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Strange Tonearm Tweak. Long

As you all know, I am a little different. I like to read and study stuff like tonearm technology. I noticed that some of the better unipivot designs have employed "outrigger" style outboard weighting systems on their arms, that work like a tightrope-walker's balance pole. This not only balances azimuth, but also gives the arm better stability to lateral deflections from the cartridge suspension, so the arm is not moved when the stylus is pushed laterally by the groove information. I began to think on this, and I wondered why no gimbal-bearing arm makers are doing this. Surely since the vertical plane rides on a vertical axis bearing, there is still some chance for the arm to be laterally deflected by the stylus, when the stylus should be doing all of the moving, not the arm. I think that this is why they use heavy arms, but a heavy arm in the vertical movement plane is not good for tracking. A heavy arm in the horizontal movement plane is good for resisting sideways deflection that would impair pickup function.

So I decided to try increasing the mass of my tonearm in the lateral plane, while keeping it light in the vertical plane, by the use of "outrigger" weights, just like a unipivot does.

I bought lead fishing weights that looked like long rifle bullets(just the lead part) They were about an inch long and about 3/8" diameter, and weighed 12 grams each. I drilled into the bases about 1/4" and press-fitted them onto the nuts that hold the arm into the bearing yoke, so they stuck out straight sideways, like sideways spikes. This put the weight out pretty far to the sides as outriggers, and kept the weight centered exactly around the bearing pivot axis so it did not increase the vertical mass significantly, but it did very slightly. It did not influence the tracking force at all.

So now the arm had outrigger stabilizers on it in the horizontal plane of motion.

I put on a record and sat down to listen. Let me tell you, fellas, this was a mind blower. I have never heard this much information come out of a cartridge before. I heard sounds on records that I had listened to for 30 years, and never knew those sounds were on the record! And I have had some pretty good analog gear in my time. And what I didn't own, I heard at the audio store I worked at. This is the most astounding mod I have ever heard on a tonearm. And it cost me $1.49 for the fishing weights, and I got 3 extras.

The only slightly negative thing about it, is that it increases the anti-skating force, so you have to cut that back a little, and if you have some marginal scratches that might skip, they are more likely to skip with this mod, due to the resistance to sideways movement provided by the outriggers. I had this happen once last night, but I didn't consider it a problem.

But the increase in dynamics, and detail and overall sound quality is astronomical. It blew me away.

I have a DL103, which is a very stiff cartridge, and it may be that this is not needed for a higher compliance cart. But, I think that it would be good for anything that is medium or lower in compliance.

The key to it, is that it only increases the resistance to sideways movement, without interfering with the effective mass of the arm, or the vertical swing movement that needs to stay light to track warps. I played some warped records with this mod, and they played just as well as without the mod, except they sounded better.

I have a pretty good analog setup now, but I can say without reservation, that this mod made my rig sound better than any analog rig that I have ever heard in my life. I have never heard a Rockport.

Stabilizing the arm against unwanted lateral deflection increases the information retrieval and dynamics by a very large percentage. If your arm is not set up like a Rega style arm, then you can glue a 1 ounce long rod across the top of the bearing housing(sideways) like a tightrope-walker's balance pole. Use lead if you can, it won't ring. You don't have to do any permanent changes to your arm that might wreck its resale value to try this out. If it has anywhere near the effect on your system as it had on mine, you won't be taking it off.

It may come close to the movement of your cueing lever, so make sure you have clearance to use it. Mine was close, and I have to come in from the side now to use the lever, at the end of a record. That is fine with me! This was a major, major improvement in the sound of my rig. It is staying permanently. As in "forever".

If you are a little tweak-oriented, and not afraid to do stuff like this. You should try it. It will knock you over.
twl
dougdeacon
3,338 posts
 
"Doug Deacon's HFNRR test record measurements with the Hifi mod installed on his OL Silver yielded a near perfect 11Hz vertical, and slightly higher horizontal with a Shelter 501 Mk II on his arm (if I remember his post correctly) Both were well below normal audio range, and above rumble frequencies."

From memory:
OL Silver
HIFI Mod
Tom's suspended counterweight (described above, I think)
Shelter 901
~ 9Hz horizontal
~ 11-12Hz vertical

The suspended C/W is not quite as heavy or as close to the pivot as Tom intended. OTOH, reducing the vertical moving mass would raise the vertical resonance frequency still higher, right?

If Alex's new thoughts are correct, then it's okay or even desirable to have the lateral resonance freq lower, and reducing it even more might have a good effect. I'll have to add some bubble gum to the weights, remeasure and do some listening. Any suggestions for the best flavor? ;-)

Doug
twl OP
3,251 posts
 
Doug, thanks for clearing that up. I couldn't remember exactly what you stated in your post, and I just made a mistake in writing that you had a 501.

BTW, I have always thought that Bazooka was the best bubble gum! :^)
zaikesman
3,017 posts
 
Double Bubble. It reinforces the effect of the divergent resonance points... :-)

Tom, your technical analysis of what might constitute the optimum range of added lateral mass and why is a good deal more sophisticated than I could manage (not that I can't follow the gist of it, i.e., what matters are the forces in play at the stylus tip with mechanical multipliers taken into account, not the raw masses involved - I think). So I will just second it with an alternative observation: the existing counterweight on any conventional tonearm is at least as massive as your 24g of added weights, and I would guess probably more often 2 to 4 times that amount, whereas the cartridge, out at the end of the tonearm lever, is roughly 1/2 to 1/4 as massive (as the added weights). At set-up, the counterweight is first balanced against gravity with the cartridge installed, then moved inward toward the pivot to effect the desired vertical tracking force. This action could be seen as 'unbalancing' the cartridge in the lateral plane by the same amount as the applied VTF - and Tom's added weights could be seen as a method of 'restoring' static lateral balance by providing a 'counter-counterweight' that operates only in the lateral plane.

