I purchased a VPI Classic 2 without knowing it had a Unipivot arm. It's a bit unsettling if you've never seen/used one. Seems to have no effect on sound quality. The main advantage seems to be a bearing that never wears out. BTW, if you haven't seen a Unipivot tone arm, it's like an upside-down cup balanced on a nail. I doubt I would have purchased had I known about it. |
There are various ways to implement unipivot tonearms, so, at best, one can only offer generalizations about how they perform. A unipivot, by apply the whole force from the weight of the tonearm and cartridge on a tiny point, means that the bearing is very highly loaded and unlikely to rattle. But even though it is highly loaded, friction is quite low because the contact area is small. From a practical point, most unipivot arms rock side to side when being handled, and that is disconcerting to some people. Whether it rocks and otherwise behaves in an untoward way when playing is a highly debated issue. Most unipivot arms employ some kind of damping fluid to damp undesirable vibration, but, even that practice has its detractors. There are unipivot arms that go through quite a bit of trouble to reduce any tendency to rock sideways by employing stabilizing mechanisms. Graham uses magnets on the arm that are attracted to magnets on a free moving structure that is on the base of the arm to stabilize the arm. Basis unbalances the arm so that it has a tendency to want to roll in one direction, and that roll is then resisted by something that sticks out and contacts a roller bearing on the pillar of the arm. Of course, these added structures do increase friction and thereby reduce one of the purported advantages of unipivots and such structures will, like any added mechanism on an arm, become a potential source of mechanical vibration. Most unipivots rely on outrigger weights on both sides of the arm tube to add stability, sort of like the giant poles that tightrope walkers use for added balance. As to sonic quality, one must judge that for oneself. There are a few such arms that have a lot of fans. Graham gets a lot of praise for their arms, as does Basis Audio. Although not as commonly seen, Moerch makes arms that, to me, sound quite good with the right cartridge. |
As I mentioned above, there are many kinds of unipivot tonearms, and different designs address performance challenges differently. One cannot say that any particular design is superior or inferior because no arm does everything perfectly. Among the somewhat unique designs is the Supatrac tonearms that utilize both a fishing line and a sideways unipivot as the moving elements of the arm. This is a unique design which I have heard, but, only in an unfamiliar system; the system did sound good to me. Viv Float utilizes a hardened ball sitting in a magnetic cup as a kind of unipivot. Magnetic forces not only reduce the downward load of the ball on the cup, it is used to increase the resistance against movement of the bearing assembly within the cup thereby providing the needed rigidity of the bearing. This arm has a lot of other unconventional design features that do away with most of the skating force on a cartridge at the expense of very high tracking angle error. But, the end result is a very good sounding arm. Again, it is hard to say how much the pivot design has to do with the sound, but, it sounds good so the pivot must be good. The Kuzma 4-point arm is closer in design to a unipivot than conventional gimbal bearing arms. It too is a very good tonearm. I don't see any basis for saying that Graham, Basis, Kuzma, Supratrac, Viv Float, Moerch, VPI, arms are inherently inferior to other arms out there. I don't think they are superior to other designs either. There are many successful ways to skin this cat. |
When I was new to this, yes the wobbly unipivots (ala VPI) were unsettling. But this was misplaced nerves. Now - it’s no big deal! Use the cueing lever / lift. Of course, it doesn’t feel like a good idea to put a stiffly suspensioned, massy cartridge (Koetsu) on one of these. But for most MCs and MM it works fine. There are many offshoots of the "pure" unipivot - usually by adding additional pivots of some sort (which is a broad canvas). I’d consider these more of a hybrid. The aforementioned Graham Phantom uses the magnetic stabilization, which works quite well and handles much like a traditional gimbal arm. Phantoms also do well with Koetsus, which seem to appreciate the enhanced stability. VPIs can add the "dual pivot" mod. Though I’m not sure how well that "swash pad" bearing holds up over time. At least it’s easy enough to replace. I liked VPI’s metal unipivots - late builds of these wands were great, IMO. Really nice build quality and "feel". I had much more issues with the 3D and Fatboy wands. Very reactive to bass frequencies in my setup (~ 100Hz). I think it was more a matter of the wand material, than the unipivot bearing itself - but that could have played a factor too. I know the 3D / Fatboys are generally more popular than metal in this ecosystem - but not for me. |
I wonder if the use of a unipivot has anything to do with cost of manufacture and complexity of same, vs the more expensive/complex gimbal. I use a variation on the unipivot design, a Well Tempered ’Black’ arm that sits the pivot via strings in a bed of silicone fluid. I do think that some of the unipivots have fundamental issues, like chattering on the point, or some other instability. The Naim Aro is a good example of this. |
It might be cheaper/easier to build a unipivot, particularly because precision machining of the point and cup is not as critical as the machining of conventional gimbal bearings, but, some very good builders with very exacting machining make unipivot arms, and some very cheap arms are made with coventional bearings. I don't think cost explains the choice made. There are arms that do seem to be quite sloppy and chatter that are made with all sorts of designs. As to the Naim ARO, that is an interesting arm. It may be a bit sloppy, and to my ears anyway "jangly" sounding, but I can see why some people like it for its lively character; I heard it perk up a system that sounded a bit too dark and dead sounding for my taste. |
Some unipivot tonearms (VPI for example) are poorly designed because they are inherently unstable, thus the tracking force is in a constant state of fluctuation as the tonearm traverses the record. I suspect this is why VPI has been moving toward gimbal bearing arms in recent years. Graham Engineering knows how to make a proper unipivot.
