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

@bukirob What sort of logic is that? 

buki is exactly on point here:

Here is what I would say about that. How many CONCERT level instruments are made out of plywood or MDF?

Since I listen to mainly jazz vocalists my speakers are made mainly of deceased jazz vocalists. You would not believe how long I waited for this pair. Touch and go for a while, I was worried the singer might recover.

Doesn't Harbeth use solid wood for its cabinets?

^ They use relatively thin MDF panels, veneered on both sides. I believe a couple of their models use a combination of ply and MDF.

Here is what I would say about that. How many CONCERT level instruments are made out of plywood or MDF?

Answer = 0

While a speaker is not an instrument in the sense that you can play it, it shares ALL of the concepts of a device, usually some type of chamber in which sound is projected for the audience to hear and enjoy.  

It would seem to me that Wood would be the obvious choice.

If the goal is to hear the resonating wood (as is the case with string instruments), then yes, solid woods are certainly the best choice. If it were the most inert and neutral material choice, we wouldn't have such large variations in the design of string instruments. Any experienced guitarist can tell you that sitka spruce and maple sounds brighter than mahogany. Hmmm...ever wonder why the call them "tonewoods?"

Further, as mentioned in the white paper linked above, solid woods are not isotropic. They also have too many inconsistencies in terms of density and grain patterns - even with cuts sourced from the same tree. This is why no two string instruments - even from the same luthier - will sound exactly the same. These issues could create problems for pair matching of speakers.