Ok, now testing again. This time I used C-weighting on Preferences and on my SPL meter, manual suggests it so it's ok to use that?
Anyway, I did left/right measurements. I noticed that there's a 3db difference with left and right, I guess my old Onkyo amplifier is doing some tricks.. Here are the new results.
The ringing on right speaker continues over 1500ms, so that's quite bad.