Pivot to Spindle distance


My P2S distance is off by about 5 mm (over). But my cartridge seams to be aligned pretty good. Is there any advantage to having the P2S distance exact? Sounds spectacular with my redoing the entire setup.
Must have had a senior moment during the P2S alignment part.

VPI Aries
JMW-10 arm
VPI jig (to get it close)
WallyTractor (final alignment)
markpao
As long as pivot-to-spindle distance is close enough, you can still get overhang right due to the slotted head shell mounting available on most arm/head shell combinations.
Mark, just went to your system page, good looking system by the way but I have a question for you. In the description of your table you make reference to the 10 inch arm doesn't sound much different from the 9 inch arm it replaced, my question is, did you use the same mounting/arm board and set up jig that you used for the 9 inch arm? This might be the reason for the 5 mm difference in your ps2 measurement. Enjoy the music
Overhang is one thing, ARC is another.

Any longer arm, any longer spindle to pivot distance will have a ’flatter/less curved’ arc, that keeps the stylus in the groove ’straighter,’ i.e. less deviation from the 2 null points of any pivoted arm.

Each arm has specified null points, based on their arms ARC. There are 3 major variations of null points, so even if you follow the recommended null points, from a ’too close’ pivot point, you are probably within the range of one of them.

There are charts about arm length/deviation/distortion values, the differences are very slight, that’s why I went for my 12.5" arm, if long, I thought lets get the ’least’ deviation! I didn’t plan on hearing any difference, perhaps a mighty minimal (miniscule) amount of groove wear, I was doing a new TT, just wanted to do it.

Overhang is the final geometry of that arc.

Critical? It’s the same as having a slightly shorter arm IF you can achieve the proper overhang, i.e. short cartridge body, long mounting slots on arm or headshell ... that let’s you ’get’ the stylus presumably ’back’ enough.
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Images of Null Points

https://www.google.com/search?rlz=1C1SQJL_enUS881US881&sxsrf=ALeKk00QjTO47rthOxtCNM83jWfclhgTYQ:...

3 null point recommended methods

http://www.dvautier.com/nullpoint/null.htm
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Sounds great! If still curious, see if you perceive any difference regarding the outer edge, middle, inner tracks, that is the essential difference for the 3 null point systems
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They make these alignment discs for specific arms, but any one of them has enough lines that you can find the distance for your Tonearm.

https://www.wish.com/product/5cd656f57be1080861950976?hide_login_modal=true&from_ad=goog_shoppin...

The other side, smooth, is good for initial anti-skate setting, then you need to confirm/refine by listening. Something with a solid center, and 'equal' l/r elements, including live audience noise (confirm it's a wide audience and performers are center on the stage.

I use side 2, tracks 2 & 3 for anti-skate refinement, 3 world class guitarists play together

https://en.wikipedia.org/wiki/Friday_Night_in_San_Francisco
I just looked again and see your distance is ’over’. The concepts are the same, in your case, a longer cartridge body, longer slots in the tonearm or headshell let you get the stylus overhang correct. Now you have achieved an ARC of a 5mm longer arm.

However, a 5mm longer arm ’might’ have a different recommended overhang than what is specified for your arm’s length/exact pivot location.

Again, sounds great!



@islandmandan 
I kind of figured that but wanted to make sure I wasn't missing out on something.

@ tooblue
Good observation. And thanks for the compliment. But no, I had to drill in a totally new arm board I got from VPI when I went to the 10" arm. The 9" had a different mounting location. The VPI jig was also new for the 10" as well as a Wallytractor.

@ elliottbnewcombjr

” However, a 5mm longer arm ’might’ have a different recommended overhang than what is specified for your arm’s length/exact pivot location.

Ok, this is interesting information. I’ll look into this.

 








Mark, You wrote, "My P2S distance is off by about 5 mm (over). But my cartridge seams to be aligned pretty good."  Define "pretty good".  Thanks.
if it ain't right, it ain't right
Sounds spectacular with my redoing the entire setup.

Yes, I could have told you that. Probably everyone here has heard this before, but the thing is most people while they want to believe they think and figure stuff out the truth is they mostly repeat what most people say. Because if a lot of people say it then it must be true, right? 

Study those diagrams above, which you might as well, I'm not about to waste any more time on it. Same old. What they show, if you think about it, is no pivoted arm is ever tracking correctly except at two theoretical points. All the rest of the time it is off one way or the other.

