no:1that isnt MDF that is pictured m8, its common chipboard. is this the actual picture of what you are building? if so throw it away and start again with decent material. go one better and use 12mm or 15mm marine grade birch ply. and use deadwieght in the enclosures, sand is good enough. and pack them with nylon fibre - it fools the speaker into reacting as it would in a larger enclosure...far better acoustic range. no:2if this is a home/cinema audio system why are you using car audio subwoofe…