Well, I'm back to chasing several pesky room reflections today, after taking a couple of weeks off. Trust me, there is such a thing as REW-burnout, and it's not pleasant.
Anyway, I have made significant progress after the short vacation. Here is what I was observing at the start:
I have three significant reflections above -20dB. I know that the first one is caused by ceiling fan blade reflections. However, if I turn the fan on, the measurement changes:
The fan blade reflection is reduced significantly. I don't know how this translates into audio reality, because I'm sure there are still reflections, and that REW just isn't capturing them because of timing anomalies with the blades rotating. Regardless, the fan is here to stay, and in the current hot summer, the blades are always rotating when I am in the listening room.
On to the last remaining reflection, shown above at 11.3ms. Time to use the Blocking Method again! First, block left:
No joy--the reflection is still there. Same joyless result with block right and block behind. However, block above (ceiling reflections) yielded this:
The reflection is gone! After taking a few minutes to calm my excitement, I thought, how can this be? I just installed two GIK 244 panels on the ceiling at the first reflection points with very good results. Where on the ceiling could these reflections be coming from? After all, the rule of "angle of incidence=angle of reflection" suggests that the first point of reflection is the only logical place the reflections could be originating from.
Wait a minute! I recall advice given to me last year by our friend and thread participant, Markus. He advised me to be aware of multiple-point reflections, and that he suspected a reflection bouncing off the ceiling, onto the back wall, and then down into the MLP. But I treated my back wall--could this really be possible? Here is the back wall:
Three 24x48 GIK 242 panels would seem to be enough to block any back wall reflections..However, there is the smallest sliver of open drywall at the very top of the picture. Could this be the source? Let's try a temporary treatment:
Note that I had to slide the 24x24 temporary panel way to the right (it's the maroon panel hanging half off the top GIK panel). Here is the result:
The reflection is completely OK now! Not only that, almost all reflections are down to very close to the -20dB level, which is my objective.
This exercise has shown me several things. First, the importance of never giving up. Second, the effectiveness of the blocking method. And third, always listen to the advice of the experts (thanks again, Markus).
It's Miller Time!!!
Edit: Keith, do you have an equivalent phrase to "It's Miller Time" over there?