surge protection, the system becomes extremely vulnerable to unexpected power fluctuations that could compromise its functionality.

PA power matching essentials

To prevent circuit hazards resulting from unmatched power in a public address system, strict adherence to power-matching principles is crucial. The efficient operation and longevity of a PA system hinge on carefully considering power handling capacities, particularly between amplifiers and speakers.

A foundational step involves understanding each speaker’s capacity, typically denoted in watts RMS. Achieving top-notch performance involves aligning amplifier power with speaker capacity to prevent sound quality issues, distortion, and equipment failure.

Technical coherence is enhanced through impedance matching, managing electrical resistance in the audio signal’s journey. It’s crucial to maintain a balance between amplifier power and speaker capacity, preventing underpowering or overpowering.

Diverse loudspeaker varieties address distinct requirements in audio systems. Flush and wall loudspeakers commonly feature a power rating of 6 to 30 W, ideal for settings requiring moderate volume levels.

Conversely, column loudspeakers cover a wider power range, from 20 W to 100 W, showcasing versatility in spaces with diverse acoustic needs. Horn loudspeakers, rated between 10 W and 60 W, find preference in applications where precise sound projection is essential.

PA system wiring diagram

In the realm of amplification, modular amplifiers come into play, providing a rated power between 100 W and 600 W, and sometimes even higher. Considerations for other components include mixers, where power ratings often vary based on the complexity of the system.

An interesting facet in the configuration of a public address system involves the joint use of loudspeakers with different power ratings in a line or group. When determining the minimum power requirement for the amplifier in such configurations, it’s not a straightforward summation of individual loudspeaker power ratings.

Instead, the key consideration is the sum of the selected power ratings at the transmitters. The nuanced approach makes sure that the amplifier can adequately support the chosen loudspeaker configuration, providing an optimal and harmonized audio output across the entire system.

Application - Specific Protective Measures

Outdoor speakers' surge protection

Outdoor speakers in a PA system, primarily featuring horn speakers, are positioned prominently as a primary component in a PA system and are mounted on high ceilings, walls, or outdoor structures, making them extremely susceptible to damage from lightning strikes and receiving higher voltage levels during a surge event, potentially leading to damage to the speakers that may be irreversible.

For dimensioning the surge arrester in the loudspeaker line, determining the maximum current I in the relevant branch is crucial. This is achieved through the ratio I = P/U, where P represents the power of the amplifier or loudspeaker group, and U is the carrier voltage.

When exterior loudspeakers are positioned on a building’s roof, they face potential vulnerability to damage from indirect lightning effects, specifically through inductive and capacitive coupling.

The susceptibility remains irrespective of whether the overall system incorporates external lightning protection, as depicted in Figure 2, or lacks such safeguards, as shown in Figure 1.

Figure 1 – Horn loudspeakers without external lightning protection system

The presence of an external lightning protection system, exemplified in Figure 2, offers a crucial layer of defense by reliably shielding the exterior loudspeaker from direct lightning strikes. This protection is particularly effective when the loudspeaker is strategically positioned within the secured volume of an air termination system.

It is essential to recognize that the threat to exterior loudspeakers from lightning-induced damage is not solely contingent upon the system’s implementation of external lightning protection. Rather, the intricate interplay of inductive and capacitive coupling necessitates a comprehensive approach to safeguarding these components.

The incorporation of an air-termination system significantly enhances the overall resilience of the setup, providing a designated space within which the exterior loudspeaker is shielded from the potentially destructive impact of lightning strikes.

Figure 2 – Horn loudspeakers with external lightning protection system

Modular PA system with surge protective devices

In large public address systems that use a modular 19” design (as shown in Figure 3), the setup is usually placed near a consistently manned workstation. Strategically placing surge arresters, within the modular 19” design is crucial for managing the risks associated with electrical surges and fluctuations.

Whether surge arresters are integrated into the points connecting to PCs and control centers depends on the cable length connecting to the PC or intercom. Importantly, surge protective devices become a must when the cable lengths exceed 10 meters.

