You know, it's been so long since I took a look at the KAB site, I guess I forgot which plane the damping operates in. Considering that the grooves are actually cut at a 45 degree angle, I would suppose that a little of both horizontal and vertical damping would be a good idea (which ties in well with my idealized theoretical above). I'll make a point of asking Kevin at KAB about this aspect.
As far as the threshold hypothesis goes, I can't agree with your analogy about lifting a weight. Weight is not the issue here, mass is. If the weight you couldn't lift was floating in space, and you attempted to push it away from you, you would move both move in opposite directions, according to your respective masses. In theory, when you or I jump up in the air, our push-off sends Earth moving infitesimally in the other direction; there is no real threshold - a practical one, yes, but no absolute one. Or to put another spin (sorry again) on it, if the arm was really so massive that the cantilever's suspension couldn't overcome its mass to move it when transcribing a groove modulation, then it also couldn't move it across the record as it played - the suspension would just keep deflecting until something gave way. If a force applied at the stylus can move the arm at all, then it can move the arm period. |
TWL, I think we are having some misinterpritations here, but when we are speculating, as I am, that will often be the case.
I agree with you on all your reasons and speculations behind your mod. I also find them highly intelligent and insightful. I also understand that you are looking for superior tracking. I get the idea that you think that I was implying you weren't. I think that our separation in understanding is in the flexing of the cantilever and the speed that I am refering to. Or, if you will, the offset from perfectly center that is encountered in the circumstances of cantilever flexing.
The speed I am refering to is the warp/wow frequency and the lowest bass frequency. The amount of movement I am refering to are very, very slight. At the level of evan a fraction of a cantilever width. I am not trying to imply that because I can see it, that it exist, or that it doesn't exist if I can't, I use my eyes as an aid. The cartridge I am using is a clavis d.c., and as you know, the arms are an older model immedia and a rb-300. I do observe movement in both, but I don't consider it unusual movement or out of spec. Just to be clear on what I use my eyes for, if I see movement, I use that for a clue, or try to find clues by looking for movement, and then I attempt to identify what I am seeing by checking the set-up and listening.
When the complience and mass of an arm are considered matched, the resonent frequency is suppossed to be between the warp/wow frequency and the lowest bass frequency, I beleive that is 5-10 khz's. THAT is the movement I am refering to. This happens as the cantilever is moving to track the record, which is determined by the mass and complience of the set-up. How much it moves and how fast it moves are two different things, I leave it open for debate as to how much, as I don't know. I know that in most proper set-ups, there is movement, and that it is desired by traditional thinking to minimize it. (I'm still refering to the amount of movement, not the frequency).
While I suggest that your canilever is moving, I am not saying that it is mistracking-the contrary. I have to suggest that it is moving more than it was because by adding weight to a given application and changing nothing else there should be more movement in the cantilever, and that is based on having the arm remain more static than it was. I don't mean to imply that it is more static than it should be, or that there is more deflection than there should be, but I do contend that at the extreme of such an experiment that there will. I am forced to consider, however, that if you increased the amount of movement but changed the other parameters, such as the frequency, or other things that I am not aware, that superior results are/were gained from your experiment at the expence of greater movement at the cantilever. Please don't take that as me saying that you are ignoring movement there, Or that you are not looking to minimize it, or that you shouldn't, but if you don't consider what movement is taking place, or what could take place, then I don't think we can be able to asses the differences that are taking place.
The way I see this, is that adding mass of that amount in the horizontal plane is unconventional thinking, evan as the theory and evidence for it may be sound. I also believe that your assessment of the improvements in sound are true, as I would say from what I have learned from you I would have to guess you are quite competent in that area. All of the evidence that I keep learning as I explore this is leading to this not only being the case, but is causing me to have to stretch in my understanding of tonearms. So I might stretch your theories. |
Basement, first, if you would like a set of these weights for your RB300, email me. They should make an improvment on the Clavis. That is not a "whippy" cartridge, and the cantilver/suspension should be quite stiff. These weights are easy to apply, and stay put, in just the right place. I really would like your feedback on this.
Next, I think I am beginning to understand what you are saying. One thing that needs clarification is your term "cantilever flexing". Is the cantilever actually flexing, or is it just moving in its rubber suspension? This is an important difference. The cantilever itself is a stiff tube, and should not flex. Flexing loses information, and imparts an unwanted resonance in the system. If the movement you refer to is small, and near the center, then it is actually suspension movement you are seeing. Flex, if it does occur, would only happen at the end of suspension travel.
If I understand you correctly, and correct me if I'm wrong, you are concerned with the very low frequencies that may be caused by warp/wow in the range below 10Hz. You feel that if the cartridge is actually tracking these frequencies, that it may be detrimental to the system, and the cantilever especially. This is because you feel that the large movements that occur at this range may bend or break the cantilever, and these frequencies should be prevented from entering the system anyway. Right? And your concern leads you to believe that the arm should move laterally at these frequencies to relieve the sidewards stress on the cantilever, and to preclude these frequencies from entering the signal chain. Right? Tell me if I understand this the way you mean it.
Now, going on the assumption that I understand correctly, you are actually referring to the matchup of the lateral effective mass/cartridge compliance. If it is minor warp or off center problems, yes the arm should move laterally on the bearing to account for these eccentricities. These problems are slow dynamics compared to the rapid lateral accellerations of the stylus during tracking of low frequency playback dynamics. An object has much more resistance to movement when a rapid accelleration is applied, than when a slow push is applied(Force=Mass x Acceleration). The slow movement of the record groove during warps and off center travel is easily handled by the arm bearing, and the arm moves laterally quite easily in this circumstance. If you are saying that the warp/off center record is causing a quick massive 1/4" or more movement that causes the weight of the arm to stay in place, and makes the cantilever move dramatically sideways because the record movement is too fast for the arm to keep up with it, then that record is a Frisbee, not a record.
