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Arriving at Jean-Michel Maumont's converted Cognac distillery in Chateaubernard of Southern France, I was naturally reminded of Samuel Furon's equivalent Armagnac digs which I visited a few years ago during my RoadTour Ocellia & PHY.

To appreciate the setting Jean-Michel has called home for the past 10 years—he recently sold his share in an audio import company distributing Pass Labs in France and was formerly involved with the Vecteur brand—visit this pictorial SideBar. It shows the pastoral estate south of the town of Cognac which gives the area its name.

Jean-Michel's wife Maria is from Colombia and a painter and metal worker. She operates a sizeable atelier on the premises for live-model sessions and supplies many local restaurants and bars with lighting fixtures, chairs, tables and railings.

In the flesh, the finalized Grande Castine is one impressive piece of matte-white industrial design art. (It was nearly finalized during my visit. What remained were certain minor cosmetic refinements as dictated by assembling the very first pair. To clear typical door widths, the rectangular horn ships in four individual panels. Those curved panels get assembled with long vertical bolts and strips of elastomeric material. The covers for the fronts of the horn-mount openings hadn't been sized properly and revamps not delivered in time so the below photo doesn't show them.)

The upper horns are hand-cast by Marco Henry in proprietary synthetic concrete after he experimented with 50 different materials in identical casts to test their acoustic properties. Hence his company's name is Musique Concrete. Through it Marco has supplied DIYers with custom horns for the past 12 years. "Most thin-walled horns actually deform under signal to constantly alter their geometry in invisible ways and introduce measurable distortion." His first complete commercial project absorbed four years in R&D. He more than once approached dead-end frustration but was constantly goaded on by his wife who really happens to—lucky man—adore large hornspeakers. Marco's spherical horns for the Grande Castine float inside a heat-formed wooden spine. Curved to lean forward, this spine's vertical layers, like cupped hands, bend open into two cylindrical opening. The horns slide into these openings on lateral pins which are then captured in metal rails. One rear bolt each has a bit of play inside its upright slot to angle the horns up and down before they get locked in position. Magnetically attached grills conceal the clearance openings front and aft.

Unfinished horns straight from casting | stacked midbass panels
Heat-formed wooden spines | curved Ply midbass panels

Back with the assembled speaker, two right-angle grills conceal the dipole midwoofer as shown below. A three-point metal brace of square tubing floats the speaker above the ground. A single pair of binding posts obliterates concerns over multi-amping and active crossovers. The latter's interactive settings tend to have owners fiddle endlessly to suffer sub-optimal results from expensive high-performance systems. Simplicity and predictable repeatable behavior are key.

92cm wide by 137cm deep and two meters tall, the Grande Castine weighs a reasonable 120lbs considering. It combines a 1" Titanium tweeter with metal phase plug, Neodymium motor and vented rear chamber with a heavily rebuilt 2" Titanium midrange and 15" paper-cone woofer. The latter too is completely rebuilt with a new spider, surround, cone and voice coil by collaborator Cyrille Pinton who, after working for Michel Ohana's HP Service transducer repair center in Paris, now designs his own drive units under the Cyrille Audio brand. System sensitivity for the Grande Castine is a high but not extreme 103dB.

The horns cut off at 3000Hz, 300Hz and 80Hz respectively, crossovers are 1st-order exclusively. The large rectangular and deliberately asymmetrical horn—a spherical diameter would have been much larger—only covers the upper bass and lower midrange. Hence this horn makes no bass, period. An intrinsic and absolutely vital part of the Grande Castine recipe is the unique planar infra sub.

Concert violinist and electrical designer par excellence* Hugues Borsarello had been working with his friend Marco on a subwoofer design related conceptually to Shelley Katz's Podium Sound panel speakers. Stiff rectangular membranes were clamped inside an open frame and driven by an exciter motor taken in their case from a commercial 15" woofer. As is often the case, others pursued similar ideas. In parallel, a separate French team around Claude Lacroix had been working on an Infraplanar which relied on a more flexible membrane, a different motor system and a less centralized voice coil.

