why does it on every single Subwoofer on the Fi website it says N/A for the sealed box size

I believe the Q is the only subwoofer that can be ran in a sealed enclosure. BL and BTL are made for ported enclosures

why does it on every single Subwoofer on the Fi website it says N/A for the sealed box size

they list sealed enclosures for the regular subs like ssd's and q's, but the people that buy bl's and btl's are using them for large amounts of bass and they get that thru ported enclosures. im sure you can still use a sealed, but you wont get the perfomance youd expect from such an expensive woofer.

Like they said, it's just that they don't recommend sealed boxes for the BL, BTL, and IB3. They are designed for ported enclosures for the BL and BTL and Infinite Baffle for the IB3. The Q is designed for sealed. They will all work in any box, but some are optimized for certain types of boxes.

The woofers you are looking at say "N/A" because they are not designed for sealed enclosures.