What is your favorite material for loudspeakers?

Upsidasium was the metal (mythical) discovered on Mt. Flatten.
Don't you remember Rocky and Bullwinkle?
Captain Wrongway.......but I'll save that for later!

Just looked at link! Yep, as I remember......
Need a new thread:: 'rocky-bullwinkle trivia'

Have you guys tried a french polish?

John
I have had some speakers in house made from birch plywood. What a relief over MDF. Much better tonal quality. I think the big difference is that MDF has so much glue in it. Much more mass and that acts like a solar heat sink holding in the resonance.. I think most speaker manufactures know that. But it does take a different and more expensive approach. You buy veneered plywood and build from that. With MDF you can build the speaker first and then if it is OK just cover with veneer. Not the degree of difficulty that working with expensive plywood has.
By the way what is french polish???

Since ply are veneered with birch I use veneer over the ply this sounds better than veneer faced ply. French polish is a hand applied shellac oil alcohol mix. Binds with veneer for best tone plus it looks great is easy to repair can last multiple lifetimes.