Baerwald? LofgrenB? Stevenson? The math behind alignment conventions
- Thread starter miglto
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Zenith error - that is how much the stylus contact edges are not perpendicular to the groove - affects distortion. The IMD (Inter Modulation Distortion) additionally increases (approximately) as 1/r. What you really want to minimize is IMD, that is:
IMD ~= Zenith Error / r
The various conventions differ in what their intention is: For example, have the same IMD at 55mm, 147mm and the maximum point in between. Or some other condition. This changes the position of the null points.
How much this affects the quality of the sound depends to a great degree on the shape of your stylus. If your stylus is conical it will matter less, if it is a very sharp fine line (eg Shibata) then it will matter more. Consider also that many records have differing min and max radii, so being very picky about which convention you choose is a bit of an academic exercise.
However, there’s an extra wrinkle here. Having chosen null points, the issue remains that your stylus is never perfectly aligned with the cantilever. What this means is even though you have aligned the cantilever perfectly with the protractor, the stylus itself is always slightly misaligned. As you would expect, the sharper the stylus profile the more of a difference this will make.
So after doing the initial geometrical alignment, you need to go further and refine it by twisting the cartridge in the direction that gives best sound. I use AnalogMagik’s zenith adjustment tool to do this, and I have found the improvement to be quite remarkable.
My cartridge are analyzed by Wally tools. I use his protractor to correct for the errors in manufacturing.
It makes sense how SRA, azimuth, tracking force and anti skate all impact the way the needle contacts the groove.
I am still not clean on why the selection of where the 2 null points on the vinyl occur impact the sound. Outside of where on the vinyl the contact is as close to optimum as possible. And maybe how a weight hung anti skate like mine may have an optimum setting that might align with a null point.
At the null points, the zenith error will be zero (assuming you used Wally Tools protractor to compensate for the stylus’s slight misalignment). As such, AT THE NULL POINTS (there are only two) the IMD will be the lowest possible your system can have. So it’s really a question of where you want the best reproduction to happen.
Baerwald and LofgrenB conventions optimize for a more or less even distortion across the record (with slightly different conditions) while Stevenson was designed to favor the regions close to the end of the record given many classical music crescendos happen at the end of the record. However, Stevenson’s alignment is done at the expense of higher distortion at the beginning of the record.
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I guess terms are mixed up here. Tracking error and zenith are related but two different things. @miglto, you're mainly talking about tracking error but referring it zenith error. Yes, they're closely related but, tracking error is related with geometry (overhang, offset, null points) and zenith is related with cartridge alignment.
- If you set overhang and offset angle correct then tracking error will be zero at null points. Depending on the geometry you've chosen you will get varying tracking error levels throughout the record except null points.
- Zenith is the yaw axis of stylus in the groove. Stylus' reading edges should be perpendicular to groove walls. This alignment is done by tilting cartridge in the headshell and AM software is outstanding for the job.
- When you set geometry (overhang, offset) right and aligned zenith perfectly (when azimuth, SRA etc are also perfect) then you will achieve the lowest possible distortion levels. Theoretically you will achieve zero tracking error and zero distortion at null points.
- If you make an error on zenith alignment (lets say zenith is 1 or 2 degrees off) then you will get increased distortion levels even if you've set the geometry correct before. This only applies to modern stylus profiles. Theoretically a spherical stylus will not increase distortion levels even with other than optimum zenith alignment because it's round and has no specific reading edges. On the other hand a spherical stylus can not read finer undulations in the grooves and inherently introduces more distortion than a modern profile stylus.
As a result:
- There is always a certain amount of distortion due to tracking error
- Depending on the diameter of reading edges of the stylus distortion level may increase
- Theoretically when zenith aligned perfectly there won't be any additional distortion.
- Zenith ---- stylus ----- distortion
- Geometry (overhang, offset, null points) ----- tracking error
- If you set overhang and offset angle correct then tracking error will be zero at null points. Depending on the geometry you've chosen you will get varying tracking error levels throughout the record except null points.
- Zenith is the yaw axis of stylus in the groove. Stylus' reading edges should be perpendicular to groove walls. This alignment is done by tilting cartridge in the headshell and AM software is outstanding for the job.
- When you set geometry (overhang, offset) right and aligned zenith perfectly (when azimuth, SRA etc are also perfect) then you will achieve the lowest possible distortion levels. Theoretically you will achieve zero tracking error and zero distortion at null points.
- If you make an error on zenith alignment (lets say zenith is 1 or 2 degrees off) then you will get increased distortion levels even if you've set the geometry correct before. This only applies to modern stylus profiles. Theoretically a spherical stylus will not increase distortion levels even with other than optimum zenith alignment because it's round and has no specific reading edges. On the other hand a spherical stylus can not read finer undulations in the grooves and inherently introduces more distortion than a modern profile stylus.
As a result:
- There is always a certain amount of distortion due to tracking error
- Depending on the diameter of reading edges of the stylus distortion level may increase
- Theoretically when zenith aligned perfectly there won't be any additional distortion.
A suboptimal zenith alignment will increase distortion while keeping tracking error unchanged.
