Confused about compliance matching with airbearing

If you are concerned about lateral mass, contact Dave Garretson via this site or via Audio Asylum. With his custom-made parts, he has taken it down way below 80 gm for the Terminator. I expect he will chime in here anyway. He is using a high compliance Pickering and some others.

I am not at all clear on the significance of lateral mass. There are posts on the internet to indicate that ADDING lateral effective mass, e.g., by fixing weights to either side of the pivot (in a pivoted tonearm, of course) has a beneficial effect. Persons who comment on this mod do not mention a differential effect for low vs high compliance cartridges. Indeed, there are several classic Japanese tonearms that incorporate the same idea, e.g., SAEC. The Dynavector tonearms (old and new) are designed deliberately to have a high mass in the lateral plane, and this is touted in their brochure as a benefit of their design without regard to cartridge compliance. On the other hand Fremer often comments that a disadvantage of most linear tracking arms is their inherently very high mass in the lateral plane. The equation for resonant frequency does not contain a term for lateral effective mass, only vertical (if memory serves; I did not check this), so I don't see that lateral mass will affect resonance. Yet, it is not hard to see why a high lateral effective mass might place undo stress on the cantilever of a high compliance cartridge as compared to a low compliance one, just as high bearing friction in the lateral plane could also do. As far as I am concerned this issue is very muddy.

It just occurred to me that Fremer cites the large differential between mass in the vertical and lateral planes as being likely to cause vertical and lateral resonance to occur at two very different frequencies. I am not sure that's a bad thing, if the two frequencies are favorably related to each other so as to broaden and flatten the net resonance. Nor do I know how the formula for resonance in the lateral plane compares to the one for vertical and how it takes compliance into account, if it does.

For those with a technical bent, John Ellison described a simple and clever way to measure actual tonearm/cartridge resonance, over on Vinyl Asylum. I suspect you can find it by searching on "resonance" or something like that. But you do need some tools to do it.