#1. List the exact volume your enclosure has (do all the math for how much your vent displaces, etc...). If you are unsure about the tuning (as in you never verified it) list the vent area (internal Height x Width) and total vent length. Do not use any metric numbers. #2. List the T/S parameters of the subwoofers you have. (There have been a variation of Alpine Type-Rs over the years, you need to know the exact model number) #3. List the T/S parameters of the subwoofers you would like to compare. This will help whomever is willing to model for you...