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Hi Konstantin, hello bear,
My bearing(single or divided string) can be built to have a restoring force(in regard to VTF), to be completely neutral or to exhibit an unstable character.
The determining factor is the size of the magnets and the attachment point of the thread relative to the magnet. On the SQ version of the Reference arm, changes in VTA will not cause changes in VTF, despite the increased stability around the armwand axis. To achieve this, the top magnet's "face" is barrel-segment shaped, the bottom magnet's face is semi-spherical.
The actual attracting force is always lower than the maximum "holding" force obtainable from a given set of magnets. In typical setups, the effect would be similar to having 10-12kg hanging from that thread, BUT, in reality, the total suspended mass is no higher than 300gr for a 12" arm with a heavy cartridge(~230gr for a 9,4"er).
Energy storage is considerably lower than on a similar size, unipivot arm that mostly relies on a mass loaded pivot/cup assembly.
Many gimballed arm are far superior in that respect. The RS-Labs arm or earlier Roksan arms with detached counterweights have a very tight bass(no overhang, often mistaken for "bass power" or "solid low frequency foundation") but the dangling counterweight can cause wavering images and puts additional stress on the cantilever suspension.
When the bearing is built to be "self restoring", the actual pivot point is below the bottom magnet, not at the lower exit point of the thread. This helps to reduce or even eliminate warp wow, without having to build the arm like the original Immedia arm(pivot point at record level).
I've elaborated on the following many times: Though I have used pretty much anything obtainable* to build armwands out of it, certain kinds of wood(or laminates) remain the best material for an arm that cannot rely on "draining" energy via it's base. Waterfall plots show what one can easily hear too: Some woods exhibit a high amount of broadband damping with no spikes or elevated areas.
Impregnating the wands increases the damping further(off course Konstantin is correct, there will never be a 100% nonresonant structure)and insures dimensional stability.
Others are the exact opposite. There are no "sympathetic" resonances, any resonance is plain detrimental to the original signal. A tonearm is not a music instrument, it ought to be seen like a measuring instrument(imho).
DIYers, stay away from kiln dried wood if you can. Go to an instrument maker(guitar, woodwinds...) and ask for a leftover piece, AIRDRIED for at least 10 years. When you tell them what you need it for, they might even give it to you for free...
* I also tried various types of ceramic wands. At the time, they all exhibited considerable ringing, newer generations can be made to be physically extremely inert(through varying thickness, pre-stressing...)
The restoring force(a change in VTA causing a change of VTF) observed by Konstantin is what you'll get when you buy or build a unipivot arm(Bob Graham's Phantom is an exception), due to the center of gravity of the arm/counterweight assembly being situated below the pivot point. The distance between the two and the associated mass determines the extent of this effect.
But you should reset VTF when changing VTA on most unipivots or other arms with "low slung" counterweights.
Krishu is correct, the term Schroeder "clone" is a misnomer. There are several features of the original which I have yet so see realized or written about by DIYers. But since nearly all who built "their" Schroeder arm seem to like it better than what they'd used before, I can go to sleep with a smile
Greetings from Berlin,
Frank
http://www.diyaudio.com/forums/analogue ... rm-15.html