Before (above) and after (below); reflections are from camera flash.
Finally, above described positive finding made me motivated enough to tackle a problem that I had known for a long time to exist, but which I had always been too lazy to address because of the work involved. It is about the window shutters in the back of the room (and on the left hand window towards the back). Already a good while ago I had mentioned on this thread the highly reflective gloss paint on them that had been a literally glaring mistake. The shutters in the back are about 9 feet from the listening seat, and 17 feet from the speaker drivers (my room, while quite narrow at 12 feet, is rather long at 24 feet). Given those distances, my reluctance to do work on the shutters had not been helped by incredulity about such far away reflections possibly having a very pronounced effect on the sound, an incredulity shared by someone else in a private conversation after I reported on my findings following the finished work. Yet from my own experience I should have known better, since I knew that partially covering up the surface with ASC diffuser panels had had a positive effect, already a few years ago by now.
After I had raised concern on this thread about the shutters in January this year, Milan (Lagonda) said that he had covered up the window plugs in his room with wall paper. After some initial enthusiasm about the suggestion (thanks, Milan), I decided that I did not want permanently glued paper on my wooden shutters, and less fixed solutions with just tape did not work out since they gave no smooth surface. I was also not quite thrilled with the aesthetic choices available.
So finally I returned to my original plan to cover the gloss paint with matte paint (see above pictures, now and then). Fortunately this new polyurethane paint is water-based, with minimal odor development. With paint that is based on organic solutions I would rather have "evacuated" my system; I don't want any vapors to get into the gear. Removing the shutters for painting in another room, and then re-installing them, would have been cumbersome and impractical; they are also extremely heavy since the outward facing side is covered with mass-loaded vinyl for noise isolation. Now with the water-based paint I just painted while letting a fan run to push air out of the room until the paint was dry. The work was much less of an effort than I had anticipated.
The result is stunning. There is another level of reduction of distortion that appears to rival the recent change from my previous 12 AWG line from breaker box to the outlet for my system to a 10 AWG line. I checked and re-cheacked problematic passages over a few days’ time, but my first impressions of a great effect on cleaner sound only became confirmed.
Before I go into more details, I want to answer a question that by now the patient people may have who are actually reading these pages. Why is a majority of posts the last few months about reduction of distortion, again reduction of distortion, once more reduction of distortion and so on? How much distortion must have there been in the first place, and how low can it go?
Several things:
1. First, obviously my room has lots of problems with uncontrolled and detrimental reflections, a fact that is confirmed with every improvement to mitigate this issue. The reflection problems are emphasized by the not so large size of the room, and by the relatively high volume at which I listen, e.g. peaks on orchestral music and some jazz at about 95 dBa (ca. 100 dB) and on string quartets at about 90 dBa (ca. 95 dB) – I like to listen to string quartets at levels that somewhat approach a living room concert. All this of course while still trying to adhere to NIOSH recommendations for daily sound level exposure; average levels on these types of music are considerably lower than peak levels (and to more constantly loud rock music I listen at lower levels). Were I to listen at just 5 dB lower average levels, detrimental reflections would play a disproportionately lesser role.
2. Most importantly, however, the more distortion from reflections or other things is reduced, the more I become sensitive to what is left of it. That sensitivity becomes more as time passes, until I take the next measure. That is a natural process, somewhat analogous to the sensitization that audiophiles experience as they upgrade their gear and it becomes more revealing, and they gradually realize how much things can be further improved with yet another upgrade, which often leads to the well-known merry-go-round.
3. There is also some music that I would like to listen to more loudly, and as I can crank it up just a tiny bit more as the sound improves, remaining problems become more evident that then beg to be addressed. In particular, some of the period instrument string quartets I am now able to listen more loudly to. Just this week I listened again to my cherished CD of Eybler quartets by the Eybler Quartet, music that I
described on another WBF thread), but now at peak levels of 88 dBa (more than 90 dB).
(cont.)