Modeling Setup Geometry

Galibier Design - Geometry Figures

We frequently field questions from owners of tonearms with "non-standard" mounting geometry. 

Examples include Jelco, Ikeda, Fidelity Research, Well Tempered, etc.  

They're "non-standard" in the sense that commonly available protractors are typically designed for  Baerwaald, Löfgren, Stevenson, and (sometimes) Uni-DIN.

Note that the ubiquitous Feickert protractor accommodates the first three alignment protocols.

Why this Matters - the TL;DR

This is a detailed, extended analysis.  If you're short on time, link down to our Final Thoughts section for a summary of this analysis.  

We're more than happy to discuss this with you on a one-on-one basis.

A few quick takeaways:

  1. If you have a fixed-mount turntable, your mounting location may limit the alignment geometry you can experiment with.  Baerwaald, Löfgren, Stevenson alignments may not be possible.
  2. We've been able to establish viable mounting parameters for these arms which have incomplete specification (usually offset angle).
  3. These derived specs can perform very well, although you may not be able to source a commercial protractor for your chosen geometry, or replacements protractors that may have been issued with the original purchase of these arms.

Some Background

In general (there are exceptions), many of the classic Japanese designs hold the overhang constant over a range of effective lengths.  

For example, the 229mm Jelco, the Fidelity Research FR64 series, and the Ikeda Model 345 (245mm long) all specify an overhang of 15mm.  

Documentation of offset angle is spotty at best, and protractors may be limited to the one originally supplied with the arm.  A few small companies have attempted to address this.

In contrast, the math developed by Löfgren (and subsequently used by Baerwaald), derives a unique set of 3 parameters (effective length, mounting distance and offset angle) for each and every effective length.  

Protractors for Baerwaald are readily available, and slightly less so for Löfgren, Stevenson and Uni-DIN.

In Example-4 below, we model the cartridge re-positioning required to align a Jelco for Baerwaald, after it has been mounted to Jelco's specification.  The cartridge needs to be moved forward in the headshell by nearly 3mm to achieve a Baerwaald alignment and slightly more for a Löfgren setting!

As Clint Eastwood once said:  "do you feel lucky?"

Disclaimer:  

There's much disagreement over the ideal alignment geometry for pivoting arms, and enough has been written about this, so we won't cover it here.  We'll mount your arm any way you wish. 

Suffice to say, a majority of individuals opt for Baerwaald, since the math is optimized to minimize average distortion across the entire LP.

Ultimately, this is your decision and there's no wrong answer.  Some of the alternate models we map out below are quite good.

We want you to understand the pitfalls, and it's our hope that this analysis helps you make a more informed decision  before drilling into your armboard (or worse) through your turntable base.  

What?  You want charts?  We'll give you charts!

Pull up a seat and pour a cup.  This is going to massage your brain cells ...

One of the best resources on the web for establishing tonearm parameters and mount points is a spreadsheet developed by John Ellison which is posted in the "Free Stuff" section of the Enjoy the Music website. 

We maintain a link to that page on our "main Support Page".  

Here's the direct link to the download.  Scroll to the bottom of the page for the download and instructions.

Galibier Design - Steaming Cup of Coffee

Next up ... some background on the Ellison spreadsheet.  Skip to Example-1 if Excel isn't your jam.

Also, you might want to download the screen captures (below) as you will find yourself comparing them.  Click to expand them to full-screen before downloading.

Ellison Spreadsheet - a Quick Excel Lesson

The Ellison spreadsheet has two worksheets.  

  • The first one is for the Baerwaald math (labeled Löfgren A)
  • The second one is for Löfgren (labeled Löfgren B). 

We'll use Baerwaald/Löfgren A in these examples and a 245mm effective length for most of them in order to model the Ikeda's 245 / 15mm specification (also the Fidelity Research FR 64 series). 

The simplest use case involves entering the effective length in cell I-3.  The results are displayed in cells A-3, B-3, C-3, and C-5 (effective length, offset/zenith, overhang, pivot-spindle).

These four cells "drive" the distortion and tracing error graph.  They're displayed using using a cell reference which insulates them from the math that derives the recommended Baerwaald and Löfgren parameters.  

This allows you to manipulate them to model alternative parameters while not disturbing the Baerwaald and Löfgren calculations.  

