Overview

 

Even though the idea of planetariums was conceived in Europe, they are very common in North America, Germany, and the UK. France has been slow to join the planetarium club, but today the country has caught up and planetariums of various sizes can be found in almost all the big cities. In Paris, of course, there is the one in the Palais de la Découverte, but the newer planetarium in the Cité des Sciences is much more up-to-date since it reopened in August 2006 following a refurbishment that included the installation of a completely new sound system with a DME64N at its core.

Capacity:

256 

Web site:

http://www.cite-sciences.fr/ 

Installed date:

08/2006 

Installed Products

Mixers:

DM1000

Processors:

DME64N

Details

A New Paradigm for Planetariums

The DME rack

In a ‘modern'rsquo; planetarium the domed ceiling is still essential for projecting images of the starry vault, but the arrangement of the audience in the room below has changed. While the classical model has the projection equipment in the centre of the room with the audience all around it, new seamless video projection technologies enable the light sources to be distributed differently. As a result the audience adopts a more ‘frontal’ position, directing its attention forwards and the eight video projectors used provide for a much greater variety of content: celestial projections, eclipses of the sun or the moon, flights over the surface of Mars, observation of the dance of Jupiter's moons or the movement of the stars, contemplation of the Milky Way, and more.

All-enveloping Sound

As for the sound, the new audience seating arrangement, which is much more like that of an IMAX geode, allows a 5.0 system to be used: three channels in front and two rear channels without LFE, plus an overhead zenith channel. This is not, however, a cinema sound system with three enclosures behind the screen projecting the sound forwards and a double series of enclosures broadcasting at the rear. The concept of all-enveloping acoustic immersion is essential here. It should be impossible to locate the loudspeaker enclosures. The 256 seats have to be covered in the most uniform possible manner, to 80% at least. As the room in the Planetarium can be used for other applications, provision also has to be made for great flexibility of use (the ability to broadcast DVDs or SACDs, for example), while at the same time delivering the acoustic levels required by cinema broadcasting standards – even if the system is most often used at a relatively quiet 70 dB SPL for optimum audience comfort.

Overcoming Inefficiency and Modes

The DM1000 console in the central control room

It is worth noting here that the interior of the dome in the Cité des Sciences planetarium is 21m in diameter, acts as a screen, is made of perforated sheet, and has an acoustic transparency of only 10%. In other words, 90% of the acoustic energy generated by the transducers hidden behind it does not reach the audience. What's more, the site had natural mode problems in the 100Hz range.

The sound system for the Planetarium in the Cité des Sciences was designed and installed by the Taylor Made System company. They had already successfully installed a sound system in the great hall at the Cité under difficult conditions, choosing a native style system of radiating cylindrical wave enclosures.

For the Planetarium, Jacques Fuchs and Patrick Thévenot relied on their factory brands: firstly to obtain enclosures that the ear, rather than measuring equipment, would perceive as identical, and secondly in order to ensure that the enclosures could not be located, to give them an acoustic signature that was quasi-identical within their angle of radiation. This required detailed planning.

"We went back to the original meaning of the term stereophony, which does not mean two enclosures, as is often thought, but sound in relief", explains Jacques Fuchs. "Stereophony is a technique based on the ideas of differences in both time and level, and enables us to create an infinite number of virtual sources – in width as well as in depth – with a finite number of actual sources. Our original idea was to go back to the principle of a system of enclosures with native cylindrical waves, similar to the system in the entrance hall. But the solution was beyond budget. The second option considered was the use of enclosures with asymmetric vertical directivity – but the models available did not allow us to cover all the seats".

The solution was to arrange the enclosures in clusters, each with a corresponding subwoofer, conforming to the ITU circle: ±30° for L and R with respect to C, ±110° for SL and SR.

DME64N Chosen for Precision and Power

The Yamaha DME64N processor was chosen for its precision and power. It manages the various listening presets as well as bass management, physio-temporal equalization (more than 250 precisely-tuned parametric equalizers), active filtering between the amplifier channels that go to the sub and those supplying the midrange/high enclosures, limiters on each output channel, and more. It operates continuously at more than 80% load.

The DME64N is also responsible for overall volume control and general muting. Its outputs are connected to five 4-channel amplifiers, for a total power of 14000W. A Yamaha DM1000 digital console located at the back of the room manages all the audio sources and has a digital connection to the DME. Equipment and wiring was installed by IEC.

The impression of being surrounded by sound is very successful. The sound literally melts into the image, but straightforward auditioning of SACD and DVD-Audio in 5.1 surround is also completely successful. No changes in timbre or balance are perceived even as one moves around the room,. The system goes right down to the lowest bass, but is not too intrusive.

And Finally, Some History

The first ‘optical’ planetarium was built by Carl Zeiss and inaugurated in Munich in 1920. Its sky projector is a movable hollow sphere – powerfully illuminated from the inside – in whose surface tiny holes have been precisely pierced to project the stars onto a dome-shaped ceiling.

This principle, with numerous improvements, continued to be used until the eighties when it was supplanted by new technology arising from military simulations: computer-assisted video projection. Today, with the unbelievable progress achieved in video projectors and computer graphics, the digital planetarium is a reality.

There are numerous planetarium societies: two examples are the APLF (Association des Planétariums de Langue Française) and the IPS (International Planetarium Society), whose chief activity is contributing to the production costs of projected shows.

System Designer/Integrator/Supplier

Taylor Made System

Country

France

Web site

http://www.taylormadesystem.com/

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