Therefore, logically, no matter how much time you put into it or how perfectly perfect you get it, it's perfect for like one nanosecond per side. All the rest of the time it is off, and a lot of the time by a lot!

Only, funny thing, no one ever seems to notice. No one. Ever. In the freaking history of records. People sick and tired of me saying this, but nowhere near as sick and tired as I am having to repeat patently obvious truth that somehow never manages to stick. Something like 90 plus percent of the sound you get is the needle being drug through the groove. If you get VTA and VTF right, there's another 5%. Very last thing on the list is the alignment that is affected by P2S or overhang. 

Absolutely the least important of all alignment parameters. AS YOUR EARS ARE TELLING YOU! But funny thing, audiophiles never really seem to trust their ears.

We now return you to our regularly scheduled non sequiturs.
Lewm,
I used that term loosely. The diamond follows the arc on my Wallytractor and the cantilever is parallel with the null points.






@millercarbon

I like the way you put it - and phrased it. 
Who CAN argue the point(s) you make?
I ... at least can't - and I won't. 👍🥂 

Michélle 🇿🇦 
If you search my posts you will find that I have answered this question over and over. The answer is an emphatic no. If you have headshell slots and can reach the overhang spot exactly, all is fine. 
There is a certain person on this board, on this thread in fact, who again and again espouses false truths. It is annoying as can be. And I ain't talking about Millercarbon who though has his own picadellos at least knows the basics of turntable set-up and geometry. 
And while I am in a mood for ad-homynym references, Lewm knows his stuff too. I am a bit surprised by his response in this thread though. 
Look, your cartridge knows nothing of P-S. It only needs to be able to trace the proscribed arc for a given alignment and if overhang is reached, it will. For a given tonearm, P-S only affords adjustment for the largest range of cartridges with various mounting hole to stylus tip distances ASSUMING headshell slots. 

Thanks for all the valuable information. Stringreen summed it up in the fewest words-  " if it ain't right, it ain't right"
I decided even though everything else is in alignment I'm still going to redo it and get it right all around.
Why aren't all overhangs the same you might ask?
elliottbnewcombjr"Why aren't all overhangs the same you might ask?"

Why aren't all tonearms 23cm long why aren't all tires the same profile?
@markpao , don't bother Mark. As long as you have the right offset and overhang with the cartridge you are using you are in business. If the cantilever is parallel to both sets of lines then all of the above is true. The P2S distance is just to get you in the ballpark. You have already found your seat. Stay there. You just risk damaging something playing around.

Longer arms are not a panacea. They have a greater polar moment of inertia which causes much more distortion than any improvement in tracking error can resolve. This is why many of us prefer shorter arms and why many tonearm manufacturer's scratch their heads in response to this market demand. There are very few modern cartridges that require tonearms that heavy. 
fsonicsmith, I admit to being overly inquisitive at times, in my search for clarity, but on this thread, all I asked for was the OP to explain the very vague term he used to indicate he was satisfied with his alignment despite the known 5mm error in P2S ("pretty good"). I am an alignment nihilist, almost like MC, but I do make the effort to get it right, once. After that, I just listen. Like the OP, I have had the experience of accidentally discovering after the fact (and after listening to LPs for hours and hours) that I made an error in P2S distance. On that occasion, I fixed the problem and thereafter could hear no increase in my already high level of listening pleasure, compared to the hours I had spent with the misalignment. But I felt better.

To MC’s point, how many posts do we see where some guy describes a mysterious problem with his phono SQ? Those posts are almost invariably followed by suggestions that he check his alignment parameters. This is evidence that most of us are true believers. Conversely, when said complainant goes off stage and "fixes" his alignment, he almost invariably comes back to us to say how wonderful his LPs now sound, thanks to his having tweaked his alignment. I don’t know whether this is evidence for or against MC’s hypothesis. As you know, I am a big believer in subconscious bias that affects our listening.
Normal people usually set up PS first and then align a cartridge in the headshell slots using chosen cartridge alignment method (Baerwald, Lofgren, Stevenson or whatever it is).

Some people do that other way around? 

If your PS is wrong and tonearm already screwed to the mounting hole (and you can’t move it), then your chance to reach desired null points by moving your cartridge into headshell slots forward or backward is very little, sometimes it’s simply impossible! Or it’s possible just with 1 aligning methods of many (and probably not the one you wish to use).