Note that we set the cell precision to 4 decimal places which is unnecessary in most cases.  We use it when we're working "backwards" to iteratively find an effective length from a pre-determined pivot to spindle distance.  We used this in Example-4 to backward calculate a Baerwaald effective length for the Jelco's 214mm mount point.

Example-1:  Standard Baerwaald

In this screen shot, note the outputs in cells A-3 (repeating the effective length), B-3 (offset/zenith), C-3 (overhang) and C-5 (which re-calculates pivot-spindle, using effective length & pivot-spindle). 

Galibier Design - Ellison Spreadsheet Modeling: Ideal Setup

Ideal Setup

Note the peak distortion is generally below .5% across the entire LP.  Baerwaald was developed to minimize average distortion across the entire LP.

Also note that the Baerwaald overhang (16.8632) is nearly 2mm longer than Ikeda's 15mm specification!  

We'll model both the Ikeda and Jelco spec below.  Compare this example against the Ikeda and Fidelity Research example (Example-3, below).

Example-2: Overhang Error  (1mm too long)

So you casually aligned, and your cartridge is 1mm "forward" of the Baerwaald ideal.  

  • Peak distortion drops
  • The range between the null points narrows to about 76 & 113mm
  • Distortion is reasonably well-behaved between the lead-in groove and the outer null point, but from the inner null point to the end of the record, it rises dramatically.
Ellison Spreadsheet Modeling: Overhang Error - 1mm Long

Overhang Error - 1mm Long

If you have basic Excel familiarity with cell references, model this error by manipulating cells A-3 and C-3.

We added 1mm to both of these cells.  Refer to the comments on the screen shot.

Example-3: Ikeda / Fidelity Research

The effective length (245) and pivot-spindle (230) are published for both the Ikeda and Fidelity Research.  The offset angle is undocumented.

We became aware of a protractor for the Fidelity Research FR64 series.  It specifies an offset angle of 21.5 degrees, although we were unable to verify it - whether it's an FR specification, and if so, if it is manufactured accurately.

We also don't know if Ikeda changed the spec from the original FR64 series.

The first graph (Ikeda "Error") assumes an offset angle predicted by 245mm Baerwaald geometry.  Yes, it's a bit of a straw man with its 24.2 degree offset angle, but it approximates what the unknowing user might arrive at if he used a standard 2-point Baerwaald protractor after mounting the arm at 230mm from the spindle.

The FR64 "Spec" graph reduces the offset angle to 21.5 degrees.  This is the only difference between the two.

It's fairly clear that the "Spec" version's offset angle is a better match for the 15mm overhang (230 mm pivot-spindle).

Galibier Design - Ellison Spreadsheet Modeling: Ikeda "Error"

Ikeda "Error"

Galibier Design - Ellison Spreadsheet: Ikeda "Spec"

FR 64 "Spec"

Comparing against Example-1, above:

  • The "Error" version has no inner null point!
  • The "Spec" version's null point is at the end of the LP.
  • Peak distortion on the "Error" version is quite a bit higher than ideal Baerwaald (Ex-1).
  • Peak distortion on the "Spec" version is nearly as good as ideal Baerwaald (Example-1).

Comments:  

We're not quite sure what to make of the veracity of the "Spec" geometry, given that Ikeda specifies a distortion range of +2° – 1°21′ for the current tonearm.  This "Spec" geometry is quite a bit better than this.  

Is the "Spec" geometry the result of someone's experimentation to improve the original FR64 alignment, or alternatively, did Ikeda make some changes for the worse?  Or both?

Two things are clear however:

  • All three parameters (eff. length, pivot-spindle, offset angle) work in concert with each other.
  • Zenith matters, and you can compensate for undocumented mounting specs by experimenting with offset angle (zenith).

The FR64 "Spec" alignment may not be everyone's cup of tea (which alignment is?), but it certainly has reasonable distortion characteristics.

Another consideration is whether you can source a dedicated protractor to meet the above specification (21.5 degree offset angle), and whether it's manufactured accurately.

Example-4: Jelco "Error"

This is another arm with a "standard" 15mm overhang - this time, with a 229mm effective length.

