Cheap tweak from Virtual Dynamics:

This thread made me wonder if my Dali Megalines might benefit from torquing the woofer screws. The ribbons are suspended in space, so they are non adjustable.

I removed the top section grill cloth on each side (of the six sections) and located in my tool chest, the Torx star bit that fit the mounting screws.

I was surprised that with all my strength I was unable to tighten any of the screws on six woofers that I checked. Granted, I gave up before testing all 24 woofers, but it appears that in the case of this particular speaker the screws have not backed off, or perhaps the factory applied a bonding agent, set the torque and it resists further movement.

Whatever the case, it was a grand experiment and got me to vacuum those dusty grill cloths. I'm looking forward to reports from others on the benefit of this. I love cheap tweaks that have potential to improve sound.

Albert,
Maybe you can check with your Dali dealer or ask a factory technician about the torque. They might pre-torque these to factory specs and then, as you mentioned, they might put some lok-tite on the screws to keep them from loosening with time. It made me cringe to see that you couldn't tighten them with " all my strength..." You don't want to break off a screw or strip the wood out.

Having been around audio for a long time and a past filled with car racing and engine building, when I say tighten with all my might I should have clarified the situation. Torx can be set up to fit two screwdriver handles or a ratchet drive. For something like a woofer I deliberately used the small handle Torx that limits leverage.

I don't know the exact amount I'm able to exert with the small drive, but it's like tightening brass parts on a carb when assembling an engine, you don't want to overdrive it and ruin the whole assembly.

I believe Dali must have used a locking compound on the screws, keeping the torque uniform over time. I have no proof but this behaves that way in my opinion.

No question that the ratchet handle and reverse motion could break the bond if a driver needed replacing, but I think they have it right where they want it and it was planned that way during assembly.

Albert,
You would make a great candidate to do the brass for steel swap out. Lotsa drivers lotsa steel. I performed that surgery on my Dunlavy 4's some years back. I used brass machine screws intead of wood screws. The machine screws had a higher number of threads and they extended all the way to the head unlike the wood screws. Made for a more tuneful sound that was also less noisey. Tom