Maybe you should hang out for a while before you start posting.. Did you say plywood?
http://images.sc1.netdna-cdn.com/D/S...iled-image.jpg
OP, thats a $3 adapter.. allows for 2 3.5" speaks.
Course you could just go with plywood.. then seal it so the sun doesnt warp it.. then somehow make it look good.. but 1/4" plywood with very little surface area will most likely crack before warp.
and my math might be rusty but if you have a 4" speaker how would one fit a 5.25" speaker in the same area? much less 2.. isnt that 5 x 10.5" in a 4x10 spot..
just me i guess.
course im just a noob here.
but id do it right and grab the adapter.