[Wayner]

Thanks vinylengine!

I spent the day listening to some music (after breakfast) and pondering. I think the purpose of my "white paper" was to address the masses in the common denominator mode. My statements, geometrically, are still true. I do have to do something with your input as well.

This is what I thinking right now and this is also because of Oneinthepipe's comment. I think when you do things like you did, hyper-extending the stylus out of the manufacturer's recommendations put you in a category that for now, I will call "superuser".

The "superuser" guy I think has many tools at his disposal, and a fairly top level of alignment technology. Surely a model for others to emulate. However, as by my geometry below, the 2 point only alignment system has been rendered inaccurate, because we have 3 curves crossing the same null points having 3 different radii and offset angles. The 2 point only system can't recognize where your distance is.

Therefore, to do this, the "superuser" has to measure the extra length he has added to the OEM table's length and then set the offset by the null points. The other problem, as I have mentioned before, is that some tables may be physically incapable of reaching the new length position.



You, yourself have even offered examples from other manufacturer's specifications on varying null points as noted below: 

(From vinylengine):

(For example here are some manufacturers null points for arms mounted at 222mm:

Audiocraft: 60.0 / 114.7
Azden: 61.2 / 112.5
Clearaudio: 66.0 / 121.0
Grace: 66.8 / 103.0
Acos: 60.3 / 114.2
Micro Seiki: 66.8 / 103.0
Rega: 60.0 / 114.7
Schroder: 65.9 / 121.1
SME: 66.0 / 120.8
Sony: 60.3 / 114.2

Each of these manufacturers chose different overhang and offset angles that resulted in these alignments - mounting distances are identical.)

So perhaps you can see where I am coming from. I believe that with certain instances, it may be better to leave the OEM tables specifications for stylus location, do reduce plain old alignment error. If they get the offset angle off by even 1/2 degree, the distortion levels go off the chart and I see a huge danger with this.

Oneinthepipe, Orthobiz and others, there are 3 factors in regards to cartridge alignment. One of them, platter spindle to tonearm pivot centers, in almost all cases is fixed. That leaves 2 other movable changeable vectors to fool with, those being overhang and offset angle. That is where the Excel calculator from www.enjoythemusic.com comes in handy. You can input any data and start doing your own table's analysis. Just remember, if you change the overhang number, you have to change the effective length as well (spindle to tonearm pivot center + overhang = effective length).

This has been a great thread and we won't leave any of you guy in the dust.

Wayner

[Wayner]

One more thought before I go to work for the day.

While we are all seeking the Holy Grail of null points, how is one supposed to measure where 18.173 mm is? I could problably divide the space between 2 mm marks in half, maybe in fourths, but this 3 place decimal thing is down to the nat's ass and for all practical purposes, impossible to hit.

If you have a mm scale, go look at the spacing between lines. Do you think you can hit .173mm? You could hit 18, or maybe 18.5, but that's where I would have problems, especially looking under the body of an MM cartridge.

Would we all be better off picking numbers (at least overhang) and doing a slight compromise for the sake of accuracy, even if it meant the null points shifted a little. I have no problem with that, as long as the distortion curves are with in reason (like around .4%)

This is just a thought from the machine shop side of me, dealing more with reality.

Wayner 

[jrtrent]

Wayner spoke of winners and losers in an earlier post, and more recently about addressing the masses in common denominator mode.  I don't know about the debaters in this thread, but for the masses to be a winner we just need a tool that will let us align our cartridges so we can enjoy our records.

Here's my summary of the issue so far: 

1.  Using IEC standards for inner and outer groove radii, the Baerwald scheme determines that the lowest average distortion due to tracking angle error for any given tonearm is achieved by setting null points (zero error points) at about 66mm and 120.9 mm (there are other null point choices, such as Stevenson or Loefgren B, that distribute the error differently).

2.  A universal two-point protractor designed to align to Baerwald specifications is supposed to let you set both overhang and offset angle so that you get null points at Baerwald's specified positions on the record.  I don't have the tools or ability to measure and set specific overhang and offset values when setting up my turntable, but the beauty of the alignment protractors is that you don't need this information--just align the cartridge in the grids as per instructions, and the correct overhang and offset angle for any length tonearm/mounting distance will be achieved.

3.  Some tonearms are too short or don't have sufficient available movement in the headshell slots to achieve Baerwald alignment.  Stevenson alignment might work well here as this alignment scheme uses less overhang (and some might prefer Stevenson's goal of minimizing error at the innermost groove at the expense of slightly higher error elsewhere).

