Eminent Technology ET-2 Tonearm Owners

Chris. Thanks for the comparison notes. I now have a clear picture of the differences.

The Dynavector arms have always been fascinating to me due to their radical design. Magnetic dampening and for a pivoted arm the unusual idea of deliberately different effective mass in the vert and horiz planes. Both of these features being recently discussed in this thread.

Have only listened to 2 of these beautiful arms and in systems that I am unfamiliar, so cannot draw any concrete condclusions.

I have included a quote here from their manual on the 507 should anyone be interested.

• 3 Bi-axis inertia separation for accurate signal reproduction and superb tracking ability
"Bi-axis inertia separation" may sound complex but it simply refers to a tone arm having two arms which operate independently in the horizontal and vertical planes. In contrast, a conventional tonearm has only one arm which moves both horizontally and vertically. This is called a gimbal type tonearm and the inertia for both planes is the same.
The DV507 bi-axis tone arm has a large inertia for horizontal movement and a very small inertia for vertical movement. We shall now explain the reasons why this is advantageous.
It is well known that a cartridge generates an audio signal by the differential motion between the cantilever and the cartridge body. Consequently, if the supporting point of the cartridge (the tonearm) vibrates, the tonearm motion affects the audio signal.
In these conditions, the signal, which causes the tonearm to vibrate is of low frequency and large amplitude.
In the currently used 45-45 stereo record cutting procedure, low frequency signals are almost entirely recorded in a horizontal direction. This means that the low frequency signal, which can cause vibration in the tone arm, exists only as a horizontal force.
The tonearm therefore must have sufficient effective mass and rigidity in the horizontal plane in order to provide a stable platform for the cartridge.
On the other hand, for the mid to high frequencies, the effective mass of the tonearm should not be too large since the combined mass of the cartridge and the head shell need to be taken into account as well. In particular, where records have a warped surface, the vertical effective mass needs to be small enough to ensure a good tracking ability on such surfaces.
To summarise, the tone arm should have a large effective mass and enough damping in the horizontal plane and at the same time a small effective mass in the vertical plane.
These conditions are almost impossible to achieve with a tone arm of conventional design using a simple gimbal pivoting system. To solve the problem, Dynavector designed a bi-axis, inertia controlled tonearm where the shorter and lightweight vertical sub arm is placed at the end of the horizontal main arm. This is the special feature of our design.

Richard, To take advantage of the Dynavector tonearm design wouldn't it require a cartridge with different compliance in the two planes? Otherwise wont only one plane will be optimized with the Dynavector arm?

Richardkrebs/Chris :
Magnetic Dampening vs Mass.

I have been away on business and my responses have been brief. I can now expand on my previous comments.

With a lower mass the arm will move more rapidly initially to align with the eccentricity of the record, minimising cantilever flex.
The magnetic dampening only commences its action once the arm starts moving, and is proportional to the rate of movement. I should point out that the dampening is created by eddy currents which are only generated when the arm moves relative to the magnet.

By contrast, adding mass means the arm will not move until the driving force from the eccentricity is enough to overcome the higher inertia. This increased resistance to movement from the added mass means that the cartridge cantilever is forced to deflect to keep the stylus in the groove. This defeats the purpose and advantage of an air bearing tonearm - the uninhibited degree of freedom to accurately track the groove.

This higher mass is not dampening, it is increased inertia - a resistance to movement.
Magnetic dampening is dampening the arm motion once the arm has commenced movement.

I'll restate this :
Magnetic dampening allows the cartridge to move to the correct position in a damped fashion.
High mass means the arm wont initially move, inducing the cantilever to bend.

Any excessive cantilever deflection in a moving coil will result in phase anomalies as the coils attached to the cantilever are driven into a position where the response becomes non linear.

Furthermore, with the higher mass, once the arm starts moving, the lateral movement is undamped. Cartridge overshoot and more cantilever flex is inevitable.
With magnetic dampening the lateral movement of the arm is always damped when moving.

Dover.
I pretty much agree with everything you say. Where we diverge is in the sublties. It is easy to add too much mass in the horizontal plane. I went there in my tests. The trick is finding a compromise point.
Dynavector put the reason for high horizontal mass far better than I could. I agree with their conclusions.
Sarcher30 Dynavector's quote covers their views on this.
Further, from memory, the ET in standard form has a horizontal to vertical effective mass ratio of around 6:1. So it is already a differential mass arm. It is just that in my view this ratio is not enough. As per before I don't care what people think about this, they are free to give it a go, or not.
Also as before, I like what Mag dampening does right, I just cannot put up with what it does wrong.

“Magnetic dampening will vary with the speed of horizontal motion whereas the added mass approach is simply increasing static inertia considerably.”

"The magnetic dampening only commences its action once the arm starts moving, and is proportional to the rate of movement. I should point out that the dampening is created by eddy currents which are only generated when the arm moves relative to the magnet."

How was no static magnetic effect achieved: did you switch off the magnet?