Yes, both speakers together, and this is why I dislike measuring both speakers together when interpreting HF information because millimetre changes in speaker location cause huge changes in HF comb-filtering. I prefer looking at individual left and right speaker measurements for HF analysis.
The above measurements show the speakers tilted backward 15mm. I have now tilted them the full 30mm like I had done before I started doing all these new measurements and the output around 5kHz is now significantly better.
The differences in the <200Hz response of the two speakers is probably due to room geometry (remember I have a bay window opposite the left speaker and a door to the right side of the right speaker.
The following graph compares the
EQd response of the speakers in their old position (64cm from side walls and toed-in to cross 2ft in front of listening position) vs their new position (103cm from side walls and toed-in to cross 4ft BEHIND listening position):
The centre imaging in the new position is much more consistent and convincing. However, the mid frequencies are more coloured sounding. I think adding absorption to the front wall and side wall reflection points, and possibly also the sides of my hifi rack will help smooth out the mids. I'm also finding the speakers' tonality much warmer in this new position, probably because the 170Hz-300Hz area is no longer scooped out. It's taking my brain some time to adjust to this new balance.
I am already using EQ. Additional bass trapping will (hopefully!) bring the benefit of reducing decay times in the low-bass to make it tighter.