Which material sounds better for speakers construction? Wood, Ply or MDF?

+1 peter.
I've wanted to play with composite sandwiches, as well as using layers of the same materials with different cut-outs to prevent panel length resonances.

I am quite keen on Panzerholz, a very dense, very dead German beech plywood with elastic properties. Costly to experiment with, though - $1000 sheet.

MDF and plywood are okay. HDF is better. Wilson uses variants of quartz and Corian countertop material. 

All sorts of composites and plastics can be ordered in sheet form from McMaster in various thickness. Methacrylate acrylic and phenol works great.

Bracing is very important. Isodamp is amazing stuff.

I would stay away from aluminum. Goldmund, Magico, and YG lost their minds. It's the worst material for a speaker enclosure.

Love aluminum Magico already sold out the first run of A1 speaker at $9800.00 pair so there are many people that love aluminum.It also depends on drivers and crossover in concert with  aluminum and yes Wilson speakers are also wonderfully made.

You've got to wonder about the motivation of a high percentage of those buyers.  They're people impressed by the Magico aura, who until now couldn't afford to own the brand.  But that's the point: they're buying the brand, not the sound.