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At the LessLoss headquarters in Lithuania, the use of natural wood was soon discovered as a great way to avoid and eliminate the odd HF behavior of resonances which metal casing always cause. This might also be why class D switching amplifiers encased in wood sound much friendlier than similar metal-clad amplifiers. Using solid aluminum or damping the metal casings with bitumen or other heavy material deadens acoustic resonances but does nothing for infrasonics. Wood however does.

With this relatively simple solution, the bouncing nodes were squashed only for another issue to crop up. The initial filter design relied on a coax geometry to trap the unwanted high frequencies between conductor and shield. Alas, the short ultrasonic wavelengths caused fluctuations inside the coax such that its outer shield began to broadcast. Hence coax was abandoned. Back to the drawing board it was for LessLoss developers Louis Motek and Vilmantas Duda. They now pursued the path of applying more skin-treated metal on the conductors with parallel filters. At a certain point they reached their initial goal of 120 times effectiveness. How they measured that is unclear but the developers were now satisfied. After further tests, it was discovered that adding a dielectric spacer to the conductors followed by another layer of the special LessLoss porous skin conductors did the trick to finally make Louis and Vilmantas happy.

So much for the design stage of the Firewall. The LessLoss site elaborates more on the theory behind the filter’s operation. The magic term is wave guide. Creating the double-layered filter skin formed a wave guide which behaves differently at different frequencies, particularly ultrasonics. Just as a prism breaks up—disperses—light into various bands we perceive as discrete colors, the LessLoss filter breaks up the unwanted noise of high frequencies via the enhanced skin effect as part of a process called group velocity manipulation. One of the more practical uses of group velocity manipulation is to be found in fiber optics. To avoid merging or canceling the various signals being sent simultaneously over a fiber optic cable, different fibers with different dispersion characteristics are employed to transmit all the original signals intact to the other side. The Firewall exploits this principle in a way that won’t filter the high-frequency components directly but makes them work against each other to maximize HF filtering.

Louis advised us to run in the Firewall well. Because this filter has basically no capacity limits, we set it up as the power distribution center for our washer, dryer, water fountain, refrigerator and freezer. That combination formed a nice power-sucking consortium active 24/7 with cyclical loads for the desired effects.  

Louis did advise us to run in the Firewall well - very well. When we committed, we had no idea that our future would bring great change. We had to said goodbye to our high-rise apartment overlooking the city of Rotterdam and moved to the countryside. With this we traded an altitude of 110 meters above sea level to minus four. That’s right, four meters below sea level. While the dikes hold and the pumps keep up the good work, our feet shall remain dry. In the big city we had very thick concrete walls and floors and our living room doubled as listening room. Franck Tchang had performed his acoustic magic during two separate visits on site and all told, it took some years to incrementally perfect our listening environment .

As with much else involving human senses, subtracting something has more impact than adding something. For some reason we acclimate to a new situation far easier than stepping back again. This is good for comparing relatively minor changes. How about changing everything? In our new house we now have a dedicated listening area of 5 by 4 meters that two steps higher opens into a living cum kitchen area of 30m². The walls are brick covered with wood paneling and the 2.5m ceiling is wood as well. Overall the brick and mortar structure of this house breathes far easier than the former apartment with its sealed concrete. All our new flooring is tiled and the abundantly large windows are double glazed.