Spindle-To-Pivot Distance

"You believe", is fine.  There really is no "correct" approach, since to begin with there is a built in error that will affect any solution.  Can you further explain what you have in mind as regards the effect of increasing overhang, to shift the "force vectors"?  Are you thinking of the skating force, or what? Of course, you would have to change the headshell offset angle, or twist the cartridge in the headshell, in my "solution", just as for your solution.

@lewm, I think my point is that you can not conserve the effective length of the are because as you increase overhang you shift the force vector clockwise to the point that the stylus can no longer maintain contact with the groove. Buy moving the cartridge back and twisting it clockwise you are turning the arm into an appropriate shorter arm which works at a SPD of 240 mm. I believe it is the only correct approach other than getting an arm that is the right length for the turntable. 
@rauliruegas , what is your opinion on this?

Mijostyn, good point but it seems to me we’re both right. Moving backward would preserve overhang at the expense of reducing effective length. Moving forward in the headshell would preserve effective length but increase overhang. Both work if you can also twist the cartridge. Neither solution is orthodox.

@lewm , think about it. He is mounting a tonearm that requires a 250 mm spindle to pivot distance at 240 mm increasing overhang by 10 mm. In order to get the right geometry you will have to push the cartridge back in the head shell, back towards the pivot not forwards. Then you would have to twist the cartridge clockwise to get the right offset angle. Moving the cartridge forwards will increase overhang eventually with the results I mention above.

@rauliruegas , That is the most eloquent post I have ever seen you do and you are absolutely right. Anyone who thinks they can hear even 5 degrees of tracking error need to run some blinded tests on their own to learn a little more about their hearing capability. People need to run these experiments to learn what they can and can not hear along with the degree to which your brain can play around with you. 

You have run into the problem that I mention in regards to linear trackers.
The vertical effective mass is too low for most modern cartridges and the bass gets screwed up. This is the reason Clearaudio made the Goldfinger so darn heavy. It makes their arm sound better. Terrible arm IMHO. Just watch one tracking and you will see the cantilever lead the arm and wiggle back and forth. Air bearing arms do the same thing perhaps not quite as bad.
Have you had a chance to hear a Schroder LT yet? I love that design.

Clearthinker, I did not say that the 10mm error in P2S contemplated by the OP would not be audible. At best, I said that if he fiddled with his head shell offset and the slots on the mounting surface, so as to move the cartridge forward, he might at least partially correct for the error. After that, I have no idea how it would sound, any more than you do. So sorry if that bothers you. Not.

@tomwh  :  Btw, calculations under IEC parameters.

R.

Dear @tomwh : " do the test I wrote about. ":

"" Maybe have a person get a album you are not familiar with then have him play it choosing different spots , with you not looking....... tell him where the null points are on it . ""

Not you, not me and I think no one can tell " him " about those null points and it’s very simple why we can’t do it:

our ears are extremely limited not only in frequency range but way limited to identify some kind of distortions especially distortions of low levels along that we are not trained on purpose to be aware of your posted test but additional to that tracking distortion levels out of the null points are changing its levels ( up and down depending if we are listening before or after each nul point. ) groove to groove and this continuty with to low distortion level groove after groove makes imposible to be aware of it.

These are examples using Löfgren B alignment that always has the null points at 70.28 mm and 116.60mm:

the tracking distortion at 140mm is 0.507% and at 130mm is 0.30%: Do you think that you can identify the 0.2% difference between those 2 grooves?

Now, at 130mm is 0.30 and at 129mm is 0.27%. Could you identify it? I think ( not even with training ) you can’t do it.

Near one null point example: at 120mm is 0.07% and at 119mm is 0.05%, the difference is 0.02% and you want that I try to identify that null point?.
Has no sense to me but was your proposal.


Regards and enjoy the MUSIC NOT DISTORTIONS,
R.

Rauliruegas  it is simple  do the test I wrote  about.  The rest is possible  hypothesis.   Also  , while your at it , let's know at what level of distortion  you hear  things going to hell in a hand basket.  Remember  the 2 null spot are just that.  So only twice in a very brief  period  of time do we have the distortion  free  music.

Enjoy the ride
Tom

Dear @tomwh : " but music reproduction has far to many variables to be able..."

Rigth and we have to add to those variables the ones that comes with any cartridge/tonearm/TT set up and that are different cartridge by cartridge, tonearm by tonearm and TT by TT.

I owned 2-3 linear tracking tonearms and all gone because its bass range quality performance was and is a little better with pivoted tonearm designs, yes other frequency ranges sounds spectacular.

