Help with outside speakers

[tisserda]

I've got 6 speakers mounted in the ceiling of my back porch.  The ceiling material is concrete board and creates lots of reverb/feedback.  The speakers mount with a screw/clamp style lock.  I was thinking about cutting out some MDF in a 2" wide ring around the speaker to provide a more secure mount and also provide more support to the board.  Other suggestions?
 
Thanks in advance,
Daniel

 

[neillt]

Use Dynamat or other material/foam designed to absorb audio vibrations.  They are usually used in automobile applications... put that up on both sides of the wallyboard.

 

[Del91574]

Fill the void(s) wherever possible with rockwool.