CARMEN in Grimaldi Forum, Monaco

Mastering acoustics in auditoriums

To every music the dedicated acoustics

Ideally every type of music requires an appropriate specific acoustics which can be characterized, among many others criteria, by the reverberation time. Reverberation time is the time taken by a sound in a room to disappear when stopped. For instance a rather short reverberation time (0.5s to 1s) is required for speech drama or conferences and a longer one (1.8s to 2.2s) is well appreciated for symphonic music, chorus or baroque pieces. For that reason very few performing halls are really acoustically multipurpose.

CARMEN® has therefore been figured out by he acoustic engineers at France's Centre Scientifique et Technique du Bâtiment (CSTB) to fulfil the highest musicians' expectation as variable acoustics is concerned and also to improve at reasonable cost the acoustically defective performing halls. It is a pure electro-acoustic system based on the Virtual Wall Principle that instantaneously adapts the acoustics of a hall to what is the most suitable for the current performance: conferences, speech dramas, classical concerts, opera or other events. Called CARMEN®, an acronym in French for Active Control of Reverberation by Natural Effect Virtual Walls (M), the system has been designed to give the best natural acoustic results, similar to that produced by the most suitable architecture.

How does CARMEN® work?

CARMEN® comprises a number of electro acoustic active cells (approximately from 16 to 40), each of them being composed of a microphone, an electronic filtering unit, a power amplifier and a loudspeaker. Placed around the walls and ceiling of the auditorium, the cells form virtual walls depending on the architecture and the acoustic problem to solve. They only communicate between each other by the acoustic way. The whole cells are controlled by a computer or an on stage remote control panel.

The innovative layout of the microphones and loudspeakers produces completely natural acoustics with a space-time coherence of the sound field preserved. Reverberation enhancement is simply coming from the mutual reflections between the different parts of the virtual walls, as for real walls in a room. No microphone on stage is impeding the normal use of the space above the stage. Besides, the natural directivity of the sound sources and stage sound images can not be altered as when picking up the sound from above the head of the musicians or close to stage and reproducing just as it is whatever the place in the hall.


CARMEN Block Diagram
Natural and optimised by the CARMEN system


CARMEN®  practically

Installing CARMEN® in a room doesn't imply special important works, except cables installation, neither carrying out preliminary architecture modification. Once it is installed, simply becomes part of the room, just like the walls and the ceiling. It makes really multipurpose any kind of performing halls, enhancing the reverberation as suitable and giving the designer precise control over a wide range of parameters, such as clarity, sound strength, speech intelligibility or listener envelopment.

Of course the system cannot reduce an excess in reverberation time, which is otherwise easy to achieve by using classical sound absorbing materials. The system cannot be compared with a classical sound reinforcement system, although two line inputs can be used to coherently enhance speaker voice or broadcast any other sounds or announcements.

Using CARMEN® is very straightforward. It is switched on and off through a simple key. It provides a user-friendly command and control interface. Choosing an acoustics (opera, symphony, etc.) is simply a question of selecting the corresponding preset switch on the PC or the remote control unit.

Thanks to the use of professional audio equipment, background noise is inaudible and high dynamic range provides a perfect response from pianissimo to fortissimo. Digital processing of the signals ensures the stability of the system functioning.

Technical Specifications


Electroacoustic system for controlling performing halls acoustics.


Instantaneously adapts the acoustics of a hall to what is required. Improves the acoustics of defective performing halls which would be too expensive to correct with architectural works.


Virtual reflecting wall composed of electro acoustic quasi locally reacting cells.


Preset acoustics are programmed in order to fit the various performance types: speech drama, conference, popular music, opera, chamber music, symphonic music…
Each setting corresponds to a particular set of acoustic parameters:

  • Sound Level and Sound Level distribution over the audience,
  • Lateral Energy Fraction,
  • Early and late Reverberation time
  • Speech Intelligibility,
  • Tonal Balance.


Turning the system on and off by centralized controller electric switch. Preset recalling by keys on remote control touch panel or control PC.


All cells are independent. Each composed of a quality recording microphone, a DSP, a power amplifier and a loudspeaker. Digital processing for each cell is centralized. Loudspeakers and microphones are usually inserted in the room decoration. The electronic rack is sustained powered.


  • Voice reinforcement (no close stage microphone) for speech drama, conference, and opera.
  • Coherent sound reinforcement.

