What is your favorite material for loudspeakers?

Mr Sounds- Yes, Tung Oil is great stuff and when applied with the bare hands: The body heat opens the grain a bit for an even deeper finish. Excellent way to bond with whatever you are finishing(gun stocks, audio cabinetry, etc). No problems with my planars and woofers. I've been actively bi-amping my systems with a pair of transmission line woofs for over 28 years now. The TLs can now stay in the corners(where woofers belong) and are aligned in the time domain by my TacT RCS 2.2X. I've always used TLs with my planars because the cone is basically unloaded, and can move fast enough(with a high slew rate/high damping factor amp) to provide a seamless crossover point. Do you ever spend any time in Indianapolis?

Concrete blocks? Were they sand filled?
I was speaking to a system I saw once where the speakers were poured in place. I suspect the chimney block effort was sabotaged by the front/rear panels.
ALL concrete is the way to go! A couple inches of Portland will never rattle.

I saw a pair of Usher monitors and stands recently with what appeared to be largely marble construction, unless it was a synthetic material of some sort like that stuff they use in countertops (Corian?). Very pretty and very heavy!

Magfan...Chimney blocks have no voids to fill. Agreed that concrete won't rattle, but it will ring, and at a low frequency.

Upsadasium