Pindac, as the length of an underhung tonearm is very flexible, in that you can choose almost any length you want within reason, I suspect that you would not have to modify an existing tonearm board or plinth in order to mount an underhung tonearm of your own creation. It would actually be very simple. You do not have to think rigidly in terms of 9 inch, 10.5 inch, 12 inch lengths. Nor do you have to think rigidly in terms of pivot to spindle distance, since an underhung tonearm does not reach to the spindle in the first place . For example, the recommendation for the Viv tonearm is to mount it such that the stylus tip is 17.5 mm short of reaching the spindle.
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Dear @cleeds : In reality the issue is not " dogmatic theorists " but common sense founded in the Löfgren theory where he proved through scientific equation calculations what for many years are the Standard for tonearm/cartridge alignment, it’s not that we accepted it’s the Standard in the industry just like the RIAA eq. VIV Labs is telling you to come back to before 1924 because its " sounds better " and he gaves you no single factible evidence/fact/measure/theory that that could be true. As I said the overall issue is common sense that I know you have in very good shape.
Here part of the history of the Löfgren Standard that VIV LAbs " want it " to forget:
"""" During the recent decades, several important contributions on the optimisation of
Wilson minimised the change in tracking angle by applying offset angle and
In 1925, Wilson published the design of an alignment protractor [2] based on [1].
In 1929, a Wireless World article [3] (author unknown) included this statement: "It is
The first discerning statement on the origin of tracking distortion was made in 1937
The formal relationships between tracking error and tracking distortion remained
Löfgren developed an optimisation method which involved applying the minimax
The introduction of this inverse radius weighting complicates the analytical solution,
The optimum solution from Löfgren provides for an offset angle and overhang which
Löfgren’s paper was followed by papers from Baerwald [7] in 1941, Bauer [8] in 1945,
It’s not easy for me to post ( I’m not good with computers. ) the Löfgren equations and here a summary of it but exist several calculators in the internet where we can see all those equations.:
QUICK AND NOVEL ’LÖFGREN A’ ALIGNMENT CALCULATIONS The following equations provide a quick and novel (but reasonably accurate) method of calculating the optimum alignment parameters for the ’Löfgren A’ alignment, certainly good enough for practical alignment calculations. Using these equations, the optimum offset angle, the optimum overhang, and the resulting maximum |WTE| (at the three WTE peaks) may be easily calculated. The only input required is the arm length in mm. The equations utilise three numbers which remain essentially constant over the range of alignment values likely to be encountered in practice. Also included for comparison purposes are the results for the ’perfect Löfgren A’ solution. You may be surprised at the accuracy of these equations! The equations are based on an inner groove radius of 60.325 mm, and an outer groove radius of 146.05 mm. Notation: L = arm length, = optimum offset angle, d = optimum overhang, WTE = weighted tracking error. 1. Quick calculation of Offset Angle: L.sin ≈ 93.516 mm (Löfgren’s Linear Offset) so sin = 93.516 / L so = arcsin(93.516 / L) For L = 250 mm, sin = 0.374064: = 21.966 degrees The ’perfect Löfgren A’ result? = 21.963 degrees! 2. Quick Calculation of Overhang: 2.L.d - d 2 ≈ 7987 mm2 (Löfgren’s Ra 2 term) so d = L – SQRT(L2 - 7987) mm For L = 250 mm: d = 16.5180 mm The ’perfect Lofgren A’ result? d = 16.5198 mm! 3. Quick Calculation of Maximum |WTE| value at the three peaks: L.cos * max. |WTE| ≈ 2.709 degrees so max. |WTE| = 2.709 / (L.cos ) degrees per mm For L = 250 mm and = 21.966 degrees: max. |WTE| = 0.01168 degrees per mm The ’perfect Löfgren A’ result? = 0.01168 degrees per mm! CALCULATING TRACKING DISTORTION Tracking Distortion Löfgren showed that at lower distortion levels, tracking distortion is principally second harmonic in nature. He developed an expression which approximates this distortion, and presents it as the product of two factors in his EQN (22). This is an historically significant expression, as Löfgren was the first to show the relationship between the four variables involved in the generation of tracking distortion. A summary of Löfgren’s derivation of this expression is included in Section S10 of this analysis. Löfgren’s EQN (22) is: ≈ 𝑉 . 