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The application of Microsorber sheets is no mere formality like the PYT panels. It requires the installation of plugs and very precise measurements for the sheets to be stretched properly. Once the steel rods are fixed to the wall, cutting Microsorber sheets must be performed with great care to ensure that each sheet will have correct tension. The margin of error is 2-3mm, no more.

But it is also possible to play with the retaining springs on each rod that may be shorter or longer for different levels of elasticity. So even though it is manageable for someone prepared for accurate DIY work, I would recommend an installer to not waste too much sheet length and fix the corner clips with the right tools. In my case the length of paper used for each panel was long enough to require almost two people to handle (Armando Fontana from TecSArt and yours truly). In lengths of 1.5 or 2 meters (the longest sheet attached to the ceiling is 3.5 meters) the Microsorber sheets, although very thin, are quite heavy and fold easily which might damage them.

Once installation was complete, the benefits were obvious. Just talking in the hallway, then entering the room I observed that the Microsorber treatment definitely made the room quieter. This does not mean an anechoic chamber but a very pleasant relaxing semi-reverberant environment. It's neither an overdamped dead sound nor too bright and tiring as modern reflective rooms can be. This result seemed impressively natural by contrast to before and aesthetics were successfully preserved, even embellished by a little modern hi-tech touch.

Flutter echo is a distinctive ringing caused by rapid echoes bouncing back and forth between hard parallel surfaces following a percussive impact like a sharp hand clap. Reflections along the ridge of the roof are particularly problematic. To reduce flutter echo we have to either absorb or diffuse reflections on these surfaces. Two Microsorber sheets stretched out straight like a kind of suspended ceiling gave marked improvement in this area. The pretty impressive feature of this treatment was that the result could be assessed across the entire audible spectrum, delivering an overall sensation of better controlled bass and more acute treble.

Custom-printed Microsorber sheet.
It was rather more difficult to address the lack of energy in the 100Hz region. As is commonly admitted, it's always more complicated to passively boost than cut. Attenuation of a specific frequency range is relatively straightforward. Boosting certain frequencies for a flat response remains a real issue whether one decides on active or passive correction. Active equalization needs to manage the distortion caused by boosting a certain frequency (3-4dB seem the reasonable max). Another solution could be one or two powered subwoofers but integration with the main speakers remains in my opinion so complicated that it becomes unlikely to attain the best results.

Approached passively, I could double the wall behind the speakers to stiffen and thus reduce vibration which caused cancellation of some low frequencies. I could also install bass traps behind the speakers to improve control. I finally decided to pursue the second option as it seemed more versatile. Acoustic double walls are an effective way to correct bass levels but it is not very flexible thereafter unless you want your wall to turn into Swiss cheese. Bass traps in turn were likely to be less effective for a seamless acoustic correction but were mobile and offered further opportunities to fine-tune my acoustics. This modular feature made me decide on bass traps despite the double wall being my first aesthetic choice.