Robatoy wrote

I know you know your dB's. JDS claims 78 dB. Is that even close?

I'd say so.

I don't have a meter anymore, so I can't measure it. @ 10 feet, it's
comparable to my DC1200, at a much lower pitch. The main note on the
3100ck is down in the 100Hz area. The ductwork makes more noise than it
did before, as the blast gates whistle a bit.

If JDS "A" weighted the measurement, it's EASILY 78, as all of the noise
from the actual unit is low frequency. You can actually talk over it.

It reminds me of firing up a large system with only the subs running.
You could talk, but there was an extremely annoying rumbling distraction
in the background.