Yes, it has to be in a box. For a quick physics/harmonics lesson, a sealed box will give you stronger bass (with the correct speaker), but will not give you correct frequency reproduction unless it is big (about 3 cubic feet for a 10inch). Whereas a ported box you loose some of the oomph, but it will sound better in a smaller box. I'm an audiophile and have a ported sub in my room.
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