Domaines de recherche2020-06-03T17:34:21+00:00

Domaines de recherche

Acoustique Fondamentale

  • Critères WST® pour la réalisation de lignes sources (AES Journal; 92, 01,03)
  • Modèle DED (Distributed Edge Dipole), effets de diffraction sur la menuiserie
  • Event à profil progressif pour une réduction des effets de turbulence
  • Technologie K-LOUVER pour la directivité variable
  • Technologie de directivité horizontale réglable PANFLEX™

Design et ingénierie

  • Veille sur les nouveaux matériaux
  • Analyses vibratoires pour l'optimisation des enceintes
  • Modélisation et conception 3D assistées par ordinateur
  • Tests mécaniques et certification pour la sécurité d'accrochage

Electronique

  • Alimentation « verte » avec PFC
  • Amplification classe D
  • Cartes DSP propriétaires
  • Appareils multi-canaux

Traitement du signal

  • Conception d'algorithmes propriétaires
  • Outil Array Morphing pour l'ajustement de la balance tonale des lignes sources
  • Protection L-DRIVE (thermique et sur-excursion)
  • Egalisation de compensation de l’absorption de l’air
  • Filtres FIR

Logiciels

  • Modélisation 3D acoustique (couverture SPL) et mécanique (sécurité d'accrochage)
  • Pilotage et monitoring à distance des contrôleurs amplifiés

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

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

Non-linear acoustic losses prediction in vented loudspeaker using computational fluid dynamic simulation

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 Analysis

AES 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.

 

Large 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

Journal de l'AES, Vol. 52, n°10 - Octobre 2004

 

Introduction

Un modèle mathématique simple est proposé pour prendre en compte les effets de diffraction provoqués par les bords d'une enceinte ayant des haut-parleurs montés en radiation directe. Ce modèle, appelé "Modèle DED" (Distributed Edge Dipole Model), est développé à partir de l'approximation de Kirchoff (KA) en utilisant des dipôles distribués dont les axes sont perpendiculaires aux bords du baffle.

Ces dipôles sont considérés comme étant des sources de diffraction élémentaires. Le Modèle DED est d'abord confronté à des mesures faites sur un baffle circulaire de faible épaisseur puis sur une enceinte rectangulaire aux bords plus épais. L'étude du niveau de pression sonore à l'avant et dans le domaine angulaire montre que les prédictions du modèle DED amènent à des résultats proches de ceux issus des mesures expérimentales.

 

Wavefront Sculpture Technology

Journal de l'AES, Vol. 51, n°10 - Octobre 2003

 

Introduction

Suite de l'analyse de Fresnel adapté au domaine acoustique, pour une approche efficace et intuitive de la compréhension du phénomène complexe d'interférence. Nos résultats permettent d'établir le critère qui permet de coupler efficacement des sources sonores et d'obtenir la couverture sur une zone d'audience déterminée pour des applications de renfort sonore. Le critère qui en découle, est la base de ce qui est appelé "Wavefront Sculpture Technology" (ou sculpture du front d'onde).

 

Wavefront Sculpture Technology

AES Convention Paper #5488

Article présenté à la 111ème Convention de l'AES, New York 2001

Introduction

Cette première adaptation de l'analyse de Fresnel au domaine acoustique, fournit une approche efficace et intuitive de la compréhension du phénomène complexe d'interférence, pour établir le critère permettant de coupler efficacement des sources sonores et obtenir ainsi la couverture sur une zone d'audience déterminée pour des applications de renfort sonore.

Le critère qui en découle, est la base de ce qui est appelé "Wavefront Sculpture Technology" (ou sculpture du front d'onde).

 

Sound Field Radiated By Arrayed Multiple Sound Sources

AES Convention Paper #3269

Article présenté à la 92ème Convention de l'AES, Vienne 1992

Introduction

Peut-on prédire le comportement d'un empilement de sources sonores (array) lorsque le comportement de chaque élément est connu ?

Le but ici est de décrire le champ sonore produit par les arrays de manière à ce que le critère d'empilement de sources puisse être défini, et de considérer ainsi une array comme étant une source unique ayant les dimensions physiques de l'array.

 

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