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

l have owned a Kuzma 4Point arm for a few years now mounted on a Kuzma Stabi XL2. l have the opportunity to change to a Kuzma Airline and was hoping to hear from members who have heard both and whether they think the switch is worthwhile. There is not much l can find on the net comparing the two.

For a similar cost l could add two motors to my XL2 converting it to an XL4, could the upgrade there be more significant than the Airline vs. 4Point?

Interested to hear fellow 'Goners opinions.

I had one of the earliest 4 points and liked it very much. But the airline is the much better arm. Nevertheless you should be careful on the matching with carts in a linear tracker (regarding rubber parts etc.)

best & fun only - Thuchan
The 4P is an excellent example for engineering which fails the sonic spot by a mile. Soft dynamics, soft soundstage, everything wrapped in clothes, a real sleeper, one of the biggest disappointments I ever listened to. But probably the right Arm for harsh, shrill reproduction Systems. It will compensate a lot.
The Airline has one big advantage: It shows the user that such a Design can work. It is better from dynamic response than the 4P (no big deal honestly), better soundstage but it won't tell you anything new when you have one of the better Arms. For that money my favorite was the DaVinci Arm.

One of my friends owns that XL Table with 2 motors, he loaned 2 more and gave them back. He said, it it not worth it (for him). He also owns a Airline.
Appreciate the replys.

l am running a ZYX 4D on the 4Point and do not find it soft in Dynamics but then its really the only high quality arm l have ever owned. l will not have the opportunity to listen to the Airline on a comparable deck prior to purchase but you both are in agreeance that the Airline is the better bet.

Syntax, great feedback on the 2 motors vs. 4. The motors would have to be imported so again, the first time l will hear them in my system is when they are mine :) Seems like the Airline is a better bet.

What kind of music do you listen to most? Be careful exciting an Airline too much. There is no place for vibrations to go but back into the cantilever if it gets over stimulated. Most definitely try before you buy.
No problem with vibrations in the Airline. I listen to Rock & Jazz Music. Currently I am driving a London Reference with it. Just a great combination!

In comparison to the ET 2.5 - which I regard as one of the really brilliant mostly underrated designs - the Airline is easy to adjust and maintain. Another story is theVacuum pump which you need using in a different room.

agree with Syntax, the 4Point is more on the soft side. If you decide going not for a linear tracker I would look for a Talea or Reed rather than deciding for a 4P. I have seen on the High End in Munich a new arm built by Frank Kuzma but so far I have no experience with it.

best & fun only - Thuchan
Music is rock and alternative (whatever that is these days!)- nothing too heavy or out of the norm. Setup and compressor noise are two concerns, l am pretty limited on compressor placement due to house layout and construction. Setting it up in a cupboard in the listening room with a wooden box over it might be easiest.

The arm has to be perfectly level and that worries me a little, my rack is very heavy and on 4 spikes, a real mongrel of a thing to get level, l understand the Airline is very sensitive so that could be tricky.

If the 4P is considered soft then the Airline might be a very worthwhile upgrade.

Thuchan, those were my thoughts. Cartridge matching would be very important. I see the FR-7f is 30grams and low compliance. Yeah, heavy cart would be my guess also. However, I might tend toward more compliance. Stone body Koetsu comes to mind.
Since Kuzma sells (or used to)rebraded ZYX carts l reckon my 4D is a pretty safe bet on an Airline.
Syntax, the 4Point is not as you describe. Perhaps there was a gross mismatch with the cartridge, or maybe the cartridge was poorly set up or imcorrectly loaded. Big, bold, dynamic, tonally rich, low noise, and nuanced are what my customers and I hear. But don't take my word for it: certainly in this price range one should pursue an audition.

Dealer disclaimer.
Thanks for the feedback in this thread. l have committed to buying an Airline so will have all the answers in a week or so :)

congrats Mondie! if you are balancing your TT after mounting you may use small paper leaves (double or more sheets) to put it under one of the TTs edges - just to reach a fully balanced condition. This is helpful for the best working condition of the Airline.

best & fun only - Thuchan
I just read Mikey's review of the Kuzma 4Point in the September Stereophile.

