Baerwald? LofgrenB? Stevenson? The math behind alignment conventions
- Thread starter miglto
- Start date
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.
Last edited:
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
Last edited:
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!
Last edited:
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)
 | Steve Williams Site Founder | Site Owner | Administrator |  | Ron Resnick Site Co-Owner | Administrator |  | Julian (The Fixer) Website Build | Marketing Managersing |