On this page
- 01Before you start
- 02Where it sits in the project
- 03Main types of sound systems
- 04Professional sound reinforcement
- 05Core audio components
- 06Loudspeaker types and what matters
- 07Public address, paging and background music
- 08100 V line versus low-impedance
- 09Analog, digital and networked architectures
- 10Conventional PA versus voice alarm versus PAVA
- 11Voice alarm components that matter
- 12Acoustic design, integration and racks
- 13Standards snapshot
- 14Sizing rules on site
- 15Design and commissioning workflow
- 16Check that it works
- 17Common problems and how to fix them
- 18Frequently asked questions
- 19Talk to PSS about public address
Sound systems cover music and live performance, routine announcements, paging, background music, emergency warnings and voice-guided evacuation. The hardware may look similar — loudspeakers, microphones, mixers, amplifiers and processors — but each job needs a different acoustic, control and compliance approach. A PA system makes announcements; a voice alarm system tells people how to leave. The second is a life-safety system with its own standards, power supply and acceptance test. The two may share loudspeakers and racks, but the voice alarm path must survive a failure in the paging path, and the message must be intelligible, not merely loud.
Before you start
- Evacuation strategy: simultaneous, staged or phased — and by which zones.
- Fire-zone drawings and compartment boundaries.
- Primary functions: reinforcement, BGM, PA, voice alarm, or a PAVA combination.
- Ceiling heights, types and finishes; hard surfaces and glazing; measured ambient noise per area.
- Required STI target, and who measures it at handover.
- 100 V line or low-impedance — circuit lengths, speaker counts, tap plan.
- Interfaces: fire alarm, BMS, access control, telephony, paging positions.
- Autonomy hours, rack location, power, cooling and ventilation.
- Active versus passive for event spaces; DSP and mixer needs for multi-zone sites.
- Local approval requirements for voice alarm equipment.
Where it sits in the project
The system sits on the fire alarm’s output side (evacuation messages), on the access-control side (phased evacuation by zone), and on the electrical side (rack power, heat, battery autonomy). Acoustics belong to the architect: ceiling height, finishes and reverberation decide whether the design can work at all. On fit-out projects, freeze rack space and loudspeaker positions before ceilings close. A hotel may use professional reinforcement in the ballroom, BGM in public areas, PA for staff, and a dedicated voice alarm for emergencies — the architecture follows the primary purpose, not one catalogue page.
Main types of sound systems
| System type | Primary purpose | Typical applications |
|---|---|---|
| Professional sound reinforcement | Amplify and reproduce speech, music and live audio | Auditoriums, theatres, houses of worship, performance venues |
| Background music (BGM) | Distribute music at controlled levels | Hotels, restaurants, retail, reception areas |
| Public Address (PA) | Announcements and paging to defined zones | Offices, schools, hospitals, factories, transport |
| PAVA | Routine announcements plus emergency voice alarm | Shopping malls, hotels, large commercial facilities |
| Voice alarm / evacuation | Emergency alerts and instructions as a life-safety system | Buildings requiring emergency voice communication |
| Conference and discussion | Managed meetings and presentations | Boardrooms, conference centres, government facilities |
| Distributed audio over IP | Transport audio and control across network infrastructure | Campuses, multi-building facilities |
| Outdoor and industrial audio | Announcements or programme audio in demanding conditions | Plants, logistics yards, parking, outdoor venues |
Professional sound reinforcement
A professional system may need a wide frequency range, dynamic music, multiple sources and consistent coverage. Typical venues: conference halls, auditoriums, ballrooms, theatres, houses of worship, lecture halls, sports facilities and boardrooms. A coordinated chain includes microphones, direct inputs and playback, a mixing console, processors, power amplifiers or powered speakers, main loudspeakers, subwoofers, stage monitors, and signal and speaker cabling. A high-quality loudspeaker cannot fix poor microphone placement, wrong gain structure, unsuitable room acoustics or incomplete tuning.
| Feature | Active loudspeakers | Passive loudspeakers |
|---|---|---|
| Amplification | Built-in power amplifier | Requires an external power amplifier |
| Signal input | Usually line-level; some support digital/network audio | Amplified speaker-level signal |
| Installation | May simplify wiring and amplifier matching | Centralized amplifier racks; flexible channel allocation |
| Processing | May include built-in DSP, EQ, limiting, crossover | Processing typically external |
| Common use | Portable PA, conference rooms, small venues | Installed sound, large venues, scalable racks |
| Key consideration | Needs power and signal at each speaker | Needs correct amplifier, impedance, cabling and crossover matching |
Neither type is universally superior. Active speakers simplify some installs; passive systems suit centralized racks and distributed amplifier channels.