As the cable length between components, like the PC or intercom, increases, the vulnerability to voltage spikes also rises. Once the cable length surpasses 10 meters, installing surge protective devices becomes a proactive step to preserve the integrity of the entire public address system.

The decision to make surge protective devices mandatory for cable lengths exceeding 10 meters stems from the understanding that longer cables can act as conduits for potential surge-related damages.

Figure 3 – Modular PA system with surge protective devices

Power supply of the control center

In any PA system, the stability and cleanliness of the power source are paramount. Fluctuations or disturbances in power can have a direct impact on the performance of the system, leading to potential audio quality issues.

Redundancy is a key consideration in designing the power supply for a PA system’s control center. Incorporating dual power supplies or backup power sources enhances system reliability.

The implementation of an Uninterruptible Power Supply (UPS) is a common strategy to address power interruptions. A UPS serves as a temporary power source during outages, preventing immediate system shutdown.

Type 1+2 surge protector FLP12,5-275 series are great options when it comes to protecting power supply of the center control unit for PA systems on TN and TT networks.

Mixers and consoles

Mixers and consoles, serving as central connecting points for the orchestration of audio signals, require careful protection.

It’s crucial to respond quickly to reroute excess electrical potential and prevent damage. Calibrating the clamping voltage, which signifies the maximum allowable electrical potential during a surge, requires precise adherence to prescribed thresholds for safeguarding audio equipment.

To protect the audio system, it’s wise to strategically place devices like the SLP40-275/3S+1 at the entry point of the power supply. This not only provides thorough coverage but also ensures optimal protection, strengthening the audio system against potential electrical challenges.

Amplifier protection

Amplifiers, crucial for boosting audio signals, are particularly vulnerable to voltage fluctuations. To ensure the integrity of the amplification process, it is essential to implement a comprehensive protection strategy. This entails employing power conditioners and surge protectors at the inputs of the amplifier to shield against abrupt surges that might jeopardize the integrity of the system.

The inclusion of the SLP40-275/3S+1 Type 2 AC SPD (Surge Protective Device) further enhances the protection level, securing reliable and clear amplification. Additionally, the implementation of thermal protection devices acts as a safeguard against amplifier overheating, especially during prolonged electrical disturbances.

Protection must extend beyond amplifiers to safeguard the speaker wire pathways, especially those connected to outdoor speakers. The SLP40 series proves invaluable in minimizing damage caused by surges entering through these pathways, protecting amplifiers and receivers from potential destruction.

Optimal placement involves installing these units where the wires exit the house, guaranteeing protection for both the amplifier and wiring within the house.

Recognizing that lighting poses a dual threat to electrical equipment and wiring, surge arresters can also be strategically placed next to the speakers, offering end-to-end protection for the entire audio transmission line.

Transmission lines to loudspeakers

Preserving the quality of audio signals is essential, and protecting audio inputs and outputs is key to achieving this. The FRD series serves as a reliable choice, it can effectively shield signal lines from potential damage.

In conjunction with surge protection, implementing balanced connections and isolating ground paths are crucial in minimizing the risk of ground loops, which can significantly reduce the potential for unwanted noise and interference to ensure the smooth operation of the audio system.

Furthermore, it’s necessary to shield cables and connectors from electromagnetic interference.

The additional protective layer not only enhances signal quality but also contributes to the overall resilience of the audio setup.

Signal processors

A signal processor is an electrical engineering subfield that focuses on analyzing, modifying and synthesizing signals. TLP-30 series is placed at the input and output lines of signal processors to shield against voltage surges.

Grounding signal processors properly is essential to prevent ground loops and ensure optimal performance.

Employing redundant processors and signal paths provides a fail-safe mechanism, maintaining system functionality even in the event of component failure during electrical disturbances.

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LSP’s reliable surge protection devices (SPDs) are designed to meet the protection needs of installations against lightning and surges. Contact our Experts!

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