Speaker cabinets: How important is inert

"One can model a number of different box volumes and see a significant change in performance under 100 Hz but virtually no impact on the performance above"

Hi Mlsstl,
I was only addressing cone speakers. VAS affects all cone speakers in a box regardless of size. It is just as important to have your midrange in the correct box size as the bass driver. Its final Qts figure will relate to a hump, flat or a dip in its frequency. If you develope a hump, it would easily portray a coloration or "smear" in frequency. As far as controlling back wave in the cone material, I was specifically speaking of mid range drivers. Back in the old days of paper cones, we treated them with Latex to stop cone break up, Later came poly, kevlar, carbon fiber, aluminum,....etc etc etc.
The latex helped control breakup. The more dense materials normally were not as effected by backwave coloration because of the stiff cone material. What I am saying is the cone material and box material are not intertwined. They both matter greatly, but independently of each other. Sorry, no disrespect intended.
Back to Enzo618. Any material that is rigid and dead would be great. Normally thinner materials require a bit more bracing, but can work. You've probably seen concrete enclosures. I've not experimented with alot of materials, I've used some fiberglass, but it had to be thick and re-damped, I like your epoxy sandwich idea.... but in the long run, a proberly damped inert material that has the proper air space will do a reasonable job. Some may be slightly better than another, but the standard braced MDF is hard to beat.... Dollar for dollar, I'm not sure that you can.

No disrespect taken (but then I've never worried too much about that issue one way or the other...)

I'm with you on that brother

I use British speakers mostly that figure cabinet resonance into their design,from my understanding.Speakers that have so called dead cabinets,aren't a guarantee for the best sound.The drivers themselves are a primitive way of making music,but that's what seems to work the best.Even 70-90 years later.A lot of musical instruments make their sound by cabin resonance. I go by what my ears like,not what electronic measuring devices say I'm supposed to like.A technically good speaker usually sounds poor.Is thick car paint fantastic sounding?If they were that dead,we could put them in a corner,or against a wall.In the 70s or 80s,a dealer had a pair of speakers that measured the best at the time. He asked me what I thought of them,I listened awhile and said ok to be polite.He asked if I would by them,I said no.He said that's why they're close to the door,to get rid of them as quick as possible.Go by your ears,and forget the rest.You must like,and enjoy them.This is just my two cents.

And then there are free resonance, that's controlled resonance speakers by Michael Green. Anyone listened to his Chameleons? I don't have Chameleons but I have his old Revolution 80i model. Very natural sound. Michael has a great ear. But I would not choose his speakers for big orchestra music especially if price is no object. Or probably for very big rooms, and I mean big. Also, ideally these speakers require iron-fist but gentle and refined amplifier, let's say like Rowland or Gryphon.