taken from a Car electronics review of this subwoofer........
Installation RE's manual offered two enclosure recommendations: a compact size of 0.85ft3 and an optimum size of 1.1ft3. Because of the sheer bulk of this subwoofer, I was surprised by just how small these two recommended enclosures were. As is my custom, I gave the manufacturer a call to get their absolute best enclosure recommendation for sound quality. When Larry Ratcliff of RE Audio gave me the specs, I was taken aback, shocked even, when the answer came back almost three times larger then the recommended size at 2.843ft3! That's one big box, but it is more in line with what I would expect.