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.
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.
I don't think that any fastener, especially those subjected to vibrations that are present in speaker enclosures, are guaranteed to stay tight unless they are lock-wired in place. A speaker enclosure is going to expand and contract (no?) with changes in moisture content of the air, and temperature variations. Unless the drivers are welded in place, I think you will have to ensure that they are firmed up from time to time. (Welded? I wonder if Krell designers read these forums?) I like to use spot torque on mine ... torque them until you see spots.
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.
The array of tweeter screws on my Maggies sounds best when tightened and then backed off about 1/4 to 1/2 turn. The screws holding the feet to the panels need to be 'spot torqued' ( thanks Massvm ) periodically.