The Grande Castine team at least for the time being shelved their own planar sub design and embraced the competing already completed Infraplanar whose unique design is presently under patent application. I was hence asked to not show it. If you scroll back up to the first photo showing the horns from the rear, you'll see the subs next to the listening seat draped strategically in white. The photo below just as strategically shows only the upper edge of their metal frames in the final position behind the listening seat.


* Hugues also has a fully discrete DAC where discrete means no chips whatsoever, not even converter chips.

Yes, time alignment isn't just vital but achievable from two directions. Upon my arrival, the twin sub panels still sat behind and between the horns. Due apparently to their 60 x 60cm membrane size vs. Jean-Michel's large room plus dipole dispersion with very effective cancellation on all sides, that subwoofer placement didn't reach the listening position with sufficient amplitude. For all intents and purposes, the system had no audible bass below 60Hz. Moving closer to the subs proved the contrary. They had fine output, simply not sufficient to span the required distance. The obvious solution was to move the subs. But to where?

With Hugues's analog crossover still set to 6dB/octave and 80Hz, the next location dictated by successful prior installations was to the right of the listening seats. This did produce proper amplitude but proved too elevated in the upper bass range. An 18dB slope at 40Hz and relocating the subs behind the seats finally made for seamless blending and truly full-range integration of real infrasonics. At first the sub panels ended up too close to the seats. This had the bass arrive ahead of time. Relocating the Hypex-powered subs farther back until their arrival times from the back coincided with the horns in the front finally clicked. The entire concept is admittedly so counter-intuitive and seemingly bizarre that even accredited engineers have vented forum steam on the planar subs by declaring the concept per se impossible and fou. Ahem.

It's not. It works exceptionally well. Lacking port boom and box colorations, this type of infra-planar bass is finally duly effortless, fast and precise. There's no overhang, no box reflection returning through the membrane delayed in time, no cabinet talk. All this matches the horn-covered spectrum. As such this bass system is distinctive and vastly superior to the hybrid Avantgarde Acoustic Duos I used to own. And yes, extremists do go after full horn-loading down into the 20s. This simply necessitates horn sizes that become categorically unreasonable for any commercial rather than DIY project that still hopes to find normal customers. Back to dipole planar bass. The apparently built-in far-field cancellation means that typical bass pressurization fails to build up in the corners. Even better, there's no bass leakage into adjoining rooms. That's very different but highly advantageous when you consider the practical implications. You hear the bass where it matters—in your listening seat—but very little elsewhere. Absolutely brilliant!

Covering just the bottom octave from 20 - 40Hz with some attenuated fill to 80Hz, directionality concerns for the infraplanar subwoofers are null and void. One does not hear their location if the low-pass and output voltage are properly set. The Grande Castine horns meanwhile are quite directional by design. To broaden their sweat spot for three or more people, Jean-Michel and Marco had originally toed them in so severely that they crossed well ahead of the seats. For my tastes, listening in the central seat this far off-axis undermined some of the incisive qualities I expect from horns. I thus requested a more conventional line-of-sight angle for the hot seat. Bingo, this upped jump and startle factor.

Our three-day listening sessions involved Jean-Michel's Supratek Cabernet Dual preamp and a big two-box Pass Labs. By consensus, we ended up with Hugues's Lightbox prototype preamp. That unconventional solution runs a photovoltaic cell energized by arrays of ultra-bright LEDs whose lumen output is amplified by tin-foil liners. Battery drive was inferior. The volume control is a TDK Ko-On potentiometer, a variable resistor triggered by light was too lean in comparison.

As the board above shows, a tiny twin-FET chip handled impedance buffering. For amps, we primarily listened to Jean-Michel's FirstWatt J2 which provided a familiar reference point for me. We also listened to Hugues's very promising 8wpc prototype EL-156 SET built by Dominique Mafrand, a high-end retailer who crafts custom low-power triode amps for his clients. This amp omits the usual tube driver in favor of a step-up transformer. The entire signal path consists of the stepup transformer, one EL-156 per side strapped to triode and the output transformer. The F2 had more upper-bass definition and impact, the SET more soundstage holography and textures. Both were excellent.