HOLOPLOT technology

This page offers an in-depth look at the evolution of sound technology and clearly highlights the distinctive features that set HOLOPLOT apart from other sound system solutions. You will learn about the core technological foundations underpinning our Matrix Arrays, which define and distinguish HOLOPLOT in the audio industry.

The evolution of Sound Control

Point sources

When a loudspeaker produces sound, its radiation pattern is determined by its shape, size, number of drivers, and properties. A point source loudspeaker produces a spherical wave that spreads equally in every direction. These wavefronts form an acoustic wave field that expands as it spreads through space and time. The energy of this wave is initially concentrated at the point source, but as it travels outward, its energy is spread over the surface of the spherical wavefronts, effectively reducing the energy as it expands. This results in a Sound Pressure Level (SPL) loss of 6dB for every doubling per distance. The rapid decline causes point sources to deliver an uneven acoustic coverage of an audience area. This is visually represented in the picture below, where the SPL level of the point source is represented as a color bar. A hot color represents a loud level, whereas a cold color represents a quiet level. Note that, although only the frontal radiation is shown in the picture below, the audio wavefronts propagate in all directions equally.

By altering the shape of the sound source, the spatial and directional properties of the sound field it produces can be manipulated. One way to accomplish this is by using a loudspeaker horn, which generates a directional wave that confines the speaker's radiation range to a particular dispersion. This technique is especially effective in the high frequencies (HF) range.

Line arrays

Another way of changing the radiation pattern is by combining multiple loudspeakers and relying on acoustic summation or cancellation from the individual transducers, forming a specific radiation pattern for the combination of them all. Signal processing also allows the manipulation of a sound field's spatial and directional properties. One way this is achieved is by applying appropriate processing to each driver's signal, which can alter a speaker array's radiation pattern, also called directivity. This process is known as digital beam steering.

Line arrays are speaker systems that use a vertical arrangement of transducers. These transducers have a wide horizontal and narrow vertical dispersion angle, offering dynamic control over the vertical radiation pattern, effectively controlling the level and propagation. However, they offer no control over the horizontal axis. Since the transducers are arranged vertically, beam steering is possible only on the vertical axis.

HOLOPLOT Matrix Arrays

The HOLOPLOT Matrix Array takes the concept of sound control to the next level by enabling 3D sound field manipulation. The HOLOPLOT Matrix Array comprises horizontally and vertically stacked Audio Modules, bringing full scalability to system performance and project needs. Each Audio Module contains a series of loudspeaker drivers arranged in a multi-layered two-dimensional design for the case of X1, or a single-layer two-dimensional design for X2. Each driver is processed and amplified individually, allowing for control in both the horizontal and vertical axes.

The radiation pattern of a HOLOPLOT Matrix Array can be defined and controlled very precisely in the vertical and horizontal plane. This allows for the creation of tailored sound fields with highly optimized coverage in terms of level and spectral homogeneity. This advanced and unique sound field manipulation presents considerable advantages compared to beam steering.

The three-dimensional control capabilities of HOLOPLOT Matrix Arrays are powered by two different soundfield generation techniques - 3D Audio-Beamforming and Wave Field Synthesis.

3D Audio-Beamforming

3D Audio-Beamforming is an advanced audio processing technique that uses an array of speakers to direct and control the propagation of sound waves in three-dimensional space. By controlling each driver's signal's relative phase and amplitude, a well-defined radiation pattern can be created by constructive interference in specific directions and destructive interference in other directions.

HOLOPLOT’s beamforming algorithms allow Matrix Arrays to be configured in two different ways.

The first one is a parametric approach where the shape of the beam is defined by a set of parameters, such as opening and steering angle. The second method uses an optimization engine to obtain an optimum coverage pattern.

Coverage Beams

A Coverage Beam is fully tailored to the geometry of the targeted zone, providing very uniform coverage and high spectral consistency at the predefined audience area compared with traditional beamforming loudspeakers or line arrays. By utilizing digital soundfield control on both axes and directing sound where needed, reflections and spills are minimized.

Using HOLOPLOT Plan, HOLOPLOT's sound system design software, a 3D model of the space or venue, along with the array set-up positions, allows the system designer to precisely define which audience areas need to be covered by each array. Additionally, the designer can identify and define boundaries or zones that should be actively avoided by the array, such as balcony fronts or other reflective surfaces. This helps to ensure optimal sound coverage by avoiding unwanted reflections or interference.

For Coverage Beams, the system design follows an audience-centric approach by defining target and avoidance areas as the main design criteria. Coverage Beams are optimized to achieve the desired SPL distribution and keep a consistent spectral homogeneity across the predefined audience areas, ensuring everyone in the audience has the same auditory experience.

Coverage Beams are optimized in the cloud using cutting-edge algorithms that further take advantage of the 3D Audio-Beamforming capabilities of the Matrix Array. Up to five Coverage Beams can be deployed from the same Matrix Array simultaneously, irrespective of the size of the array (5 for X1, 4 for X2). The calculation of Coverage Beams relies on an internet connection.

Parametric Beams

A Parametric Beam is a beamforming technique used to control the radiation pattern of a Matrix Array by using a set of geometric parameters. When a HOLOPLOT array emits a Parametric Beam, its direction (i.e., vertical/horizontal steering angle) and width (i.e., vertical/horizontal opening angle) are defined relative to the physical position and orientation of the array.

Parametric Beams allow for easy 3D control of the directional characteristics of an array, as compared to Coverage Beams. The design and calculation of Parametric Beams is done using HOLOPLOT Plan software locally, which is a simplified method but lacks the optimized level and spectral homogeneity benefits. However, it offers a quick and easy way to design and deploy beams within the array.

Up to 8 Parametric Beams can be deployed from the same Matrix Array simultaneously, irrespective of the size of the array. The calculation of Parametric Beams does not rely on an internet connection.

Wave Field Synthesis

Virtual Sources

Wave Field Synthesis (WFS) is a cutting-edge sound reproduction technology designed for spatial audio. It simulates and synthesizes virtual acoustic environments using a large number of loudspeakers arranged in a Matrix Array. The key innovation of WFS is its ability to reconstruct sound so that it appears to originate from a specific virtual starting point, known as a Virtual Source. This allows for a highly realistic and immersive audio experience, where the location of the sound source can be perceived accurately from any position within the listening area.

Unlike conventional sound reproduction techniques like stereo and surround sound, Wave Field Synthesis (WFS) does not depend on stereophonic principles, which create an acoustic illusion known as "phantom sources" in a small area (the sweet spot) at the center of the loudspeaker setup. Instead, WFS allows listeners to experience accurate localization of virtual sound sources from any position within the reproduced sound field. This means that WFS provides consistent spatial audio perception throughout the listening area. Additionally, WFS offers the highest spatial resolution among all spatial rendering techniques, delivering an unparalleled immersive audio experience.

The position of Virtual Sources in HOLOPLOT Plan can be defined using global, local, or angle coordinates, allowing them to be placed either behind or in front of the Matrix Array. Virtual Sources positioned behind the array are "visible" and correctly perceived within the audience area defined by the Field Of View (FOV). Listeners within the FOV can move freely while still accurately perceiving the location of these Virtual Sound sources. Conversely, when Virtual Sources are placed in front of the MatrixArray, the audio wavefronts from all transducers in the Matrix Array constructively add to the Virtual Source, also known as a Focus Source, resulting in a relatively high sound level compared to the rest of the listening area.

Virtual Sources are a powerful tool for creating in-field localization, targeted reflections, and special effects at specific listener positions, significantly enhancing the creative capabilities of system designers.