I am always intrigued by clever design and technology. (I really enjoyed reading and understanding the design of the Well Tempered Turntable and Arm. Also the Garrard Zero 100 from earlier years.) The review suggested that the Kuzma 4Point was innovative and clever in its design.

But for the life of me, I could not understand Mikey's description of the bearing. It was completely opaque to me.

I am glad to find that some of you have some experience with this arm. Can you share with me your understanding of how the bearing is implemented? I am intrigued and itching with curiosity!
Jameswei: "Can you share with me your understanding of how the bearing is implemented? I am intrigued and itching with curiosity!"

2 points + 2 points = 4 points

Extra point: HiFi Plus review by Roy Gregory.

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.

Aha! Finally, I understand it. Thank you Hiho for your pics and comments; they really helped me a lot.

In your post, you have "2points + 2points = 4points" pics. The "4points" pic shows the pivot structure with two vertical cylinders. The big cylinder is clearly for VTA adjustment.

The small cylinder is a hollow sleeve that encloses a vertical post upon which it rests. The hollow sleeve contacts the vertical post inside it at two points, as shown in the second "2points" pic, where two hands are holding an unpainted cutaway cylinder horizontally. The two points are (1) at the end of the post and (2) from the side, with a spike touching the post near the other end of the cylinder.

The first "2points" pic shows the arm upside down, revealing two small spikes (like rose thorns) sticking up. These apparently will rest in two cups, shown in the "4points" pic. The two cups are in the horizontal base attached to the smaller vertical cylinder.

Thus, the arm will rest on the two rose thorn spikes on the base attached to the cylinder. And these spikes allow the arm to pivot the head up and down. Additionally, with the base attached to the smaller cylinder, the arm can pivot horizontally because the smaller cylinder can turn about the post that is captured inside of it.

(As you point out, the partial cutout in the post, where the second "point" contact is made inside the cylinder, causes the horizontal pivot movement of the arm to be limited to only 45 degrees.)

I can also identify now the damping troughs, both of which are accompanied by screw-rods secured by knurled-wheel nuts.

Upon further thought, I perceive that the second "point" inside the cylinder must be weight loaded because the arm is resting on the base to the side of the cylinder. This would cause the cylinder to want to tip sideways, and the second "point" inside the cylinder prevents that, keeping it vertical.
In my view the use of the word unipivot is misleading - the 2 vertical bearings are like a double knife edge as in the early SME's except that they are points/cups instead of knife edge/groove. Unlike a true unipivot the whole arm tube will chatter with a low compliance cartridge..
Dover, the comparison of two points with a knife edge is flawed since the force is concentrated at two points, not over what is presumed to be a line but due to machining accuracy and tolerances cannot have the forces uniformly distributed.
Dover: "Unlike a true unipivot the whole arm tube will chatter with a low compliance cartridge.."
Conceptually similar to SME but I don't see how two needle points sitting on two cups with the entire mass of the arm preloading the bearings can chatter or chatter to the level of conventional gimbal bearings. I agree with Brian.

I did not say it is a unipivot but clearly and explicitly the designer had the concept of unipivot tonearm, which Kuzma also makes, in mind. Check specification page. (Sorry about the early post that I uploaded the wrong spec image.)

Hi Essential, yes I agree with the line analogy, but my thought was that with 2 points of contact the arm could potentially chatter - does seem a halfway house between captured bearing and unipivot, which may be a good thing, but I guess my point was it is not a unipivot.
In this bearing set up, the positioning of the two rose thorn spike tips must be exactly in the centers of the two cups in the base. In a normal unipivot, the spike point "finds" the center of the cup, but with two spikes, one spike will probably find its cup's center while the other spike will fall where it may.

Of course it is very important that the other cup be centered exactly where that other spike falls. If it is off by even a little bit, there will not be a properly rigid contact, and chatter could result.

In other words, the distance between the tips of the spikes must be exactly equal to the distance between the centers of the cups. They must not be off by even a little bit. I see from the first "2point" pic that one spike tip position appears adjustable since there seems to be a set screw for the spike.

