Sub’s volume control knob is at 7? That’s just barely off minimum if I remember correctly. You might try and lower the receiver’s trim so you can get the sub’s volume control knob up a bit. What’s your room dimensions? Mine’s 12 X 16 with 8.5’ ceilings. The sub is about 9 o’clock (maybe 25%) with the avr trim at – 5 and it’s quite loud when it wants to be.

What is the trim on the sub’s amp?? Run that flat if it isn’t already.