Core audio components
Microphones convert sound to electrical signals. Selection depends on source, environment, pickup pattern and use.
| Microphone type | Characteristic | Typical application |
|---|---|---|
| Dynamic | Robust; electromagnetic induction | Live vocals, presentations, general speech |
| Condenser | Capacitive transducer; usually needs power | Detailed speech, studio, selected live use |
| Wireless | Transmits to a compatible receiver | Presentations, events, stage performance |
| Lavalier / headset | Worn; hands-free | Lectures, fitness instruction, mobile presenters |
| Gooseneck | Flexible stem; directional or semi-directional | Conference tables, podiums |
| Boundary / beamforming array | Surface or multi-element focused pickup | Meeting tables, modern collaboration rooms |
Account for sensitivity, frequency response, polar pattern, feedback resistance, handling noise and compatibility. Cardioid, supercardioid and omnidirectional patterns behave differently — place them with loudspeakers and room acoustics in mind.
Mixers combine sources and control routing, levels and tone. Digital models add scene recall and remote control.
| Feature | Analog mixer | Digital mixer |
|---|---|---|
| Processing | Primarily analog circuitry | Digital signal processing |
| Interface | Physical knobs, faders, switches | Controls, displays, touchscreens and/or software |
| Scene recall | Generally limited | Commonly supports saved scenes |
| Best fit | Straightforward systems; direct physical control | Complex events; many sources; repeatable setups |
A Digital Signal Processor (DSP) sits before the loudspeakers: parametric EQ, filters, crossovers, compression and limiting, delay and time alignment, feedback control, automatic gain, matrix mixing and zone routing, loudspeaker processing, and acoustic echo cancellation on conferencing platforms. Excessive EQ or wrong crossovers cut quality and headroom.
Power amplifiers feed passive loudspeakers. Match continuous power at the specified impedance, channel count, load, protection, cooling and remote monitoring to the loudspeaker, required SPL, programme material and site conditions. Nominal wattage alone is not enough — account for peaks, crest factor, limiters and power handling. Subwoofers need correct crossover, phase, placement and level. Stage monitors belong mainly to live sound, not building-wide paging.
Loudspeaker types and what matters
| Loudspeaker type | Main characteristics | Typical applications |
|---|---|---|
| Ceiling | Discreet; distributed coverage | Offices, corridors, retail, hotels |
| Wall-mounted | Surface mount; configurable coverage | Meeting rooms, classrooms, commercial interiors |
| Pendant | Suspended for high ceilings | Retail atriums, warehouses |
| Column / line array | Useful directivity in selected designs | Auditoriums, transport terminals, reverberant spaces |
| Horn | Directional; higher background-noise environments | Industrial yards, outdoor paging |
| Full-range professional | Broad audible spectrum | Event halls, stages, presentations |
| Subwoofer | Specialized low-frequency output | Entertainment, theatres, performance |
| Outdoor / Voice Alarm | Weather rating or EN 54-24 approval as required | Terraces; buildings with voice evacuation |
Frequency response, sensitivity, maximum SPL, dispersion, impedance and power handling, environmental rating and intelligibility matter most. High output alone does not mean a message will be understood.
Public address, paging and background music
A PA system distributes speech and other audio from one zone to many floors, buildings and outdoor areas: live paging, all-call, BGM, scheduled messages, source selection and volume, priority handling, and links to telephone, security or building systems. Larger sites add network audio, DSP, remote paging stations, automatic message players and central management software.
Zoning routes audio to selected areas. A shopping centre may separate retail, food court, parking, service corridors and offices. Routine zones follow operations; emergency zones follow the approved evacuation strategy and may differ. Background music may need multiple sources, independent zone volumes and schedules — and must be overridden when the emergency system’s approved priority requires it.
