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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
twl OP
3,251 posts
 
Rauliruegas, yes I agree that if the tonearm is properly designed, that there will be no need for my tonearm mod. Unfortunately, it seems that many are not properly designed. So, improving the lateral mass is appropriate in many cases, but not all. Also, it depends greatly upon whether the cartridge is low, medium, or high compliance, as to whether additional lateral mass is even needed. In any case, this mod is strictly for OL Silver and Rega tonearms, and it has been demonstrated that they perform better, with many cartridges, by having additional lateral mass placed in the proper location.

I have never presented this modification as a "panacea" for all arms and all cartridges, but strictly for Rega and OL Silver arms with lower and medium compliance cartridges. Other arms may also benefit, but that would have to be determined on a case-by-case basis.

Thanks for your comments.
zaikesman
3,017 posts
 
Tom brings us back to the point about cartridge compliance and the efficacy of doing a mod like his. I have been thinking about this recently since I installed a van den Hul DDT-II Special in place of my previous Benz-Micro Glider M2.

The vdH's have higher compliances than is usual for most MC carts (and their upper-line models even more so than mine), yet the DDT does not seem to suffer from being run with the same viscous fluid damper settings I used with the Glider. But I'm not sure this would be the case if I had Tom's mod instead of the KAB damper, due to the point I made somewhere above about the added mass imparting not only increased resistance to lateral deflection of the tonearm (as does the viscous fluid), but also continuing intertia once put in motion (which damping fluid does not have).

This sheds some light on a problem that baffled me near the top, namely why Tom felt the mod increased susceptibility to skipping on scratches: it's the intertia - I just didn't put the two together before. There's probably a 'threshold' effect at work: light scratches may actually be less prone to cause skipping with the added weights installed, but these kind of scratches might not normally cause skipping anyway - while scratches beyond a certain magnitude (that acutally cause the stylus to break contact with the groove) may cause a lateral arm deflection that is less easily brought back under control once begun due to the added mass inertia.

Anyway, we see that increased lateral mass mandates matching to a relatively low-compliance cart, such as Tom's Shelter. This is of course no different a concept than the standard one about matching compliance to overall effective arm/cart mass, with the exception that Tom's use of increased *lateral* mass *only* means that there will be little or no effect on system resonance excitability due to infrasonic warps, footfalls and the like, or LF mechanical feedback (which tend to be primarily vertical in nature), nor due to the low bass content of lateral-cut (mono) or diagonal-cut (stereo) recorded music (since the added mass only lowers the resonance point, presumably already below the 20 Hz maximum). So bass performance is enhanced, tracking is maintained, and skipping susceptibility is worsened (but not if your records don't have scratches).

Still, you could say about viscous fluid damping that the bass performance should be likewise increased, tracking may even be slightly improved (fluid does provide a bit of extra vertical damping, though not as much as laterally, due intentionally to the shape of the paddle), and susceptibility to skipping is ameliorated (or at least reduced in magnitude when it occurs). At least one could think so. In my own listening tests with the fluid damper, I mostly heard a cleaning-up of the soundstage, a purer, more extended treble response, and bass that sounded more natural in timbre but not necessarily more extended or dynamic (those tests done with the Glider). I can state that the damper doesn't worsen skipping, but haven't done the tests to state that it really improves this aspect either. In any case, fluid damping does seem to permit the use of carts in any compliance range (indeed, the KAB product, dedicated as it is to the Technics SL-1200 table/arm, will likely be most often used with high-compliance MM carts featuring relatively high-mass tips and cantilevers, such as the models made for club DJ's and hiphop turntablists).

But since KAB evinces no interest in coming out with a fluid damper for Rega-sourced arms (despite my opinion on the market potential there), Tom's mod would seem to be it for owners of such arms - provided (as he states) that they are running a cartridge of suitable compliance. Looked at that way, what he essentially did was come up with a clever method to improve the match of his tonearm to his choice of cartridge, without paying a penalty in reduced trackability.
twl OP
3,251 posts
 
Thank you Alex, for your succinct description of the pros and cons of the mod, and the importance of matching the application.
basement
245 posts
 
