That tune activated neglected parts of my brain. I could actually see infected mushrooms marching toward me mid-way through.

Good that you're experimenting with room response. Just remember that acoustically heterogenous materials result in reflections with heterogenous frequency responses. The Family of Curves therefore distorts in unpredictable ways.

To fix that in your case, nail a cloth recliner to each side wall and glue an area rug to your ceiling.

House of the Rising Sone
Out in the mid or far field
Dedicated mid-woofers are over-rated