- Regarding I-beam and weights: I often used BluTak to adjust or increase the counterweight mass to a certain degree and never felt it was compromising the sound in any way. I also form tiny balls of ca. 0.05g (or less) to precisely adjust the VTF in a repeatable way (by putting on and taking them away). For this I measure these balls on a 0.01 precise Mapleshade scale. BluTak is simple & very practical.
- On the website of the Adanalog MG1 arm – which is similar to the ET2 – several of the user images show Lenco drives with new plinths, and I heard very good sounds from a Lenco / Reinders PTP / limestone plinth with an MG1 arm.
In my experience idler wheel or direct drives work very very good for air bearing arms, ie. optimal. (Better in my system than a very good Merrill Heirloom, a medium weight belt / subchassis ET 2 combo).
- I think this has to do with the tendency of a belted subchassis to slightly (counter-) rotate around the platter axis at low subsonic frequencies and the way this continually decenters the air bearing a bit, compromising (to a certain degree) bass quality and others. The very low horizontal resonance of air bearing arms adds to that effect.
A radial arm has the center of its horizontal mass (almost) in the rigidly placed bearing and so the cartridge/arm combo is not displaced by horizontal accelaration (or much, much less).