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.
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.