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Most modern (meaning brought to market within the last 10-20 years) unipivots are not really unipivots in the original sense of the term, because most manufacturers have modified their unipivot designs to reduce or eliminate their capacity to rotate in the plane of the pivot, which makes the azimuth unstable. These modified Unipivots are also made less prone to "chatter" at the bearing point, by use of magnets, etc. As a result, the better modern unipivot tonearms, like the Kuzma 4-point or the Graham or a VPI with their add-on modification, are really excellent tonearms, but expensive. |
One of my favorite turntables was an LP-12 I got used in 1975. This was before they added electronics to it…just a Scottish AR or TD150. My roommate was in the UK on a fellowship so I asked him to bring me a Keith Monks arm for it. I mounted it with a Sonus Blue Label I selected from our store inventory as having the straightest cantilever, and used it with an ARC SP-3a, a Dyna PAT-5 and a DB Systems 1A until our home was burglarized. All that remained of it were the little dusty blobs of liquid Hg on the floor! The KMAL unipivot was silicone damped, so its rocking motion was not readily apparent. The arm wiring ran through 4 baths of liquid mercury in lieu of copper wire to eliminate, not merely reduce, any torque effects on the stylus. |
Long-time unipivot user here, starting with a Magnepan Unitrac I way back in the day. Having compared current top-end unipivots such as the Graham Phantom and Reed 3P against SME and Tri-Planar on identical tables, I can opine with some confidence that the perception of a difference in sound, quality, tracking ability and so forth is entirely psychological. Not only has no one been able to traceably document bonafide differences in channel separation, azimuth accuracy, anti-skate "error" or compliance. Manufacturers wouldn’t still be making both bearing and unipivot designs if they significant cost or performance problems. As much as folks on this forum are hobbyists, the folks making the tools of our hobby are hard-nosed businesspeople making engineered solutions to support it. If they couldn’t make money, they wouldn’t do it. That was empirically confirmed for me during the auditions I mentioned above. Using the same source material choices (a Sheffield Harry James, a Mobile Fidelity Donald Fagen and a first edition Getz and Jobim), I couldn’t hear enough of a difference to call one a gimbal and another a unipivot. They were all using the same Ortofon LOMC (I can’t recall which now). It was a remarkable demonstration of engineering excellence. One does get what one pays for. Especially for designs incorporating VTA on the fly. anyone claiming that there are VTF errors resulting from it or the bearing configuration don’t fully appreciate how the geometry is supposed to be employed. Geometry is geometry and the physics applying to it don’t change just because the bearing surfaces supporting the transcription engine have different designs. If the design is correct, that’s the end of the story. I actually had a long conversation with Tri Ma before I purchased my Graham. I found him a brilliant man with a true gift for how to extract excellence through continuous evolution of a fundamentally well-engineered design. The only reason I didn’t go down that path was some advice from the inheritor of my table design (Kirk Bodinet) about the physical modifications my Sota Sapphire III required to accept the Tri-Planar. The Graham was a drop-in with more adjustability. I held my breath, dropped the notably higher coin and have been totally satisfied ever since. Moral of the story: Audition, touch, adjust and buy the one you like. Forget about anything else and be happy.
