Kuzma 4Point vs Airline - is it worth the upgrade?

jameswei: glad you said that on mikey's bearing description. I read it about 5 times over 3 days trying to figure out what I was missing ! Now I don't feel (quite) so stupid!

It is interesting the polarization on this arm. Some I respect above have a different opinion....I know lot's of variables...but surely not to this degree so I am assuming matching is critical overly ...

Hiho, thanks for the pics ! Now I understand the bearing! So Mikey kept saying chatterless...seems like their can be chatter is this bearing to...maybe he means less via the 3 points in a cup. 4th on a post...

Jfrech: Two bearing points are the horizontal plane and are permanently hidden, and two points are in the vertical plane. The latter are clearly visible and are akin to two inverted unipivots. It's obvious when you see it.

Kuzma dealer.

Hiho, thank you as well. The photos are very helpful.

Jfrech: "So Mikey kept saying chatterless...seems like there can be chatter in this bearing too...maybe he means less via the 3 points in a cup. 4th on a post..."

I think you got it confused. It should be 2 points for vertical and 2 points for horizontal movement.

The whole point (pun intended) of this design is not to use any ball racing bearings and/or gimbal bearings. The concept is derived from unipivot style bearing but using 4 of them. It's like 4 unipivot arms merged into one to combat unnecessary azimuth/torsional movement. 4 spikes in 4 cups, very simple and effective and cleverly arranged. Check pictures below.

The two spikes are for vertical movement so there are only two contact points, low friction and no ball bearings that can chatter. On the pivot post, the female part, one spike is on the top for horizontal movement and another spike for keeping it from swinging around. So the whole column can only rotate about 45° which is just enough for a pivot to swing from rest position to the spindle. It's an ingenious design that allows the lowest contact points (4) without resorting to a unipivot (1) that exhibits azimuth movement. On top of that, both vertical and horizontal motions have fluid damping troughs so each can be damped individually, whereas typical unipivot or gimbal arms damp both at the same time. Again, clever. Also notice the two cups are located not at the middle cross section of the column? It's intentionally off-centered so whole arm's mass is concentrated at the horizontal spike. Essentially all 4 points are preloaded with mass. Simple and clever. Oh, don't forget the two spikes for vertical bearings are positioned 19.50° off-centered (less than typical 9" arms at 23°) to match the headshell so VTA would not affect azimuth angle. Also nice. The bigger counterweight is on the same horizontal plane as the two vertical spikes so render the arm neutral balance without any pendulum effect, low inertia. Good.

Some more pictures:

4 point locations & Specifications

I am not surprised by the positive reviews as it clearly shows, to me at least, good engineering in many parameters of a good tonearm. The designer has done his homework. As for the negative reviews, it maybe is in the material and execution, over damping, wires, energy transfer, etc..., anything is possible. Since I don't have the arm to play with, I have no comment on the sound. The above is only my observation. From what I saw, Mr. Kuzma has earned my respect as a designer. Tonearm design is fun to look at and think about for me. As a student of the art, it's nice to see some clever thinking these days.

Have fun.

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