@lewm , I am not arguing about the coefficient of friction. That would be silly. However, play a blank record then have a look at it under the light. Then talk to me. If you do not have a blank record The Lumineers Cleopatra has a blank third side.
Millercarbon hit the nail on the head. Whenever you do anything to the arm except adjust anti skate you neutralize the anti skate.
@ozzy62 , I beg to disagree. Zero anti skating never sounds better but too much is just as bad. In the absence of an accurate measurement device such as the WallySkater or my Gizmo (see my system page, last picture) the anti skate should be set so that the arm drifts slowly towards the center of a groove less record. You can also use the runout area if you are quick.
@bpoletti , doubtful? Michael Fremer can:-) I have a Schroder tonearm so you know where my affections lay.
I am not sure where the 10% of VTF came from but It seems to be the consensus in the industry.
I use to use a test record with four increasing groove velocities. The consensus is that this overestimates antiskating but then wouldn't you want the antiskating set to track the most difficult passages? The issue is after all tracking or miss tracking. The lower velocities will track fine even if the anti skate is overestimated. It is nice to have a specific target number (even if it is just an averaged value) Makes me feel better.
@larryi , I really like your analogy with the arm. I think it is easier for people to understand than the water-skier analogy.
Can a tonearm be made that does not skate? Theoretically yes, in reality probably not. But, you certainly can make one that skates very little. The Reed 5T and Schroder LT are good examples. They have to be perfectly set up and the tonearm has to be dead level. Keeping everything perfect is an impossibility so, there is always going to be a small amount of skating...that only Michael Fremer can hear.
Of course Michael Fremer totally disagrees with Peter Ledermann and Frank Schroder. However, Michael Fremer is wrong when he asserts the friction on a groove less record is lower than in a normal groove. It is higher.
@clearthinker, The aeroarm is just as bad as any any other air bearing arm. It's horizontal effective mass is way too high. This causes the cantilever to oscillate side to side. Damping helps somewhat but still. You can prove this to yourself. Find a record in your collection that was drilled off center. Play it and watch the cantilever it will move side to side. It may be hard to see if you are using a very stiff cartridge like a Koetsu but then you will have a vertical mismatch. With a properly tuned pivotal arm you will never see the cantilever move unless the bearings are shot. If you are determined to have a tangential arm check out the Schroder LT or the Reed 5T, they side step this problem.
The best way to set anti skate is to measure it. It should be 10% of the VTF +- 1%. The only two ways I know to do this are with the WallySkater
(very expensive) or my Gizmo (dirt cheap, see picture my system page)
I will not chase you for patent infringement if you decide to make one yourself. The only important part you have to buy is the instrumentation bearing. Ceramic is the best. Otherwise, you could make it with some scrap wood, a scroll saw and a drill. If you want to wait I will probably sell it to a company like MoFi once the patent is pending.
Clearthinker, will an airplane fly without wings? No, I do not have to hear one. All I have to do is look at it. Every tonearm must deal with the laws of physics even if you do not understand them. Bow Wow. (dog barking). I think you might want to consider changing your user name. I'll change mine to "dogmatic"
@justmetoo, friction is much lower in the record groove than it is on a blank record. This is counter intuitive but lets see if I can explain it so it makes sense. The major determinant of friction in a record groove is VTF. Next is the surface area contact. The greater the surface contact the lower the friction. What will have greater friction, the point of a knife or a marble.
In the groove the stylus has two contact points and distributes the VTF between the two. On the surface of a blank disc there is only one contact point and the full VTF bears on it, the point of a knife. At the same VTF line contact styli will have less friction than elliptical styli. This is why line contact styli can get away with higher VTFs without increasing record wear. Yes, modulation plays a role but minor in comparison to contact pressure. In the groove the contact pressure is 1/2 that on a blank disc.
@lewm, N is not necessarily gravity. It is the force applied perpendicular to "ground" which is not necessarily horizontal to the earth's surface. You are right, there is no unit of surface in the equation and I am not sure what the work around is but it is probably going to be a change in "u."
The same force on a knife tip is going to generate more friction than the same force on a marble. "u" for the knife tip is going to be much higher than "u" for the marble. Whatever.
@larryi@, all this agrees with Frank Schroder's approach (which Peter Ledermann adopted) Letting the arm drift slowly inward on a blank area is going to require less anti skating force than holding it still because friction in the groove is lower than friction on the blank surface.
