What Is Directivity?

A speaker’s directivity refers to the spatial distribution of the sound it emits. It is represented using polar patterns, which are diagrams that show sound intensity at various angles relative to the speaker’s central axis.

Omnidirectional speakers: Emit sound uniformly in all directions. Ideal for background music systems or large spaces requiring general coverage.
Directional speakers: Focus sound on specific areas. Preferred in auditoriums, concerts, or installations where clarity and control are paramount.

Practical Example:

A speaker from the IBZA Series, like the IBZA12, offers a controlled coverage pattern ((50°-100°) x60°), allowing acoustic energy to be directed toward the audience while minimizing reflections from side walls.

Measuring Directivity: Directivity Index and Q Factor

Directivity Index (DI):

This represents the difference in dB between the sound pressure on the speaker’s main axis and the average pressure in all directions. A higher DI indicates a highly directional speaker.

Q Factor:

This is the ratio of power radiated in a specific direction to the power radiated uniformly in all directions. A higher Q means better directivity control.

Relation:

For example, a line array system like the CLa21PLUS can exhibit a significantly high DI along its vertical axis due to its controlled directivity design.

Factors Influencing Directivity

Speaker Size:

Smaller speakers tend to be less directional, especially at low frequencies.
Larger speakers or array systems allow greater control, particularly at mid and high frequencies.

Sound Frequency:

Low frequencies are generally omnidirectional due to their longer wavelengths relative to speaker dimensions.
High frequencies are more directional because of their shorter wavelengths.

Cabinet Design:

Technologies such as waveguides in systems like the Array Series allow precise control of sound dispersion, ensuring uniform coverage.

Directivity Control in Professional Applications

Line Array Systems

Line array systems, like those in the Array Series, are designed to control sound dispersion along both vertical and horizontal axes:

Vertical: Modules work together to limit dispersion, preventing sound from reaching undesired areas like ceilings.
Horizontal: Provide wide and uniform coverage for the audience.

Practical Example:
In a stadium, a properly configured CLa21PLUS system can maintain uniform coverage with a horizontal range of 75° while limiting vertical dispersion to 13°, avoiding energy loss toward the ceiling.

Controlled-Directivity Subwoofers

Subwoofers like those in the SW Series can be arranged in cardioid or inline configurations to control low-frequency dispersion, reducing rear reflections and improving clarity for the audience.

Cardioid Configuration:

This involves using multiple subwoofers with phase and amplitude differences to cancel sound at the rear of the array.

Practical Example:

An SW218 subwoofer can be paired with an inverted unit behind it, using a delay applied through a TDAP Series amplifier to achieve a cardioid pattern.

How to Optimize Directivity in a Space

Acoustic Simulations:

Use software like EASE Focus to model sound dispersion within the space and anticipate coverage or reflection issues.

Adjusting Angle and Orientation:

For line array systems, adjust module tilt to ensure the main sound axis is directed toward the audience.

DSP Processing:

T Series amplifiers allow delays and filters to be adjusted, optimizing phase alignment and coherence among speakers to enhance directivity control.

Environmental Treatment:

Install acoustic panels to minimize reflections from walls and ceilings, particularly at mid and high frequencies.

Case Study: Sound Design for a Theater

Scenario:

A 1,000-seat theater requires a system with uniform coverage for the audience while avoiding reflections toward side walls and the ceiling.

Solution:

Equipment Selection:

CLa21PLUS line arrays for main coverage.
Cardioid SW Series subwoofers for low-frequency control.

Simulation:

Use EASE Focus to design the array modules’ tilt and dispersion, ensuring horizontal coverage encompasses the entire audience without reaching the side walls.
Configuration and Adjustment:

Install speakers with angles adjusted per simulation results.
Set subwoofers in a cardioid arrangement using the DSP in TDAP Series amplifiers.
Testing and Optimization:

Measure SPL and polar patterns at different locations in the theater.
Adjust EQ and delays to maximize system coherence and clarity.

Conclusion

Controlling directivity is essential for any professional audio system. Understanding how to design and optimize coverage patterns enables sound engineers to deliver high-quality experiences, maximizing clarity and minimizing acoustic issues.

If you need assistance designing sound systems with controlled directivity, contact us. We offer advanced acoustic simulations and customized configurations using cutting-edge Tecnare technology.