plywood boxes are fine, the only bad thing about them is the void's in plywood. They can flex and even blow out leaving you with a box with holes in it. If you want to build a box out of plywood I would reccomend marine greade(void free) but it is much more expensive then MDF. A sheet of MDF is about $25 then some glue and screw's and your golden.
alot of people use plywood but the stuff james is tlaking about that is void free cause it is lighter tha mdf so it doesnt weight ther cars down as much and it sounds just the same and actually the way people were tlaking about it on another site plywood doesnt flex as much as mdf and it doesnt create as much saw dust when cutting
wat up? You eva been to NM James??? Tha land of enchantment is fu*kin tight. Where u from conneticut, damn u live way in tha fu*k on tha east coast. O sh!t Hunter u from NM too!!! Tight your the first i see on this site from here.
i used 2 build boxes of good grade plywood yrs ago b4 mdf was as common as now - ply used 2 work fine but seeing now that mdf is just as available & its a better box building material thats actually cheaper too - hands down go with mdf ......