4.  The point of the original post in this thread is that these protractors don't perform as intended. 

5.  There has been some counter-argument to suggest that maybe they really do what they say they do. 

6.  I've been happy with the results using my Geodisc, which is supposed to give the same alignment as a two-point universal protractor; I just find it easier to use.

7.  I'm really confused by the ongoing discussion of manufacterer's overhang or attempting to measure and set a specified overhang value.  With a two-point protractor, the overhang and offset angle are set simultaneously (see instructions below), and you never know just what those values are.  What you do know is that your null points are at the specified radii on the record.  I'm hoping the conclusion to the issue is that that is good enough.


Instructions for using a universal two-point protractor.
http://www.vinylengine.com/protractor-user-guide.shtml

First use the grid closest to the spindle hole. Put the cartridge in the middle of the headshell; twist the cartridge clockwise or anti-clockwise in order for you to observe the alignment with the grid. When it?s right, go to the second grid.

If the cartridge must be rotated clockwise (or anti-clockwise) to be aligned with the second grid, move the cartridge forwards (or backwards) in the headshell, then go back to the first grid. Align the cartridge and check with the second grid; repeat until alignment is achieved at both points.

[doug s.]

yup, jrtrent, i am with you.  (and w/the protractor instructions on the winylengine.com's website)  yust follow the instructions; you do not need to worry about calculating offset and overhang - it is what it is...

doug s.

[Wayner]

Well, I just proved with geometry that there is a flaw just using the 2 point system. If you look at my recent drawing, we have 3 arcs with different paths (depending on overhang) and it proves (at least to me that the two point alignment system has a mis-que. The alignment tool will line up with all three positions, so it is not accurate for setting distance, you would need to set the overhang distance first, then dial in the null points, which will set the offset angle.

Wayner

[Wayner]

In fact the 3 arcs all cross each other at about 89.306mm. Now we have 3 different positions on each null point location, and you can line up your catridge to the null point locations, but what arc did it set your stylus in?

This all goes back to my original statement. The 2 point alignment system alone is flawed. I'm not sure it was ever intended to be used alone.

If you look at the perimeters for Baerwald, he does give all the information needed, with spindle to pivot, overhang and offset angle. I think he assumed that you would first set your overhang distance. Then you would use the 2 null points to set the offset angle.

I would have to move the card to a differnt locations just to set to the lower null point for each of the different arcs and each time I'm doing that, I'm changing the overhang distance (as well as the offset angle) and if I don't know what that distance is, I'm screwed.

Wayner

[jrtrent]

Well, I just proved with geometry that there is a flaw just using the 2 point system. If you look at my recent drawing, we have 3 arcs with different paths (depending on overhang) and it proves (at least to me that the two point alignment system has a mis-que.

I'm not sure where the three arcs came from.  You had said, ". . . we have 3 curves crossing the same null points having 3 different radii and offset angles. The 2 point only system can't recognize where your distance is."  I'm just confused by your phrasing because I thought the two-point system didn't need to "recognize" your distance, but is used to actually set the distance.

Are you saying that you used a two-point protractor on three trials and came up with a slightly different overhang each time, resulting in three different arcs?  Or are you saying you set the overhang yourself by some other means and only used the two-point protractor to try to set the offset angle?  If it's the first, that sounds plausible as none of us have perfect eyes and fingers.  (There's probably even more scope for variance with my Geodisc's sight line approach, but I've found it works well enough that my ears don't hear a problem.)  If it's the second, then that's just not how the protractor was designed to be used.

[doug s.]

a two-point protractor, w/its distance points set by the platter spindle, (like what's on the winylengine site), will work on any tonearm, as long as the arm in question has its pivot point set a reasonably close-to-mfr-recommended distance from platter spindle, and there is a reasonable amount of adjustability in the arm's headshell slots for sliding the cartridge around.

doug s.

[jrtrent]

The 2 point alignment system alone is flawed. I'm not sure it was ever intended to be used alone.

If you look at the perimeters for Baerwald, he does give all the information needed, with spindle to pivot, overhang and offset angle. I think he assumed that you would first set your overhang distance. Then you would use the 2 null points to set the offset angle.

