New room - new challenges

[thexder]

Hi fellow acoustic sufferers! ;-)

This year I decided to do my own little misagi: build (and actually finish) a new room and try not to repeat the same acoustic mistakes as last time. ;-)

The space is 5 × 7 × 2.5 m. Above a perforated ceiling there is 50 – 60 cm of glasswool insulation, so there’s roughly 3 m total ceiling build-up to work with. The room is still very much in construction mode: walls are open, unfinished and I currently have direct access to about 15 cm of mineral/rock wool behind the fabric/vapor barrier. No door yet, no real furniture.

I’m attaching measurements and would love feedback - especially on what they suggest about modal behaviour, decay and whether this plan makes sense before I commit to sacrificing more space to treatment (the intiial plan is to add 45 cm of additional insulation on all walls).
I’m trying to understand whether my main LF problem is caused by room modes / cancellations or whether a significant amount of bass energy is simply escaping the room through the structure.

What puzzles me is:

• bass is weak and dry almost everywhere in the room
• moving the listening position along the length changes surprisingly little
• I don’t really get strong pressure buildup anywhere
• subjective impression: as if the room doesn’t 'hold' low frequencies

Before sacrificing more space for large traps, I’d like to understand whether this looks more like:

• classic modal distribution / cancellations (so more trapping + placement work will help),
• significant LF energy loss into the structure (in which case internal absorption won’t fix the core problem).

Based on these graphs alone, does anyone see indicators that point more in one direction than the other?

Any insight appreciated!