What speakers are you using?

Looking at the combined response I could guess there is some combing cancellation, due to reflected wavelengths correspondingly to 4 times the distance from the back wall. Give the frequency I roughly calculated about 42cm.You could try to reduce the distance of speakers from the back, inserting in the meantime the supplied port plug to avoid bass response increase. A possible position could be over the subs. Obviously a new set of Dirac measurement will be needed but likely the combing effect should be reduced. I have the same speakers and for the same reason I put them about 10cm from the back wall and with theirs plug, the bare response it's flat and Dirac has less holes to correct.
Let we know... 😎
I’ve always had the ports on the LS50 Metas plugged since I got subs.

I’ve actually adjusted the delay and crossover settings to 160Hz (the room’s actual Schroeder frequency) with 8.15ms delay and the crossover point is a lot better. Now, these sweeps don’t look as flat anymore because instead of calibrating for a single point like I did for the above sweeps, I’ve calibrated it with sweeps at 9 different points (the MLP plus eight spots surrounding the MLP):
Combined:
IMG_7399.png

Left:
IMG_7400.png

Right:
IMG_7401.png

-Ed
 
I’ve always had the ports on the LS50 Metas plugged since I got subs.

I’ve actually adjusted the delay and crossover settings to 160Hz (the room’s actual Schroeder frequency) with 8.15ms delay and the crossover point is a lot better. Now, these sweeps don’t look as flat anymore because instead of calibrating for a single point like I did for the above sweeps, I’ve calibrated it with sweeps at 9 different points (the MLP plus eight spots surrounding the MLP):
Combined:
View attachment 23828
Do you still have one woofer facing to the front and one to the back of the sub?
 
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