Well, that's a tricky one,

I have heard that you can't use suction from a vacuum cleaner, as it may damage the lenses. There are however cans with compressed air avaible at specialist electronic shops, which might do the job. I have also heard the rumour that if anything else fails, you can use a soft, dry paintbrush. I have no experience with the brush and it's against B&O instructions, so I am not recommending it.

Good luck solving this one!

I'd suggest a soft blower brush of the type used to clean camera lenses. Use only a high grade one; blow the dust first (lightly, not by squeezing hard and then gently brush the remaining dust forwards. If any dust remains and is stubborn to remove, leave it!

Hope that helps! 

Thanks for the information.

I guess between the two options, soft paint brush is probably the least expensive way to go about it.

As I know there has neever been problems with touching/cleaning  the tweeter gently, and I can`t see why its shuld bee difference with a BeoLab 3

 The cap are strong and constructed to make movemens as the pictures shown

 link

But dont make a dent in it, its not nessesary for cleaning it, for making a dent, you have to push very hard,

Children like to make dent in a tweeter ;-) but  normally it will still work without problems !) therefore I say that the tweeter are a strong unit that you can clean with a brush.