alpine type x 12 enclosure

What would be an ideal air space size for this sub, I have seen a custom box on eBay sealed wich has an airspace of 1.25, is this to big of a box for this enclosure? If not what is a suitable size for this sub? Thank you

Ideal is in the eyes of the beholder. If you check your owners manual you'll see what Alpine thinks is the ideal enclosure volumes. Personally, subs like the type X, that have a XMAX as they do, I like to run them ported. A friend of mine has his in 1.5ft3 with 2200w, using 2 layers of 5/8 mdf all around. I hate Alpine, but I gotta admit, it drops.

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I put my Type-R 12' subs in a 2.5 cubic foot box (after sub and port displacement) ported man and they hit like a truck. I broke 140 Db's with 2 of them so i would say somewhere around there maybe to start with try maybe 2.7 or so it takes experimentation to be honest and depending on the vehicle lower air-space may be optimal. Try it out 1.25 cu. foot would prob be ok sealed but i wouldn't put a sub that massive in a sealed box unless i had no space to work with. Ported is optimal for sure with at least 2 cu. foot of space but thats what Alpine recommends for a Type-R 12" woofer. like Ianarian said check the manual first and play from there experiment and adjust it could take you several boxes before you find the right one.