What is your favorite material for loudspeakers?

Guidocorona
I suspect you could build a speaker enclosure to operate like a fine string instrument.
You could make one, or perhaps even a matching pair.
There is almost no possible way, for a reasonable amount of money, to mass produce such an instrument.

As for a practical (advisory) perfect enclosure, why not concrete? Heavy and inert, it would add nothing to the sound of the drivers. Add dampening to taste.

I'll stick to my panels.

Cerrot, How is your stat held? By frame metal or wood so is resonates just like a cabinet thus has coloration just like a cabinet. Don't believe place a stethoscope on material holding stat play music.. Also stats can have forward backward movements as membrane moves forward and back this cause planar to rock. Most designs don't fully address this thus all the aftermarket stat stands. And Guidocorona I fully understand the differences in musical instrument construction and loudspeaker cabinets. And a few loudspeaker in the market today have cabinets similar to a musical instrument construction. I don't offer for I feel designs are to colored.

Johnk,

Actually, its a metal frame, but my point is that I don't (or didn't) want my drivers in a box. I have the Eros Mk II and, yes, the woofer is in a box, so I am kind of speaking out of both sides of my mouth but the 60hz or so sounds don't seem to be effected as much by box coloration as mids and highs do (and I do like going down to 28hz so need the hybrid design). In the price range of my stats, I haven't heard any box speaker that comes close. At multiples the price (I like the B&W 800d, Magico minis -only down to 40hz, and Kharma Ceramique), I would be happy upgrading but not looking to spend $20,000+ right now. Actually, I would go $20k+ but I would also need to upgrade my amps (eyeing either Ayre MXR for SS or shindo for tubes) and would also need to upgrade preamp to better match the amps. So, upgrading will run me close to $50,000 or so, so waiting. Speaker design has progessed greatly over the years and I have heard less (in the products mentioned above)or(almost) no cabinet coloration but, when I bought my speakers, in the price class, box speakers just didn't do it for me.

Johnk, Sonus claims their cabinets are built like Cremonese string instruments of old. . . fabulously effective markcom. . . reality is different though. . custom ply cabinets of Sonus do not vibrate. . . they are desirably dead as doornails. But yes, it would be interesting to develop a speaker that truly vibrates like a fiddle. . . would probably be incredibly efficient. G.

Magfan...I tried concrete once. Chimney blocks are a good size for a bookshelf speaker...all you need is front baffle and rear panel. Only problem is that concrete rings. Not dead at all.

Suggestion...try styrofoam, well braced and/or curved. It is dead.