So the issue could be: which are each one of us the best choosed trade-offs that could mates better with our room/system MUSIC reproduction targets?

I learned a lot with unorthodox changes/up date/up grade in my system but till today nothing of what I already experienced in the subject tells me the way to go is with pivoted straight tonearm designs ( underhung ), I’m orthodox in this specific regards.

Can I move in the near future from there? could be, I’m married not with my room/system way of thinking set up but only with MUSIC, this is my compromise always make " moves " in favor of MUSIC no matter what.

Btw, : " I have not heard any wild distortion issues..." of course not and that is the issue for this controversial " situation ": off set angle or no angle at all.
In a blind tests probably several of us can't detect which one has no off-set and only the ones that know very specific what to look for through the LP tracks could do it and I mean using cartridges and LP track knowed by the listener under test.

R.

Dear @lewm : ""  I have to wonder what Baerwald and Lofgren heard with what must have been...""

that does not changes in any way the orthodox alignments.

In the other side I know you are not deaf and as you I owned the RS tonearm that I bought by some kind of " curiosity " but never was for me something other than " interesting " and was sold.

As you and I posted at least twice in otjher threads I made once a mistake with the overhang set up, I made it longer and was unawarte of that mistake.
I did it with a very well know ( for me ) cartridge quaklity performance and I was listened to it by 5-6days and I took in account that for " whatever " unknow reason the high frequency range performs better than ever with more definition and " transparency " but at the same time something was not good enough at the other frequency extreme where lives the music foundation and I was very sensible to that range as with the other one.
My common sense told me that something weird could be happening down there and I recheck the tonearm cartridge alignment at found out my error.
After fix it " things " settle down but I tested on purpose with other cartridges and results were similar.
Can I live with? of course I can it sounds really good but that bass range performs better under the rules.

R.

Guys, forget the null point issue. It is not the problem. Overhang is the problem. Getting the right overhang would require sliding the cartridge back in the head shell towards the bearing. There is no arm I know of that is that adjustable given the limits set by the turntable. Running a tonearm with an overhang 0.5 cm over spec increases the skating force. The force vector will shift clockwise as the tonearm travels towards the spindle and eventually the stylus will pop right out of the groove and arm will zing right across the record with obvious results. 

You will either have to manufacture a special tonearm board as jasonbourne52 recommends or get a 9 inch arm that will fit. Long arms are not a panacea. They do lower tracking error but at  significant expense. Many of us, myself included think it is a raw deal. 

@Lewm.  If you think it sounds OK with 10mm too much overhang that's fine with me.  Just don't bother us.

It's possible to use the arm with a slightly shorter spindle-to-pivot distance, but the standard geometry for the arm will not work.  A new geometry and alignment system has to be generated.  There is a geometry generator on vinylengine.com .  

Will that setup work as good as the one designed for the arm?  Maybe.  Will it be as easy to set up as the stock alignment?  Probably not (IMO, 95%+ probability of being more difficult).

Rauliruegas if you read through the posts carefully  you will see  both lewm  and myself  are questioning  the null point concept.   I  am not sure about  about  how important  the whole thing is.  You might want to listen to a RS tonearm and  see it breaks all of the status quo rules yet still sounds spectacular.  

Maybe  have a person  get a album you are not  familiar  with then have him play it  choosing different  spots , with you not looking.  Then  tell him where the  null points are on it .  Then you will know first hand  if you can  or if it matters.  Another  test would be have your friend  change the offset on the cart then play album.  Have them change the offset around  including the right spots.  Write down you hearing findings then compare  notes with  his placements. 

When I did  the test the two arms where attached  to the same table and if you noticed  I  said I really did not do enough testing to give you a  any  real findings.  But I can say I  have not  heard any wild distortion  issues  with underhang and 1 null point.  

I realize  humanity  wants absolute  answers to all their questions  but music reproduction  has far to many variables  to  be able to do the the  math run the test equipment  and have great sounding gear.

So back to the OP  all the stuff was brought  up  give him some ideas different  than the status quo.  Weather they are better or worst  is up in the air.  You already know they move the null points around  so where are the perfect spots.  

