I had 2 12's in a custom Isobaric Reflex Box. I had the subs firing in a dipolar pattern. Because of the dipole, I had the port forward firing to maximize the slightly shorted wavelength. Having your subs work together and not fight one another really crisped the bass and made the 12s respond like 8s without losing any low end, And hit as hard as 15s when the Bass got gritty. This was in a 73 3.0 CSL.