  • This example illustrates how mounting to the manufacture's recommendations may prevent you from achieving a Baerwaald alignment.
  • If you mounted it to specs (i.e. 214mm) and later wanted to align for Baerwaald, you would have to move the cartridge forward in the headshell by 2.8935mm (nearly 3mm!).  Löfgren would add approximately .5mm to this.
  • We also experimented using the standard 229/214 parameters and varied the offset angle with encouraging results - similar to the FR/Ikeda example above.

In the first graph (Jelco "Error"), we modeled the standard specification of 229/214.  As with the FR/Ikeda example above, we accepted the Baerwaald recommended offset angle for 229mm effective length.

For the second graph ("Offset Angle Correction"), we started with the first graph (recommended 229/214) and experimented with offset angle.  The 21.5 degree angle shown produced encouraging results, and you'll note the similarity to the Ikeda "correction" above.  

The null points are a bit closer together in comparison with the Baerwaald alignment, and distortion is under .5% within these bounds.  At the lead-in groove side, maximum distortion is a bit over 1%.

For the third graph (Jelco Baerwaald correction), we keyed 231.8935 into cell I-3 (replacing 229).  This netted a  Baerwaald alignment for the standard mount (214mm pivot to spindle).  This models what you'd have to do to produce a Baerwaald alignment if you mounted your tonearm at the recommended distance of 214mm.

Note that we mount Jelcos at the "Kuzma distance" of 212mm and this yields a cartridge position that's "shorter" and is very close to the mounting slot centers.

Comment:  

As with the Ikeda (above), we haven't found a documented offset angle specification, but experimentation shows promise.  Finding a protractor for this alignment may be difficult.  

Are you beginning to see why Baerwaald is a safe choice - especially when you take protractor procurement into consideration?

Galibier Design - Ellison Spreadsheet Modeling: Jelco "Error"

Jelco "Error"

Galibier Design - Ellison Spreadsheet Modeling: Standard Jelco (229/214) with Proposed Offset Angle

Proposed Offset Angle Correction

Galibier Design - Ellison Spreadsheet Modeling: Jelco Baerwaald correction

Jelco Baerwaald correction

Modeling Zenith Error:

Zenith is the new azimuth ... right?  

The following two examples model a zenith variance that is within cartridge manufacturers' specs of +/- 2 degrees.  

If you align your cantilever to your protractor, but your stylus assembly has errors of 1 or 2 degrees, these are the results.  See why zenith matters?

Galibier Design - Ellison Spreadsheet Modeling: 1 deg. CW Zenith Error

1 deg. CW Zenith Error

Galibier Design - Ellison Spreadsheet Modeling: 2 deg. CW Zenith Error

2 deg. CW Zenith Error

Compound Errors

OK ... you fired up your AnalogMagik and nailed both azimuth and zenith.  Huzzah!

In order to optimize zenith, you had to rotate the cartridge in the headshell, and you invariably changed the overhang.  We feel your pain.  

With a traditional two-bolt headshell mount, you'll find yourself pivoting the cartridge back and forth on one of the two bolts, and you may find your overhang has changed by as much as a mm or two.

In this example, we modeled a tonearm with a Schröder style cartridge mount.

The cartridge pivots about a central bolt instead of the cartridge's two mounting bolts.  This helps you more easily maintain your overhang setting.  While not perfect, it does simplify tuning azimuth.

Below, our our CAD model shows the effect of a 2 degree cartridge rotation on effective length / overhang. The effective length is shortened by only .120mm.  The graph shows the minimal impact of this overhang error.

We'll let you decide whether it's worth your time to iteratively adjust overhang as well as zenith to get both parameters "spot on".  

One thing is clear however:  A zenith error has much more impact than a slight overhang error.  Thank goodness for the little things.

Galibier Design - Ellison Spreadsheet Modeling: Overhang Effect

Overhang Effect

Galibier Design - Ellison Spreadsheet Modeling: .120mm Overhang Error

0.120mm Overhang Error

The 9 vs. 12 Conundrum

We're long overdue for a full analysis of 9" vs. 12" arms.  But this is a question we field too frequently to leave out of this commentary.

From the perspective of tracing distortion, a long (12") arm has no significant superiority over a short (9") arm.  None!

Go long, if you your table architecture requires it, if you like the look, or you've found a better mass match with your cartridges, but don't fool yourself into thinking that there are any advantages resulting from the arm's geometry.

This simulation shows an arm with a 310mm effective length, aligned for Baerwaald.  Compare against example-1 and the third trace in example-4 (Jelco Baerwaald correction).