Enjoy the ride
Tom

Dear Raul, I don't understand what you want me to say.  I can only say (again) that my experience with underhung tonearms using zero headshell offset angle suggests that precise adherence to any algorithm that posits minimizing tracking angle error as its primary goal (I guess this would include Baerwald, Lofgren, Stevenson, and any other similar solution) is over-rated as it applies to maximizing SQ from vinyl.  I nevertheless do adhere to such geometries when I set up my conventional pivoted overhung tonearms that have a headshell offset angle.  I have two "reasons" for thinking the practice may be over-rated: (1) Like I said above, the underhung tonearms with zero offset generate very large tracking angle errors other than at the single null point one can attain with such tonearms.  So if there is zero tracking angle error (TAE) at the null point at the center of the playing surface, there will be several degrees of error (on the order of +/-10 degrees for a 9-inch underhang tonearm, as I recall) both at the inner grooves and at the outer grooves.  You can do much better than that with Baerwald, Lofgren, Stevenson, etc. Yet, I don't hear the problem.  You can argue that I am deaf or that my system is not good enough to allow me to hear the problem, if you want, and (2) I have once or twice inadvertently set up conventional pivoted tonearms incorrectly, only to discover my error weeks or months later.  I then "fix" the error, but I don't hear a big upgrade as a result of doing so.
I realize that I am in violation of a vinylista mantra, but that is my opinion.  No big deal in the course of every day life.  I still play by the rules.  I have to wonder what Baerwald and Lofgren heard with what must have been 12 or 16 inch shellac 78 rpm mono recordings played with spherical styli.

Dear @tomwh  : "  arms with no offset ......... Seems to be a little more dynamic. "

Well sure it performs/soind different but from where do you think comes that higher " dynamic ". ? you are very precise in your statement: " more dynamic ". So what are you listen on it against your similar offset one tonearm?

Thank's in advance,
R.

Dear @lewm  : " , and how their work applies to modern stereo gear.....""

of course that you are free to post whatever you want it but it's weird that on almost each alignment isssue threads post the same " question " but you never posted a different solution or why you are " wonder " the same one and again.

Obviously that you have not an answer/different solution and with all respect: what are you lokking for?

R.

This is all really good stuff.  Thank you all.  I think I'm going to mount the turntable on an oversized plate, mount the tonearm where the edge of the turntable platter is closest to the platter, and put the darn thing where the manufacturer says to put it.  It looks kind of goofy but so do I. I ran the vinylengine calculator and the numbers that it gave me correspond to the alignment points on an ancient cardboard protractor that I have, so if it ends up wrong well, what can I do.

What tonearm and what turntable?

" Why would moving the cartridge forward in a headshell with elongated slots “look ugly”, and who cares?"

Indeed.  That is where my Hana rides on my VPI . . . . . . 

...mind the 'jerry rigged' comments, puleze....I've been spending a lot of time giving that a positive spin in my own meandering fashion.... ;)

The thing is that an under hung tonearm will yield massive amounts of tracking angle error when the stylus is not located at its single null point on the surface of the LP. Way more tracking angle error than is developed in a properly aligned overhung tonearm with a correct headshell offset angle. And yet I hear absolutely no problem. With your 14 inch tonearms, of course you have dramatically reduced the tracking angle error at any position on the LP, compared to that of the RS Lab, but I would wager the actual error is still higher or not much better than one gets with a 9 inch overhung tonearm. I bet the soundQuality is excellent.

Lewm  the arms are my own.  The ones with the zero offset  are Brazillian  rosewood with a straight  aluminum headshell.  I use a spacer block of aluminum  or wood for now, between the cartridge  and headshell,  so any angle is available including  zero.   Better check the blood pressure  at the rigid camp.  In fact if you showed them your  RS tone arm you would have to take them to the emergency  room after they see the headshell can move.  Need we forget it wobbles  with no silicone  and  the  pivot is  no where near where it should be.   

The 2 arms are  the same table.  One is rigid on plinth  the other on a massive pod.  Oh dear  the rigid camp is going to lose it.  Now  something that make a real sonic difference  is I can run my tables  either  belt/tape or  idler.  Can change back on forth  around 5 minutes.   Even the  density  and thickness  of the o'rings can change the sound.  Go Figure!!!

Well I went a little  off topic but I hope  the OP gets  what you brought up  about  Did the so called Masters of the old days, using mono,  know  what sounds the best or just like whatever the machine told them.

Enjoy the ride
Tom

Been mathematics alignment overall parameters can be manipulated by any one and only has to make the new calculations for the alignment.

As a fact the Stevenson alignment comes by Stevenson parameter manipulation using the Löfgren equations: he took the equations input " most inner groove " distance and converted it in the inner null point.

R.

I always wonder what sort of (mono) systems were available to Baerwald and Lofgren in the late 1930 or early 1940s, when they published their analyses, and how their work applies to modern stereo gear. Yes, geometry is still geometry, I know.

TomWh, I own an RS Labs underhung tonearm, and it is my experience with it that leads me to be a bit nihilistic when it comes to alignment algorithms.  What 14-inch tonearms with zero headshell offset are you using? I guess I assume you mount them so as to underhang the spindle. (Meaning the stylus tip does not overhang the spindle.)

