I had Duntech Princess loudspeakers for 11 years, which had two 240 mm Dynaudio drivers per side and two smaller midranges. I periodically had to tighten the screws holding in the bass drivers, and (less often) for the midrange drivers. They just loosen over time with the vibrations, I guess. Always seemed to sound better after I tightened them, but I wouldn't want to take a blind test.
A good speaker question
Over the years ive had speakers come and go in my system and noticed that many times the screws that mount the drivers into the cabinent arent tightly mounted. Ive always bought used and wonder if that was the intent of the speaker maker or is this a case of the screws coming loose over time. Has anyone done any research on sonic differences with a tightly mounted speaker? I would assume that the tighter the mount, the better the sound, but in the last 2 pairs of speakers that I have checked on, they were not tightly clamped.