@lewm, I discussed the problem with my brother the mad scientist (MIT PhD) When you play a blank record the stylus leaves a visible scratch mark in it's path. The pressure on the very tip of the stylus is so high that it is actually digging into the vinyl so the friction equation no longer applies. It would be more appropriate to call it "drag" on the stylus which would have to be measured in order to compare it to the frictional pull on the stylus under normal conditions. The "drag" on the stylus is obviously higher since it requires more antiskating force to hold the tonearm steady.
@dover , I think you might do better with a straight line tracker.
@millercarbon, no reason to be condescending. Dover was probably an English major and missed the lecture on force vectors.
People who are having a hard time with this, get a blank record and do an experiment. Defeat your anti skating mechanism and put the stylus down on the rotating blank record. It will go zinging straight for the spindle. It will not stop at the null points. If the spindle doesn't stop it it will continue right off the other side of the record due to the overhang. If your overhang is not set up correctly you could smash your cantilever and do a number on the stylus's zenith not too mention it's tracking angle, azimuth, SRA and your wallet.
@dover, good thing because the forces acting on the tonearm cartridge system ( they are imminently attached to one another) are very simple.
But since you Mention the Eminent Technology arm, it is a rip off of the Walker Proscenium arm. Both are arms in search of a cartridge that does not exist. The cartridge would have to have three times the horizontal compliance in relation to vertical compliance. Thus both arms exhibit much more distortion than proper pivoted arms. Air bearings are simple devices. You can easily buy a bearing and make your own air bearing arm more easily than you could make a gimbal pivot arm. Companies like SME or SAT could easily make air bearing arms but choose not to for good reason. The distortion added by tracking error is far less than what is added by an inordinately high horizontal effective mass. Linear trackers with motorized carriages are superior but difficult to design and build, far beyond a company like Eminent Technology or Walker. Better yet are arms like the Reed 5T and Schroder LT. Both arms have secondary horizontal bearings, one motorized the other magnetically guided that otherwise function as normal pivoted arms. They just stay tangent to the groove but, more importantly do not generate any skating force which is even more important from a tracking perspective. IMHO the Schroder LT is a brilliant design powered by the pull of the record on the stylus which transfers it to the cantilever, which transfers it to the cartridge, which transfers it to the tonearm and finally to the bearing platform pulling it forward while a magnet keeps the arm properly aligned. Brilliant. I wish I were that smart.
Excellent Lewm. Nothing to add to that explanation.
@dover , I looked into it and you are right about the Eminent Tech vs Walker. I had always assumed Walker was first. Assumptions are the mother of all f--- ups. Thank you for correcting me.
However, you can not uncouple effective mass. If it is attached to the tonearm the tonearm must move it. You can change it's resonance characteristics but you can not write it off as mass. A tonearm must move in two directions and only in two directions, vertically and horizontally. Pivoted arms have about the same distribution of mass in both directions. There is usually a little more horizontal mass in the form of the bearing housing which is good it breaks up the resonance peak a little so with a specific cartridge the horizontal resonance point might be 8 Hz and the vertical 10 Hz. Now looking at your air bearing arm, the vertical effective mass is quite similar to a pivoted arm. Most of the mass is at the axis of the vertical pivot which means it contributes very little to the effective mass. The more the a mass is out by the cartridge the more it contributes to the effective mass. The cartridge is literally one to one. If it weights 10 grams then 10 grams is added to the effective mass. If one were to mount the cartridge at the vertical pivot (a bit weird but for the sake of argument) it would only add perhaps one gram to the effective mass. In the horizontal direction we now run in to the big problem. The entire tonearm has to move the same distance. A mass at the back of the arm contributes 1 to1 to the effective mass. If the arm weights 150 gm then the effective mass in the horizontal direction is 150 gm. If a pivoted arm weights 150 grams the effective mass would only be perhaps 20 gm. So now with the same cartridge whose vertical resonance was around 9 Hz it's horizontal resonance is 2 Hz or worse. You can see the oscillation on an oscilloscope. With a higher compliance cartridge you can frequently see it with the naked eye. You are depending on the stylus/cantilever/cartridge to move the arm. Anything that aggravates that resonance point will start the cantilever oscillating side to side. You can add viscous damping but then you increase the work required for the record to move the arm and you increase record wear. This is the problem the Reed 5T and the Schroder LT are circumnavigating. Very successfully I might add. This makes them hallmark products I believe as they dispose of tracking error but still interface with the cartridge correctly.
