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Designed with meticulous care, logical heir to the Offrande, the Grand Opéra is, even more than an achievement, a true masterpiece.
EQUIPMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
LOADING PRINCIPLE AND WOOFER
Lots of loading methods have been designed around a truly exceptionnal transducer, but only one has been singled out: a "double bass-reflex", extremely difficult to tune but which offered the best technical and musical results: frequency response, drag and distortion on the one hand, articulation, phrasing and melodic follow-up on the other hand.
The 215 mm woofer is built around a massive zamac basket.
Its HDA cone, coated with carbon, is equiped with a double-magnet engine, and with a double moving coil in oxygen-free copper.
This moving coil is wound edgewise on a glass fiber and kapton former. Its flat spider is positionned in the middle of the former instead of being situated at the base of the cone, as usual.
This original technique allows better symetry in the displacements of the cone, decreases mechanical constraints and suppresses possible resonances from the former.
The double suspension design allows perfect guiding of the moving unit, and considerable improvement in the mechanical resistance of the loudspeaker.
The same transducer, equipped with a single suspension, reaches its maximum stroke at 40 hz with 10 volts applied to the moving coil.
With the double suspension, maximum stroke is reached with 30 volts! Mechanical resistance is thus increased from 11 to 110 V at 40hz!
DOUBLE SUSPENSION SYSTEM
Two half-rolls, positive and negative, are assembled face to face, perfectly sealed.
The internal negative half-roll is regularly and evenly perforated. When strongly stimulated by low-frequencies, the air inside the two half-roll is alternatively driven out and sucked in by the decompression holes, thus gaining a high viscosity which ensures the pneumatic damping of the positive half-roll section in proportion to the displacements' amplitude.
This system endows the speaker with a very low resonance frequency - which is not usually the case of double-spider systems - and, consequently, with a wide pass-band. Deep bass can thus be obtained in a reasonnable enclosure.
Up to now, increasing the mechanical resistance of a transducer meant fussing with the rigidity and the movement of its surround suspension. Deep bass performances were considerably altered by such techniques, and could only be compensated with very large enclosures.
MIDRANGE
6,7'' transducer, featuring a HDA cone also coated with carbon.
Equipped with a double magnet, a double moving coil wound edgewise in flat oxygen-free copper, a massive zamac basket.
It is a true masterpiece, difficult to match with other components used under the same conditions. A central nose cone, turned on a digital lathe and uncoupled from the magnetic core, suppresses stationnary waves generated by the bottom of the cone and improves directivity.
The suspension, in negative half-roll, is acoustically shielded to avoid the emission of time-shifted peripheral signals. Its two moving coils have independant crossovers.
The 6,7'' size was chosen for its wide emitting surface.
This is an essential asset for a midrange transducer, necessary to obtain a large image and to avoid compression problems when submitted to strong electrical impulses
TWEETER
28mm polyamid dome, unsuspended, of very advanced technology.
Central anti-vortex plug. Its star-shaped phase plug reduces directivity up to 40° off-axis. Equipped with a double magnet.
Its cone is specially treated to avoid any coloration due to its material.
CROSSOVER
This is a 4-way crossover.
The boomer is filtered at 12dB/octave, midrange at 6dB in "high pass" (for a good respect of the phase), at 6dB/octave in "low pass" for one of the moving coils and 12dB for the other, mounted in "serial" configuration with the tweeter.
Crossover frequencies: 350 Hz, 1100 Hz, 3800 Hz.
Air-selfs are hand-wound, and capacitors have tin framework for the tweeter's crossover.
Cabling is made with no circuit-board, and components are ideally orientated.
The crossover is installed in the stand of the speaker, being thus isolated from vibrations and from the magnetic radiations coming from the transducers.
GENERAL DESIGN
In view of the outstanding results obtained by the speakers, the cabinet had to offer optimal inertia characteristics.
The technique used for the Offrande was thus remployed. All the parts of the cabinet are machined in a 28 mm solid beech battenboard, whose heterogenous structure prevents resonances.
Panels are assembled with slots and tongues and glued under press, to obtain once again perfect inertia.
The midrange's load is isolated from the boomer's load.
The "double bass-reflex" is damped with a sandwich structure of natural rubber (8mm) and felt-wool (10mm).
The magnet of the boomer is attached to a non-magnetic threaded rod whose other end is fastened, by means of a captive bolt, to the bottom of the cabinet. This design increases inertia and avoids micro-movements of the basket.
MIRROR DESIGN
Grand Opera is manufactured by pair according to the mirror design.
Its transducers are placed asymmetrically on the front baffle in order to improve they linearity performances (less stationnary waves).
The inner and outer ports of the load were designed according to this theory.
Consequently, the Grand Opéra must be installed so that their outer ports are inside the listening plane.
SUPPRESSION OF STATIC CHARGES
The cone of a driver, when moving, is submitted to frictions with air that generate static electricity. Its superficial molecular structure is thus modified, and signal reproduction is disrupted.
Tonal balance is more or less modified, according to the amount of static electricity accumulated by the transducer.
The exclusive system we designed allows a permanent draining of those static charges.
How does it work?
Cones are rendered electrically conductive thanks to a special coating under the carbon layer.
They are bound, by means of a ground braid, to a terminal near the binding post.
This terminal must then be linked, thanks to an ordinary wire, to the mains'earth (recommended solution) or to the frame of the amplifier.
Results
Audiophiles are well aware of the sonic damages generated by static pollution, and many use brushes to "clean" their transducers, with appreciable results.
Although effective, this treatment is not lasting and must be frequently repeated. Otherwise, timbres are altered and some harshness appears. No such thing will happen thanks to our design, and listening will stay enjoyable and fatigue-free.
(This design is applied to the Offrande, Grand Opera, Odyssée).
CABLING
We are using copper/silver cabling, under kapton sheath, whose construction is similar to our HP 216A. It is equipped with a ground braid that can be used to eliminate static charges (see above). We strongly recommend using this system, since we took it into consideration when optimizing the Grand Opéra.
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