For whatever reason, MDF is actually not a good sounding speaker
material and cabs from multi-ply laminated wood, such as piano pin
block stock, offer many of the theoretical benefits of MDF while
providing better mechanical ruggedness, repairability, appearance and
they "seem to sound better"-no A/B/X proof, just seems to. Maybe it's
my imagination.

duPont Corian is a cool and underutilized material as well. The
Japanese use it in some of their nifty, but too heavy to
cost-effectively import, cabs for classic coax drivers such as the
Altec 604, which I consider to be the "Marilyn Monroe of speakers".