@dover , and there you have it dover. Horizontal effective mass is 25-35 gm and vertical is 7 gm. A normal pivoted arm might be 12 gm vertical and 13 gm horizontal. 20 gms is much to wide a divergence. Your use of terminology is a bit odd. I am looking at a picture of the ET2 as I type. The counterweight is very much a portion of the arm's effective mass. ANYTHING that moves with the arm is part of it's effective mass. In no way shape or form is the counterweight "decoupled" in this manner.
Over the years many companies have tried to pull this one off thinking that somehow they could get around the laws of physics the last being Frank Kuzma. It should be no great surprise that people resoundingly like his brilliant 4 Point arms better. The fact is it can not be done, at least not that way. They are all destined to failure just like the ET 2. Straight trackers with a motorized carriage carrying a more typical pivoted arm might be able to do it if it were not for the difficulty in overcoming the noise and vibration of such a drive. Reed and Schroder have it right.
Ditch the ET 2 or use it as an antenna or coat rack or something and get yourself a Schroder LT. You will be much happier and people will think you are a clever guy. It is good that you realize a cartridge has to be chosen to work correctly in a tonearm, that they have to be matched. There is no match for tonearms like the ET 2, none. There are only compromises., compromises you do not have to make with other arms.
Tracking error is not near as much of a problem as it is made out to be not that minimizing it is not a good thing. But, the price you pay with air bearing arms is just too high.
@larryi , high horizontal effective mass does not mean the cartridge does not move. It means it resonates at a lower frequency. The penalty for that is the same as it is for any pivoted arm and remember on the other side of this equation you have the much lighter vertical effective mass which is going to do exactly the opposite in the vertical direction destroying the bass and even causing feedback under certain circumstances. You can not separate the two. You are caught between a rock and a hard place.
@lewm , and that is the problem with the argument with a high effective mass being "OK" On top of that the slow oscillation of the cantilever at the resonance point is going to place the cantilever in a less linear point in it's travel increasing distortion and tracking problems. The market usually figures things out. No air bearing arm has ever gained traction in the market and I do not think it is because of the complexity of having a compressor. The Clearaudio straight line trackers are lighter but still cursed by the same problem on top of hygiene issues and people in general do not care for them. No compressor.
I also object to your coloring this as my "ideology." It is not my ideology any more than the sun rising in the east. You can hypothesize that this issue does not cause a sonic problem but the issue exists.
Finally, IMHO a good pivoted tonearm is going to function and sound better. If tangential tracking is your thing check out the Reed 5T and the Schroder LT. The Schroder in particular is genius. It accomplishes the goal of tangential tracking while maintaining similar vertical and horizontal effective mass and avoids the use of motors and compressors.
@larryi , The LT is much less expensive, $8K to $10K depending on where you get it from and which version you get. I would get it directly from one of Frank's dealers in Europe. Yes, the Reed is very expensive and complicated. The Schroder does exactly the same thing but in a much more elegant fashion.
There are other factors than just the quality of the bass. No record is perfectly flat or concentric. With high horizontal effective mass the cantilever reacts before the arm, remember the cantilever and stylus have to pull the arm along, then the arm gets going and continues on taking the cantilever and stylus along with it and you get this low frequency oscillation which causes a lot of distortion. I have watched several air bearing arms and Clearaudio arms and you can usually see it happening. The same problem occurs with arms that have a high polar moment of inertia. This is the rational for limiting mass at the end of the arm and is why SME changed their approach to tonearm design with the model V and all the best arms followed suite avoiding removable head shells and unnecessary mass out there. I hate to say this but removable head shells are for lazy people. Some designs like the Kuzma and the method Schroder uses are tolerable. The Kuzma looks bulky but the alloy is very light. He is trying to maintain stiffness and may be going a little overboard. The Schroder design looks sort of flimsy but it is not. The cartridge locks in solidly. I have a new Schroder CB which is waiting for it's turntable. I think if you are a cartridge jockey multiple arms or tables is a better solution than removable head shells of the old SME type that the Japanese are so fond of. Most of us install a cartridge and leave it be for years. I have multiple cartridges but there is always one I like best and that is the one that stays in the arm. The others just sit in a draw. I sold a bunch of them. I decided I'd rather collect records.