Here are the results of new REW ETC measurements taken this morning. My objectives were:
1. Re-assess a reflection originating from the back wall behind the MLP. This wall is well-covered by GIK 242 panels, but the blocking technique reveals that there is still a reflection coming from the wall. As a temporary solution, I have placed a second treatment on the back wall, two ATS Acoustics 2'x4' panels I had lying around. In the measurements, the label "with extra panels" refers to having the ATS treatments in place as well.
2. Remove the "Extra panels" and test Jim's hypothesis that the edges of the 242 panels might be the source of the reflections. I cut several strips of pink fluffy and taped the strips over the vertical joint first, and then the horizontal joint, and measured both.
3. Finally, Jim commented that one of the ETC measurements from earlier in the week showed significantly better reflection control than the others. This measurement was labeled "block above", which means a panel was placed to temporarily block reflections from the ceiling direction. I re-measured the effect of blocking ceiling reflections today.
Measurement 1: Center channel with "extra panels" in place -
Measurement 2: Center channel with "extra panels" removed -
Measurements 3 and 4: Use pink fluffy to cover edges of the 242 panels -
Measurement 5: With "extra panels" in place, measure center channel, blocking ceiling reflections -
1. The pink fluffy had no effect on reducing the reflection from the rear wall (sorry, Jim).
2. The extra panels are effective in reducing the reflection from the rear wall, and should stay in place (at least until a better solution presents itself).
3. Blocking ceiling reflections seems to produce desirable results. This suggests that additional treatment on the ceiling might be worthwhile to consider.
Adding additional ceiling treatments is tricky. First of all, it is difficult to place temporary treatments on the ceiling to assess effectiveness. Second, there is no way to reduce the reflection from the ceiling fan, other than to relocate or remove the fan. I am unwilling to do either, so I will live with one undesirable reflection. So, if I decide to proceed, I will order the treatments, install them, and then cross my fingers while I take a new measurement. If the expected improvement is not there, I am out the expense, and have a couple more holes in the ceiling. Such is the joy of hunting reflections...