From my reading of the directions for the two-point protractor, in effect you use the inner null point grid to set offset angle and the outer grid to adjust overhang.  You start with a cartridge centered fore and aft in the headshell slots, put the stylus on the crosshairs of the inner grid, then adjust the angle.  Next you check the alignment with the outer grid, adjusting the cartridge forward or backward in the slots to change overhang as per directions.  Then you re-align the offset angle at the inner grid without changing overhang.  Then you go back to the outer grid, again adjusting overhang as needed.  You go back and forth until the cartridge is properly aligned at both grids; this gives you the correct overhang and offset angle so that your null points are at the pre-specified radii.

If I'm understanding it correctly, you don't need to worry about tonearm length, manufacturer's suggested overhang, sample-to-sample variation, or mistakes in measuring--if the cartridge is aligned at both grids, you've set the overhang and offset angle needed to achieve those two null points for your arm and cartridge.

[Wayner]

jrtrent,

If you read a little back on this thread, vinylengine came up with a couple of table examples that I have imposed onto the same drawing as with the original Baerwald curve, that is my reference and example I'm using.

Doug s.,

All of this stuff was done way before computers or CADs. Until I'm convinced in my own (if stubborn) head, I'm not going to take the "status quo" as gospel. I really wonder if anyone on earth has challenged the existing with some good hard nails to wall geometry. I'm trying to keep an open mind on the topic, I think everyone reading this thread hopes I find the right geometrical answer, so we can all help each other in the end. For all I know, you could be right. But I am a stubborn old coot and I not going to quite until the geometry says good enough.

There are some inherent problems that I am realizing, and that one maybe that there is more then one right answer.

Wayner 

[doug s.]

Doug s.,

All of this stuff was done way before computers or CADs. Until I'm convinced in my own (if stubborn) head, I'm not going to take the "status quo" as gospel. I really wonder if anyone on earth has challenged the existing with some good hard nails to wall geometry. I'm trying to keep an open mind on the topic, I think everyone reading this thread hopes I find the right geometrical answer, so we can all help each other in the end. For all I know, you could be right. But I am a stubborn old coot and I not going to quite until the geometry says good enough.

There are some inherent problems that I am realizing, and that one maybe that there is more then one right answer.

Wayner 

wayner, what i think you would find, is that if you yust use the two-point protractor method, moving the cartridge to get the proper alignment at the two points after roughly mounting the tonearm so its pivot point were close to mfr recommendation; then went back and reverse-measured - ie: get exact tonearm-pivot length, exact offset, exact overhang; and then plugged those dimensions into the chart/graph, you would end up with the numbers/dimensions needed to get proper alignment per whichever method protractor (baerwald/loefgren/etc) you were using.     of course, the trickiest part is being able to accurately align it w/the naked eye...   

you are correct - this was done before computers/cad.  but, not before the geometry and calculations; they don't change.   

doug s.

[Wayner]

OK, well, I spent over an hour setting the Technics cartridge using just the 2 null points. Please believe me when I tell you I gave 'er it all to make sure I was paralleling in both positions (I used the extended numbers offered by vinylengine).

After being satisfied with the alignment process, I viewed the overhang number with my alignment card. I was off about 1.2mm. ending up with a value of 16.3mm.

I think this shows very effectively that the two point (alone) alignment system is truly flawed in its accuracy.

I then set the overhang first:



I used the value given to me again by vinylengine of 17.817, then I used the null point scale to check (at the null points) for parallelism,



 and with minor adjustments, was able to dial in both targets. Note that in the bottom view at the null point scale, the stylus guard looks crooked. I didn't align to the guard, I aligned to the body. I had almost no room to spare with the slots. So whether this proceedure will work on all turntables is not etched in stone for this guy.

Wayner

[doug s.]

OK, well, I spent over an hour setting the Technics cartridge using just the 2 null points. Please believe me when I tell you I gave 'er it all to make sure I was paralleling in both positions (I used the extended numbers offered by vinylengine).

After being satisfied with the alignment process, I viewed the overhang number with my alignment card. I was off about 1.2mm. ending up with a value of 16.3mm.

I think this shows very effectively that the two point (alone) alignment system is truly flawed in its accuracy.

I then set the overhang first:



I used the value given to me again by vinylengine of 17.817, then I used the null point scale to check (at the null points) for parallelism,



 and with minor adjustments, was able to dial in both targets. Note that in the bottom view at the null point scale, the stylus guard looks crooked. I didn't align to the guard, I aligned to the body. I had almost no room to spare with the slots. So whether this proceedure will work on all turntables is not etched in stone for this guy.

