That sounds like a good method, Christian. It is simple and repeatable. Do you check the headshell with a level to assure that the azimuth has not changed? Perhaps it does not matter if the stack of cards is wide and flat enough to assure the arm post is going up and down plum and does not tilt slightly. According to a dealer I know who was very close to Alastair Robertson-Aikman founder of SME, ARA used a spirit level on the headshell to confirm azimuth when he made adjustments to arm height.
My thoughts on cartridge/arm set up
- Thread starter PeterA
- Start date
That sounds like a good method, Christian. It is simple and repeatable. Do you check the headshell with a level to assure that the azimuth has not changed? Perhaps it does not matter if the stack of cards is wide and flat enough to assure the arm post is going up and down plum and does not tilt slightly. According to a dealer I know who was very close to Alastair Robertson-Aikman founder of SME, ARA used a spirit level on the headshell to confirm azimuth when he made adjustments to arm height.
Exactly - what is the height figure that matches perfect horizontal of the tonearm (and surely cartridge top plate)?
On a SME 3012R, a change in arm height will always result in an azimuth change due to design of its knife edge bearing. This is because the axis of its vertical pivot is not offset to the same angle as the headshell. In contrast, the vertical pivot axis of the SME V and its derivatives is offset to match the headshell. But on a 3012R, the change in azimuth in going from a 180g record to 200g is extremely small and may be difficult to notice on a small bubble level.
Getting back to this, with my 10" arm, I recently measured a 4% increase in VTF, when I dropped the arm 3mm. From the above table using your arm, I am extrapolating that you would measure a 2% increase, going from 18.5mm to 15.5mm. However, because your arm is longer, to get the same SRA adjustment that I got, you would need a longer vertical drop, which might bring your VTF change perhaps to 2.5% or more. The difference in arm lengths between our arms would account for part of that difference (2% vs 4%), but also the geometry would play a role. It was claimed by Al M in another thread that you had measured VTF changes by raising and lowering your arm, and that it wasn't significant, but without a reference to any data. Now you presented this data, which is great. Do you consider a 2%, or 2.5% VTF change significant? If not, what's your cutoff? To me, whether it's 1%, 2%, 2.5% or 4%, I call that quite significant, which is why I always contend that adjusting SRA/VTA must be done is such a way that preserves all other parameters, including VTF, because in my experience, even tiny VTF adjustments can have a huge effect on tonal balance and tracking. So how do you feel about all that? Does Al's statement represent your thinking? It must, since you don't care to reset any other parameter when raising or lowering your arm.
Last edited:
Hello microstrip. I do not know if you want me to measure the arm being horizontal while the stylus is resting on the platter. Perhaps you are referring to the height figures in my original post. The height figures in my original post of this thread where I quote arm height measurements in mm and VTF figures in grams are calculated by measuring the distance from the top of the SME arm board to the bottom of the arm rest platform using the mm scale on the side of my SME paper protractor. These figures, corresponding to different arm heights which I set for the range of LPs in my collection varies from 16.0mm to 18.5mm. There are six values.
If I place an LP on the platter for which I have assigned a VTA value of 17mm, and then raise the arm so that the SME printed lines on the arm tube are level or horizontal while the stylus rests on the LP, the arm height measurement found by the process I outlined above, is 17.5mm. If I place an LP on the platter with a VTA value of 18mm, the arm height is 18.5mm. So, using just these two examples, it seems that I lower my arm from horizontal level by 0.5mm to achieve what I prefer as a VTA/SRA setting.
Michael Fremer wrote that it takes a vertical movement of 4mm for a 9" arm to change the SRA by 1 degree. So, 1mm is 1/4 of a degree in a 9" arm, and even less in my 12" arm. So, lowering an arm 0.5mm down in back from horizontal, the SRA changes by 1/8th of a degree. With my 12" arm, it is about 1/10th of a degree. Of course, I don't know the SRA when my arm is perfectly horizontal, I am simply saying that whatever it is, it seems I prefer it down about 1/10th of a degree.
I should emphasize that I do not adjust arm height by record thickness. That is only an approximation. I listen for best sound, which is lowest distortion. I assume this is the SRA angle which most closely matches the original cutting head angle when the record was made. I have many examples of records of slightly different thicknesses which have the same arm height settings in my collection of LPs.
Thanks. My question is simple - the tonearm is a very simple system - a rigid system supported at two points, the stylus and the vertical bearing. The center of the gravity of the tonearm is fixed once we set weight and does not change. In a statically balanced tonearm we adjust the COG in such a was that we get the correct VTF and the remaining force is supported by the vertical bearing. This adjustment is independent of tonearm angle as moving the tonearm up or down does not change the COG - if people perceive changes they are due to additional forces, such as bearing or wire friction - not a good thing, IMHO.
