Update:
Did 9 Newell style absorber on my ceilling. (a tad more than the first 1/3 of my room)
Room is 19' wide by 39' long
Ceiling is 8' (floor height, bottom of the joist are more like 7'9'')
Used the staplegun to attach R12 on my main floor.
All of the ceiling has been treated this way even if no airgap between the fiberglass and the ceilling was possible.
this single layer of fiberglass start to be really effective above 400hz.
-----------------
For the trap, I used 5/8 chipboard covered with R12 insolation batt on both side (fluffy).
spaced 16'' appart and the whole width of my room (about 17' since I can't put trap where my HVAC duct are passing)
panel are 24'' long and disposed at an angle of about 30degree.
Can't really post good measurement since the room is still in construction.
---------------------------
https://drive.google.com/file/d/18eH73S ... sp=sharing
this first pic show the room from the rear before the trap where installed
https://drive.google.com/file/d/18fRdT6 ... sp=sharing
this pic show the R12 fiberglass between joist across all of the room
https://drive.google.com/file/d/18kOy-I ... sp=sharing
this pic show the panel from the side. Yes, I do miss 8'' to complete the fiberglass layer, will be added later.
https://drive.google.com/file/d/18rXQT4 ... sp=sharing
more panel view.