I have read reviews where the reviewer always tightens the drivers down (if possible) before the listening session begins. This would lead me to believe that many have come from the factory's assembly line that way. Some (most likely small high end) manufacturers are good about tightening down the driver screws before they box them up. This is a good question to ask the speaker manufacturers, and see what they have to say. If anything, it will make those that don't, increase their attention toward this aspect perhaps a little more.
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.