My theory on this issue is this. The transducer should respond all the way down to DC. All frequencies begin at DC at the beginning of the attack, and quickly rise to the fundamental tone, and then decay back down to DC again. This is the structure of all notes. If we avoid the reproduction of the lowest octave, then we change the structure of the note, as we hear it. Even if the rest of the system cannot reproduce this, it has its effect on the sound. It is an attack, sustain, decay, timing issue. The resonant frequencies in the cartridge/tonearm cannot be avoided, but can be tuned out of the most offensive areas.
So, IMO to purposely allow the tonearm to move laterally at these frequencies, for the purpose of avoiding their reproduction, as a preventative of cantilever stress, is a counterproductive measure. It is my view that all frequencies from DC and up, should be included in the information chain of the source transducer, regardless if the other elements in the signal chain can reproduce them or not. If not, the natural structure of the tones, and the PRaT will suffer.
So, to sum up on this subject, I feel that the cantilever should be subjected to all these forces, but should remain in its properly centered relationship with the groove at all times, if possible. This may not be entirely possible, but it is a goal that we should try to attain with the improvements we are considering.
If the record is defective or warp damaged to the point of causing extraneous peaks in the frequency response at very low frequencies,or causing undue stress to the cantilever, that is a problem with the record, not the playback system. The playback system should track all the information on the record, if we are to even hope to get the best reproduction.
Regarding my unconventional thinking, it may be somewhat unconventional, but it is not original, or new. Others, such as Dynavector have addressed this directly, with an entire design(the 505-507 series) with this idea as the goal. And Graham, as well as other unipivot makers are using some form of this also. The Transcriptors Vestigal arm, addressed inertia and had 35 times more lateral inertia than vertical inertia. And the Vestigal was made in the 70's.
Hopefully, I have understood your idea, and have addressed some of the points you raised. If not, please re-explain, and I will try again. |
Oh yes, I gotta try the weights. I would highly appreciate a set of yours, as then I can be sure I am trying exactly what you are using.
My statements regarding cantilever flex are exactly as you say. It is not actually the cantilever that is flexing, but the suspension. That can get confusing. I dont know or remember what that peice is called that the cantilever is attached to, that peice of wire, but anyway, I am observing the movement at the center more or less as you desribe.
The warp/wow that I am refering to is not nessessarily something that I would expect to tame, but the way I understand it, all combonations of arm mass and complience have or produce a resonent frequency, a frequency that is the natural frequency that will cause them to vibrate in sympathy. That is why usually the goal is to set that between the lowest frequency produced by the record, (or for clarification, the music or noise pressed into the record) and above the frequency of the warp/wow.
If the resonent frequency is in a place that is likely to get "exited" then that may have a tendancy to mask or alter the information we want.
I'm not sure if this is conventional, but I am trying to define that there is a difference in the speed of the cantilever movement and the amount of movement altogether.
I'll try to dig up some references so I can be more accurate in my descriptions and definitions, and also you can see what you think if I can find them and get some to you. I also seem to remember the SME use to have a damping trough available, so I'll have to see if any are available. The KAB site I checked out, and the damping trough seemed as though it would require quite a bit of modification for use on a rega, and zaikesman, if you are reading this, it will be very interesting to hear what this does for you.
I also think it would be interesting for us to try and measure these things. If anyone has any info on what is required, I would be extremely interested. |
Yes, there is a difference in cantilver speed, depending on the frequency of the "bumps" in the groove that it is trying to trace. Larger amplitude bumps, in the lower frequencies, require faster velocity than the smaller "bumps" in the high frequencies, because there is more lateral deflection and return, for a given amount of rotation of the record. Also, the speed differs at the outside of the record, and the inside. The record is larger diameter at the outside, and therefore has different speed at those grooves, than the inside.
Also, I feel that the warp excitation of the mass/resonance is far less critical in the horizontal plane, because the warp movement is primarily in the vertical plane, and that is not being changed by this mod.
As an experiment last night, I played an extremely good recording by John Klemmer, recorded direct-to-disk on virgin vinyl. This beautiful record suffers from some of the most complex warping of any record in my collection. It has a dish warp, and several varying radius warps all around the perimeter(a real shame). However, I played this record on my TT(with the weight mod on the arm) and I found that the arm tracked the warps very well, and also the slight out-of-round that was there. The only noticeable thing was the woofer cones were bouncing, like would normally happen on a large warp anyway. Believe it or not, even with the intermod that this woofer bounce makes, the sound of this recording is unbelievably good, and the cartridge tracked even the most difficult dynamics like a train on a track. So as far as I can see, this does not hinder the vertical performance of the arm at all. And it shouldn't, because the design is only applied on the horizontal performance parameters. This arm with my mod, was able to track the most difficult warped record I have, and provide awesome audiophile sound quality and tracking while doing it. Just for fun, I turned on the CD player, and played one of my CD's, while I was making a cup of coffee, and it sounded like the system was broke! The sound of this TT, makes a very good CD player sound like something is wrong with it. A good record on this TT absolutely destroys a CD player, even with my best CD. Like I said, the Sony 9000ES CD player sounds like it has something wrong with it, in comparison to this TT setup. If anyone ever came over here, and listened to that comparison, they would laugh out loud. |