Technical specifications:

    Number of cells: 16 to 48 depending of the requirement.
    Loudspeaker output power amplifier: 150W rms
    Maximum sound pressure level produced: >100dB (pink noise) for a 24 cells system.
    Maximum sound pressure level on the microphones: 130dB
    Frequency band: 80-16000Hz.
    Background noise produced: < 25dB(A), or NR 15.
    Stereo line input (sound reinforcement): +26dBu max.
    Output lines (recording): 2, +26dBu max.
    Digital processing:  24 bits A/D and D/A converters DSP Motorola 56003, 24/48 bits. Processing dynamic: 110dB(A)


One year full warranty service, prolonged by maintenance contract.

Two options:

  • Installer intervention on site, 48h warranted system restart.
  • Intervention by client under the installer control through remote maintenance line; immediate system restart.
CARMEN Electronic Rack
Remote Control Touch Panel

CARMEN equiped halls

Monaco : 

“Centre de Congrès Auditorium de Monaco” (1100 seats).     
Demonstration of the CARMEN® system for the Monte Carlo Philharmonic Orchestra during two months. (End 1996)

Grenoble :

 “Maison de la Culture Le Cargo, Grande Salle” (1100 places).          
24 cells system with stage reinforcement. Presets for theatre, opera, chamber music and symphonic concert. (1997-1998) (taking down of the system for deep refurbishment works of the venue).

Echirolles : 

Multipurpose Hall “La Rampe” (Grenoble) (800 seats).    
24 cells system with stage reinforcement. Presets for theatre, opera, chamber music and symphonic concert (1998).

La Côte St-André - Festival Berlioz : 

Yearly temporary installation in the medieval covered market during the time of the music festival (900 places).       
24 cells system with active orchestra ceiling reflector. Preset for soloist recitals, symphonic concert, oratorio. (every summer since 1999)

Besançon : 

“Micropolis Congress and Exhibition Park”. Multipurpose hall (2000 seats). 30 cells system with stage reinforcement and intelligent P.A. Presets for opera and symphonic concert. (September 1999).

Monaco : 

“Salle des Princes” of the Grimaldi Forum (1900 seats).          
29 cells system and stage reinforcement. Presets for conference, theatre, opera, symphonic concert. (July 2000).

Monaco :

 “Salle Prince Pierre de Polignac” of the Grimaldi Forum (800 seats).  
24 cells system. Presets for chamber music, concerto and symphonic concert.( July 2000).

Brighton : 

“Brighton Dome and Museum”. (1900 seats).         
30 cells system including active orchestra ceiling reflector. Presets for chamber music, opera, symphonic concert. (February 2002).

Paris :

“Théâtre Mogador”. (1800 seats). House of the Paris Orchestra   
31 cells and stage reinforcement. Presets for chamber music, concerto, symphonic concert, oratorio. (September 2002).

Miskolc :

Miskolc Place of Arts. (580 seats).
27 cells system with Public Address and an active orchestra shell. Presets for speech drama, chamber music, recital, concerto, classic symphony, romantic symphony and oratorio (September 2007).

Norwich : 

Theatre Royal (1280 seats).
27 cells system with stage reinforcement. Presets for speech drama, chamber music, opera, concerto, symphony and oratorio (November 2007).

Aylesbury : 

Waterside Theater (1200 seats)
27 cells system with stage reinforcement. Presets for speech drama, chamber music, opera, concerto, symphony and oratorio (October 2010).

CARMEN cell integration example in Brighton Dome

Installation in a performing hall

A professional installation

There are two steps:

  • Before order: Preliminary design in close connection with the acoustician of the project, the architect and the hall managers. Technical and commercial offer. Auralisation of the room with the proposed system if required.
  • After order: Detailed system design, detailed cells positioning and insertion in the decoration with architect, detailed drawings and mounting instructions, cables pulling, cells mounting and system installation by a digital audio engineering specialized company, commissioning and fine tuning of the system for all the required presets, reception test, users training.

A conspicuous installation

Microphones and loudspeakers are usually hidden in the room decoration in such a way they couldn't be seen. In some cases it is not possible or not required. The CARMEN® cells are therefore let visible, which is possibly cheaper.

High quality hardware

High quality professional audio components don't produce audible electro acoustic background noise, with high dynamic giving the system a perfect response from the pianissimo to the loudest fortissimo. Digital processing insures high system stability.