100 V line versus low-impedance
| Feature | 100 V line | Low-impedance |
|---|---|---|
| Typical applications | Building-wide PA and distributed paging | Professional sound reinforcement; local zones |
| Speaker connection | Matching transformer with selectable taps | Direct to compatible amplifier output |
| Multiple speakers | Many speakers on one circuit via taps | Series/parallel per supported impedance |
| Long circuits | Often well suited when correctly designed | Cable resistance and load need careful design |
| Power calculation | Sum of transformer tap ratings | Resulting impedance and power requirements |
In a 100 V line system, each loudspeaker is set to a supported tap (for example 3 W, 6 W, 10 W or 15 W). Example: 24 ceiling speakers at 6 W → 24 × 6 = 144 W nominal load. Select the amplifier from this load, manufacturer guidance, cable losses and design margin — typically keep total tapped load below about 80% of amplifier rating, and line loss below roughly 10% (~0.5 dB).
Low-impedance loudspeakers commonly use 4 Ω, 6 Ω or 8 Ω. These systems dominate professional reinforcement, where output capability and local arrangements matter most. Choose the method by circuit length, speaker count, acoustic goals, power and cabling — not by loudspeaker purchase price alone.
Analog, digital and networked architectures
| Architecture | How it works | Strengths | Design considerations |
|---|---|---|---|
| Analog | Electrical audio over suitable connections | Straightforward; broad compatibility | Cable length, noise, grounding, levels |
| Digital | Digital interfaces or digital audio networks | Multichannel; fewer analog conversions | Format, clocking, latency, interoperability |
| Audio over IP | Supported network protocols for audio and control | Distributed routing; multi-building flexibility | Latency, multicast, bandwidth, security, resilience |
| Hybrid | Analog inputs, digital processing, IP distribution, local amps | Flexible with existing infrastructure | Clear interface definitions; coordinated commissioning |
Networked audio may use Dante, AES67 or manufacturer protocols where supported. A networked PA may use IP paging stations and local amplifiers without an IP link at every loudspeaker — describe that accurately in the design. For life-safety functions, judge network dependence, power continuity, fault supervision and redundancy against the applicable requirements.
Conventional PA versus voice alarm versus PAVA
| Feature | Conventional PA | Voice Alarm / Evacuation | Integrated PAVA |
|---|---|---|---|
| Routine announcements | Yes | May be supported | Yes |
| Background music | Often supported | Not its primary function | Often supported |
| Emergency messages | May be technically possible | Designed for emergency function | Supported when properly designed |
| Fire alarm integration | Optional | Common / required by design | Via compatible approved interface |
| Emergency priority | Depends on configuration | Core design requirement | Must be correctly implemented |
| Fault supervision | Varies | Per applicable standard | Must meet voice alarm requirements |
| Emergency backup power | Application-dependent | Must satisfy applicable requirements | Must satisfy life-safety requirements |
Terminology varies: PAVA, PA/VA, or Sound System for Emergency Purposes (SSEP). The product name is not the test — whether the complete system is designed, approved, installed, commissioned and maintained for the intended emergency function is. ISO 7240-16 covers emergency sound-system control and indicating equipment; ISO 7240-19 covers design, installation, commissioning and service. Apply them with national codes and the project specification.
Voice alarm components that matter
Voice Alarm Control and Indicating Equipment (VACIE) — EN 54-16 certified — manages emergency audio: message and zone selection, priority, status and the emergency microphone. A normal paging microphone is not assumed suitable for emergency use without design and approval.
Prerecorded emergency messages give consistent instructions; content, language, priority and zones follow the approved plan and must be tested.
Amplifiers and standby amplification — commonly N+1 on voice alarm duty — with automatic changeover where required. Supervised loudspeaker circuits help identify open circuits, shorts, amplifier failures and other defined faults; state which faults are detected and how they are reported. Supervision does not guarantee every loudspeaker defect.
Emergency power — EN 54-4 supply with batteries and charger — must support required operation on loss of mains. EN 54-4 requires recharge to 80% within 24 hours and 100% within 72 hours; standby autonomy hours come from national rules or the client specification. Battery sizing: standby current × standby hours + alarm current × alarm hours, then derate; a rack of amplifiers in full alarm dominates the figure.
