Thiel Owners

Starting with a pair of Dunlavy SC4s back in the 90's I have replaced all the steel fasteners with brass in all my electronics and speakers. Steel will bend the flux field of the electronic path. Easily heard on a circuit board stand off and its fastener.
Back plates that hold speaker lugs should also be non ferrous and their perimeter steel mounting screws should go away. Steel screws that hold down crossover boards should be gone. All the drivers will improve sonically with brass and not steel. Finding and then mounting with brass is somewhat difficult and time consuming..Start with the crossover and then move on to the tweeter. McMaster Carr is a great place to shop for brass fasteners including metric sizes mostly used around tweeters. Brass reduces interfering energy compared to steel in any audio part I have encountered. Tom

@tomthiel - 

I emailed Rob and he was kind enough to put screws in the mail to me.  I'd be interested in trying brass - just want to be wary of stripping the material the screws go into.

Tom - your missive runs parallel to my experience. In the case of my outboard crossovers, and mounting my internal crossovers and back-plates - I am using all nylon. Drivers need more strength so I use brass.

naimfan - stripping is an issue with screws directly into MDF. I use "Wood Hardener" from Minwax available at the hardware store, or you can use thin super glue dribbled into the hole since the internal threads are already formed via previous screws.
Take care with brass screws; they're not as strong as steel.

On my mids or woofers I use brass inserts into the wood or in my case cast granite. I then seat the drivers with mortite/rope caulk and thread in the brass fasteners. Tom

Thiel migrated away from direct wood fastening to inserts sometime after I left. There are advantages of reliability over multiple uses. However, metal on metal under vibration will (reliably?) vibrate loose. Breakaway Locktite helps as does Mortite onto the threads. But over the years, inserted fasteners seem to come loose and direct to wood fasteners seem to remain tight. I'm going with plan A and use direct fastening. Of course castings need inserts. Brass is a good solution, or other non-magnetic substances - non-conductive is even better, since electrical fields are affected by any conductive material, magnetic or not.