15" phoenix gold XMAX

My cousin has it, and it sounds shitty (not loud) in the box he's got... not to mention he has it in the trunk with a 12" kicker comp. I told him to just use one and build a new box for it. I think we should build a box for the Phoenix Gold. He doesnt have the manuals for it or anything so I need to know what kind of box to make for it and how big. Can anyone tell me, or tell me where I can find the information? Its got a 1500 w amp on it, I dont remember what kind, it may be a phoenix gold as well. Thanks...

Rick

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