- Zenith ---- stylus ----- distortion
- Geometry (overhang, offset, null points) ----- tracking error
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Interesting separation of tracking error and zenith misalignment. I sort of blend them together because at the end of the day it is the cartridge angle and the “fix” for both (in terms of angle) is the same: rotate the cartridge to minimize distortion. But I get your point.
Barring the use of Analog Magik (which is fairly expensive), you can tune zenith (once you have done the geometrical alignment) by listening to a well recorded track with a female vocalist. Important here is that this track is well recorded and more importantly, that the position of the track is close to one of the null points you chose - ideally the outermost one as that’s where the distortion is lower. If the track position is elsewhere you would be optimizing for a different null point effectively, which defeats the purpose.
The Analog Magik zenith and azimuth track is effectively where the Baerwald and LofgrenB outer null points are (Baerwald is about the middle of the track, LofgrenB closer to the end of the track).
So if you’re doing this by ear, listen to a female soprano and listen for silkiness of the upper octaves - harshness will generally mean your zenith is off.
What track would I use? Elly Ameling + Dalton Baldwin performing Schubert Lieder - the track would be “Nacht und Träume”. This is a Philips 1974 release. The track position is approximately where the Baerwald / LofgrenB outer null point is. When I used Analog Magik to optimize zenith and then played this track, the result was a revelation!
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If your pivot-spindle and overhang are correct, you only need to line up to one null point and the other one will be correct, in principle. It is useful to line up to both since “lining up” is prone to error.
Indeed. But the inner null is the important of the two.
That is a good decision, settling on more suitable standard with your record collection. The only problem is printing out new protractor. Unfortunately I couldn't find an error free printer to print the new protractor. I tried more than 50 times and only used 5 meters long industrial printers but no success.
So, the formulas are great but Im a real visual guy, I wanted to see what it actually looks like. I had to find a really long album such as Todd Rundgren's Initiation at ~:35 minutes on side 2. What the red high-lights are, are the outer null range and the inner null range. The ranges are the minimum and maximum nulls using all 3 of the major alignments and using the top 3 groove radii protocol (excluding JIS) 9 points in all for each band.
The outer range was between 11:00 - 13:00 minutes (of a total of :35 minute album side) and the inner groove began at :32 minutes.
What I find is that many albums never get to the inner null point, especially newer, modern albums.
I would love to see a track radius chart vs distortion (2X frequency?) at various alignments as well as same test with a 12" tonearm.
Im running a VPI Prime that came with an alignment jig that uses only 1 point located towards the outer-most OD of inner red track.
Im wondering if you owned a turntable with 2 tonearms if it might be good to use 2 different alignment methods based on your album track design.
.
What does ^this^ even mean?
Are you talking about the length of the recording/groove spacing?
Most cutting is done with a linear tracking set up, so there is no standard for radius points…
And if “the thing cutting” it is turning at 33-1/3 platter speed, then “the thing playing” it would ideally need to be turning its platter at a slightly different rate than 33-1/3 to achieve 33-1/3 relative to the stylus arc.
^That^ is also geometry, but I just draw a radial line, and look at the outer track, and then move the arm to the inner track, and see how many degree more that platter needs to move to put the radial line under the stylus. It’ll be a “bee’s ####” above 33-1/3. Something like 20 degrees over 15 minutes... <— Angle and time respectively.
Good for you, however I would have created a poll if I was interested in which percentage of users understand the meaning of the quoted post.
Would then be so kind as to translate it into what the cutting engineer does when they cut the track, to make it better for the various aloignments Upon playback? (please)
What a great discussion.....some points to be considered...
mtemur ...is absolutely correct null points are more specifically determined by the measurement of the inner and outer groove radius..the groove line [across] from the label to the outer edge of the record. Many including SAT, Kuzma, Graham, Wally etc change these figures based upon there experience of record groove distance thus altering inner and outer null points......thus miglto may be interpreting his figures slightly incorrectly or misunderstanding mtemur's language......[I have no intent of being rude...only trying to resolve]
re Analog Magik.......it has been shown quit extensively now that the software itself "IS" correct.......[tested against oscilloscopes]
The AM albums can be way of in there stamping or lathe cutting causing significant errors in readings....large swing differences in figures between V1 and V2 and 33 or 45 albums and readings as also different using Adjust+, Analogue productions and Cardas etc LP's.....you are assuming your albums are cut correctly [you may be lucky] but we are finding huge inaccuracies in LP albums. Thus Azimuth and Zenith can actually be miles out based upon these records....sad but true.....
We have shown that over many analytical records used for setting up using AM your can be lucky and be spot on or unlucky and miles out....
Search and read https://www.whatsbestforum.com/threads/analog-magik.25735/
Listening is unfortunately still the best final analytical tool....but ....how good are our ears...
The outcome we want as individuals is to be able to enjoy our albums...and all else only helps achieve this....
