This is a request by e-mail for two Orion HCCA 12" subwoofers and a blowthrough in an F250.
Has a very high sensitivity and still has good output down to 30hz. Passband is 30-60hz.
As a small design example:
Design can be found here: 2xHCCAs Series-tuned 6th order blowthrough - $30.00 : TheBoxHouse, Enclosure designs
Wish I could be there to hear this one!