Perhaps there is some step in the setup procedure that ensures both spike tips are completely centered in their cups.
Jameswei: "In other words, the distance between the tips of the spikes must be exactly equal to the distance between the centers of the cups. They must not be off by even a little bit. I see from the first "2point" pic that one spike tip position appears adjustable since there seems to be a set screw for the spike."
Very good point, Jameswei. I think as long as one spike/cup contact is secured, the other one may fall wherever it may be in the cup and still not chatter, though not as elegant. Another solution is on the female side to be one cup and the other a groove and this way the tolerance need not be so tight. The Morch DP6 tonearm is a two point bearing design and one spike/cup is height adjustable in order to change azimuth. Perhaps the set screw on the spike of the Kuzma 4Point is for that too.

The Origin Life Encounter tonearm is also a two point bearing design that does not allow azimuth change at the bearings and they are factory set to ensure perfect contact.

Hiho, I was not able to connect using your "Origin Life Encounter" link.

Perhaps you wanted us to see this page --

The Morch DP6 tonearm is a two point bearing design and one spike/cup is height adjustable in order to change azimuth. Perhaps the set screw on the spike of the Kuzma 4Point is for that too.
Adjusting one of the spikes to adjust azimuth has some problems. For one, it is a relatively crude adjustment. For another, adjusting it would very slightly increase or decrease the distance between the points (Pythagoras' theorem).

The 4Point azimuth adjustment is accomplished nicely via the grub screw in the bottom of the arm tube which is perpendicular to it, seen in the photo of the upside down arm for the purpose of showing the vertical bearing spikes. The section of the arm tube near the pivot is about 1 1/4" long, to which the rest of the arm tube is attached. Very fine azimuth adjustments are possible.

Yes, Jameswei. That is the link. I was very sloppy with my links. Thanks.

Here's the jpeg link explaining the Origin Life tonearm.

Don't take me wrong but it seems funny to me that MF discovered the 4point as the last in the row :-) To have a fair comparison one needs to run both arms (Airline and 4 point) on similar TTs with the same arms and carts which I did. Memories from a test long time ago are not a great support for real comparisons.

best & fun only
Thuchan -- "Don't take me wrong but it seems funny to me that MF discovered the 4point as the last in the row :-)"

You make a good point about too much time passing between reviews to make a reliable comparison.

Part of it must be that the 4point was introduced years after the Airline. Or so I seem to recall.
Jameswei, you are right, the 4 Point arrived later, at me in May 2008.the Airline I have since December 2005 (I believe it came to market in 2004). It was one of the first units of the 4 Point I received and it was a pleasure to compare both units. In the meantime Mr Kuzma did some small improvements on the headshell etc.

best & fun only
So, sorry to revive ancient history, but where did you guys come out on the Airline v. 4 Point debate? Did anybody have both set up at the same time for comparison? I've been using the Airline for a while, the arm is great, the pump is a PITA. I'd love to get away from it, and go with something that requires less attention, but obviously, I'm not interested in compromising the sound. Thanks and hi syntax, nice to see you.
Hi Whart,
sad to hear that you are not in love with that pump :-) The one I had worked
day by day without any problems or noise (there was an additional valve which
can be closed to reduce noise). Normally it is simple to replace the unit (I would
do that). There are lots out there which are used for dental labors and they
aren't expensive.
Syn: it works fine, but it is noisy, it is in an adjacent closet to the music room, and there is nasty electrical snap when it cycles, even with the extra relay Kuzma provided- the only way i got rid of the electrical snap was to plug it into a big 240 volt isolation transformer! I did reach out to Scott M re the upgraded pump, which has a bigger tank, and arguably requires fewer duty cycles, but i thought if I could go 'pump less' there might be joy! When i move, i could relocate the pump to the outhouse or whatever, but I'm trying to simplify my life.
btw, just got the lamm L2 back in the system, and it is kicking some serious ass with the Allnic H3000, which is now further along in its break in cycle.
Still be curious if anybody did a direct compare between the Airline and 4Point for sonics.