Not much you can do with the sub turning off at low volumes, that is an internal factory setting. I’ve had subs that do that.
For best sub performance set your sub on the "in room" EQ setting and switch the 0-180 phase switch until you get the best volume. Turn your crossover to 80hz or more. That’s the only thing I can think of.
The other thing that comes to mind is that with the JBLs being fairly efficient, the subs just aren’t getting enough signal to stay up with the loudspeakers.
Scource content with no bass?
For best sub performance set your sub on the "in room" EQ setting and switch the 0-180 phase switch until you get the best volume. Turn your crossover to 80hz or more. That’s the only thing I can think of.
The other thing that comes to mind is that with the JBLs being fairly efficient, the subs just aren’t getting enough signal to stay up with the loudspeakers.
Scource content with no bass?