𝑅 This shows that the tracking distortion is proportional to the recorded velocity (𝑉) and tracking error (), and inversely proportional to the angular velocity of the record () and the radius (𝑅). As Löfgren notes, the first factor is independent of the position of the needle on the record, while the second factor changes continuously during play. We also must ensure the units are consistent. For example, if 𝑉 is in mm per sec, then R has to be in mm, and if is in radians per second, then has to be in radians. For the LP record with a typical peak recorded velocity of 100 mm per second and a speed of 33 1/3 RPM, the angular velocity of the record equals 360 (degrees per revolution) * 33 1/3 (RPM), or 12,000 degrees per minute, or 200 degrees per second. For consistency of the units, tracking error is then in degrees and groove radius is in mm. So the maximum distortion is: = 100 / 200 * tracking error / radius For example, with a tracking error of 2 degrees at a radius of 130 mm, the maximum distortion = 100 / 200 * 2 / 130 = 0.0077, ie, the second harmonic level is 0.0077 of the fundamental or 0.77%. We refer to the tracking error divided by the radius as the weighted tracking error or WTE, which means the tracking error weighted by the inverse of the groove radius. Thus, the maximum distortion is: = (100 / 200) * WTE = 0.5 * WTE (WTE in degrees per mm) RIAA De-emphasis. An added factor which Löfgren did not include, and which needs to be included, is the effect on the distortion of the RIAA frequency de-emphasis in the phono playback preamplifier. In accordance with the RIAA playback response curve, over the frequency range from 20Hz to 20KHz, which is about 10 octaves, the gain changes by about - 40dB. This averages at -4dB per octave, as Stevenson states. For the harmonic distortion components, this has the effect of attenuating the second harmonic by 4dB with respect to the fundamental, which means the distortion is lowered by this amount. This is a gain change of 10-4/20 , so we must allow for this by multiplying the distortion in EQN (22) by 10-4/20 . Thus, distortion = 0.5 * 10-4/20 * WTE (WTE in degrees per mm) In summary, the constant 0.5 * 10-4/20 converts the WTE figure in degrees per mm to a second harmonic distortion figure 30. At any playing moment, the actual level of distortion being produced is proportional to the recorded velocity (𝑉) at that moment. Thus, the distortion factor is the maximum expected distortion level. As a brief aside, we can convert the distortion constant = 0.5 * 10-4/20, which is approximately 0.3155, to the constant 1.76 used by Stevenson on page 215 of his paper. Stevenson used 100 mm/sec RMS (not peak) recorded velocity, so we must multiply the distortion constant by the square root of 2. He also used radius values in inches (not mm), so we must divide the distortion constant by 25.4. Stevenson also calculated percentage distortion, so we must multiply the distortion by 100. Thus, the distortion constant becomes 0.3155 * SQRT (2) * 100 / 25.4 = 1.7566, or 1.76, per Stevenson’s article. Thus, the maximum percentage distortion = 1.76 * WTE, where WTE is in degrees per inch. The RMS Value Löfgren based his ’Löfgren B’ alignment solution on the minimisation of the RMS distortion caused by tracking error. We’ll now investigate how we determine the RMS distortion. The RMS value of a varying quantity is a single figure which is a statistical measure of the magnitude of the varying quantity. In this application, the varying quantity is the distortion level occurring at each radius point across the record surface. The RMS distortion level is the single figure representing all these distortion levels. The %RMS distortion is simply the RMS distortion multiplied by 100. Procedure to Determine RMS Distortion To determine the RMS distortion, we perform two fundamental steps: 1. Define a distortion indicator or distortion factor, which is an expression indicating the level of distortion being produced at any point. 2. Apply the necessary mathematical procedure to the distortion factor. Löfgren’s EQN (22), described above, is a suitable distortion factor, as it indicates the level of second harmonic distortion caused by tracking error. As noted, it consists of two parts - a fixed part and a changing part. The fixed part, 𝑉 , is comprised of the peak recorded velocity on the record, divided by the angular velocity of the record. This is considered a constant, with a value of 100 / 200 or 0.5, as described. The changing part, 𝑅 , is comprised of the tracking error divided by the radius R, and it continuously changes during the play of the record. We refer to this part of EQN (22) as the weighted tracking error or WTE. The calculation of the tracking error is based on the inverse sine trigonometric function. The WTE is calculated using EQN J on page S9-6. Of course, the RIAA correction still needs to be applied to EQN (22) as discussed. In summary, the underlying method to calculate an RMS value includes the integration of the square of some function. In this case, the function is Löfgren’s EQN (22), where the WTE part is given by EQN J .