Dear @mrearl :"" Suppose I have a tonearm that wants to be mounted 250mm from the spindle . ""

first that all is not that the " tonearm wants ", that could be the manufacturer spec ( normally the manufacturer gives the tonearm EL. ) and nothing more than that.

If you need to mount from the spindle at 240mm what you are doing is changing not null points but tonearm effective length, overhang and off-set angle.
So what you need is that the tonearm/cartridge new alignment be made it with a new overhang and offset angle.
A shorter effective lenght gives you a little higher overall distortion levels that maybe you can't even be aware of.

Here the parameters value you need for 250mm and you can choose between those 3 alignments:

https://www.vinylengine.com/tonearm_alignment_calculator_pro.php?arm1=Arm+1&l1=ps&a1lv=250&a...

here for 240mm:

https://www.vinylengine.com/tonearm_alignment_calculator_pro.php?arm1=Arm+1&l1=ps&a1lv=240&a...


If you use a good protractor then normally there will be no cartridge mistraking.


Btw, it does not matters the changes in tonearms EL the null points inside each type of alignment: Lögren A or B or Stevenson always are the same.

In 1938 Erik Löfgren stated over his calculation equations to find out the cartridge/tonearm overhang, off set and the alignment null points where the input parameters in his equations were and are: tonearm EL, innermost groove and outer most groove distances and the equations outputs: overhang, offset angle, null points and by difference P2S distance.


Regards and enjoy the MUSIC NOT DISTORTIONS,
R.

Lewm you brought up the question  that 1st popped  in my head.   Could you move it  10mm  and still have 2 null point.  With the calculator  on vinyl  engine  you should be able  to solve with the variables  he knows.  He could also go to vinyl  asylum  and ask John Elinson (sp)  he has his own spread    sheets.  He could figure this out quickly  and will recommend  to play by the rules.  

As a side note I have been playing around with 2 of my 14 inch arms  with no offset  and 1 null point.  Seems to be a little more dynamic.   If the average distortion is higher  it  is not apparent.   Need to really  sit  down and listen and go back and  forth.   Took up  Kayaking last year  so haven't  been building and listening much.

Enjoy the ride
Tom

PS.  I like the looks  of a cartridge  all the way forward in the head shell.  Although  I  don't remember  the OP  asking  about  this issue.

Whether exactly correct alignment could be achieved with the OP‘s situation is definitely a good question. I share your opinion that most headshells would not have that much adjustability room. But that is different from saying not to do it because it would be ugly. Whether  exactly correct alignment is critically important is also another question.

Why would moving the cartridge forward in a headshell with elongated slots “look ugly”, and who cares?

Do you know what is 10mm ? Try to move a cartridge 10mm forward than usual, it most cases it’s impossible to move that much. The difference between alignment methods is within 2-5mm max, no one have to move a cart 10mm forward in normal situation. And we are talking about different detachable headshells. On a tonearm with fixes shell the slots are much shorter.

I have over 30 different headshells and very few of them (with overhand adjustment like AT Technihard) will allow me to move a cartridge 10 mm forward than normal position which is usually in the middle if the slots. 5 mm is ok, 10 mm forward is too much and in this position headshell is behind the 1/3 of a cartridge body - this is ugly. Normally a cartridge body is under headshell.

Most of the audiophile are excited about ugly things, but in my opinion OP can change the armboard instead and everything will be perfect if he could.

No big deal. Go to turntablebasics.com and look at their table of mounting dimensions. As long as you have enough adjustability in the tonearm mounting slots you can adjust the overhang and the angle to get correct alignment. For 249.5mm P-S the overhang should be 15.51mm and the angle 20.65deg. For 239.9 mm P-S the OH should be 16.09mm and the angle 21.41deg. Recall eff length = PS + OH. They make a very good protractor.

What will happen, if you use a 240mm P2S distance where 250mm is recommended, if you do nothing to compensate for that error, is the null points will move farther apart from each other.  If the tonearm is designed for an algorithm like Stevenson, where the inner null point is already close to the run-out grooves, then there is a danger that the inner null point will now lie IN the run-out grooves or even on the label itself, where of course there is no use for it.  But if the tonearm was designed for one of the other two popular algorithms, the inner null point might still be useful on the playing surface.  That might be no big deal at all, depending upon the LP. But of course also the tracking angle errors before, between, and after the null points are traversed will be altered, probably increased in magnitude. (I haven't done any math on that.)