Fire alarm interface starts the response from the approved cause-and-effect matrix and must be tested at commissioning. Loudspeakers for voice alarm need the applicable product approval (EN 54-24 / ISO 7240-24 subject to project and national adoption). Fire-rated cable is required on alarm circuits.
Sound pressure (SPL). BS 5839-8 calls for the voice message above 70 dB LAeq in acoustically simple spaces, at least 10 dB above measured ambient, with a 10 dB signal-to-noise ratio. Where ambient exceeds 75 dBA, put an acoustics engineer on the design team. Higher SPL is not always better.
Intelligibility. STI runs from 0 to 1 (EN 60268-16, measured in the field as STIPA); the usual acceptance threshold is 0.5, with 0.5–0.6 considered comfortable. A loud system in a reverberant hall can still score below 0.4 — that failure shows up at handover, when it is most expensive to fix.
Placement (BS 5839-8, simple spaces): centre spacing no more than 6 m for unidirectional loudspeakers and 12 m for bi-directional; loudspeaker-to-listener distance no more than 4.5 m (unidirectional) or 7.5 m (bi-directional).
Certification chain: EN 54-16 for the VACIE, EN 54-4 for its power supply, EN 54-24 for the loudspeakers. Dual power paths where mandatory indications require them, redundant amplifiers where specified, and impedance monitoring so a failed line reports as a fault.
Priority ladder: emergency > live paging > recorded messages > background music, with automatic ducking of lower priorities.
Acoustic design, integration and racks
Good design delivers clear, consistent audio — not merely enough nominal watts.
- Frequency response — music needs broad, balanced reproduction; paging emphasises clear speech.
- Coverage and directivity — mounting height, orientation, listening distance, room geometry and overlapping coverage.
- Reverberation — hard surfaces, high ceilings and large volumes may need careful directivity, placement, delay alignment or acoustic treatment.
- Speech intelligibility — critical in emergency systems; verify with STI / STIPA when required.
Compatible interfaces may link fire alarm, security control rooms, BMS (status and selected faults — supplementary to local indications), IP telephony / SIP, and video-conferencing platforms. Emergency operation must not depend on an unverified software feature or unsupported third-party connection.
Cabling: balanced analog (XLR, TRS) for professional signals; speaker cable sized for amplifier output, load, length and allowable loss; Ethernet for IP audio endpoints and networked amplifiers. Confirm level, wiring, pinout and interface — connector type alone does not guarantee compatibility. Racks: ventilation, cable management, service access, labelling, power distribution, grounding and surge protection. Amplifier heat matters in high-density racks.
Standards snapshot
| Reference | General scope |
|---|---|
| EN 54-16 | Voice alarm control and indicating equipment |
| EN 54-24 | Loudspeakers for fire detection and fire alarm applications |
| EN 54-4 | Power supply equipment for fire detection and fire alarm systems |
| ISO 7240-16 / -19 / -24 | Emergency sound system CIE; design/install/service; fire alarm loudspeakers |
| BS 5839-8 | Voice alarm systems for buildings (where applicable) |
| NFPA 72 / EN 50849 | Emergency communications / sound systems for emergency purposes within their scopes |
These references are not interchangeable. Verify applicable editions, national adoptions, product approvals and local regulations. Conventional reinforcement and BGM still need proper engineering even when they are not life-safety systems.
Sizing rules on site
Amplifier sizing (100 V). Forty ceiling loudspeakers tapped at 3 W = 120 W; add 20% headroom = 144 W → select 240 W or 2 × 120 W. Put rack mains load and heat into the electrical schedule.
Battery sizing. Standby current × standby hours + alarm current × alarm hours, then derate.
Loudspeaker density. For a 3 m ceiling at 6 m spacing, roughly one loudspeaker per 30–36 m²; verify against the 4.5 m listener-distance rule, not the ceiling grid.
Zoning. Align voice alarm zones with fire compartments, then add operational paging zones. One zone per floor is rarely enough on a large floor plate.
| Application | Design priorities |
|---|---|
| Corporate offices | Clear paging; BGM where required; simple zone control |
| Conference / boardrooms | Microphone performance; DSP; echo cancellation; conferencing integration |
| Hotels and malls | Multiple music zones; paging; event audio; suitable voice alarm |
| Industrial / warehouses | High-noise coverage; horn or directional speakers; robust equipment |
| Auditoriums / worship | Speech intelligibility; music reproduction; room-specific tuning |
| Multi-building campuses | Distributed / IP architecture; centralized control; resilience |
Design and commissioning workflow
- Requirements — audio functions, areas, sources, users, life-safety needs.
