Public Address (PA) System for Factories and Buildings

The Public Address (PA) system market in Vietnam is estimated to reach VND 850 billion in 2024, with an 18% annual growth rate, driven by the continuous emergence of new industrial parks and high-rise office buildings in Da Nang, Quang Nam, and neighboring provinces. Surveys indicate that over 60% of workplace accidents could be mitigated if emergency announcement systems were functioning promptly and clearly. This article provides comprehensive technical guidance on designing and installing PA systems, from speaker selection to announcement zoning and emergency broadcasting integration.

Types of Speakers in a PA System

Ceiling Speakers — Ideal for Offices and Supermarkets

Recessed ceiling speakers distribute sound downwards in a conical pattern. Features:

• Sound dispersion angle: 90°–120°, suitable for ceilings 2.8–4m high.
• Common power ratings: 3W, 6W, 10W (with built-in 100V transformer)
• Impedance: 8Ω or 100V depending on the version
• Applications: Open-plan offices, supermarkets, hotel lobbies, schools, apartment building corridors.

Typical installation density: 1 speaker/16–25m² (3m ceiling), distance between speakers is 1.4–1.7 times the ceiling height .

Horn Speakers — Essential for Workshops and Outdoor Use

Horn speakers use a funnel-shaped sound duct to amplify and direct sound, achieving high sensitivity (105–115 dB/W/m) and a long coverage range.

• Sound coverage range: 50–200m depending on power and horn design.
• Power: 10W–50W, temperature resistance: -20°C to +55°C
• Durability: IP65–IP66, resistant to rain and industrial dust.
• Applications: Factories, yards, industrial parks, parking lots, stadiums

Disadvantages: The background music sound quality is not as good as ceiling speakers; more suitable for announcements than playing high-quality music.

Line Array Speakers — High-Rise Buildings and Auditoriums

Line arrays combine multiple small audio drivers arranged in vertical columns, creating a narrow sound field horizontally but a wide sound field vertically — ideal for narrow, long spaces such as hallways, train stations, and airport waiting areas.

100V Constant-Voltage System: The Backbone of Enterprise PA Systems

Operating Principle

Unlike home audio systems (low-impedance 4–16Ω), commercial PA systems use 100V (70V in the US) wiring : the amplifier raises the audio signal to 100V, and each speaker has an integrated step-down transformer that lowers the voltage to the appropriate level for conversion into sound.

Technical benefits:

• Signal loss on the cable is very low — it's possible to run the cable for 300–500m without additional amplification.
• Connect dozens to hundreds of speakers in parallel using a single pair of wires (simple 2-wire system).
• Adjust the power of each speaker independently using the tap selector on the transformer (25%, 50%, 100% power).
• Easily add/remove speakers without recalculating the entire system impedance.

Amplifier Power Calculation

Basic formula:

Tổng tải loa (W) = Σ [Số loa mỗi loại × Công suất mỗi loa] Công suất amplifier cần thiết = Tổng tải loa × 1,25 (dự phòng 25%) Here's a real-world example: Tổng tải loa (W) = Σ [Số loa mỗi loại × Công suất mỗi loa] Công suất amplifier cần thiết = Tổng tải loa × 1,25 (dự phòng 25%)

A 2,000m² factory building, equipped with 20 10W horn speakers and 30 6W ceiling speakers:

• Total load = (20 × 10W) + (30 × 6W) = 200W + 180W = 380W
• Minimum amplifier power = 380W × 1.25 = 475W → Choose a 500W amplifier

Comparison Table of 100V vs 8Ω Low-Impedance

Criteria

100V Constant Voltage

8Ω Low-Impedance

Wire spacing

Up to 500m

<30m (high attenuation)

Maximum number of speakers

Hundreds (in parallel)

4–8 speakers/channel

Type of wire

2-core speaker cable 1.5–2.5mm²

2-core speaker cable 4–6mm²

Adjust the speaker volume.

Yes (tap transformer)

Difficult, requires volume control.

Wire cost

Lower

much higher

Sound quality

Good (sufficient for notifications/background music)

Better (HiFi)

Application

Commercial PA, buildings, factories

Studio, theater, bar/club

Sound Zone System Design

Zone Selector and Matrix Paging

Audio zoning allows different content to be played in separate areas — for example, playing background music in a shopping mall while emergency announcements are only played in the warehouse, or playing shift-specific music in a production workshop.

