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

@lonemountain: Right you are! To see how NOT to build a speaker enclosure, look inside a Tekton (no offense owners of them. They have their strengths, but a non-resonant enclosure is not one of them).

Another cost-effective way to damp enclosure wall resonances is a product designed by and made for Danny Richie of GR Research: NoRez. It has a  damping layer (with self-stick adhesive for attaching to the wall) topped with a 1" thick layer of open cell foam.. For an even cheaper method, Danny recommends gluing heavy floor tiles onto the interior walls. That works especially well with open baffle loudspeakers, which don't need the foam layer.

Make your loudspeaker enclosure braces out of carbon fiber if you want.

@sounds_real_audio: Incorrect. The primary and most important reasons for and benefits of bracing is to:

1- Minimize the ability of the enclosure to expand (like a balloon being blown up)---thereby propagating sound---in reaction to the internal pressure created within the enclosure when the drivers move inward. That pressure is extreme, like a pot of boiling water with a tight lid on the stove with a high flame. Wall-to-wall braces prevent the enclosure from doing that. Again, look at how Jim Salk braces his subwoofer enclosures, and how Magico braces their loudspeaker enclosures.

2- Raise the resonant frequency of the enclosure panels to that above those excited greatest by the most problematic of the enclosure frequencies---the low ones (bass).

The most cost-effective way to reduce enclosure and/or panel resonance is to brace like Hell. Look at the bracing Jim Salk uses in his subwoofer enclosures (into which he installs the Rythmik Audio 12" or 15" DIY kits).