Test as done at 10 feet to the present listening area where the sofa is, ECM8000 was positioned behind and slightly over the back of the sofa, at ear height.
What I have done here is taken three frequency sweeps with (REW) Room EQ Wizard, the first one is with all three ports on JBL4645 18” sub as is.
Second frequency sweep is with one port hole plugged up, and as you can see there is mild difference between the, first frequency sweep.
Third frequency sweep is with two port holes plugged up, and as you can see again there is difference.
So am I winning or not LOL.
Thanks.