which ceiling design for a small room with drop ceiling

hi, my "control room" ist 5m long and 3,5 m wide. the backwall ist treatet with hangers (best improvement, thanks to this forum) i have a drop ceiling (2.3 meters) with homosote plates.the problem ist they dont absorb much low frequencies , so i have a very disturbing mode @148hz. i have angled for experiments the ceiling above mix position and i seems much better. should i go for "expansion ceiling" with a "V" or only going higher from front to rear.....or maybe compression ceiling :roll: ...or just place some aborbers(which i dont really like) cheers

Do you have pix? Might be a bit easier to comment on.

hey there, *pics updated*

don't see any pictures attached...