How Can I figure out my Effective Tone Arm Mass??

Effective mass calculations are not only considered in the initial tonearm design criteria, but also in the weight of the raw tonearm components. Also, effective mass is established in the static and axial weighting of all components comprising the tonearm assembly. Tonearm mass and cartridge compliance go hand in hand.

What tonearm are we discussing?

A Systemdek Profile tonearm on a Systemdek llX TT. It will go eventually but right now I want to get the TT going as best I can. I have 2 cartridges; A Grado Sonata and a Denon DL103. The first is light and the Denon is heavier. So I am trying to figure out which one would seem to be a better match.

You can use the method Dougdeacon described and look up the chart at the bottom of the FAQ posted on the VDH web site. This FAQ also contains over 200 Q&A covering almost everything related to vinyl playback, some of them are quite insightful.

http://www.vandenhul.com/artpap/phono_faq.htm

Great info, thanks!

The Profile arm is an OEM model made by Sumiko in the 1980s, for the lower cost audiophile market. It is a medium mass tonearm, and the bearings are designed for mid-compliance type cartridges. Therefore it would be better matched to the Grado, because the DL103 will chew the bearings up in that arm. You have to have top grade bearings with close tolerance adjustment for a 103. However, it may be not be the greatest match with the Grado either. It could hum because the Systemdek has the motor under the platter, which is known to induce hum in Grado cartridges. I'd suggest a Goldring 1042 or a Dynavector 10x4 or 10x5 for that tonearm.