Obsolete Focal woofer...

Nelson,

I found some specs for the 27F on the internet, and it seems that it had a high Qts (0.82) so is suitable for a sealed box only!
A sealed box in itself is quite forgiving, and according to the specs I found that a box of 3cuf. (~85L) would yield a box Qtc of a little over 1.
Not perfect for home use but might work just fine. It will have a bit of a bump and should be crossed not higher than 200 Hz max.