I think it is worth pointing out that what a properly designed tonearm IS, is the result of continuing to try to improve the design, that is, further the knowledge and design of the technology. That is why it is so much fun that twl shares his improvements with us. Any tonearm can be improved. If it interest you, go back toward the beginning of this long thread and you will see what fun we all had in trying to determine the validity of Tom's modification. There is actually enough here to demonstrate that the modification is of proper design. This is a LONG and old thread. The mod (lateral mass) is proven in listening test, compatability, the theory behind the mod is also put to the test, and it is shown to be an improvement not only to the overall sound, but is a more properly designed arm with it.
If you are truly interested in what a properly designed tonarm is, and want to have real fun, notice how many highly regarded and well designed tonearms DO NOT take note of the the aspects of TWL's design, and if you execute it properly, many arms could be improved the same way. (notice that some arms have uprades that go in this direction). The rb-series of tonearms have some really good aspects to them, namely the design of the armtube and the bearings, as well as some aspects that are overlooked.
The mod works so well that the performance of the arm comes scary close to some VERY good arms, and evan surpasses a lot of very good arms in certain, important areas. It is amazing what you can achieve with a little knowledge of tonearm design.
zaikesman
3,017 posts
 
I want to go just a bit further and break down just why I feel Tom's idea constitutes a intriguing and enlightening approach. In the past, before coming to some understanding (with the help of the contributors to this thread) of what the HiFi mod represents, I had - I'll assume like most of you - regarded effective mass as a monolithic quantity. Tom's insight made me aware that we should properly take into account two separate quantities of mass, vertical and lateral.

The reports above of those who've tried his mod testifies to the validity of his fundamental underlying proposition: that information retrival may benefit if these two quantities are not treated as being always interchangable - that in fact, performance may be improved if these two quantities are made slightly divergent. Two divergent effective masses instead of one also implies there being two divergent points of resonance (cartridge compliance still assumed to be constant in all directions). I wonder if this presumably 'double-humped' resonance distribution might itself be partly to credit for perceived performance gains, as a result of the altering of the system's "Q" characteristic to be less intensly concentrated at one specific frequency ; in other words, maybe simply making the lateral and vertical mass - and therefore resonance - components somewhat different from each other could be as significant a reason for improvement as the action of additional lateral mass itself.

This an untested hypothetical of course, but we do know that there is a several-Hertz range within which 'proper' system resonance may ideally fall, usually given as from 8 to 12 cycles per second. This value range is considered low enough not to be excited by music, but high enough not to be unduly excited by record warps, big dogs, passing 18-wheelers, distant earthquakes, etc. So there is obviously 'wiggle room' to for instance make the vertical-mass/cartridge-compliance resonance point = 10Hz while the (higher) horizontal-mass/(constant) cartridge-compliance resonance point may be brought closer to say 5Hz without having to worry about extraneous inputs of (primarily vertical) infrasonic energy ruining your tracking day.

The viscous fluid approach , while not imparting inertial effects (and in fact counteracting them), does little to damp such low frequencies, and won't really alter the distribution of the system resonance. (I want to stress here, in relation to this inertia business, that Tom's added weights do not encumber the cartridge suspension in a discriminatory manner that is out of the ordinary ; the suspension must deal with the tonearm's mass inertia anyway, whatever its value. Gravity helps maintain groove contact in the vertical dimension through the VTF setting ; laterally - particularly with really good bearings - it seems to me that inertial mass ought to be able to stand an increase at least roughly equivalent to the VTF.) I observed near the top that fluid damping ought to be superior to the HiFi implementation in terms of HF damping, and this analysis suggests that maybe the two concepts are actually complimentary.

Funnily enough, after so long since this thread began (and after having previously inspected my own tonearm to see if it could be made to accept something like Tom's mod, which I concluded it really couldn't due to its physical design), this late conversation spurred me to go downstairs and look once again - this time with a new notion in mind. And hot damn, there it was: the 1200 tonearm already incorporates added mass in the lateral plane! I'd been looking at it the whole time (the brain sure can work slowly... :-) I think a lot of gimbal tonearms have been made like this: it has a 'carriage' containing the vertical-plane bearings which itself rotates in the horizontal plane (it's mounted within the 'tower' assembly holding the horizontal-plane bearings, which is itself stationary). This 'carriage' structure is basically a rectangle, open in the middle (the arm passes through it), made of cast alloy about 1 1/2" wide by 3/4" tall by 1/4" thick, which incorporates the steel vertical bearings ; when the tonearm moves vertically it remains put, but it rotates in the horizontal plane right along with the tonearm when it is moved laterally. I would estimate its total mass as being roughly in the ballpark of Tom's fishing weights. D'oh!
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