Basic zone selector solution:

• Passive zone selector: Mechanical relay, selects one signal source for N zones, low cost.
• Matrix mixer (active): Allows N sources to → M zones, for example, combining background music + announcement microphones + emergency alerts to each zone independently.

Modern PA systems (Bosch Praesideo, TOA, Inter-M) allow for automatic broadcast scheduling (chime announcements, hourly announcements) and connection to BMS (Building Management System).

Microphone Paging and Chime

• Paging microphones have a zone selector and often feature a chime (a warning sound) to attract attention.
• Pre-recorded message: Messages are stored in the amplifier's memory and automatically played upon remote activation or from the BMS/SCADA system.
• Standard chime: Westminster (4 notes), Ding-Dong (2 notes), or customized according to brand identity.

Integrating Emergency Broadcasting

EN 54-16 Standard

EN 54-16 (Voice Alarm Control and Indicating Equipment) is a European standard widely adopted in Vietnam, particularly in buildings with foreign investment and international industrial parks. The core requirements are:

• The VA (Voice Alarm) system must have absolute priority over other sound sources (background music, regular announcements).
• The backup amplifier automatically switches to the main amplifier when it fails, with a switching time of less than 20 seconds.
• Continuous line supervision — immediate alert in case of wire breakage or short circuit.
• Emergency announcements must achieve a minimum SPL of 65 dB(A) or be 6 dB above the background noise level at all points within the building.

Integrated with Fire Protection Systems

Emergency PA systems are typically integrated with a fire alarm control panel (FACP):

• When the FACP activates the fire zone, the PA system automatically broadcasts a pre-recorded evacuation message.
• Phased evacuation schedule: evacuate the burning floor and adjacent floors first, then the entire building.
• Combine this with exit signs and LED display panels to increase evacuation efficiency.

Integrate Background Music (BGM)

Background music in supermarkets, shopping malls, and hotels should meet the following criteria:

• A volume level of 55–65 dB(A) is sufficient for listening but not tiring.
• Music copyright (register with VCPMC if playing commercial music in public spaces)
• The mixing system allows for instant background music fade-out upon microphone notification.

PA System Design Checklist

Survey and Design

• Measure the area of each zone and the ceiling height.
• Determine the ambient noise level in each area (using a sound level meter).
• Choose the appropriate type of speaker (horn/ceiling/column) based on the space and distance.
• Calculate the number of speakers and amplifier power.
• Draw a zoning diagram and wiring route.

Installation and Operation

• Install the amplifier rack in the air-conditioned technical room.
• Pull 2-core 1.5–2.5mm² (100V) or 4mm² (8Ω) speaker wire with shielding.
• Install and test each zone selector.
• Connect and test the paging and chime microphones.
• Measure SPL at representative points and adjust tap transformer if necessary.
• Integrate with FACP if urgently required, test the entire scenario.

Quang Duc's PA Sound System Services

Quang Duc Electronics and Telecommunications Co., Ltd. provides comprehensive PA (Public Address) sound system solutions:

• Surveying, designing, and installing PA systems for factories, industrial parks, office buildings, and supermarkets in Quang Nam and Da Nang.
• We supply and install horn speakers, ceiling speakers, column speakers, and 100V amplifiers from brands such as TOA, Inter-M, Bosch, and JBL.
• Integrate the PA system with the fire alarm control panel (FACP), BMS, and emergency public address system according to standards.
• Program audio zones, automatic broadcast schedules, and pre-recorded announcements.
• Regular maintenance, sound calibration, and upgrades for existing PA systems.

Quang Duc has implemented PA systems for numerous factories, apartment buildings, schools, and supermarkets in Quang Nam and Da Nang, ensuring consistent sound quality and high reliability in industrial environments.

Conclude

A public address (PA) system is not only a tool for internal communication but also a mandatory safety feature in buildings with strict fire safety regulations. Investing in proper zoning design, selecting the right speakers and amplifier power will create a system that operates stably for 15–20 years without major replacements.

With the development of smart buildings and IoT, modern PA systems are increasingly integrated with IP cameras, access control, and BMS—creating a comprehensive smart security platform for next-generation buildings and factories.

Contact Quang Duc for consultation on designing a PA system suitable for the scale and technical requirements of your project in the Quang Nam-Da Nang area.

Hotline: 0903 306 126 (Mr.Vũ Trần) | Website: cameraquangduc.vn