However, your tonearm is dynamically balanced with a rotational spring - after you get it horizontal - zero VTL force - you set the VTF force with a spring. This force is proportional to the spring rotational angle, it is why you get the nice graph of variation I plotted, considering that the average 17.25 mm was the horizontal. What you see is just the increase of VTF when you increase torsional angle of the spring, as expected.
This to say you have been debating apples versus oranges - what you get and other people get is completely different because the mechanisms of establishing the VTF are different.
Some people prefer static balance because using it the VTF in independent of tonearm angle - something that does not happen with dynamic VTF. However, this would only affect severely warped LPs, something no audiophile will put on his turntable. And yes, MF got it wright.
Attachments
Thank you microstrip. I have two questions:
1. If the dynamically and statically balanced arms are each set at 2.0g VTF for a 110g LP then how would VTF change for each arm if it were to then play a 200g LP which is 1mm thicker?
2. If each arm is raised by 1mm to play the thicker LP, would the VTF remain the same at 2.0g for each arm?
“Some people prefer static balance because using it the VTF in independent of tonearm angle ...”
This is incorrect. VTF dependence on tonearm angle is only a function of the height of the arm CG in relation to the vertical pivot. It is basic physics. The only arm whose VTF is independent of tonearm angle is one whose CG is coincident with the vertical pivot, known as neutral balance.
PeterA - your SME arm will exhibit an increase in VTF when going from a thinner to thicker record basically as a result of it being a design with weak stable balance and not necessarily due to increase in spring torsion over such a small distance.
This is incorrect. VTF dependence on tonearm angle is only a function of the height of the arm CG in relation to the vertical pivot. It is basic physics. The only arm whose VTF is independent of tonearm angle is one whose CG is coincident with the vertical pivot, known as neutral balance.
PeterA - your SME arm will exhibit an increase in VTF when going from a thinner to thicker record basically as a result of it being a design with weak stable balance and not necessarily due to increase in spring torsion over such a small distance.
Peter,
have you ever experimented with;
--whether small degrees of change in the tightness of your set-screws for your height adjustments make any sonic differences?
--whether time 'settling' and 'calming' after you 'disturb' your arm when you tighten your set screws effects the performance?
and no doubt no apparent difference is one possibility. I find anything that get's tightened on a tone-arm has effects on performance in both these areas.
Sorry, it is not. If you have a static system supported at two points the algebraic sum of torques related to the COG is zero independently of the position of the COG and the sum of vertical forces equates the total weight.
For example, if you have a bar supported at two points with a suspended weight at point anywhere in the bar, the distribution of vertical forces actuating on the supports does not change if you replace the string by a longer string, although the COG of the total system changes in height.
Anyway, as far as I see it is not relevant, as SME sates that Peter's V12 includes *Underslung weight housing corrects centre of gravity and provides non-reflective tone-arm termination.
Last edited:
For a spring arm : 1. playing a thicker LP is equivalent to decreasing tonearm height, so it would increase VTF 2. no difference.
For a static toneram - no difference any case, unless there are secondary effects.
“For a static toneram - no difference any case, unless there are secondary effects.”
WRONG. A tonearm achieving VTF by using gravity to unbalance the arm (“static balance”) has nothing to do with its inherent balance. It is stable, neutral or unstable, depending on the location of the CG with respect to the vertical pivot. Take an arm with stable balance, as nearly all tonearms are, and that uses the counterweight position to set VTF (“static balance”). Now measure the VTF on a digital gauge. Then put a thin spacer underneath the gauge to raise it up, say an eighth to quarter of an inch, and measure the VTF again. It will have increased. An arm having inherent unstable balance will exhibit the opposite behavior where VTF decreases as the stylus position is raised. A neutrally balanced arm like the Phantoms will not show any change in VTF
WRONG. A tonearm achieving VTF by using gravity to unbalance the arm (“static balance”) has nothing to do with its inherent balance. It is stable, neutral or unstable, depending on the location of the CG with respect to the vertical pivot. Take an arm with stable balance, as nearly all tonearms are, and that uses the counterweight position to set VTF (“static balance”). Now measure the VTF on a digital gauge. Then put a thin spacer underneath the gauge to raise it up, say an eighth to quarter of an inch, and measure the VTF again. It will have increased. An arm having inherent unstable balance will exhibit the opposite behavior where VTF decreases as the stylus position is raised. A neutrally balanced arm like the Phantoms will not show any change in VTF
Bruce B
WBF Founding Member, Pro Audio Production Member
Hello Tasos. I can not speak for Al, but I am assuming that he is referring to the data which is in the OP and which you quote in your post. I first posted that data on WBF in this thread on 9/20/17: http://www.whatsbestforum.com/showthread.php?23930-VTA-and-VTF-How-one-affects-the-other I posted it on AudioNirvana before that.
