Loose driver mounting screws on Velodyne HGS-18

Hi folks, I recently removed the grill from my Velodyne HGS-18 (purchased in 2001), and while the grill was off, I figure I would tighten the 6 hex screws securing the driver to the enclosure. I noticed that all 6 screws were quite loose (by several turns). Anyhow, I tightened them all up, and the bass was noticeable tighter afterwards. I contacted Velodyne and asked them if they have heard on seen this happening on the HGS series subs, and they said no. So does anyone out there with an HGS series sub want to take the grill off the sub, and check to see if the screws are loose, and hence you are missing out on some tight(er) bass. Maybe this is a common occurrence, but that people never remove the grill cover and check, so they never realize it, and have been living with loose(er) bass.
This happens to speakers of all sorts, with time or shipping even the tweeter screws will need tightening. It is a good thing to check periodically. You should do it when you first get the speakers, usually the shipping will have loosened them.
It happens - the wood dries out (wood breathes) especially after a year or so and then the screws become slightly loose and vibration does the rest. You probably will not have to tighten them again.
I find that once I discover a loose screww I remove it completely. Then I injects a small (very small) amount
of glue and replace the screw. I tighten it as much as it will require and I never have had one loosen up again.
The reason you want to use a small amount is that you have enough applied that will keep the screw from self-loosening, but still be able to break it loose and remove it should a driver ever fail.
There is a special glue for this - Loctite.
Yes, as Shadorne said, Loctite is designed to solve just that problem. Be sure you use Loctite blue, not red, in case you ever need to remove the driver. The red version is designed to keep the screw from coming out under almost any circumstances. A tiny bit of fingernail polish also works.
One note on Loctite - It is intended for metal on metal, and not for metal in wood. Not sure how it would work in the latter application, but I'd choose a different adhesive if your screws are going into wood.

Totally normal for drivers to come loose. In fact, in a recent (November?) issue of TAS it was among a list of ten cheap tweaks you could do to improve the sound of your system (tightening the drivers).
Do not over tighten and strip the threads.
If they are threaded into the wood on any speaker and becomes striped out,its best to use "T-NUTS".They are metal and inserted from the rear.This link is for picture purpose.Link>>>[http://www.stafast.com/products/tnuts.html]
Anther T-NUT link>>[http://www.parts-express.com/wizards/searchResults.cfm?srchExt=CAT&srchCat=829&CFID=2764090&CFTOKEN=49784390]
Locktight makes a special formula for this particular application. It is called "TITE'N". I used it once with good success on the side rails of Magnepans. This is designed for wood, rather than metal materials.