A design I first saw
in the Fried Model H was the "coffin" woofer. Fried used an OEM version
of the Kef B200 -- the DIY community often used the Kef B139. Essentially two single fold lines laid
side-by-side with woofers firing out either end.
The picture here and the plans are from the Perfectionist Audio version (I choose this one
because the web site has detailed construction information & more pictures).
I have plans for one I built after seeing the Fried H which except for some dimensional
differences is essentially the same. Since the B139 is very hard to come by these
days a suitable pair of 10" or 12" drivers could be assembled into a suitably
modified version of this box.