So Fostex makes a 31.5" woofer with really strange specs. It will put out a reasonably flat signal to below 10hz if you have an eclosure that's just over 2,000 cubic feet. Or you can get flat to 18hz with a sealed enclosure of just 664 cubic feet. Xmax is only 2.3mm. But it's 96db efficient. http://www.madisound.com/catalog/product_info.php?cPath=45_228_311&products_id=304 Only $2,282 each.