Understanding the Different Suspension Systems Used for Main PA, Side PA and Relay Towers

Line array loudspeakers are among the heaviest suspended components found on a modern concert stage.

Unlike lighting fixtures or LED panels, a line array does more than produce sound. Its position directly affects audience coverage, sound pressure distribution and listening consistency across the venue.

For this reason, engineers do not simply hang every line array from the nearest structure.

Instead, each array is suspended from a structural system specifically designed for its location, loading requirements and acoustic function.

During the construction of the 2026 Guangzhou Pearl Beer Festival Music Festival, three different line array suspension methods were observed:

• The main PA system was suspended from cantilever beams beneath the roof apron.

• The side PA systems were suspended from truss beams mounted on independent Ringlock structures.

• Relay speaker systems were suspended from approximately 20-metre-high relay towers positioned in the middle of the stadium.

These observations reveal an important engineering principle:

The safest suspension point is not always the highest one—it is the structure specifically designed to carry the required load while delivering the correct acoustic coverage.

The overall sound system layout is discussed in How Is a Stadium Concert Sound System Distributed?, while this article focuses on the structural engineering behind safely suspending those systems.

Engineering Observation

Three independent suspension systems were used during this project.

Although all three systems supported line arrays, each served a different engineering and acoustic purpose.

Why Are Line Arrays Suspended Instead of Placed on the Ground?

Large line arrays are suspended for several reasons.

Suspending the speakers:

• Improves audience coverage.

• Prevents sound from being blocked by spectators.

• Creates better vertical dispersion.

• Reduces reflections from the stage floor.

• Allows sound to project over long distances.

The suspension height is therefore determined by acoustic performance as well as structural safety.

Main PA Arrays Are Suspended from the Roof Apron

The primary line arrays were positioned at the front of the main stage.

Instead of hanging directly from the roof truss, they were suspended from cantilever beams extending beneath the roof apron.

This arrangement offers several engineering advantages.

Better Audience Coverage

Positioning the arrays at the front edge of the stage reduces obstruction from:

• The roof structure.

• Lighting equipment.

• The LED backdrop.

This allows sound to project directly into the audience.

Independent Structural Support

The cantilever beam is specifically designed to transfer the concentrated speaker load into the main roof structure.

This creates a dedicated load path rather than distributing speaker loads across multiple roof members.

Easier Rigging and Maintenance

Suspending the speakers from the apron area also provides convenient access for:

• Chain motors.

• Rigging hardware.

• Safety cables.

• Angle adjustments.

This arrangement is closely related to the roof engineering explained in Why Is the Roof Higher Than the LED Screen?.

Side Line Arrays Are Suspended from Ringlock Structures

Another suspension method was observed on both sides of the main stage.

Each side Ringlock tower supported a dedicated truss beam installed across the top of the structure.

The line arrays were suspended directly from these truss beams.

The load path can be summarised as follows:

Line Array

↓

Rigging Hardware

↓

Aluminium Truss Beam

↓

Ringlock Structure

↓

Base Plates and Ground

This system separates the side arrays from the main stage roof.

Why Use Ringlock Instead of Extending the Main Roof?

There are several reasons.

Independent Structural System

The Ringlock tower carries its own loads.

The main roof therefore does not need to support additional speaker weight beyond the primary PA system.

Flexible Positioning

Ringlock towers can be positioned according to acoustic requirements rather than roof geometry.

This provides greater flexibility when different venues require different speaker coverage.

Simplified Installation

Because the truss beam is installed at the top of the Ringlock tower before the speakers are lifted, installation becomes safer and more efficient.

The structural principles behind these towers are explained further in How Do Ringlock Structures Support Large Concert Stages?.

Relay Towers Support Long-Distance Sound Coverage

One of the most impressive structures observed during this project was the relay tower system.

Two independent towers approximately 20 metres high were positioned near the centre of the stadium.

Each tower supported two line array clusters.

Unlike the main stage arrays, these speakers were not intended to increase volume.

Their purpose was to extend sound coverage to audiences located far from the stage.

Why Are Relay Towers So Tall?

The height serves several purposes.

Clear Sound Path

Elevating the speakers reduces obstruction from:

• Audience members.

• Temporary seating.

• Production equipment.

This allows sound to travel over long distances.

Better Acoustic Coverage

The elevated position enables sound engineers to direct the arrays toward the rear audience areas while maintaining even coverage.

Reduced Delay Problems

Relay systems are carefully aligned with the main PA using digital processing.

The structural height ensures the sound reaches distant listeners from an appropriate angle while maintaining timing consistency.

The role of these towers is discussed in greater detail in Why Are Relay Speaker Towers Needed?.

Safety Is Designed Into the Supporting Structure

A line array may weigh several hundred kilograms.

The structural system supporting it must therefore be designed to resist:

• Vertical dead load.

• Dynamic loading during lifting.

• Wind forces.

• Vibration during operation.

For this reason, professional suspension systems typically include:

• Certified rigging hardware.

• Chain motors or manual hoists.

• Steel suspension points.

• Independent safety steel cables.

• Structural verification before lifting.

The loudspeaker itself is only one part of the suspension system.

The supporting structure is equally important.

Different Locations Require Different Suspension Methods

The suspension systems observed during this project can be summarised as follows.

Each system was selected according to both structural capacity and acoustic performance.

Engineering Lessons from This Project

Several important engineering principles can be drawn from these observations.

1. Suspension Method Depends on Function

Not every speaker should be hung from the main roof.

Different locations require different structural solutions.

2. Load Paths Must Be Clearly Defined

Every suspended line array transfers its weight through a dedicated structural path.

Understanding that load path is essential for safe temporary structure design.

3. Acoustic Design and Structural Design Must Work Together

The best structural position is not necessarily the best acoustic position.

Successful concert engineering balances both disciplines simultaneously.

4. Independent Structures Improve Flexibility

Using Ringlock towers and relay towers allows engineers to optimise sound coverage without overloading the main stage roof.

This modular approach also simplifies installation and adapts more easily to different venue layouts.

Conclusion

Large concert line arrays are not suspended from a single universal structure.

Instead, each system is supported by a structural solution specifically designed for its function.

During the Guangzhou Pearl Beer Festival Music Festival project, three suspension methods were observed.

The main PA arrays were suspended from cantilever beams beneath the roof apron to provide direct front coverage.

The side arrays were hung from truss beams mounted on independent Ringlock towers, creating flexible and structurally independent support.

The relay arrays were installed on approximately 20-metre-high relay towers positioned in the centre of the stadium to extend sound coverage to distant audience areas.

Together, these systems demonstrate one of the fundamental principles of concert engineering:

Safe line array suspension is achieved not by using the same structure everywhere, but by matching each loudspeaker system to the structure best suited to its location, load and acoustic purpose.