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Effischer, Thanks for your detailed description of your experience. I heard a same table/cartridge comparison of a Graham arm and an SME arm. There were subtle differences in sound, but nothing so major that one would even think it had to do with some major fundamental difference in design. There are many good arms out there of all sorts of design. I’ve owned gimbal arms, an air bearing tangential arm, a Well Tempered monofilament (fishing line) arm and two unipivot arms (Graham and Basis Vector); I currently use the Vector arm. The easiest to set up and adjust is the Graham. The arm that seems to attack almost all theoretical issues is the Reed T-5 and it is quite elaborate and expensive. I’ve heard it, but not in a system I knew very well. Fortunately for my finances, it would not fit on my table. |
@helomech Re: "Some unipivot tonearms (VPI for example) are poorly designed because they are inherently unstable, thus the tracking force is in a constant state of fluctuation as the tonearm traverses the record." Uhhh, no. They are no more unstable vertically, the axis of tracking force, than any other tonearm. There is no mechanism that accounts for what you describe, varying the vertical force simply from the arm moving laterally across the disc As for the 'wobble', no one has ever been able to quantitatively measure any impact of the unipivot bearing during playback. It only makes inexperienced users uneasy during cuing. Finally, a unipivot bearing, by design, is incapable of rattling, chattering, or moving forward and back during playback. That's it X, Y, and Z axes. There is no 'inherent instability' in a unipivot arm during playback. What you describe sounds more like a cartridge compliance/arm mass issue which I'll affect any improperly paired arm and cartridge. The classic example being a low compliance MC mounted in a low-mass tonearm. We knew this 50 years ago when people tried mounting an Ortofon or Supex MC in a Grace 707 or Infinity Black Widow tonearm. Those bad matchups yielded a very high arm resonance frequency that wouldn't track well and lacked bass. The reverse was an ADC XLM or Sonus Blue (both very high compliance carts) in a Technics or Denon medium-high mass arm. The too-low resonant frequency was extremely susceptible to footsteps, and often the cantilever suspensions just failed from trying to push around a high mass arm. If you want an arm whose tracking force is unimpacted by warps and such, then get an arm with spring loaded rather than gravitational VTF, like a Rega 330.
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@dynacohum : The Keith Monks unipivot arm with its four mercury baths is certainly unique! I wish I had kept mine! I sold it because I had problems with the liquid silicone contaminating the mercury contacts, causing channels to drop out. I bought the Australian JH Formula 4 unipivot instead. |
@dynacohum : I have a NIB Mayware unipivot awaiting installation, also a NIB Shure V15 mkV that would match well with the Mayware compliance-wise. |
You’d be correct regarding the VPI’s stability in that they act similarly to a lab scale—they have a “stable” balance configuration. As such, they are constantly counterbalancing any change in vertical height. Take a digital stylus force gauge and any record with a slight warp and measure the difference in VTF of the VPI’s unipivot between the high and low portions of the disc. You’ll measure a difference for sure!! In fact, you can even do this experiment with a flat record and measure a difference between the inner and outer disc grooves. The tiniest fluctuation in elevation will change the VTF with a balanced-stability tonearm. So yeah, they are stable in the static academic sense, but we are discussing a dynamic system. They are unstable in terms of tracking force. Think about the fact that VPI’s upgrade/flagship arms are now gimbaled. There’s good reason for that other than the “wobble” that so many found disconcerting. “Tonearms come in three three balance flavors: "stable" "neutral" and "negative". A "stable balance" arm is one where the center of gravity of the moving system is located below the pivot point. That's true with most unipivot arms, where the lower center of gravity aids stability. A "negative balance" tonearm is one where the center of gravity is above the pivot point, and a "neutral balance" arm is one in which the center of gravity is in line with the pivot point. If your tonearm is "stable balanced," the further from the record surface you measure tracking force, the less accurate will be your result. That's because a "stable balanced" arm wants to return to its resting position on the record surface. The further up from the record surface you measure the tracking force the greater will be the measured force because the arm wants to return to its resting point on the record surface. In practical terms that means if you measure 2 grams well above the record surface, the tracking force will be lower and perhaps too low at the record surface. That is one reason the simple Shure "teeter-totter" device is not accurate with "stable balanced" arms. A "negative balanced" arm means the higher up you measure VTF the lower will be the tracking force at the record surface. A "neutral balanced" arm doesn't care where you measure VTF. It will remain the same high or low. If you have a unipivot arm like a VPI, Kuzma Stogi S, or pre "Magneglide™" Graham arms, it will be "stable balanced". Kuzma's 4 Point is negative balanced. Most gimbaled arms close to neutral balance. Graham's Phantom Supreme is neutral balanced. Each of these balance conditions produces different results under dynamic conditions such as when encountering a warp, but that's best discussed in a tonearm review.”