Of course that's not a literally true analogy, because gravity is operating only in the vertical plane, but the lateral accelerations applied by the spinning record at the stylus tip are real, and they can be presumed to be basically equivalent to the vertical accelerations (caused by same) that gravity is enlisted to help manage in the vertical plane. Now, because the groove wall is cut in a 45-degree "V" angle, the downward VTF applies the same restorative force in the lateral plane as in the vertical when the stylus is deflected side-to-side. There is a difference however: in practice, the cantilever is always deflected vertically upward by the VTF, even at rest, whereas laterally it always returns to center. Given that scenario, plus the fact that warps which need to be tracked by the tonearm are mostly a vertical phenomenon, there would seem to be elbow room so to speak for increasing what we might call the 'lateral dynamic tracking force' against which groove accelerations act in the lateral plane. In other words, we can think of Tom's approach (of increasing lateral mass) as effecting a sort of separate, and higher, "VTF" for the lateral plane.

These musings inspire a vision of what Basement refers to as a 'properly designed' (pivoted) tonearm: maybe such a creature would have not just a rear counterweight, adjustable forward and backward to effect proper tracking force, but also side counterweights concentric with the pivot point mounted on extensions of the fixed axle, adjustable in and out from the pivot in order to effect optimal lateral counteractance to forces applied at the stylus - while the whole shebang would be fluid-damped. (And: might such adjustable side-weights even be able to effect some form of dynamic anti-skating compensation?) This seems to me the logical extrapolation of Tom's mod...
dougdeacon
3,338 posts
 
Zaikesman,
I remember posting somewhere (maybe on this thread but who could find it) that side weights threaded for in/out adjustability would be useful. I think the tungsten side weights on the Graham 2.2 are like that (4yanx?).

My thought was just an instinct, not as well thought out as what you and Tom are doing. I really appreciate the continuing contributions to tonearm theory engendered by this thread. Maybe I'll uprade my HIFI Mod some day, though I can't imagine how I'd get the existing weights off without wrecking the arm.

To heck with this pivoting nonsense. I want a Kuzma Air Line! I'm off to buy a lotto ticket...
basement
245 posts
 
There are some really interesting thoughts here in the last few post, as far as thoughts or ideas that eventually turn into knowledge. It is for one useful when we attempt to measure and discover that the measurements are not exactly what we expect- we figure out there is something else going on and we learn something. One thing pointed out here is that the grooves of a record are cut at a 45 degree angle-so then how could a horizontal mass not have an effect on vertical mass? (as it relates to its affect on the suspension). I wonder how these grooves are cut into these various test records that are able to relate to being able to determine separete vertical and horizontal resonences, and wheather these are still existing the same way when the same system is playing a record with grooves cut at 45's. My ears suggest that as I listen to the differences with this particular mod is there is greater channel separation.
We all know that resonence points are important, and tonearm designers are sure to make sure they're designs fall within these parameters. There is also a definite importance on mass, and the placement of such, as it relates to the evacuation of energy, and it is clear in the more recent trends of the better tonearms that have recently added mass to they're arms in particular areas and gained improvements.
A little earlier on in this thread it was brought to our attention that the sidewieghts could be used to effect a change in anti-skate behavior. It made me think about the effects of bearing placement, as it relates to weight (or mass) placement, as it relates to the behavior and tracking ability of the arm. In both the immedia and the sme, the bearings are placed by the designers to minimize tracking error, according to the relative travel of the arm, BUT, changing the placement of the mass in a similar way, such as some of the aftermarket rega counterweights, and the upgrades on the graham, show similar results, without changing bearing placement.
The best unipivots in use today, namely the graham, the immedia, and the vpi, pay close attention to the placement of mass because they have to-it relates directly to the stability of the arm as it relates to tracking- and as designers shift and add mass, they continue to get better results. It is also, perhaps, that as the same attention is payed to pivoted arms, we get the same results, which might lead to the conclusion the while there are advantages to a unipivot as it relates to bearing quality/cost and friction, that perhaps it has more to do with the placement and attention of the mass.
Another case in point might be the popularity and performance of air bearing designs. Very complicated, and while they do show themselves capable of a high level of performance, it was a matter of time until pivoted, and unipovoted arms showed many of the positive aspects of the air bearing designs without the complications. Could very well be, that the sole advantage in actual use, of these air bearing designs is the vertical/horizontal mass relationships inherent in they're designs.
Of corse, the very best arms are very expensive, and rightly so because of the costly construction, as it seems that often certain improvements and uprades are costly to execute. There are some aspects of some costly arms where the quality of the construction relates directly to the performance. And then there are some aspects where improvements are made to the design that are by chance, or because the designer thinks the improvments are the result of what the intention is. That is why this thread is so fun. That is where this thread is at, and that is also why it is so amazing that as TWL comes up with these ideas and experiments that seem to break the rules, it not only forces us to change our perception of what a "properly" designed tonearm is, we make great sounding improvements that I am convinced would further the technology the more we understand them.

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