Fully secured hardware complies with current standards and regulations. The system is protected against non agreed users. A sustained power supply makes the system insensible to electric fluctuations or failures.

Short delay between ordering and installation

After the order minimum two months are required for manufacturing and assembling the system. Two weeks are usually required for the detailed study and three for installation and commissioning (associated works excluded). Three to five days are required for fine tuning and listening tests with musicians.

Unbeatable price/quality ratio

No special preliminary works are required for CARMEN® to be installed. It is a modular system where the number of cells depends on the initial acoustic as well as the expected ones depending on the various types of performances given in the hall and the architectural constraints. Compared to the cost of architectural works and/or effective movable acoustic elements CARMEN® is very affordable and produces high quality acoustics.

A profitable investment

Profitability of the auditorium is improved because shows and performances can be programmed which would have been impossible without CARMEN®.

Easy to use

CARMEN® is easy to use. Once it is commissioned asking for the right acoustics (chamber music, jazz, opera, concerto, symphonic…) is simply a matter of selecting the corresponding preset on the control panel. The system is easily switched on and off with a key on the CARMEN® controller.

CARMEN and other systems

Brief History

The idea of using electro acoustic means to control or enhance the acoustics of a room is as old as the development of the electro acoustic techniques. In fact the problem is rather more difficult than those related to sound reinforcement, quite soon solved in a more and more satisfactory way.

The first realization of such a system happened during the sixties. The system called AR was designed and developed by Prof Peter PARKIN and only once installed at the London Royal Festival Hall.

Few years later (1968) Philips Inc. has proposed a new system called MCR. It was quite successful at that time, being more or less the only one available on the market. As the AR system, with no longer acoustic filters but electronic, it was based on late sound acoustic feedback, the sound field being multiple amplified in about hundred electro acoustic independent channels. The microphone and loudspeaker in each channel were located at rather long distance from each other and randomly spread in the room volume, especially in the upper part. The acoustic effect of the MCR system was basically limited to the late sound, enhancing the natural reverberation of the room by a factor usually not exceeding two.

With the development of the digital signal processing techniques three systems have been proposed on the market in the eighties (two Dutch, one American), ACS, SIAP and LARES. Those systems, although not exactly similar, are all based on the same "in line" principle, which consists in picking up the direct sound as close as possible to the sources through several microphones, reverberating and delaying the signals in a given number of channels (from few units to twenty around) and feeding it into the room through a large number of loudspeakers spread all around the room walls and ceiling (up to more than 250 LS).

CARMEN® was designed considering the already marketed systems shortcomings.

Six years research and technical development have been required skirting around the "in line" systems' shortcomings and designing a new system that fulfils as much as possible the musicians' requirements. It was presented to the press and professionals in Monaco in 1996. Considering that the acoustic of a concert hall results from the walls and ceiling architecture, the Acoustic Virtual Wall principle was used for designing the new system. The sounds as produced by the musicians propagate naturally up to the walls where it is picked up and reflected on a controlled way by the virtual walls' cells, as if the nature and the position of the room inner surfaces were changed. We think CARMEN®, we manage it and we commission it as for architectural elements.

After CARMEN® two more "in line" systems were put on the market in Japan and in the States, the systems AFC and VRAS. They are even more relying on signal processing and artificial reverberation filters.

"In line" versus "feedback" systems

Because of the layout of the "in line" systems they are capable of producing very wide acoustic effects. As a matter of fact digital signal processing techniques being now quite powerful, it is possible to precisely control each channel for early reflection or late reverberation. Especially it is possible to produce very long reverberation time. Independently controlling the length and the level of the reverberation looks very attractive. This is the reason why most of the recent systems are "in line" type. In fact, setting up "in line" systems leads to a lot of acoustic limitations, often severe, more especially in relatively already reverberant room, giving artificial coloured sounds or disturbed sound images.

Contrary, "feedback" systems seem to be more restricted in the effects they can produce because they influence mainly the late reverberated sound, as if the acoustic absorption of the room was partly cancelled. On another hand the reverberation produced sounds usually very natural.

Practical limits of "in line" systems

The close sound picking up required by the "in line" systems, in order to take as few as possible room reverberated sound, is responsible for the observed shortcomings. As a matter of fact, although the microphones could be placed very close to the instruments, the sound recorded could not be totally free from room reverberation. When such sound are electronically reverberated, the occurring double reverberation process alters the modes statistical distribution of the sound field, which produces sounds as much coloured as longer reverberation is looked for.