So if you go by there methods you have 2 null point with everything is supposedly perfect and the rest goes into various degrees of distortion. Love to meet the guy ,without seeing the record, who could pin point the null points with his ears

.
Good answer.
https://youtu.be/k9DO26O6dIg?t=135

Why would moving the cartridge forward in a headshell with elongated slots “look ugly”, and who cares?

I know I’ll get hate mail, figuratively, but anal attention to alignment is overrated in my opinion, as regards the effect of slight misalignment on audible distortion.

10mm error in PS distance is too much! 

But theoretically if you have detachable headshell with long slots for the mounting screws you can compensate 10mm. In the end it will be ugly as hell. Your cartridge will be moved way too forward in the shell (10mm more) and twisted a bit. 

I would’t do that, you’d better change the armboard with correct mounting hole for your tonearm and given PS distance (using original template). 

What’s your tonearm?

Well, this collection of answers gives me a good grounding.  And a minimum of snotty gay comments like I get in other forums.  Thank you all.  I could as well mount the arm off the original 'table but I think that there's something to having a strict connection from platter to tonearm.  But there's certainly a hierarchy of considerations.
Over and out.  Thanks.

If the slots in your head shell, presuming you are using a head shell, are long enough you could possibly make up the deficit by moving the cartridge forward in the head shell and twisting it slightly with respect to the long axis of the headshell. Then you might achieve only a small tracking angle error, rather than a large one. Use a good protractor if you go this route. While I respect the opinions of the other knowledgeable persons who commented here, I personally do not think there would be such a dramatic reduction in sound quality, if you were able to make up for the pivot to spindle distance in the manner that I described.

If you are looking  for a answer to your question  you probably  came to the wrong forum.   Some engineers  way  back in time came up with the two null point system and the various percentage of distortion  from there.  There  seems to be 2 to 3  popular  null point systems.  So if  you go by there  methods you have 2 null point with everything  is supposedly  perfect and the rest  goes into various  degrees of distortion.   Love to meet the guy ,without seeing the  record, who could pin point the null points with his ears.

Now you are talking 10mm which is  a pretty good distance.   If you have  reasonable math/ engineering  skills you can go to vinyl  engine and use there calculator  to see if you can get 2 null points and where they would be  using the 240 and  250 mm  mounting  distance.   Then maybe take  a record that  did cost 100.00  and try it  at 240 mm.  

I do not know how  involved  you wanted to get  but  thought  I would give you the option  to be able to understand  a little bit  of what is going on.  There are  guys on other forums  who will do the math for you or  run the calculators for you.

Enjoy the ride 
Tom

Install a slidable arm base, slide to 250mm to play a record, slide to 240mm for good looking.

https://i.ebayimg.com/images/g/hz4AAOSwuhheVlOd/s-l1600.jpg

Make a mounting plate that will hang over the edge of the plinth. Wood will do fine! Or use acrylic! A rectangular piece with a mounting hole.

If someone actually did this and heard it sound that bad then there you go.

Sounds like you could do it right and only have to put up with it looking bad. If that is the case looking bad is better than sounding bad.

You asked whether I have experienced this. The answer is yes. About 25 years ago I once fitted a Rega arm to a Project turntable in place of the Project arm. The effective lengths of the arms were different by a similar margin.
I didn't know much about tonearm geometry then and I wanted to see if it would be an improvement. It wasn't. The result was exactly as I described - mistracking and distortion.

So I can tell you from both a theoretical perspective and from experience that it is a bad idea.

some headshell/cartridge mounting flexibility might allow for adjustments of a mm or two.....but it’s not a good way to jerry rig things as you would be forever fighting it.

in addition to distortion, miss-mounting the arm could cause records to skip, and harm the grooves. it’s basically not an option. you would be better off listening to digital.

maybe you could approach this differently; and ask for help with arm board ideas to solve your geometry/spindle to pivot distance problem, assuming you are stuck with that particular tt, plinth and arm. tell us about the tt and arm.

possibly does it use an arm board which could be made larger/longer?.........over the edge of the plinth? can an inset into the arm board possibly allow for a different mounting point for the arm? i’m just trying to help you visualize a way to mount the arm at the correct distance.

or.....let's say you have a wood arm board now. and making a longer wood arm board might not be stable enough. but if you had one that hung over the plinth made from stainless steel, then it would likely still be stable. not sure that is relevant, but getting a hunk of stainless drilled properly might be cost effective.

Have you experienced this?

The stylus will mis-track, and you will get distortion, probably quite noticeably. Not good for your records and it will also sound unpleasant.

If your tonearm cannot fit on your turntable at the specified distance, you need to replace either the turntable or the arm.