Headshell lots are different size, depends on the headshell model.

Some headshells have fixed screw holes (you can't twist a cartridge in such shell changing alignment method).

Tonearms without removable headshell will give you even less possibilities, sometimes the slots are very small.

So the BEST method is to start from correct PS (always) !


clearthink
1,179 posts02-10-2021 11:50amelliottbnewcombjr"Why aren’t all overhangs the same you might ask?"

Why aren’t all tonearms 23cm long why aren’t all tires the same profile?
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Why can’t all people think clearly?

Joking aside, I am curious: different arms, same P to S, will have different overhang specs. What’s the process/science that leads the designers/engineers to those differences?

I thought by asking: dazzle em with brilliance or baffle em with bullshite would occur.

I thought some interesting links might be posted.
If it really bugs you so much?!? Get an SME tonearm - any!
No headshell slots and P2S adjustable in a more wide range than you’ll ever need.
Problem solved? 🤔

Of course not, as per standard, every suggestion has an infinite number of new and other suggestions. 🙄

Michélle 🇿🇦
Elliot, In the end, it's effective length that counts, along with headshell offset angle.  Since effective length is the sum of P2S + overhang, since different designs feature different headshell offset angles, and since there are at least 3 different commonly used geometries that all result in two null points on the surface of the LP (and actually a myriad of such solutions that just haven't been associated with the names Stevenson, Baerwald, or Lofgren), there are many "solutions" to the problem.  Depends where you want to place the two null points (closer to the spindle or closer to the outermost grooves, for example) and how much tracking angle error you are willing to tolerate when the stylus is NOT on a null point.  And I am as bored as anyone else with this topic.
lewm

thanks,

It does make me respect the people who engineer our great stuff!
Elliott, It is only a matter of rather simple geometry. Lewm has said everything else that needs to be said.
Lofgren and Baerwald published their papers on tonearm alignment in around 1940, when the only records were made of something other than vinyl and all were mono 78s. And most people still owned wind-up Victrolas with megaphone speakers.
Mark,
IMO, when the manufacture designed a tonearm, they calculated and set the P2S distance and all the geometry of the tonearm to get the best out of the cartridge with the least of distortion possible. When you changed the P2S distance, it will lead to the change of the offset angle of the cartridge mounted on the tonearm. It works, but it might cause more distortion (the ear might not detect it) and affect the life of the tonearm (might cause more friction on the pivot bearing).
In conclusion: If it was mine, I would spend sometime to reset as the manufacturer recommended.
Enjoy,
Calvin
Mark,
IMO, when the manufacture designed a tonearm, they calculated and set the P2S distance and all the geometry of the tonearm to get the best out of the cartridge with the least of distortion possible. When you changed the P2S distance, it will lead to the change of the offset angle of the cartridge mounted on the tonearm. It works, but it might cause more distortion (the ear might not detect it) and affect the life of the tonearm (might cause more friction on the pivot bearing).
In conclusion: If it was mine, I would spend sometime to reset as the manufacturer recommended.
Enjoy,
Calvin
This is the exact type of misconception I have been trying to remedy. I should just give up. People try to reason it out for themselves that if the pivot point is further or closer to the spindle than specified that ipso facto the arc traced by the stylus must change. This is incorrect SO LONG AS the slots in the headshell allow you to reach the proper total distance from pivot plus overhang. 
As mentioned above, one (you) only need to look at the SME design to see that this is true-with SME arms there are no slots in the headshell and the mount is fixed but the pivot point is variable on a sled to go back or forth. One also can look at the plinths made by many plinth builders that have sliding leaves on them so that P-S can be varied (though that design also is there to provide maximum flexibility as to choice of tonearm. 
Let's go back to Stingreen's comment above. Ironically, he is a VPI fan. VPI is notorious for being sloppy in their manufacturing process and varying from the specified P-S (which Harry and Mat like to keep to themselves-hmmmmm). And guess what, most times IT DOES NOT MATTER because the VPI owner can still achieve alignment and overhang anyway. Where VPI gets into trouble with their sloppiness is when the owner uses a specified P-S distance to order a protractor such as the Mint and then the P-S is other than specified leaving the owner with an expensive paper weight.