So some people have already used a basshorn in a car ;-)
but did they hornresp it! no sealed rear chamber,so horn must be a little longer for same low freqs.
"149.6db DEATHMATCH Score, Average over 5 minutes!!!!
"

• MASSIVE HORNSUB

perhaps 100db/1watt only ...

Id use the lab12 because its such high xmax,with LF youd need the excursion.

The question is,do you need it,really i think a labhorn or similar will suit the task just as well. 30hz clean is very impressive on its own

Cheers!