Appreciate the comments, Guys!
I ran some more measurements:
'Just' the noise floor. It looks 'clean' to me: quiet (measurements confirms that there is no freeway or airport near by
) and this huge bump in the lower frequencies is not there.
Measurement over full signal range. This time I expanded time range to 1500 ms. It seems that above 80Hz the signal decays relatively quickly (200ms), but LF takes over a second(!).
This tells me that the measurement setup and method is OK
=> is my thinking correct?
If so, this leaves me with either:
* an issue with the subs/signal to the subs (3x EP4000, driving dual stacked 18" SI in sealed 4' flat packs, miniDSP, currently with default settings)
//I already tried plugging the amps into a different power outlet - no change//
or
* an issue with the room i. e. my acoustic treatments are not effective
Room:
- dedicated room in basement 23'x14'x8'
- walls: 3x concrete, 1x drywall (side): covered with mix of Knauf and OC703
- ceiling: exposed wood, but partially covered with acoustic foam
- super chunks made of OC 703 in all 4 corners
- riser 14'x7'x14", wood, vented, filled with R35 pink fluffy
- floor: concrete and wood (riser), no carpet/padding yet
Any suggestions where I should go from there?