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You can achieve neutral balance with a unipivot, as you achieve it with other designs. Graham arms, for example are neutral balance arms. The Graham does not rely on the center of balance being below the pivot point to minimize wobble; that is done with magnetic stabilization. There is no one inherent quality of unipivot arms that someone has identified here that cannot be addressed by correct design. A good unipivot arm is a good arm, as is the case with all other designs. |
I was lucky enough to get one of the last production Schiit Sol tables after they fixed all their qc issues. The arm is mildly "stable balanced" and I know to adjust for measuring correctly for increased height. Same is true for measuring vta. I will say setup of this table was tedious just due to being able to adjust so many parameters in a very mechanical way, but the sound is fabulous. Lively, clear, and very consistent. No concerns with it being a unipivot. Old school, simple design much like a well functioning carburetor on your car. |
dynacohum: One of those Keith Monks mercury-dampened arms came with a vintage Thorens TD124 I bought. Scared the heck out of me, though I appreciated the inventiveness of the design. I called the city and a guy came out in a hazmat suit with a specialized vacuum and sucked up all that Hg. They treated it as a spill, which, thank heavens, didn’t happen. Needless to say, I rebuilt the Thorens and added an Ortofon (Jelco) arm and a Cadenza mono cart. To play all those used mono’s I keep buying 🙄. Happy listening! |
@helomech First, you need to quantify the amount by which VTF varies over any vertical displacement (warp), say 5mm. That would be a seriously warped record. Next you need to assess any impact that has on the cartridges tracking ability. And the map those, if any, to changes in SQ that can be attributed to those variations in tracking force, and not the warp itself. Finally, you need to assess any variation in VTF as a function of arm length, as well as changes in Stylus Rake Angle (SRA). Let's throw in one last variable, F=MA. To function at all, the stylus and associated motor, MC, MM, or MI, must move relative to the cartridge body and arm. Ideally the arm mass would be infinite, and the resistance to movement vertically or laterally should be zero. Obviously mutually exclusive requirements. Instead, we are left with a mass (the arm) suspended by a compliant spring (the cantilever, stylus, and it's suspension) that results in a resonant system that has been objectively determined to be optimal around 9-10Hz. This enables the relative motion and generation of the electrical signal, while not being excited by the lower warp frequencies. Get that too low and even a small warp can throw the stylus out of the groove. Too high and 'the tail wags the dog', the system is too stiff and the sylus/cantilever pushes the tonearm, wiping out the bass. A dancing bear, to be sure - the miracle being mechanical not that it dances well, but that it dances at all. With that data, you can begin a conversation on this dynamic system. Until then, the model is incomplete, and the discussion theoretical at best. |
My thinking is that Uni Pivot Arms addressed an issue with bearing manufacturing tolerances, materials, and quality control. I think the bearing industry has caught up, and perhaps surpassed some of the Uni Pivot Arms out there (I have a couple of very vintage Mangepan arms, one installed on a vintage Realistic direct drive that has been converted to manual, from semi-auto. It is seldom used these past twenty years, newer equipment has taken over the dedicated mono role.) Uni Pivots have a loyal following, and for that upper echelon TT and cartridge set-up, when set up properly, may remain unbeatable for awhile yet. |
I have ownd a Naim Aro for 25 ears along with a myriad of other arms. It is very stable due in part to the low centre of gravity ( below the pivot point ). You either had a faulty arm or maybe it was your bouncy castle ( Linn ), though Martin Colloms used the Naim Aro on his Linn for many years and one of his key criteria in choosing the arm was its resistance to the problems of footfalls on his sprung wooden floor. |
I helped with installing a Naim ARO on a Linn table. The combination sounded good to me in the right system. It was quite a lively sounding combination which sounded good in the somewhat dead system I hear it playing. Whether it would sound good in my more lively horn-based system is another matter. Like any other component it matters how it works with other components and the sound one is trying to achieve. But in the most gross terms for a tonearm/cartridge--whether it tracks properly, is not susceptible to troubles with warps, etc., the ARO performed well. |
"I have ownd a Naim Aro for 25 ears along with a myriad of other arms. It is very stable due in part to the low centre of gravity ( below the pivot point ). You either had a faulty arm or maybe it was your bouncy castle ( Linn ), though Martin Colloms used the Naim Aro on his Linn for many years and one of his key criteria in choosing the arm was its resistance to the problems of footfalls on his sprung wooden floor."
