Replacing driver screws with brass screws

oldhevymec, seems you're saying vibrate when what you mean is rattle. Tight won't rattle but everything vibrates, only question is how. You're probably right about torque to tone. Tighter probably is higher in the same way a guitar string is adjusted higher by tightening. The difference being the relatively stronger screw is going into MDF and probably cannot be tightened anywhere near enough for this to be noticeable. What probably would be noticeable is tightening compressing the gaskets. Just not to the degree of tone you're talking about. Lots of people tighten mounting screws, I sure have, never heard anything like this though.

What about gold-plated brass screws?
Remember the first Krells?  KSA50 and KSA100.  They have these fixing the front panel to the chassis.

Now I had always thought they were there as decoration????

Brass is an alloy of copper and zinc.  Small amounts of other metals are often added.  Crucially the proportions of all the contituents is variable.  So the content of brass is not fixed as for say iron.

Point no.1       Not all brass is the same, so why expect the same results?


Brass is non-magnetic (if there is no iron in the mix).  Speaker drivers have big powerful magnets in them.  In the case of a smallish speaker the fixing screws will be within a few inches of the magnet and within its magnetic field.

Point no.2     Clearly the lack of magnetism in the fixing screws will have a real and MEASURABLE effect on the action of the magnet on the driving coil, as compared with steel/iron fixing screws.

In a properly designed speaker, the drivers will not be fixed to the cabinet with wood screws.  Obviously these will work loose very quickly because of the vibrations of the driver.
They should be fixed with bolts running right through the cabinet wall and held in place by locked nuts that cannot unscrew.
They should be torqued up very tightly to ensure that the cabinet wall and gasket material are compressed as far as possible to minimise any looseness that may be caused by future compression.
Gasket should be as thin as possible to minimise variable compression.
Not rocket science, just sensible and simple engineering.

MC, yes for our purpose, call it "rattle". If it's tight, (driver to cabinet) it is as ONE... If you listen with a scope say 2" from the screwface, note that tone and THAT SPOT (need to mark your measurement spots)
Torque, and listen.. If there is a "Rattle", that's real bad. The two pieces are NOT bound one to the other. Torqued properly...Recheck for TONE. Kinda see the difference?

We don't want a "given amount of movement" between the two pieces.
EX: Head to block, they move....

"No movement torque"...different kind of torque spec. This is the engineers job.... Not the mechanic... BUT, we'll fix it anyway. 

I'm not trying to come off as a "SQUINT" OK!!! Get to "squinty"
I can't keep up. :-)
  
We are looking to TUNE each securement to the same tone, via ear.
I suppose you could measure it pretty easy, if you need to, (for the measurement crowd). Then move your scope (pickup) over the securement. I TRY to get them all the same (tone) 2-4-6" away.
I try to TUNE/Torque so I don't have to do it again.

The above method will show you how BAD Big Box store 11-15 plywood really is..  HUGE voids... (internal wood rattle).  It will DRIVE you nuts, kind of noise. HARD to fix outside and look good, kind of NUTS... :-(

If you have a breakin (tone gen) for say 24-36 hours, recheck your securements. I've done it so many times, I can still hand torque to within 10 inch lbs of torque. Then see if it holds. It always does NOW..
If they come loose (never have), they NEVER come loose again. Silicone/thread locker/JB weld/binding head SS lock washers/nylock nuts/pinch nuts!!!

I use a (2-3) stage CROSS pattern torque too. 

OR Torque to tone if YOU want to. You know, learn something. :-)

MDF is easy to OVER torque... If it's too tight, it will warp the speaker rim and or pull the threads... If it's to loose, it will come loose again and pull the threads. When it's torqued RIGHT, and the screw HEAD is bound, it CAN'T move. If you can't get it tight enough, Half moon hardwood backers for the bass drivers. 3/8" thick 1-2" wide. Oak or Apatong. 60-160.00 usd PER driver.

Load 20 BASS drivers, gets spendy. You can make your own.  20.00 for 8", 30.00 for a 12", 1/2 red oak. few tools..

Regards