Are carbon fiber speaker cabinets inherently better than wood or metal ones

Sorry, johnk, but this is wrong:

Alunimun is a cheap material marketed as a luxury item in audio because audiophiles don't remember that it's used in beer cans.

The machined aluminum cabinets by Magico and Rockport (for example) are both complex and very vexpensive to make. No one applies more engineering to their speakers than those two companies, imo (there are others on par I assume). 

Rockport has combined a carbon fiber exterior shell with an aluminum interior housing for their newest speaker, which saves some money. Their top of the line speaker uses aluminum interior/exterior shells. Magico is all aluminum. 

"Are carbon fiber speaker cabinets inherently better than wood or metal ones"

The answer is no. All materials have specific characteristics and need to be used correctly and in the right application. No material is inherently superior across the board, including aluminum or wood.

Actually Rockport used cast aluminum enclosure sections which is very different than machined cabinets. Magico used extruded and machined section. Their designs have more to do with the implementation than the materials. 

We just concluded a year long evaluation of different materials, including cast aluminum and carbon fiber, for our Gen 2 Apollo speakers. For our speakers design we found that a fiber reinforced molded custom engineered polymer had the best characteristics. Cost is between aluminum and composite, aluminum being the cheapest.

Well I would say yes. Carbon fiber cabinets have a huge advantage over other materials...Sound/energy coming off the back of the drivers should be directed away from the thinnest part of the speaker which is the cone. Carbon fibers when done properly are alined to direct the energy away from the drivers. Energy travels thru them at an astonishingly high rate of speed, from memory it is about 18 thousand feet per second. Wood is about 500 feet per second. 

Carbon fiber resonants at a very high frequency, as we know high frequencies are easy to dampen...ping a fine wine glass and then simply put your finger on the rim to stop the vibration. Heavy cabinets vibrate a lower frequencies and thus are much more difficult to dampen as well as taking more time to dampen, thus the hangover or lag, 

Wilson Benesch has done so much research and development. Check out their site for more info. 

patrickdowns -$2700 a ton for billet, baltic birch ply is about $160 a sheet. If you do the math birch ply is more costly. 

Carbon fiber is a great material for many applications because it is both light and strong. That said, no material has been more overhyped in recent times, and used to make all kinds of junk, from cup holders to toilet seats. But do they use it to make acoustic guitars or violins or a bass viola? That would make me skeptical that it's a superior material for speaker enclosures. I'm sure it's a great sales gimmick that adds lots to the cost of a product that is likely to be priced extra high as a result. But better for speakers? Naw, it's just another material, and like others have said, you have to account for its strengths and weaknesses just as with any other material. I think it is way over-hyped but I'll tell you one thing that I just bought that really benefits from carbon fiber- a photography tripod-- where its strength and light weight really makes a difference. I don't find it all that attractive usually, so it would not be my first choice for a speaker enclosure unless it was painted or coated with something.