Galibier Design - Ellison Spreadsheet Modeling: 310mm Arm / Baerwaald

310mm / Standard Baerwaald

Final Thoughts

Experiment

Don't judge a tonearm design until you've revisited your setup, and tried a proven geometry, paid attention, and used precision setup tools.  While obvious, this bears repeating.  

Choosing an alternate alignment may unlock your arm's potential.  

Having said that, we can't begin to enumerate how many times someone has reported an improvement by changing from "A" to "B", only to return to "A" and notice yet "another" improvement.  

We attribute this as much to the randomness of setup errors, as much as to the the psychology of A/B testing.  The lesson here is to pay attention.

Control your destiny: 

Armed with the Ellison spreadsheet, you can determine and mount to Baerwaald or Löfgren geometry, as long as your tonearm allows for you to adjust offset angle (zenith).  

In all likelihood, you can accommodate some of the above "vintage geometries", allowing for all of the choices you'll ever want to try.

Using the Ellison spreadsheet, key in the arm's effective length as the starting point.  

Caveat:  we found one popular tonearm who's effective length was misstated.  We can show you how to determine/verify your arm's true effective length.

Cartridge Variance

Unfortunately, the position of the stylus relative to the mounting bolt holes is non-standard.  This has an effect on the effective length of your setup, and is one reason for providing adjustment slots in headshells.  

Statistically, the mean distance hovers around 9.25mm (Lyra, Hana, My Sonic Lab, ZYX, and many other cartridges).

To help you visualize this, here's a drawing of the Dynavector XV-1s/XV-1t (courtesy of Dynavector).  Note the 8.00mm stylus offset (one of the shortest ones we've encountered):

Galibier Design - Dynavector XV-1t Drawing

XV-1t and XV-1s (click to enlarge)

Use your common sense:

You will hear claims from tonearm designers that adjustment features like azimuth (and even zenith!) should not be necessary - that it's the cartridge manufacturer's responsibility to deliver a perfectly aligned cartridge.  

This is is an unrealistic expectation, and the reason designers implemented adjustment features in the first place! If you'd like to read more about the limitations of cartridge manufacturing, read Jonathan Carr of Lyra's comments on the topic.  Jonathan is one of the "good guys" in our industry.

Azimuth 

Azimuth adjustment is beyond the scope of this article.  Suffice to say that it's an important setup parameter.  

Zenith & adjustable offset angle:  

Refer back to the zenith section if you have any doubts about it's importance.  Fortunately, arms without this feature are very rare.  Among the exceptions are the modern SMEs (models IV & V) and the Well Tempered arm.

 Zenith is the "new azimuth".  Experimenting with it matters ... a lot!  This bears repeating.

Tradeoffs  

Correcting a zenith error at the expense of a slight overhang error is a worthwhile tradeoff if you have to make it.  

Of course, we prefer to get everything "perfect", but at the same time, it's comforting to know what you can prioritize and address over time (not in one session).  Your patience will be rewarded.  Refer to the "Compound Errors" section above.

Your opinion matters!

The only correct geometry (and setup) is the one you like, but remember, you won't know better until you hear it.

Plan:

Planning for mounting flexibility isn't rocket science, but if you have any doubts or questions, reach out to us.

Disinformation

Here at Galibier, we're all about slaying the sacred cows.  Most of the disinformation we encounter is well-intentioned and is by no means nefarious, but the effect is the same.

We run the risk of offending some, and we'll leave it to you to judge.  

We've worked long and hard at this over the decades, and we recognize that no single individual is the repository of absolute knowledge.  Neither Galibier, nor anyone else is the final arbiter of truth.

With that in mind, one of our guiding principles with respect to vinyl playback is WWFD:  (what would Frank do).  We're referring to Frank Schröder and Franc Kuzma - two of the most level-headed thinkers we've encountered in the vinyl playback realm.

AnalogMagik Note

The AnalogMagik test record has a multi-use track used for establishing azimuth, zenith, and VTA. 

The end of this track is near the outer null point, so the distortion measurements will not compound as they would if the track was located near the center of the record.

Related Posts

To DIN or NOT to DIN

To DIN or NOT to DIN

Treating Your Connections

Treating Your Connections

Burning in a Tonearm

Burning in a Tonearm

Winter Static

Winter Static

Thom


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