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We paid various visits to Acoustic System in Paris and each time Franck would confront us with a further development from his theories of working with air in an acoustic environment. During one visit we not only saw various resonators located in their standard spots, there were also many tiny wooden blocks attached to walls in what seemed willy-nilly fashion. Franck called this new project noise filters.

When sometime later our listening room and the rest of the house were acoustically treated with a selection of resonators, Franck also placed one noise filter on every large window pane in our house. Each noise filter was placed at a different spot on those glass panes even though many of them are the same size. None of the filters was right in the middle nor was it perpendicular to the windows frame. They all were more or less turned off kilter. As the noise filters were attached to the glass with a bit of tack, they were easy to relocate and turn. After some adjusting, the result was a substantial blockage of traffic and wind noise entering the room. Our room has a large glass bay that faces the predominant south-westerly winds. Next to blocking external noise, the filters also had their influences on in-room sounds. When playing music, the reflections from the large glass area were noticeably less abundant.

Each noise filter consists of a minuscule Indian rosewood cube. In the middle of one face of the cube, a 1mm hole is drilled all the way through to the other side. Two adjacent holes are drilled in the face perpendicular to the former, leaving two opposing faces unadorned. Each noise filter is attached to a wall or other surface with a tiny dot of tack on an unadorned face.

Several months later now, Acoustic System International or ASI has turned the noise filters into a product called Sugar Cubes. The product package consists of 17 noise filters, an ASI diffuser, some white tack and an instruction sheet. Considering the amount of work involved to cut, sand and drill out each sugar cube -- all done by hand -- the asking price of €10/per is very friendly. Add €30 for the handmade diffuser and the whole package sets you back €200 including tax.

A small envelope arrived with a small ziploc bag containing the new ASI product. From the instruction sheet we quote: "The noise filter should be installed with two holes up. Start from the floor. The interval between the noise filters should be 70cm on each vertical line. If the room has too strong reflections, it can be 50cm between them. If the room is overdamped, go for 1 meter between them. You may need to install the noise filters with one hole up if your system generates stronger HF noise. We have four zones from bottom to top, vertical and horizontal."

ASI proposes to start on the wall straight behind each of the loudspeakers and work towards the middle. We cleared our front wall of paintings and removed all equipment to have easy access. First we attached a small amount of tack to each of the 17 sugar cubes. For tools we reached for a 1-meter metal ruler, a spirit level, a piece of rope with an attached weight and a pencil. As per ASI's instructions, we laid out an initial grid of 70 x 70 cm starting at the floor and working towards to ceiling from left to right and right to left. Working from the outsides to the middle this way, a center area unrelated to the 70cm grid parameter was left open. At the height of the speaker's tweeters and exactly in the middle between the speakers, we attached the 17th sugar cube with the diffuser 10cm above.

The instruction sheet mentions fine-tuning the sugar cubes by turning those on the left two rows counter-clockwise and the ones on the right clockwise. This is very sensitive. We started out with the cubes' two holes pointing straight up. When the initial setup was completed with the help of the ruler and the weighted rope to align all cubes within 1mm offsets, we put the electronics back in places and connected them. At this time Marja reported an unsettling pressure in the room not unlike the sort we had encountered at ASI's Paris headquarters when too many resonators were active. This pressure can lead to headaches and general discomfort. Mind you, ASI's stuff is powerful - experiment before you judge prematurely. When the first CD produced its initial tones, it was immediately apparent that the room was completely overdamped to sound dead and veiled. By using the 70 x 70cm grid, the resonant space between the lines of sugar cubes was resulting in overly short delay times. To get some life back in the room, we had to widen the grid. For this we left the outer vertical lines of cubes in place and moved the inner lines further toward the center where the 17th sugar cube and diffuser were located.

In an endless process of subtle iterations, we finally arrived at a position for the inner vertical lines of sugar cubes at 99cm from the outer line as best. In total, there are 4 areas of vertical resonance space between the leftmost and the next to the right, between that one and the center line where the diffuser and the 17th resonator are and then the two mirrored areas to the right.

In the horizontal plane there are also 4 areas of resonance space. From the floor cube to the next cube covering and influencing the lowest frequencies, the next resonance space influences the low mids and mids and the last resonance space between the two top cubes manipulates the highest frequencies. The final resonance space is that between the top sugar cube and the ceiling. After quite some trial and error, we selected a 68cm grid interval in the horizontal plane to give the most satisfying sound image.