The only thing a resonance frequency test and/or compliance formula can tell you is whether an arm/cartridge combo will resonate inside or outside the the "preferred" 8-15Hz band. This simplistic piece of data rarely has much effect on sound quality.
Still, to save you time and trouble, here's the answer:
18gm effective mass is a medium mass arm. As such, it will accommodate the large majority of contemporary cartridges (including ZYX and many MMs) without exciting resonances outside that so-called safe zone.
No mathematical formula or resonance test will help you find a good sounding cartridge. There is no "perfect" cartridge for the Reed or any other tonearm. Stop looking for certainty or objectivity where there is none.
The important question is this: how does the tonearm interact sonically with various cartridges. This has a far larger effect on music reproduction and it can't be measured with any test record or formula. That's the kind of user feedback you should be hoping to receive.
Still, to save you time and trouble, here's the answer:
18gm effective mass is a medium mass arm. As such, it will accommodate the large majority of contemporary cartridges (including ZYX and many MMs) without exciting resonances outside that so-called safe zone.
No mathematical formula or resonance test will help you find a good sounding cartridge. There is no "perfect" cartridge for the Reed or any other tonearm. Stop looking for certainty or objectivity where there is none.
The important question is this: how does the tonearm interact sonically with various cartridges. This has a far larger effect on music reproduction and it can't be measured with any test record or formula. That's the kind of user feedback you should be hoping to receive.