Originally Posted by Gazzer55
Ok thanks Michael - Given the front baffle for the mini marty is doubled up I thought that would be sufficient to hold the subwoofer in place! I see a lot of people flush mount the driver the the inside layer of MDF, so recess it inside the outside layer of MDF. Would it be a stronger cabinet overall if I cut an equal size hole in both front baffles and use longer screws through both layers?
Marginally stronger. How much deflection do you think you will get on that 3/4 inch thick x 20 mm thick ring that would form the driver mounting shelf?
From the webpage, the UM-18-22 cutout is 422 mm, and the outer frame diameter is 462 mm. Even if you gave yourself 2 mm around the outer frame diameter for paint and clearance, that is still only 22 mm of material to deflect, and will be attached to the driver frame with screws.
RE: fasteners... no need to over think. Simple screws that have sufficient length and diameter will work, provided they fit in the recess in the basket. Pre-drill holes to slightly under the root diameter of the screw. Gasket tape is highly recommended for a proper seal.
T-nuts and 10/32" machine screws can be used, but you aren't touring with Metallica, so the cabinet does not have to survive being thrown down a flight of stairs loaded.
KISS principle here. If it makes you feel better, you can use a double layer to screw into, though even an 80 pound driver can be held in place with simple screws in a single layer.
If you plan on removing the driver multiple times, a T-nut and a machine screw is a better option. If the holes loosen in the MDF from repeated assembly and disassembly, you can always rotate the basket some and drill new screw holes.