Custom sub box mount pics.

[ian ashton]

3/4 mdf and seal it will a couple coats of resin inside and out , then carpet it grey to blend in.

MDF will soak up water, no matter how much resin you coat it with. My first box had a full gallon of resin inside and out and it still got destroyed by water. I would (and did) go with a nice ply, like Birch.