[Beowulf] [OT] acoustic engineers around?

[C Bergström]

This is the smartest list I subscribe to - I'm not sure if anyone has
the knowledge/time, but I'm trying to solve a general problem.
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Moving condos and new location is *very* noise sensitive. I feel
fairly confident I can spam absorbent material as needed to reduce the
db from high frequency sound going out the door, but bass is going to
be more of a challenge.

My crazy ideas

#1 Raise the subs 1-1.5 meter off the ground and decouple them from the floor
#2 Put some highly dense material directly under the subs.
#3 low pass filter so only dealing with 80Hz and not even more
problematic lower frequencies

I'm a little fuzzy on the details of if subwoofers typically produce a
directional sound and or if it depends on the box.

"bass traps" appear to be more marketing hype than actually
functionally useful for my case.

(lowering the volume to the subs and adding "buttkickers" is an
option, but that's more for fun and less about sound quality/general
problem)
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My walls are at least 150mm thick concrete fwiw.

Thanks