Meeting Topic: Low frequency mode control using active subwoofers
Moderator Name: Veronique Adam
Speaker Name: Véronique Adam (AudioNetworks SA / Goldmund), Alain Roux (Relec SA / Psi Audio), Antoine Pittet & David Strobino, (HEPIA GE), Hervé Lissek (EPFL)
Meeting Location: Yverdon (VD), Swizerland
Around 50 people gathered on this Thursday afternoon in the premises of Relec SA, in Yverdon-les-Bains.
Véronique Adam opened up the meeting with a brief presentation of the CTI/KTI project named "INTERACTS" for Intelligent low-frequeNcy acoustic Equalization of Rooms using Active ConTrol Subwoofers. She explained the framework of this project and the original feature of gathering four un-competitor partners: two academic partners (EPFL and HEPIA) and two industrial partners (Relec SA [Psi Audio] and AudioNetworks SA [Goldmund]). She explained their innovative idea to develop active subwoofers acting as sound absorbers to equalize naturally in time and level the low frequency behaviour in different types of listening rooms.
The first speaker was Alain Roux, who gave an overview of the basic principles of acoustics and especially of those related to the low frequency behaviour in standard size rooms.
After this theoretical introduction to the problems generated by low-frequency modes, the next presentations explained the two technical solutions developed in the framework of the Interacts project:
1. The analogue architecture solution called "Low frequency absorption by velocity control through acoustic resistance" was presented by Antoine Pittet and David Strobino from the Hepia GE. They described the theory of porous layers and the implemented solution using an acoustic resistance (micro-perforated metal sheet) and a subwoofer used as a velocity transducer
2. The digital architecture solution called "Low frequency absorption by hybrid sensor-/shunt-based impedance control" was described by Hervé Lissek from the EPFL. He explained the theory of loudspeaker diaphragms used as membrane absorbers and the implemented solution using an hybrid impedance control architecture enabling the absorption on a wider frequency range to be optimized.
For both analogue and digital architectures, the speakers presented some very convincing measurement results based on the preliminary tests carried out with the prototypes in real conditions.
After the presentations, the attendees were invited to test both technologies in the Relec SA demo room. They had the possibility to test the room absorption using one to eight prototypes, in order to grasp the naturalness of these absorption solutions provided in time and level.
After the official event, the discussions about this interesting topic went on in a friendly restaurant nearby.
The Swiss AES section would like to thank warmly Mr Roger Roshnik and the Relec team for their kind collaboration and for the aperitif offered in their premises.
NB: The PDF of the presentations are available on the website of the AES Swiss Section.
Written By: Veronique Adam