I am glad you asked these questions because they made me want to learn what the actual numbers are in a real world scenario. Here again is the data for how the VTF changes when the stylus is placed on the digital scale and my 12” SME arm is raised and lowered through a 2.5mm range. The midpoint, 17.25mm has a VTF of 2.0g:
16.0mm: 2.019g
16.5mm: 2.011g
17.0mm: 2.005g
17.5mm: 1.993g
18.0mm: 1.988g
18.5mm: 1.970g
The variation is 0.049 grams: an increase in VTF of 2.5% from the lowest value to the highest value. I have this 2.5mm range because I have chosen to try to match the SRA of the original cutting head. But if we were only concerned with record thickness, the figures would be much less. Remember, a 110 gram LP is only 1mm thinner than a 200 gram LP. So then, there would only be a variance of about 2.008 to 1.990, or about 9/1000ths of a gram up or down. That is only 0.45% variance in VTF due to change in thickness of the LP. miniguy wrote in post #9: “Bottom line is that most arms are designed with fairly weak stable balance so that variation in VTF due to thickness of discs and warp conditions are pretty small and would be difficult to discern audibly.” This supports the idea of not adjusting arm height.
However, the fact that I hear sonic improvements through a range of 2.5mm which is 1.5mm greater than the difference in the thicknesses of the LPs, suggests that trying to match the cutting angle of the groove may have a greater sonic effect than changes in VTF. So, I made some new measurements today of the changes to VTF on my actual LPs of varying SRA/VTA settings.
Using a digital caliper, I measured the distance that my digital scale’s platform is above the platter surface: 3.0mm. I then raised my arm 3.0mm higher than where it would be while playing these six LPs with different arm height settings and measured VTF with the scale resting on each LP. This way I can more accurately measure the VTF at the LP surface for each of the different LPs. Here are the results:
16.0mm: 2.013g
16.5mm: 2.008g
17.0mm: 2.001g
17.5mm: 1.992g
18.0mm: 1.987g
18.5mm: 1.980g
The variance in VTF is now less from one extreme to the other. Again, the LPs only vary in thickness by 1mm, so the LPs that I used are based on my sonic preference for lowest distortion, or my attempt to match the original cutting angle by listening. Here, the variance from 16.0 to 18.5 is 0.033g or a 1.6% increase in VTF from 1.980g to 2.013g.
In the previous set of measurements, where the scale was fixed on the platter and I just moved the arm up and down the 2.5mm range, the variance in VTF was 0.049g, or a 2.5% increase in VTF between the extremes. With the real world measurements that I took today using my actual LPs under the scale, the 0.033g change in VTF is a 48% decrease over the older figures which had a 0.049g change in VTF.
So to answer one of your questions, Tasos, I presume that Al meant the 0.049g change in VTF was not significant. In actual use, the difference is even less - 0.033g - as I just demonstrated. That is a change of 1.6% between the extremes. You think this is significant. Al does not, perhaps because he hears the improvements that these changes in arm height make to the sound of my system. I am not sure how significant changes to the other parameters are. I did listen to my cartridge set at 1.95 and at 2.05 VTF which are even greater differences in VTF than the 0.033 figure (1.967g and 2.033g), and I found that arm height impacted the sound to a much greater degree than just a change in VTF. I also know that if you leave your VPI arm fixed, VTF, SRA and overhang do change very slightly as you play LPs of different thickness in that 1mm range.
Regardless, I do prefer the sound of my LPs when I adjust the arm height through this 2.5mm range, even though I understand the VTF is changing up to 0.033g from one extreme up to the other, and the SRA and overhang are changing also. I don’t know by how much though. When I have some more time, I may look at my overhang under magnification to see how much it changes through the 2.5mm range in arm height changes. SRA is not so clear cut. If you keep the arm fixed, then you know that your stylus is not matching the original cutting angle of each of your LPs. If you listen for distortion and adjust SRA, then you may reduce the SRA error over someone who does not attempt to do this.
Al M. also prefers the sound of my system when I adjust the arm height for different LPs. If a string quartet sounds slightly off, we check arm height, and usually improve the sound by adjusting the arm. I also preferred the sound in your system when we adjusted the height of your arm for different LPs. My conclusion is that adjusting arm height to try to match the original cutting angle by listening for decreased distortion is more significant than the effect of the resulting changes in VTF and overhang. In the end, I adjust things by ear to create as engaging and convincing a sound as possible.
Bruce, what if adjusting arm height makes you enjoy the music more? My approach is to set it many times and to not forget it. I understand full well that others may not want to be bothered. That is fine.
Hi. For FR 64s, SME 3012r, Brinkmann arm, and Schroeder LT...would changing 110g LP to 180g or 200g Speaker's Corner or Classic Records cause an audible issue if one does not change height of the arm?
That depends on the hearing acuity of the listener, and certainly would be independent of tonearm type. Some may find any difference warranting a change in arm height. IMHO, any difference is not at a level to justify the inconvenience of adjusting arm height, especially if the arm lacks a calibrated provision. I just set SRA for average record thickness and leave it at that.
