Reed 5T Opinions

@lewm , yes you did. Sorry about that. 

@dover , yes, I am talking about any air bearing arm. The problem is that the vertical effective mass of these arms is much lower than the horizontal effective mass. The cantilever, the suspended part, has to move the tonearm in two directions, up/down and side to side. Up/down the cantilever only has to move (suspend) the wand, bearing housing, counter balance, headshell and cartridge. The masses farthest away from the fulcrum have the most significance. In the horizontal plane there is no fulcrum. The masses of everything mentioned above plus the mass of the air carriage count in full force as they all have to move the same distance as the stylus. It does not matter if there is no friction. If you tune the system so that the vertical resonance point is within reason the horizontal resonance point is going to be very low, 2-3 Hz. What happens is the cantilever starts moving towards the spindle and it takes a bit for the tonearm to respond. Once it starts moving the cantilever has to stop the arm, the arm overshoots and the cycle repeats. Under every circumstance I have looked at you can actually see this happening. The cantilever shifts back and forth. Even if you can not see it the stylus is oscillating from one groove to the other. You can attenuate this by adding a horizontal damping trough which some arms do but then the right channel groove wall has more work to do moving the arm through the damping fluid, the opposite of skating. There is no good way to make this work. Straight line trackers that move a more or less standard arm along in a mechanized carriage is theoretically a better way to do this if the mechanism can be kept quiet and reliable , The B+O table is an example. The Reed arms and the Schroder LT side step both problems by moving the bearing housing of the arms along a specific trajectory. The 5T does this in a motorized fashion again bringing up the noise and reliability issues. The 5A and the Schroder LT animate the bearing housing by capturing the force generated by friction in the groove. The same force that generates skating in offset arms. I have not had the chance to listen to any of these arms yet but I have enough confidence in Frank Schroder that I would buy an LT on the bet that it works as designed. Unfortunately at this point I do not have a table it will fit on...yet. I am of the belief that the major benefit of an arm like this is not it's reduction in tracking error but the absence of significant skating. I am all for low friction bearings but even with no friction you still have to deal with mass and inertia in a system with a spring loaded suspension no different than your car. Also, what on god's green earth makes you think the counter balance of the ET arm is decoupled? It has mass does it not? It moves at the same speed and distance the rest of the arm moves, right? Sorry dover but, it counts just as much as everything else and when you get a really good pivoted arm you will realize this. You you are determined to have as little tracking error as you can there are some excellent choices out there now.

@thekong , do your self a favor and add some lead weight to your arm until you get the combined resonance down to three Hz and let us all know what happens. Better yet make a You Tube for us! Give us a little forewarning so we can get the popcorn ready. Frank Kuzma is a very interesting fellow. You might notice that he makes one of everything. He makes mass loaded tables and suspended tables. He even makes suspended turntables that are not really suspended. He makes unipivot arms, gimbal arms, 4 point arms and air bearing arms. He definitely has moments of genius but he will make whatever people think they want to buy so, he makes one of everything and is committed to not much. 

@molly , Incredible rig molly. That is my favorite turntable. I am waiting patiently until it is offered with a vacuum platter which Dohmann has said is coming along. I did not know the 5A had been released. For those who do not know what it is, it is a manual version of the 5T using the same geometric trick but with clever bearing management instead of lasers and motors. The Schroder LT is another manual arm that uses the same trick. All three arms are not offset (they are straight) remain tangent to the groove within a fraction of a degree and do not require anti skating. What the arms are doing is using the frictional pull of the record on the stylus to drive the mechanism of the arms. Normally this friction just generates heat. 

Good luck with your table. I'm jealous!  

For those who have not heard the term, Zenith Error it is a new factor that Wally Tools has jumped on. Zenith error is a rotational error of the stylus. If you were looking down on the tip of the stylus the long axis of the stylus is not perpendicular to the groove. To correct it you would have to rotate the cartridge. In order to measure it you need a good microscope which Wally Tools will also sell you. Of course if your cartridge is built correctly you do not need any of it. You can see well enough with a decent and inexpensive USB microscope. The two cartridges I currently have, a Soundsmith and a Clearaudio are good enough that I can not see any zenith error. 

@larryi, Of course they would say that. I have a relatively cheap USB microscope and I can see the long axis on modern extreme styluses such as the Gyger S. I do not have a measurement grid so I have to ball park it and since you can not see the cantilever you have to make sure it is perfectly aligned in the field which with a decent stage is not that hard. If the styluses i currently own have an error I am confident it is less than 1 degree. If I bought a cartridge that had a significant zenith error I would not be sending it to Wally Tools. It would be going back to the manufacturer as defective.

@lewm , quite correct in an offset arm but in these arms the wand is straight so little to no skating force is generated. More bearings are always a liability as you suggest which is why I prefer the Schroder LT. It has normal vertical and horizontal bearings and a magnets control the position of the single secondary horizontal bearing.  I would have gotten the Schroder LT but it requires a turntable that takes a 12" arm. The only table I am interested in that will do that is the Dohmann Helix but I refuse to waste money having to buy the vacuum up-grade when it is released if ever. If not then I am not interested. I am toying with the idea of modifying the Sota's plinth for the LT but in order to get an idea of what it would take I would have to have an LT in hand meaning I would have to buy one. That is a pretty big leap for something you might not be able to do.

@dover that is not the way it works dover. The motor is running continuously and the laser is pinpoint. It simply adjusts the motor's speed. If you look at the arm wand it's vertical and horizontal effective mass is virtually identical. In the case of your arm it is wildly different. What this amounts to is a very low horizontal resonance point. Your arm bounces across the record at 2-3 Hz. You can stop this with damping but then you generate reverse skating. In short, It is a terrible design.

@lewm , I forgot to mention. Your analysis of the significance of Zenith is right on. We should all go back to spherical styluses and give Wally one less angle for barter. Next will be barometric pressure.

@thekong , Very few of us get to utilize equipment in our systems at length if at all before we purchase it and awareness of technicalities is helpful in making decisions as to what you buy or not.

Kuzma makes some excellent equipment. He also makes some not so excellent equipment. Few of us can score a hit every time.

The basic design of the Safir is excellent like the 4 Points. Its effective mass limits it to a small number of very low compliance cartridges. Mr Kuzma's assertion that you can run cartridges with a resonance at 3 Hz would be true in a perfect world but, it is not. Records are not perfectly flat and turntables are not perfectly quiet. There is plenty of very low frequency noise that would energize a resonance that low. I have done this experiment. For yuks you should try it. You won't break anything. Just be ready to use the lift.

@ dover, there are many people who are very capable of analyzing the design of a turntable without having built a single one. By your own argument you are obviously not one of them. Instead of attacking me personally why don't you just explain why I am wrong. Usually, when you see attacks like this it is because the individual is incapable of having a discussion about the technicalities of an issue. Your analogy of the car door totally fails. The door is not suspended by a spring. Although it has detents to hold it open at certain points it will not spring shut when you open it and let it go (unless you are parked on a hill). By having the counter weight on a spring you just add another resonance frequency. The counter weight moves at the same speed and distance as the stylus it's mass is part of the system and can not be divorced. 

Turntables (unless you are Nakamichi or B+O) are extremely simple devices. There are many people who have built their own turntable. Precision bearings are readily available as are great motors and control systems. Only and audiophile can make such a simple device as complicated as a General Electric GE90.