L-Acoustics White Papers
L-ISA HYPERREAL SOUND: Why amplitude-based algorithms are best suited to frontal loudspeaker configurations?White Paper, May 2020
Abstract
L-ISA technology enables the sound of a performer to be perceived as coming from their location on stage and creates natural separation of the multiple sounds. This is allowed by a combination of loudspeaker system design recommendations and a custom amplitude-based panning algorithm. In this white paper, we show the L-ISA algorithm generally outperforms delay-based algorithms for any type of shows, from soft natural voice lifting to high SPL performances.
Measurement quality at low frequencies
White Paper, April 2020
Abstract
Background noise affects the quality of measured frequency responses of a loudspeaker system. Repeated measurements can reveal very different results, especially at low frequencies, compromising optimal system tuning decisions (EQ, quality of summation for time alignment, etc.).
Combination of multiple acquisitions with appropriate test signal parameters can help getting more consistent and qualitative measurements at low frequencies.
Measurement quality at high frequencies
White Paper, April 2020
Abstract
The frequency response of a loudspeaker system can vary over time due to changing atmospheric conditions such as:
- Temperature and humidity (slow variations),
- Wind (fast variations).
Multiple acquisitions may reveal a large spread of frequency responses, especially at large distances and high frequencies. This spread makes EQ decisions taken from a single capture irrelevant. In the M1 tool, multiple sweeps can be recorded and combined. The obtained measurement accounts for the fast variations of atmospheric conditions and offers a more reliable representation of the frequency response of a loudspeaker system.
Optimum measurement locations for loudspeaker system equalization
White Paper, April 2020
Abstract
A loudspeaker system tuning ideally aims at optimizing the whole audience area. However, onsite EQ choices must be based on a limited number of measured frequency responses. To avoid EQ mistakes, the key is to capture a representative set of measurements. It should:
- Smooth spatial variations in the average frequency response,
- Reveal spatially stable patterns in the individual frequency responses.
Publications
Audience effect on the response of a loudspeaker system in the low frequency range, part 1: magnitudeAES Convention Paper #10398
Article presented at the 149th Convention, October 2020, online
Abstract
The response of a loudspeaker system is affected by the presence of the audience. However, the loudspeaker system tuning is performed without an audience, applying equalization filters and delays for time alignment system components. The validity of these decisions with an audience is of primary importance. In this paper, the magnitude response of a loudspeaker system is simulated at low frequencies using Finite Element Method over a flat listening area for multiple source heights and audience densities. The results show that the audience modifies notches due to the floor reflection for a flown source and creates a build-up associated with a low-pass behavior for ground-stacked sources. The implications on typical loudspeaker system configurations are presented and discussed.
AES Convention Paper #10359
Article presented at the 148th Convention 2020 June 1-5, Online
Abstract
Bass-reflex designs can exhibit strong non-linear behavior around their resonant frequency with significant acoustic losses and parasite noise emission. These phenomena are mainly due to turbulences and flow separation at the port’s inlet and outlet. This work proposes a method to predict the resulting non-linear acoustic losses for a given loudspeaker, enclosure volume and port geometry. The approach consists of coupling computational fluid dynamics (CFD) simulation with loudspeaker non-linear motion modelization. Four different ports geometries mounted on one given loudspeaker enclosure are tested. The computed acoustic losses are compared with measurements and show a good agreement. The obtained results prove that the proposed method can predict non-linear losses with an average error less than 1 dB around the Helmholtz frequency.
Optimum Measurement Locations for Large-Scale Loudspeaker System Tuning Based on First-Order Reflections AnalysisAES Convention Paper #10234
Article presented at the 147th Convention 2019 October 16–19, New York, USA
Abstract
This paper investigates how first-order reflections impact the response of sound reinforcement systems over large audiences. On the field, only few acoustical measurements can be performed to drive tuning decisions. The challenge is then to select the right measurement locations so that it provides an accurate representation of the loudspeaker system response. Simulations of each first-order reflection (e.g., floor or side wall reflection) are performed to characterize the average frequency response and its variability over the target audience area. Then, the representativity of measurements performed at a reduced number of locations is investigated. Results indicate that a subset of eight measurement locations spread over the target audience area represents a rational solution to characterize the loudspeaker system response.
On the Efficiency of Flown vs. Ground Stacked Subwoofer Configurations
AES Convention Paper #10051
Article presented at the 145th Convention 2018 October 17–20, New York, NY, USA
Abstract
Modern live loudspeaker systems consist of broadband sources, often using variable curvature line sources, combined with subwoofers. While it is common practice to fly the broadband sources to improve energy distribution in the audience, most subwoofer configurations remain ground-stacked because of practical constraints and alleged efficiency loss of flown configurations. This article aims at evaluating the efficiency of flown subwoofers for large audiences as compared to their ground-stacked counterparts. We use finite element simulations to determine the influence of several factors: baffling effect, trim height. We show that flown configurations remain efficient at the back of the venue while reducing the SPL excess at the front of the audience.
Larg
e Scale Open Air Sound Reinforcement in Extreme Atmospheric Conditions
AES Convention Paper #P2.3
Article presented at the AES International Conference on Sound Reinforcement – Open Air Venues (August 2017)
Abstract
Extreme atmospheric conditions have a profound effect on sound propagation. This paper presents two installations where this problem must be accounted for: the main stage of the Coachella Valley Music and Arts Festival and the Hollywood Bowl. The approach presented here combines an optimized sound system design combined with signal processing for partial compensation of remaining loss in selected areas.
The Distributed Edge Dipole (DED) Model for Cabinet Diffraction Effects
AES Journal, Vol. 52, n°10 - 2004 October
AES Journal, Vol. 52, n°10 - 2004 October
Abstract
A simple model is proposed to account for the effects of cabinet edge diffraction on the radiated sound field for direct-radiating loudspeaker components when mounted in an enclosure. The proposed approach is termed the Distributed Edge Dipole (DED) model since it is developed based on the Kirchoff Approximation (KA) using distributed dipoles with their axes perpendicular to the baffle edge as the elementary diffractive sources.
The DED model is first tested against measurements for a thin circular baffle and is then applied to a real world loudspeaker that has a thick, rectangular baffle. The forward sound pressure level and the entire angular domain are investigated and predictions of the DED model show good agreement with experimental measurements.
Wavefront Sculpture Technology
AES Journal, Vol. 51, n°10 - 2003 October
AES Journal, Vol. 51, n°10
Abstract
The Fresnel approach in optics is introduced to the field of acoustics. Fresnel analysis provides an effective, intuitive way of understanding complex interference phenomena and allows for the definition of criteria required to couple discrete sound sources effectively and to achieve coverage of a given audience geometry in sound-reinforcement applications. The derived criteria from the basis of what is termed Wavefront Sculpture Technology.
Wavefront Sculpture Technology
AES Convention Paper #5488
Article presented at the 111th AES Convention, New York 2001
Abstract
We introduce Fresnel’s ideas in optics to the field of acoustics. Fresnel analysis provides an effective, intuitive approach to the understanding of complex interference phenomena and thus opens the road to establishing the criteria for the effective coupling of sound sources and for the coverage of a given audience geometry in sound reinforcement applications.
The derived criteria form the basis of what is termed Wavefront Sculpture Technology.
Sound Field Radiated By Arrayed Multiple Sound Sources
AES Convention Paper #3269
Article presented at the 92nd AES Convention, Vienna 1992
Abstract
How to know whether it is possible or not to predict the behaviour of an array when the behaviour of each element is known?
Our purpose is to describe the sound field produced by arrays in such a way that criteria for “arraybility” can be defined.