In addition, it is easy to understand that reproducing sounds in different points at the inner room surfaces signals recorded at several points on stage will introduce very inappropriate delocalized sound images, as well as a disturbed orchestra balance, some instruments being more favoured than others due to their position related to the microphones or their natural directivity.

When the room where the system is installed is not very dry, it is rather disturbing to be in the situation of listening to two spatially and temporally non coherent sound fields. In addition most of the "in line" systems have time or frequency variant filters used to reduce the double reverberation induced colourations. The resulting sound field instability enhances even more the lack of coherence and naturalness of the acoustics.

In spite of those shortcomings it happens in some cases that they can be minimized in such a way not very hard to please people are approximately satisfied.

Comparative CARMEN® advantages

Contrary to the "in line" systems CARMEN®, when it is correctly installed and commissioned, presents none of the above mentioned shortcomings. Because the difficult sound picking up problem doesn't hold and no electronic reverberation units are used, the acoustics effects produced by CARMEN® are sounding very natural. The sound images as well the orchestra balance are fully preserved and the time space coherence of the sound field is really unspoiled.

CARMEN® doesn't intend to produce highly amazing acoustic effects, which would be of no practical use. As a matter of fact musicians and concert goers look for very specific acoustic conditions as offered by naturally sounding concert halls. Functioning as a real assisted architectural acoustics system freeing the architects from usual room acoustic constraints, CARMEN® effects are limited to that is only required to give the musicians and audience the best acoustic conditions as possible, as found in the best designed concert halls in the world.


Modelling of reverberation enhancement systems
J. Rouch, I. Schmich, M.-A. Galland
Proceedings of CFA-IAO Acoustics 2012, Nantes (April 2012)

The benefit of a CARMEN® electroacoustic system in the Aylesbury Theatre

I. Schmich, H. Butcher, C. Rougier
Proceedings of the Institute of Acoustics, Auditorium Acoustics, Dublin (May 2011)

Contrôle actif de l’acoustique du "Palace des Arts", Miskolc, Hongrie

C. Rougier, I. Schmich
Proceedings of CFA 2010 Lyon, (April 2010)

CARMEN in the Norwich Theatre Royal, UK
C. Rougier, I. Schmich, P. Chervin and P. Gillieron
Proceedings of Acoustics’08, (June 2008)

CARMEN: A physical approach for Room Acoustic Enhancement System
I. Schmich, J-P. Vian
Proceedings 7th CFA DAGA, 22 au 25 mars 2004, Strasbourg FRANCE

CARMEN: A new Acoustic Enhancement System, based on the Virtual Wall Principle.
J-P. Vian
ICA 2004, April, Kyoto JAPAN

Acoustic versus architecture – two different approaches:  the acoustic variability by CARMEN in the Grimaldi Forum Monaco and the National Grand Theatre of China opera house project.
J-P. Vian
Auditorium Acoustics: Historical and contemporary design and performance, July 2002, London, United-Kingdom

On Microphone positioning in Electroacoustic Reverberation Enhancement Systems
O. Vuichard, X. Meynial
Acustica 86 (2000), 853-859

Objective Measure of Sound Colouration in Rooms
X. Meynial, O. Vuichard
Acustica 85 (1999), 101-107

Virtual Reflecting Walls for improving Acoustics of Defective Halls
J-P. Vian, X. Meynial, O. Vuichard
J. Acoust. Soc. Am. Vol 103, No 5, Pt. 2, May 1998

On controlling Early Energy and Speech Intelligibility in Rooms equipped with Reverberation Enhancement System

X. Meynial, M. Buret, O. Vuichard
Submitted October 1997 to J. Acoust. Soc. Am.

La réhabilitation acoustique des salles au moyen de systèmes électroacoustiques
J-P. Vian
28ème Colloque CSTB / CFI, December 1996, Paris, France

Active materials for application in room acoustics
X. Meynial
Recueil des textes présentés au 3e ICIM/ECSSM 1996, pp. 968-973

Simulations numériques de systèmes de réverbération assistée
O. Vuichard, X. Meynial
Congrès Français d'Acoustique CFA 1996, Marseille, France



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