Presented this summer at the Théâtre de l’Archevêché, as part of the Aix-en-Provence Festival, La Calisto was the setting for an acoustic design both ambitious and finely nuanced.
The Théâtre de l’Archevêché presents particular acoustic challenges; its naturally low reverberation and three distinct listening zones: an open-air stalls, a highly absorbent under-balcony, and an overhanging balcony. The goal was to create a coherent, immersive environment that preserved the baroque character of the work, without resorting to obvious amplification.
Instead of being used as an effects processor, the HOLOPHONIX system functioned as a real-time virtual acoustics instrument. Powered by a HOLOPHONIX Ultra (128/64) processor, the design relied entirely on Wave Field Synthesis (WFS), allowing sources to be positioned and reverberated with extreme precision, independently in each listening area. A dedicated WFS reverb bus was added, making it possible to adjust the space’s acoustic envelope live, adapting it fluidly to shifts in performance, aria, recitative, or ensemble. The system was piloted via Open Stage Control on iPad, with real-time values mirrored in the Yamaha DM7’s User Keys, seamlessly integrated with QLab.
The sound processing was built around three core layers: direct sound, early reflections, and algorithmic reverberation. Unlike convolution or regenerative approaches, the fully parametric reverb software enabled precise control of dynamics, tonal color, and temporal behavior, adjustable in real time to suit stage movement and orchestral density. This adaptability addressed practical listening issues in specific zones and allowed the acoustic envelope to evolve throughout rehearsals, in constant dialogue with the artistic team.
For the orchestra, around thirty static microphones (Schoeps, Neumann, DPA) were deployed, along with six DPA 4011s on active cables across the stage and two miniature DPA 6061s integrated into the set for discreet reinforcement. Signals were routed through multiple Rio racks (pit, stage, control room, upper control), feeding a Yamaha DM7 for front of house and a CL5 beneath the stage for monitoring. An RMio handled MADI conversion for Radio France’s recording, while a Mac mini captured the entire Dante stream for multitrack recording and OSC control.
The project was led by Pidou (mix), Alban Moraud (recording), and Félix Perdreau, who managed sound spatialization with HOLOPHONIX as well as all real-time active acoustic adjustments. Together with the conductor Sébastien Daucé, their flexible, responsive approach remained fully aligned with musical priorities.
Front speakers, initially considered too close to the musicians, were ultimately reintegrated during quiet passages to improve intelligibility in distant vocal zones. The balance between directionality, clarity, and naturalness was refined continuously through rehearsals, with local teams progressively mastering the system.
Over the course of performances, the technology disappeared behind the music.
The fact that one of the operas playing at the Theatre was unamplified gave us a direct comparison. With HOLOPHONIX , the benefit was obvious for me and for the Festival team. Without treatment, the acoustics felt flat, lifeless, without dimension. With real-time acoustic processing, the stage quite literally opened up. The sound became unified, the music breathed again full of air and vitality,
explains Félix Perdreau, sound engineer responsible for spatialization.
In this production, HOLOPHONIX achieved two essential goals: to recreate a flexible, credible acoustic in a naturally dry space, and to provide imperceptible support that delivered consistent, comfortable listening for over 1,300 open-air spectators.
This project also highlighted new avenues for refinement: a higher speaker array could allow finer vertical balance, while additional surround speakers beneath the balcony would enhance envelopment in that zone,
concludes Félix Perdreau.
