I think you are going to find that the wood your using wont work. First off what type woofer and whats the weight of the woofer. If its like most now days there a good 20 lbs atleast. 3/16th is not strong enought to handle that. As stated before look for atleast 1/2 MDF 5/8 or 3/4 would be better. Most 12" subs require atleast 2.0 cubic feet of air space right now your at about 1.7. To get this number just take length x width x height then divide it by 1728. Good luck!!!
