custom sub box

I have 2 12 inch apline type r's hooked up 2 a 1800 watt kenwood amp. I have the subs in a 1 cu. ft sealed per sub. Does anyone have any suggestions on building a bigger box. thanks

Build it out of mdf. I believe those call for atleast a 1.5 cu ft per sub(sealed). I would use 3/4" mdf also. Sperate chamber per sub. I prefer to use adhesive and screws to secure the enclosure together. Some guys like using 1" for the face side also although with the type r's I am not sure if its necessary, maybe somebody familiar with alpine can chime in on that.