Actually, I think the Naim Aro is one of the few non-Linn arms that works with the old fruit box. However, since we are discussing Uni-pivot designs, the basic issue with the design is the problem with the dynamic azimuth error as the arm encounters irregularities in the groove. Resulting in ’rolling’ side to side. Not ideal, IMO. |
Daveyf, To the extent that a unipivot might tilt when encountering some sort of irregularity in a groove, might this degree of freedom be a plus in that the stylus will tilt to accommodate the shape of the groove rather than plowing through the groove? This is at least an interesting theoretical issue. Thank you for raising it. |
I have a VPI, the arm doesn't bother me. I rotate carts every month or so and it's like setting up any other cart like on say a Rega. Now that I use a unipivot, it kinda bothers me that a gimbaled arm can only track in two axis, while the unipivot is free to track along a theoretical infinite axis. Last time I looked, most records aren't perfectly flat. |
Another Schiit Sol owner here, The first time you send that tone arm flying with the slightest touch is pretty scary. I mean, it is totally unconstrained! You read the manufacturer’s info to see if that’s supposed to happen. But like anything else, once you’re set up and everything is working smoothly, you just get used to it and life is good. I still sometimes wonder how that big old cartridge body (Grado Opus3) remains stable balanced between the pinpoint of the stylus and the needle point of the unipivot. But it does. |
After 30 years using the original Rega arm, I have no doubt that the unipivot 3D arm on my VPI Prime is a significant upgrade. However it sounds a bit better since I added the Dual Pivot, which also solves the possible problem with azimuth because it doesn't wobble anymore. Setup is easier because now I adjust azimuth by turning the screw on the Dual Pivot which is dramatically easier than rotating the counterbalance while try to keep the tracking force from changing. I don't know why VPI decided to start using gimbal bearings. I think they are just responding to the market and the anti uni-pivot chatter. I say that because when I met Harry W in the late 80's and told him I was thinking about switching the aluminum platter on my 1st generation HW19 turntable to his newer ones with a more vinyl like surface he told me not to. He though the aluminum sounded better but Sota was kicking his butt with its claim that that records sound better on a surface that was more like vinyl. I'll point out that now, all VPIs use metal platters.
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It's just a matter of preference. There's something very appealing about the precision of an arm such as a Triplanar or SME V. It's a tactile thing. By comparison, a wobbly unipivot feels imprecise. Again, just a matter of preference. |
People often say they don't like how the arm tilts if they just stick their finger under the lift and trying to pinch the lift leads to them accidentally sliding the needle across the groove. I say never touch the arm when you are ready to play the record; use the cuing mechanism. I also hear people talk about accidentally bumping the arm while cleaniing the stylus or changing a record, or whatever, and having the srylus hit the platter. Again, this never happens if, when play is done, one returns the arm to the rest and does not cue down. It is just safer and more convenient to always be cued up until lowering the needle to play. |
I have had two undamped VPI unipivots, a 9" on the Scoutmaster and a 10" on the Prime. Yes, they are "fiddly" and need to be handled with care, but I like the simple technology and have never noticed any distortion or noise that I could attribute to the arm. VPI has now moved to a gimbled arm(s) and may not make the the old unipivot any more. I suppose there is a good reason for this change. |
I agree with the sentiment that it is all in the execution. Each implementation has theoretical advantages in some way and if properly designed and executed, any of them can shine. A tonearm is a precision instrument so the best are not inexpensive, but I think once you reach a certain level they all are very capable performers. |
Like I said at the beginning of this thread, there are many modern tonearms that could be categorized as "unipivot", but the best ones are actually modified unipivots so as in one way or another to cure the inherent issues with a pure unipivot. Graham, Kuzma, VPI (with the add-on option), and I am sure many others are in this category. Results can be superb. But a pure unipivot, like the Keith Monks (which I also once owned) is passe’, in my opinion. Besides, the mercury bath contacts (Keith Monks) were a nightmare. |
I had a cartridge trial back in the 1970s which definitely had a mismatch with the tonearm as it couldn’t track any warp. Prior to using a gimbaled arm, my Brooks Berdan highly modified SME IV from 1989, I used unipivots. I still use an Ultracraft 400 unipivot arm on a VPI 19-4 with a Grado G+ 78 cartridge with no dampening (silicone in the base). It works great. For my LPs, I use the SME above with a Dynavector 20X2 L (previously with a Benz Ruby 3). It is so great other than setting up it’s VTA (spring loaded and coarse adjustments). My best friend has an upgraded VPI Scout with a unipivot VPI arm. We don’t notice any problem with the bass using a Dynavector 20X2 H. Tight and deep bass, tracks warps great. This is a very interesting forum. If I were to purchase a "unipivot" arm in the future, I will ensure that it has some type of balancing/range mechanism rather than a totally free floating (like my Ultracraft) arm. The Tri-Planar arm was a second choice to the SME but more expensive at the time. |
