Installation of public address systems and fire-fighting equipment.
For efficient operation of the public address system (PAS), it must be carefully designed. Depending on the type of installation, the requirements for the equipment and its placement may vary. The overall goal is to achieve efficient system operation and sound clarity.
Specialists from leading foreign companies share their experience on the pages of the asmag website.
Placement plan
When installing the system, it is necessary to adhere to the appropriate hierarchical placement. When an emergency message is activated, all other audio sources should be muted. «The call recorder is an easy-to-use system that records calls for automatic playback in areas that cannot be accessed because they are occupied by a higher-priority call,» says Terence Ng, senior product marketing manager for public address and conference systems at Robert Bosch (SEA), a subsidiary of Bosch Security Systems.
The number of speakers must be calculated and their placement must be thought through. The speakers must be positioned so that the sound pressure level (SPL) is the same at any listening position at any desired frequency. The equipment usually comes with instructions that specify the recommended number of speakers, as well as the distance between them. A certain balance must be achieved to accurately position the speakers. «It's a compromise between the uniformity of the frequency response and the number of speakers used,» Ng emphasizes. «The more speakers you use, the more uniform the sound becomes. At the same time, the wider the angle of the speakers, the better the frequency response at the position between two speakers.» That is, the purity of the sound directly depends on the speaker design. Zone mixers prevent excessive differences in sound volume in different zones. “With zone mixers, users can control the output of each zone independently of the other zones, which in turn allows them to control the output level of each individual speaker,” says Grant Murray, Loudspeaker Specialist in the Trade Marketing Department. Measuring the gain and impedance required in each zone during the design phase helps to create an effective system. “We provide both solution and technical support, as well as testing the relative loudness and impedance in each zone,” says Marco Morimanda, Product Manager at Paso. “The 100V technology allows for different taps from the same speaker.” Depending on the size of the installation, system requirements may vary.
«In cases where multiple announcements are made simultaneously, such as at airports, digital PA systems are preferable, as they provide a large number of dynamically distributed audio channels,» says Terence Ng of Robert Bosch (SEA). «Analog PA systems use one or two such channels.» In a typical configuration, one channel is used for calls and the other for music, so that music is not interrupted in areas not receiving calls.»
Indoor and outdoor installations
In both indoor and outdoor installations, the equipment is used for warning purposes, but the design of the equipment is different. Outdoor systems must be durable and, above all, protected from weather conditions. According to Antonio Ferrari, Contract Manager of Audio Marketing at RCF, the design of the equipment can be very different: cones and diaphragms, as well as the housings of the transducers are made of durable plastic obtained by rotational molding and treated with UV. Coated materials, reinforced with steel, equipped with waterproof connectors are used instead of wood. The specification and material of the additional accessories can also vary.
The installation location of the speaker should be chosen based not only on the design of the outer cabinet, but also on the weather conditions. “The outdoor environment changes periodically,” says Kaz Shimizu, head of product marketing at TOA. “If the wind direction and strength or temperature change, the SPL may also change. When it comes to speaker installation, you need to consider the changing environmental conditions.” Indoors, you need speakers that can deliver clear sound in a small area. “A typical ceiling-mounted speaker is often in a vertical configuration,” notes Grant Murray. “These speakers are curved, have different vertical coverage areas, and their coverage is limited to a relatively short distance.” Another consideration is the appearance of the equipment. “In shopping malls, aesthetics are more important than SPL,” says Grant Murray. says Marco Morimanda from Paso. — However, in outdoor installations, where high SPL is required, the clarity of the loudspeaker's sound becomes more important than its appearance.»
Self-diagnosis and redundancy
A reliable system must be self-healing. «Our self-diagnosis function automatically monitors data transmission, audio channel and power lines,» says Kaz Shimizu. «If any failures occur, the error is detected and the faulty equipment is switched to the backup unit.» Full-control circuits and redundancy for amplifiers and speakers ensure the reliability of the system. «Every failure and system delay is recorded and the user is notified in various ways, such as via LCD displays, LED indicators, buzzers and PCs connected to the network,» says Antonio Ferrari.
The equipment’s fail-safe design ensures impeccable communication quality. To prevent short circuits and system overloads, the amplifiers are made of robust components. “A forced-air cooling system and numerous electronic and thermal protection devices ensure maximum operational reliability,” says Marco Morimanda. “Each speaker is equipped with a thermal block (which may be built-in or not) with a fuse and ceramic bushings for each amplifier.” The equipment used for notification must be resistant to voltage surges. “In outdoor systems, the main controller may be equipped with a special integrated circuit that protects the system from lightning strikes,” notes Penny Wu, Marketing Manager at BXB Electronics. “If lightning strikes the system, only the circuits will burn out, not the entire system.”
Clipping limiters, according to Grant Murray, improve system stability: “There is nothing wrong with the occasional clipping, but excessive clipping can have adverse effects. If signals are clipped too often, the efficiency of the amplifier circuit is greatly reduced.” The limiter ensures consistency of sound. “These ‘flat tops’ of distorted output waveforms, caused by improper biasing or input overload, do not in any way affect the strength of the output signal at the desired frequency,” Grant Murray notes. “If the amplifier is under severe stress, the clipping limiter automatically detects the exact point where the overload has occurred and maintains the amplifier at its maximum possible load, which prevents excessive signal distortion without reducing operating efficiency. Each channel of the low-pass filter and clipping limiter is usually adjusted separately.”
Digital and Analogue Systems
GS systems are equipped according to the customer's wishes. The system becomes most effective if it meets the specific requirements of the installation.
Digital PA systems in their original configuration have much better sound quality. «A fully digital PA system processes and transmits audio signals and control data only in digital form,» says Terence Ng. «A redundant ring network topology is designed for distributed positioning of system elements.» When designing PA systems equipped with wireless microphones, it is necessary to take frequency interference into account. «High-quality wireless microphones eliminate frequency interference and provide high-quality sound,» notes Kaz Shimizu. «There are microphones today with different shapes, directions and signal transmission methods.»Despite the many functionalities of digital VA systems, the greatest demand is still for existing analogue systems. This is primarily due to their low cost. «Analogue systems are used in small or medium-sized installations,» says Terence Ng. «The functions of voice evacuation systems such as system control, switching to a spare amplifier, loudspeaker channel control, digital message management and interfacing with a fire brigade console can be combined.»
As a result of technological developments, PA systems and voice evacuation systems will become easier to operate and more efficient. «Class D amplifier modules for powered speakers are currently being developed,» notes Grant Murray. «They are intended for fixed and mobile installations, their power from 150 to 2500 watts significantly increases the efficiency of the system and reduces energy consumption.» Such a system will be compact and lightweight, have a higher degree of protection against direct current, current overload, excessively low or high voltage, microwave and temperature.
Prospective tasks
Antonio Ferrari is convinced that the most promising development is flexible systems characterized by ease of installation, adjustment and maintenance. At the same time, they must comply with standards, be energy-efficient and sold at competitive prices.»
There are no specific standards for the installation of PA systems. Therefore, according to Marco Morimand, in the future, standards need to be developed for design offices that define who needs to install which systems.»
In the future, it is planned to integrate various systems, while paying attention to the compatibility of equipment. The integrators who carry out the installation must have relevant experience in working with digital systems. The manufacturer is required to provide training and technical support.
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