Wayner

wayner, when you were finished, did you end up w/perfect alignment at the two null points?  if so, do you have the means to precisely measure overhang, offset and tonearm-pivot to platter-center distance?  this is what i'd be interested in knowing - if these dimensions correlate w/your alignment card's numbers formula for getting proper cartridge set-up...

you have way more patience than i do, regarding this issue!   

best,

doug s.

[Wayner]

Yes, Doug, everything lined up real good. And what you are seeing for the first time is a glimpse of a new product to be offered by AVA when the website is done, and it's not done yet.



It has all the scales at hand, including the offset scale, the null point scale and an anti-skate scale (more on this later). We've created a playground for everyone. As you can tell by the way this thread has gone, there are  many opinions on this topic, many folks unsure of the correct course to take, and so are we (to a point). So why not offer a tool that lets people decide for themselves. If you like Baerwalds scale, use his null points, if you like Loefgrens A or B, use them, if your turntable can't get there, play with your own numbers. The CAT TWO as it is called also comes with an alignment stringer to point directly at the tonearm pivot center, to dial in the overhang scale.

Wayner 

[Seb]

Hello to all

JaS (aka vinylengine) is too busy this week but he indicated me this discussion a few days ago. As the vinylengine protractor designer (and incidentally the designer of a few tonearms), I feel I can add infos to this thread.

Please note that, as a French, English is not my mother tongue... all vinylengine users know that, I hope you'll be as patient as they can be with me

So, we all now agree on the fact that Baerwald (Loefgren A in fact) null points are unique whatever the mounting distance. All you have to do is to set up your cartridge with the correct overhang and the correct angular offset. For every mounting distance, there is an UNIQUE couple of overhang and angular offset that will give you the Loefgren A null points.

Ok, let's show this with a draw:



And if not convinced by this draw, read that paper written by Graeme Dennes:
http://www.vinylengine.com/phpBB2/viewtopic.php?t=19199

Now, the two grids protractor (aka for instance, "the stupid protractor" you can download at the Vinylengine): this kind of protractor is, in theory, perfect. Since the overhang/offset angle to achieve Loefgren alignment is unique for a given mounting distance, if your cartridge body is aligned with the grids at the two null points, you'll have the correct overhang and the correct angular offset.

Now, the problem with this kind of protractor: you've just having a pair of eyes to achieve this alignment. Firstly, aligning the cartridge body is a very rough way to proceed... in fact, this is not the cartridge body that should be aligned with the grid but the cantilever, yes, that less than 10mm long piece, angled by 20? with the record surface should be used as a guide to your alignment process...

Imagine now that some people don't disengage the antiskating force when they set up their turntable... a complete nightmare.

The setting process must be done very carefully. Small errors will lead you really away from the null points you'd like. As a example, consider a 237mm effective length tonearm. To obtain Loefgren A null points, your setting process should lead you to have an overhang of 17.477 mm and an offset angle of 23.221?. What will you obtain if you do not proceed carefully? Null points quite far from the one you wanted as shown by the next two draws.





So, what else can we do ?

Arc protractors could be a solution. See for instance the various arc protractors I designed for the VE. (http://www.vinylengine.com/cartridge-alignment-protractors.shtml)

I believe that this kind of protractor, if in theory is able to give you the same null points than a two greed protractor, is more practical to use and more precise. BUT there is a condition! Your mounting distance must be exactly the one stated on the draw. If not (if the error between your real mounting distance and the one stated on the draw is superior to +/- 0.5mm, you'll go far from what you want as I demonstrated in this paper :

http://www.vinylengine.com/arc-protractors.shtml

Wayner, my point now, by reading this paper, you'll see various arcs on the same draw. If now, you take a look at the Kearns protractors, you'll see lots of arcs. There is no real reason for those arcs to have a particular point in common. On the Kearns protractor, the Loefgren A inner null point is chosen as the common point, on my paper about arc protractors, two points I choose are used.

A second point: the fact that various tonearm manufacturers of the 60's, 70's and 80's choose other values than the Loefgren A values shows nothing. Loefgren and Baerwald papers were rediscovered in the 80?s. The first paper that shows that manufacturers of the past didn't understand basic tonearm geometry was written by Kessler and Pisha in 1980 and can be downloaded here:
http://www.vinylengine.com/phpBB2/viewtopic.php?t=1142

Just one fact to convince you: check the data of various Japanese tonearms. Most of them (say 95% of them) are indicating an overhang of 15mm whatever the effective length. It makes no sense and there is no theory behind that 15mm.

