Put them in the "A" pillars below ear level and, wrap them in matching speaker cloth.
This is the right way to a great soundstage. Anything else is second rate.
The vents are the wrong way to go.
133whp-126ftlbsTQ Eclipse CD8443,JBL Px300.4, JBL GTO7001, PPI 356cs, JBL p1024(Hooray!) SubThump enclosure, RAAmat BXT, Damplifier Pro
Hatch Nation #140
Caeci caecos ducentes