Here's what Steve sent me on the eff. mass:
The hardwoods add effective mass and tend to favor lower compliance carts, although only slightly. In any case, don't get hung up on wood choice. It matters very little in sonics and cart choice, unlike most other arms. There are SO many more factors involved in arm/cart matching than effective mass.
I don't have the A-90 any longer so unfortunately I can't make the comparison to the Kansui in the Reed. The Kansui was more natural and solid than the A-90 in my previous VPI 12.5 though.
The hardwoods add effective mass and tend to favor lower compliance carts, although only slightly. In any case, don't get hung up on wood choice. It matters very little in sonics and cart choice, unlike most other arms. There are SO many more factors involved in arm/cart matching than effective mass.
I don't have the A-90 any longer so unfortunately I can't make the comparison to the Kansui in the Reed. The Kansui was more natural and solid than the A-90 in my previous VPI 12.5 though.