General question on Carbon fiber tonearms versus aluminum

@slaw Why would one material sound better with MC cartridges than MM?  

@testpilot Agreed, although  I was thinking more in general terms.  That is, it could be easier to make a better sounding tonearm with CF than AL.  Clearly, it is that way with bicycle frames, it is far, far easier to make a frame stiff in one direction and flexible in another with CF, or make it a more comfortable ride with less vibration than say AL or even steel.   

This has been a very interesting and enlightening post.  Earlier when I made a comment about bicycle frames, a lot of what was mentioned in this post echo's what folks have found comparing frames made of steel, aluminum, and carbon fiber.   Granted, early fiber bicycles were not as good as steel or aluminum and had a tendency to crack and break, but over a ten year period, it is hard to beat fiber today for a  comfortable ride, yet still have a frame that climbs like aluminum, and is non fatiguing like steel.   With carbon, the vibrations that come up from the pavement dissipate (think damped) and don't tire your legs, arms, and butt like aluminum.  But climbing hills, the last thing you want is a soft frame as what little horsepower you develop goes into making the frame bend rather than to the rear wheel.   Try riding 100-120 miles in a day, climb 10 to 12,000 vertical feet, and do it in high altitude and this lesson will be branded in your brain.   That was my basic training ride back when I did extreme endurance  cycling.

This is pure speculation on my part, but it is possible that the live sound from aluminum, if indeed  it is from the arm itself, could be energy from the cartridge that is causing the arm to color the sound in a rather pleasing way.   The dead sound from fiber, if indeed it is from the arm itself, could be the lack of this coloration.  If you remember, Ray Dolby had the same problem selling his Dolby Noise Reduction to tape manufacturers.   That subtle lack of noise and distortion in the upper frequencies were considered a lack of "air" and consequently colored the sound in a bad way.  He had a real problem for a while until folks realized what he was selling was a lack of coloration and distortion.

Frankly, I don't know which technology is better.   The best sound I had was from my aluminum Grado arm and top tier Grado cartridges.   The carbon arm got the second rate cartridges.   Recently, I upgraded cartridges and now that carbon arm is producing the finest sound my stereo has ever produced.   The Grado setup sounds great and I would be very happy with it, indeed it is better than ever, but I do have that carbon setup right next to it and it beats Grado in a noticeable way.   

It is a tough call since I'd like to upgrade my arm to a modern, transcription length unit.

@cleeds Thanks for pointing that out.  The Dolby equalization curve concept is no different than the RIAA concept we all live with when we play vinyl.  There is a Dolby pre-equalization of the music and a post equalization when playing, which reduces hiss.   RIAA pre-equalization and post equalization reduces surface noise.   

Since I wrote that first post, I realized I forgot about Titanium.  My first high end tonearm, a SME III, had a titanium tube, as do several tonearms today.   So, we have Carbon Fiber, Aluminum, and Titanium to consider as tonearm materials which can influence sound.