- Site survey — dimensions, ceilings, surfaces, ambient noise, pathways, existing plant.
- Architecture — reinforcement, BGM, PA, voice alarm, or integrated combination.
- Equipment selection — microphones, mixers, DSP, amplifiers, loudspeakers, control, network.
- Acoustic and electrical design — coverage, loads, circuits, routing, power, redundancy.
- Installation — drawings, manufacturer instructions, regulations; label everything.
- Configuration and tuning — gain structure, EQ, crossovers, delay, zones, limiters.
- Functional testing — sources, microphones, zones, amplifiers, controls, integrations.
- Emergency testing — messages, priorities, zone responses, supervision, power, fire interface.
- Handover — as-builts, configuration records, schedules, test results, operating instructions, maintenance plan.
Check that it works
- Every zone plays the intended source; priority ladder ducks BGM under paging and emergency.
- Voice alarm messages, zones and fire-alarm cause-and-effect match the approved matrix.
- Supervised circuits report open and short faults; standby amplifiers change over where specified.
- Emergency power holds for the required autonomy; recharge meets EN 54-4 timings where applicable.
- STIPA (or the project method) meets the agreed STI target in critical listening positions.
- Both ends of loudspeaker circuits are labelled and match the as-built zone list.
Common problems and how to fix them
Equipment chosen by wattage alone
Ignore coverage, directivity, frequency response and room acoustics at your peril. Redesign from the acoustic objective, then size amplifiers to the tap plan and margin.
Loudspeakers tapped too high
The amplifier clips and speech distorts. Lower taps, keep total load under about 80% of amplifier rating, and retune gain structure.
Speakers laid out on the ceiling grid
Coverage holes appear beside hot spots. Space by acoustic coverage and the listener-distance rule, not tile centres.
Horns over a reverberant car park
Loud and unintelligible. Use directional placement suited to the space, or treat the path; verify with STIPA.
No STIPA after handover — only “can you hear it?”
Agree the measurement method and STI target before commissioning, then measure at critical positions.
Emergency microphone with no priority over routine paging
Implement the priority ladder so emergency always wins, with automatic ducking of lower priorities.
BGM and voice alarm on one amplifier with no bypass
Separate paths or a designed bypass so a BGM fault cannot take down the emergency path.
Ordinary PA treated as voice alarm because it can play a recording
Specify VACIE, supervised circuits, approved loudspeakers, emergency power and fire interface — or keep the systems separate and honest in the documents.
Unmonitored loudspeaker line
A dead line discovered during an evacuation. Specify supervised circuits and test fault reporting at commissioning.
Fire-rated cable replaced with ordinary cable “because it is only audio”
Replace with the specified fire-rated cable on alarm circuits. Issue a complete as-built zone list so the operator does not page the wrong floor.
Frequently asked questions
Is a PA system the same as voice alarm?
No. PA distributes announcements and programme audio. Voice alarm is a life-safety system that must meet applicable standards for control equipment, loudspeakers, power, supervision and intelligibility.
When is 100 V line the right choice?
For building-wide PA and long distributed circuits with many tapped loudspeakers. Prefer low-impedance for professional reinforcement and short local zones where quality and local control matter most.
What STI score should we accept?
The usual acceptance threshold is 0.5 (STIPA in the field), with 0.5–0.6 often described as comfortable. Agree the target and measurement positions in the project specification.
Do all voice alarm loudspeakers need EN 54-24?
Where the project and national adoption require it, yes — along with EN 54-16 for the VACIE and EN 54-4 for its power supply. Wattage alone does not prove suitability for voice alarm service.
Can BGM and emergency voice share the same loudspeakers?
Yes, when the system is designed as PAVA with correct priority, supervision, power and approvals. Sharing speakers does not by itself make a conventional PA a voice alarm system.
Talk to PSS about public address
PSS designs, installs and commissions public address and voice evacuation for buildings, campuses and industrial sites. Contact the PSS team to book a first site survey.