Good luck and enjoy your LP' s
mtemur ...is absolutely correct null points are more specifically determined by the measurement of the inner and outer groove radius..the groove line [across] from the label to the outer edge of the record. Many including SAT, Kuzma, Graham, Wally etc change these figures based upon there experience of record groove distance thus altering inner and outer null points......thus miglto may be interpreting his figures slightly incorrectly or misunderstanding mtemur's language......[I have no intent of being rude...only trying to resolve]
re Analog Magik.......it has been shown quit extensively now that the software itself "IS" correct.......[tested against oscilloscopes]
The AM albums can be way of in there stamping or lathe cutting causing significant errors in readings....large swing differences in figures between V1 and V2 and 33 or 45 albums and readings as also different using Adjust+, Analogue productions and Cardas etc LP's.....you are assuming your albums are cut correctly [you may be lucky] but we are finding huge inaccuracies in LP albums. Thus Azimuth and Zenith can actually be miles out based upon these records....sad but true.....
We have shown that over many analytical records used for setting up using AM your can be lucky and be spot on or unlucky and miles out....
Search and read https://www.whatsbestforum.com/threads/analog-magik.25735/
Listening is unfortunately still the best final analytical tool....but ....how good are our ears...
The outcome we want as individuals is to be able to enjoy our albums...and all else only helps achieve this....
Good luck and enjoy your LP' s
Couple of points:
The math I started this thread with shows the zenith error for a given pivot-spindle and overhang. The shape of that function is given with these two numbers. When you introduce the offset angle ("Tau" in the formula) you move that function up and down on the plot, and doing so changes where the null points are.
But the point remains is: you can choose Baerwald, Lofgren B, etc and that will change the places where you have the nulls. You might need to change overhang to match both points. But after all this, you still have an angle variation of about 2.5 degrees give or take, the choice is just where to make this smaller, but those choices are fairly subtle.
What you see with AnalogMagik is that getting the zenith of the stylus, not the cantiliver, right is key. You can get a large improvement in the IMD with just a 1/2 degree adjustment. If you align with your cantilever, and you don't use AM (or possibly using Wally's optical analysis), your zenith will be off almost surely.
As for the quality of the pressing, for most parameters (eg azimuth and zenith), all you need to check was done right is the lacquer, not every pressing. I am pretty sure AM has put a lot of effort in verifying their cutter head was aligned and working correctly.
Ultimately, the proof is in the listening, and I can tell you record after record, getting zenith right makes a huge difference.
The math I started this thread with shows the zenith error for a given pivot-spindle and overhang. The shape of that function is given with these two numbers. When you introduce the offset angle ("Tau" in the formula) you move that function up and down on the plot, and doing so changes where the null points are.
But the point remains is: you can choose Baerwald, Lofgren B, etc and that will change the places where you have the nulls. You might need to change overhang to match both points. But after all this, you still have an angle variation of about 2.5 degrees give or take, the choice is just where to make this smaller, but those choices are fairly subtle.
What you see with AnalogMagik is that getting the zenith of the stylus, not the cantiliver, right is key. You can get a large improvement in the IMD with just a 1/2 degree adjustment. If you align with your cantilever, and you don't use AM (or possibly using Wally's optical analysis), your zenith will be off almost surely.
As for the quality of the pressing, for most parameters (eg azimuth and zenith), all you need to check was done right is the lacquer, not every pressing. I am pretty sure AM has put a lot of effort in verifying their cutter head was aligned and working correctly.
Ultimately, the proof is in the listening, and I can tell you record after record, getting zenith right makes a huge difference.
Zenith error is unrelated to the chosen geometry (Löfgren, Baerwald, Stevenson). The correct term for the error caused by the chosen geometry is tracking error. Zenith error, on the other hand, refers to cartridge alignment. Even with perfect cartridge alignment, you can theoretically achieve zero zenith error, but tracking error will still remain due to the chosen geometry. Zenith error adds up to tracking error.
• Tracking error: related to the chosen geometry
• Zenith error: related to cartridge alignment
I agree.
It has more to do with plating and pressing than with cutting. You’d be surprised at the difference in readings on AM software when using a test record before and after flattening, or the results you get with a vacuum hold-down turntable.
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Further to AM LP problems.....
Borrowed from Balle Clorin
https://www.whatsbestforum.com/threads/analog-magik.25735/page-23
My Figures:
AM I and AM II software was tested against an oscilloscope and was shown to be accurate.....so the software is great..
Borrowed from Balle Clorin
https://www.whatsbestforum.com/threads/analog-magik.25735/page-23
My Figures:
AM I and AM II software was tested against an oscilloscope and was shown to be accurate.....so the software is great..
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Thanks Kingrex....based upon your cartridge analysis being correct [not questioning JR as I am sure it is ] and you have it set in your arm / cart within absolute tolerances [not questioning as I am sure it is ]...
Would you be in a position to test your Azimuth / Zenith/ VTA etc readings against the Analogue Productions, Cardas and borrow [if not owned] the AnalogMagik discs..both 1 and 2 [would lend but I am in Perth Australia] albums .....
Using AM calculations or another oscilloscope method with trusted calculations...AM is by far the easiest and proven accurate.....publish or advise your figures to us.....
We may all then be in a position [based upon averages ] that we can use the record that shows to be closest to equal Az for our own setups.....
Again....Many Thanks
What kind of track should be used for this zenith check? I have 30 test records to choose from, but not Analog Magic..
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