Cleeds, you said you read all the thread then I suppose between all posts you already did it with mines and especially the 3-4 latests ones that describes why I’m talking of common sense.
Look, the VIV Labs is not the first and not the last Stampede in audio where audiophiles " runs " with out really know why are inside the Stampede that arrives nowhere, that impedes to stay nearer to the recording. Yes, its develops a sound that they like it but that is far away from what it’s in LP groove modulation . Each one of us have our specific targets, the VIV followers has only one: I like it no matter what, good for them.
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@lewm It sounds a easier sell, when explaining the -17.5mm dimension as a guideline. It won’t be the worse mistake I made with a Tonearm, when it comes to resting on laurels and believing enough is achieved, that one is today looking like the sitting on the usage of the SME IV for such a long period. After a recent experience of being demonstrated the latest guise of the Tonearm I use with the Signal Wire of choice in the Wand, DIN> RCA, Phonostage Signal Path, Phonostage Power Chord, RCA>RCA, Speaker Wire. Along with a New Speaker in use, I am lost for words, dumbfounded, and still remain scratching my head trying to work out, how the experience as been super impressive and standout over other encounters which yielded a impressive experience. Looks like this Tonearm Designers work is now ’out of the bag’ beyond the UK. The Tonearms have has now gone Global, there are users now in Mainland Europe, Australia and America, which one of three in the USA is with a user based in Washington. |
@cleeds , Like @raulirugas said, what you think you hear is meaningless. I include myself in that category. With issues like this science always knows best. Everything else is alchemy. I have made my own missteps in the past and have learned not to buck the reality of the situation. Viv owners seem not to understand that reality and that they have been taken advantage knowingly or not by the purveyors of snake oil. There is a sucker born every minute and I have to admit I have been suckered plenty. In order to be old and wise you have to be suckered a lot. @ pindac, like I said above there is a sucker born every minute. Consumer beware. " A bose radio can sound good to some people." There is no such thing as a perfect tonearm. Each one has a slew of compromises which should be aimed at minimizing all significant sources of distortion in a balanced way. The offset pivoted tonearm with anti skating is the solution scientists came up with over a period of 100 years and most of the work was done 90 years ago. In state of the art systems the sonic benefits of this design executed intelligently are obvious. My suggestion to those Viv owners who are looking for the best sound quality is to suck it up and get rid of that arm. That it sounds good to some people is meaningless. @rauliruegas , you may not be so hot typing English but there can be no doubt you know how to read it :-) |
@mijostyn Ague your point and make all the analogies required to get your point across, I don't see it being heeded, iif a individual has their mind set on experiencing a device they will. If such a experience has proven more satisfying through demonstration, than a design that has aligned itself to minimising a host of Mechanical and Geometry concerns as being presented within this thread, it is looking quite likely the most satisfying option is to become a priority pursuit. When looking at the Tonearms now being reported on, as less preferred, even superseded, by the Viv Lab Arm, it is going to take a lot more than futile Argument or fanciful Analogies to steer one to the course being proposed by yourself. It looks like, from my perspective a enjoyment has been discovered and is one worthy of maintaining, which pretty much suggests the entertainment factor of listening to recorded music is being met. Who has a goal that does not include that?
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