What is effective mass of Versa Dynamics 1.2 tonearm

I think what you might need is a way to hook up a paddle in silicone type of damping system for low compliance cartridges with this arm
My ET 2 ( Eminent Technogoly) has such a system, but not needed at present.
You might even give them a call and buy the trough or build one.
Might not even need one, since I have never seen one with this table/ arm combination before
I,m still looking to buy one of these someday

Regards
David
 
It's very short. So I suspect the effective mass is low. I may be all wrong. But, if I am correct, nothing prevents you from adding real mass to both ends of the vestigial arm, increasing the effective mass...

I don't think it is possible to use a damping trough on this arm, possible, but difficult to install, since the arm swings...

_-_-

PS. I would be interested to know the real numbers... also how they are computed.
 
The effective mass is from the pivot to needle with cartridge included. Then when you add your counterweight and balance it all out plus your tracking force, the moment of inertia comes into play.
Unless you know exactly what mass will make your cartridge work, you then change everything by changing how far the counterweight is from the pivot and so forth. Definately an interactive issue with no simple answer
Theres all kind of math you can get involved in with this if you search around and doubt if it will really do anything better than getting out your favorite bass albums and listen carefully for detail down low.
Varying different counter balance weights and distances from the pivot points will solve any issues and be less confusing in the long run.
Your vacuum platter rules out any problems with distance from pivot and the weight may be beneficial if placed further out with very low compliance MC,s
Its a 3 dimensional problem that careful listening will cure this side of test records and instrumentation.

Regards
David
 
The higher mass horizontal point would be lower in frequency, and so somewhat irrelevant?

Is it a good assumption that the horizontal mass is any different than the vertical for this airbearing arm? One motion is rotational the other linear...

And is not the moving mass for most "long" arms going to be substantially higher than for the Versa's very short arm?
 
What groove t says is right. With straight line tracking air bearings you wind up with 2 small resonant bumps rather than one big one that occurs in regular arms

The horizontal mass is considerably higher and somewhat an advantage when you consider what the stylus is forced to do. The needle is carrying and responsible for movement in 2 planes instead of 1 fixed pivot point of regular arms and hence the 2 resonant points occur
The Dynavector 505/7 tried the same thing, with high horizontal mass and another shorter arm with similiar effects due to 2 different pivot points
They also used an internal spring bob and spring to cancel out resonance that worked well but the arm suffered from warp wow because of the short pivot arm transversing warps
The splitting of the pivot points gives you different motional impedences in comparison to one fixed mass over the stylus. You have a moveable weight carried and moved horizontal differently by the stylus compared to vertical.
You wind up with 2 effective masses instead of one
The goldmund would be still be a single fixed pivot point seen by the stylus since a sled is pulled and you still get one resonant point
I sure someone can explain it better

Regards
David

Regards
David
 
What groove t says is right. With straight line tracking air bearings you wind up with 2 small resonant bumps rather than one big one that occurs in regular arms

The horizontal mass is considerably higher and somewhat an advantage when you consider what the stylus is forced to do. The needle is carrying and responsible for movement in 2 planes instead of 1 fixed pivot point of regular arms and hence the 2 resonant points occur
The Dynavector 505/7 tried the same thing, with high horizontal mass and another shorter arm with similiar effects due to 2 different pivot points
They also used an internal spring bob and spring to cancel out resonance that worked well but the arm suffered from warp wow because of the short pivot arm transversing warps
The splitting of the pivot points gives you different motional impedences in comparison to one fixed mass over the stylus. You have a moveable weight carried and moved horizontal differently by the stylus compared to vertical.
You wind up with 2 effective masses instead of one
The goldmund would be still be a single fixed pivot point seen by the stylus since a sled is pulled and you still get one resonant point
I sure someone can explain it better

Regards
David
 
Bear, look at it this way, and this the first time i,m looking at it BTW...,,.

Your the stylus and whether its a unipivot,knife edge, gimbal the mass on top of you is always the same whether you move left or right or up and down.

Now consider that you can only move up and down with very little mass,., no problem!
But now just try to move left and right with way more mass in this direction only!
Only you can move with no other pivot support to help you, and there,s nothing to lessen the load in that direction.
Your the one that must move along this rail that can,t be changed no matter what!
Your horizontal to vertical movement is restricted in comparison

Regards
David
 
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Sure, I see it.

But the question is how the horizontal mass on the short air bearing Versa arm compares to a typical 9" or 12" arm?

And, generally speaking two small resonances may be better than one larger and/or higher Q one.

Either way the stylus has to "drag" something... the question is how much, I suppose.

Inertia is something to consider as well...

The Goldmund and things like the earlier Rabco used gimbal type arms but with a sled that tracked, the idea is to minimize maximum tracking error.
 
The vertical mass of the short arm can be trimmed to Fres apx 11Hz with Wight and Counterweight. Lou Souther demonstrated this 30 years ago.
This Fres must be trimmed, otherwise tons of problems with warped records, next that the wow & flutter is much worse than with a long arm.

The horizontal mass is given and the Fres can calculated with compliance of cartridge, with shoul be basically low, otherwise you below 7 Hz and get real problems with some warped or not well centerd records.

The Goldmund acts like a pivoted arm, the sled weight is absolut not important, it is controlled by servo.

There is big difference between real mass and effective mass.

Short arms are very critical in adjustment and very critical when records are not absolute flat.
Two resonance points creates two problems and there is some interaction.
Thats why i avoid the short arms strictly, altough they can sound good with ideal pressed and flat records. My records are almost not perfect.
 
Vacuum Pumps are usually noisy and need some maintenance.
Vacuum hold down records have lesser warp in the 2 - 6 Hz Range , but shorter warps and bumps from 8- 20 Hz are still a problem, altough maybe slightly reduced.
Luxman did vacuum hold down also, but new problems appeared, some records were damaged from the sealing gaskets and the cheap vacuum model lost the vacuum after 10 minutes..
Some records are also excentric.
Thats why nakamichi created the TX 1000 Turntable with excentercompensation.
 
These are some stated and measured resonant frequency,s for various mc cartridge compliances and counterweight combinations
.................................natural frequency.............counterweights

............................vert...horizontal
45 x 10/6 cm/dyne 10hz. 3.5hz Only large

15 x 10/6 cm/dyne. 13hz. 5.5hz Only large

15 x 10/6 cm/dyne. 12 hz 4.5hz Small & large

These are from a manual for the original ET1 from Eminent Technogoly
They stated that the design doesn,t allow what is happening in the vertical domain to contribute to the horizontal plane. They have graphs and pics to prove it so.

As mentioned a vacuum platter is mandatory with any short arm and a good idea anyway regardless. I use a Sota Star vacuum personally and it makes a difference along with the ET2

Regards
David
 
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