General question on Carbon fiber tonearms versus aluminum

Carbon fiber definitely sounds better on odd days of the month, and aluminum on even days.  This is especially true when you hear the tonearm installed on a turntable you don't own yourself, with  a cartridge you've never heard before, and played through electronics that are new to you.  The best way to get an accurate comparison on material performance!

We do every thing we can to insure that the only movement/vibration that occurs is the tiny magnet or coil within the cartridge.

This transcends throughout the system all the way to the cantilever material: less weight, higher stiffness best.

Tonearms with maximum stiffness: Carbon easily wins over aluminum, it’s calculated differences are shown here:

https://dragonplate.com/carbon-fiber-vs-aluminum

Carbon is -40% density; +70% specific stiffness +289% specific tensile strength.

To achieve a total tonearm weight, to meet a design goal, carbon can be thicker. In any material, thickness increases strength.

My 12.5" effective length arm is Carbon, and the designer can use a greater thickness to achieve his design goal. So, carbon in equal thickness is much stiffer, increase it’s thickness, it is extremely stiffer.

Carbon is the viagra of tonearms.

Looked at the other way, to keep weight down, aluminum must be thinner, thus weaker, thus less damping, less attenuation of vibration.

Pro-ject uses a combination of carbon fiber and aluminum in some of their arms, although the 9cc is full carbon fiber. Linn used the arm on their majik turntable model, so they must think its a pretty good arm. Same arm on my music hall mmf-7.3. My other table is the pro-ject the classic sb with the combo CF/Aluminum 9 inch arm, I honestly hear no difference in sound quality. In my opinion, both pro-ject and music hall provide the most value for one's money today, unless you are rich and splurge for a 10k or more table. They have been very well reviewed in countless periodicals. 

Had Infinity Black Widow which is carbon fiber now i have TW ACUSTIC 10.5 which has better bass,midrange,depth,detail and dynamics.

Note that I and several other very experienced listeners have independently come to the same conclusion regarding carbon fiber in the vinyl reproduction path. It tends to kill the liveness of real music. Theories involving stiffness, hardness, compliance, damping, and blah blah blah are meaningless compared to actually listening to music. Theory is useful after the fact, to explain what you thought you heard.