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Because I'd made the acquaintance of the Grand Cru Audio Horizon speaker before the Apertura Edena whose Christian Yvon had clearly inspired both his former dealer Jefferson Torno and his former subcontractor Joseph Szall with his crossover invention, I thought it important to get more background on the true progenitor of the DRIM filter. But first, some general information on Apertua. "The special shape of our cabinets meets two requirements. One, reduce as much as possible the surface of the two most emissive walls which, contrary to widespread belief, are the top and rear walls. We must keep in mind that a speaker cabinet is no musical instrument and should be as neutral as possible. Two, add an aesthetic signature that's easily recognizable and distinctive to Apertura.

Screen capture of YouTube video in which Christian Yvon explains his background during HighEnd Munich 2014. This video was posted by the French Cinenow magazine.

"The mechanical design of a speaker cabinet is not equal in terms of sonic signature. Our laminar structure is far more efficient for vibration damping because of induced break-up modes in the material thickness and mechanical constraints of our molded panels. Our curved cheeks consist of multiple layers of thin high-density MDF foils bonded and molded at high temperature on dedicated presses. Depending on model, certain sensitive panels like the bottom and top will double up. Internal damping is mandatory for good performance. Too many speakers pay no or insufficient attention to the importance of good internal damping which isn't merely a question of randomly placed small pieces of foam or glass fiber. Ask yourself what happens to the acoustic radiation inside a box which equals that in the room but occurs in a far smaller cubic volume? By what miracle should we expect no influence or feedback on the drivers or the behaviour of a bass-reflex tube? Contrary to audiophile myth, having no parallel walls does not cancel or reduce standing waves. It merely modifies their envelope. And no internal damping does not serve a clearer more relaxed sound. Quite the contrary. Hence properly engineered internal damping is one of the most important steps in the process of Apertura speakers. Here we use several types of material at very specific quantities and locations.

"We prefer two-way architectures compared to which three-ways are far more complicated and costly. The qualitative gain of a 3-way speaker is almost always seriously reduced or zero compared to a properly designed 2-way and always to the detriment of far more complex filters. Here simplicity is better. Which gets us to manufacturing consistency to insure that every customer of a given model buys the same speaker.

"Don't assume that drivers in a batch are perfectly identical. They aren't. Hence our speakers get matched driver pairs which are then measured together in a test enclosure with a dedicated adjustable xover. We successively modify the value of certain parts until the measured response of the pair matches the reference unit. This filter adjustment matched to specific drivers is time-consuming and expensive but the only guarantee for consistency.

"Mass is good for cabinets but not for drivers. Hence we only use drivers of the lightest possible moving mass joined to high-performance powerful motor systems. Because all diaphragms must exhibit high self damping, this becomes a compromise between weight and damping ratio. But in general all heavy material must be rejected to avoid high break-up modes on woofers. We use long voice coils for wider linear excursion. Music consists of transients, hence playback must accelerate and brake hard. There are many myths surrounding ribbon tweeters and they can indeed sound dull when incorrectly filtered. But they are wonderful drivers of superlative speed and musicality which simply suffer no fools in their filter networks. Due to great advances made with Neodymium magnets, this type of driver can now also be used in smaller speakers. Christian Yvon has worked with ribbon drivers for 15 years. Thanks to his proprietary crossover, he can take a ribbon tweeter to a lower cut-off frequency to extend its benefit over a wider bandwidth."

"Take nothing away from the signal but above all, add nothing to it. Contrary to conceived notions, the hardest part by far is adding nothing. This is the essence of Apertura's philosophy. Speaker drivers are electro-mechanical devices which generate sound waves from diaphragm motion. In theory the driver gasket is the mechanical reference of this device. In reality sound waves are also generated at the back of the driver but in opposite phase. These excite the cabinet and generate vibrations which propagate inside the cabinet material to create structure-born noise and distortion of the mechanical driver reference. Drivers themselves are subject to mechanical constraints and forces which produce vibration and torsion on their sub-assemblies. To summarize, one must consider vibration damping and dissipation as part of one's mechanical design. As a non-exhaustive list of dedicated vibration treatments in Apertura speakers, we can mention the heavily braced cabinets; the damped driver diaphragms with locking gaskets; baked coil wires and heavy parts glued to the filter PCB; and one-point plinth drainage at the center of gravity with the floor.

"Neutral parts are another myth. All parts—capacitors, coils, wiring, damping, diaphragm materials—have their own sonic signature. Some differences can be measured, others can only be determined by ear. We use quality parts to arrive at the least colouration in the final mix of complementary qualities. This is the principle of the right part in the right place. Even the most exotic costly parts are rarely ever best and will only give a marginal improvement versus price compared to very small adjustments in internal damping or the length of a port tube. But a 2mm shorter vent lacks all buzzword compliance compared to boutique filter parts."