building a sub box

i have a single kicker l7 15 i currently have it in a 3 cuft ported enclosure that i paid a local car audio shop to build i am unhappy with the low frequencies this box produces typicaly 40 hz and down.my question here is if i build my own enclosure witch id go sealed this time due to lack of experiance in building sub boxes how can i get the sealed enclosure to produce strong deep bass at 30hz  i am obsesed with low bass and need help to achieve this can someone help...............

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4 12s cvr sealed
2 hifonics bxi608d
1 kinetic hc 800
alpine reciever
infinity kappa door speakers

Actually you won't hear those frequencies unless you're in a bus.  Wavelength at 30hz is approx 33ft!   What you're hearing are harmonics eg 60 and 90hz.  In your mind no outsider is going to satisfy your needs,  I suggest visiting your local library,  getting out some books on the subject and building your own.

thanks for the advice my freind but your very wrong..I actuelly just built my own ported box tuned at 35hz and im catching every low note possible its exactly what i wanted..and its not in a bus it was stuffed into the trunk of a 2dr honda civic..I see you have a high status on this website but your information is misleading and wrong..i have plenty of freinds that compete in spl contests with nissan maximas chevy malibus and honda civics that can hit a 30hz note like its their  job i am fimilier with the distance the note travels 30ft etc but that doesnt mean if u build the box rite you cant get a small car to sound good when producing low frequeincies

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4 12s cvr sealed
2 hifonics bxi608d
1 kinetic hc 800
alpine reciever
infinity kappa door speakers