I have a dual 12" enclosure that was built to do some testing with. Had some AQ subs in it for a while. It is 38.5 wide x 19 tall x 18 deep(I think). Has two slot ports. Has around 4.5ft3 and tuned to 31hz. Sounded great and worked with out issues.
If anyone is interested in it I will get actual dims and take some pics. It currently does not have a double baffle but I can add one with no problems if needed(I would add one if you plan on using a good amount of power). It is also currently not carpeted again can be done if required.
Price....um dunno $75 plus shipping as is....
$100 plus shipping with double baffle and carpeted