We know more actually about optimal tonearm geometry that we did 20 years ago. Thanks to Internet and people like John Elison, Brian Kearns and Graeme Dennes. All the basic papers can now be downloaded by anyone with an internet connexion, even the Loefgren paper, in German, is now translated in English (thanks to Klaus).
http://www.vinylengine.com/phpBB2/viewtopic.php?t=15875

About Graeme Dennes, if you're interested by tonearm geometry issues, do not hesitate to read his (108 pages long) paper you can download here:
http://www.vinylengine.com/phpBB2/viewtopic.php?t=4854

Every formulas by all major authors are checked! feel sure that there is no 'error' in those papers wrote, most of them 70 years ago.
 
This is not to say that there's nothing to do about alignment issues... we're working on this

Best regards

Seb

PS : BTW, there is no 'perfect' arm in Baerwald, Loefgren, Stevenson etc... papers   

[Seb]

If you like Baerwalds scale, use his null points, if you like Loefgrens A or B, use them

Baerwald null points and loefgren A null points are identical.
Baerwald simply rediscovered (in 1941) Loefgren A solution (established in 1938)

best regards

Seb 

[JackD201]

I remember some of those linear tracking tonearms from B&O, HK, Rabco (IIRC), Revox, and others.  I don't remember why they didn't become the standard. 

I believe the answer is the F word. Friction that is. The cost of producing the "rails" as well as the bearings be they air or actual are prohibitive. The rails have to be perfect and as should the bearings lest the cartridge fail to track. Imperfect rails and bearings equals tracking distortion across the entire length of the record. Even perfect rails and bearings if ill maintained can cause the same problems.

That brings us to maintenance. For arms that don't use air bearings the rails must be kept immaculately clean. We all know how dust and moisture turn into something like cement over time. This is a problem conventional pick up arms are not as prone too because the pivots or bearing assemblies are encased for the most part. For linear tracking arms that do use air bearings the traditional problem has been the accumulation of moisture as the air cools after having been compressed by the air pump and squeezed out of them tiny holes not to mention the integrity of the pumps themselves.

I do have high hopes for this thread. Maybe someday we'll have the Wayner to use as well as the Loefgren or Baerwald. It sure as heck would be easier to spell and pronounce!

Just a couple of things though:

1. We obsess about the relative cart alignment to the grids but just approximate the pivot point on which the grid's position is totally dependent?

2. Why align to the cart body and not perpendicular to the cantilever?

[Seb]

me again

I don't believe in overhang scales : we're dealing with 1/10 of millimeter as shown in my second and third draw, a little 0.1mm more of less and you're obtaining others null points than the one you wanted.

best regards

Seb

[Wayner]

Seb,

No-one is able to set a scale to that level, unless they have super eyesite or other very distictive tools to use. As I have discovered with all of my geometry, and trial and error, things that you have already brought out. Correct, there is no perfect tonearm. It's a compromise to a problem.

We also haven't discussed the problems with the record it self with the many defects that have an effect on proper playback, nor have we discussed anti-skating. Good point, don't set your stylus with any anti-skating, it will simply pull off to the outside.

Wayner

[TheChairGuy]

By the way, for those of you who are reading the thread, vinylengine is a worthy opponent! I truly expected challenges, and I got them. This is what makes us great. The fact that we can disagree on just about everything (you bastards!), yet there isn't a better place I'd like to spend my Saturday!

Indeed Wayner...JaS and Seb luuuuuuuv this stuff.

Me? - my eyes gloss over when those guys go at it on geometry over at VE (not that I can't appreciate it all...it just sails over my head)

As my grasp of the subject will likely always be limited and higher fidelity the goal always....I have done the simplest thing a consumer can do to limit tracing distortion - I've foresworn off 9" arms and moved to (minimum) 10" arm.  Tracking distortion (and resultant null point issues) are generously muted by some 10% using a 10.5" arm.

If anyone else is lost in this gangle of brainiac mathematicians here ....just use 10"+ arms and you'll be dealing a winning hand on your precious vinyl

An added benefit of better tracing is that stylus placement is less critical, as well, I've found.  Vinyl is such a pain in the keyster...any way to make it easier I'm in serious favor of

Enjoy all (welcome JaS and Seb!)  John