Geometry for pivot tonearms - calculation errors??

Dear Johnbrown, thanks for the input.
A good start for this thread.
And the above mentioned links are useful indeed.

However - this is all included in the G.F.Dennes Tonearm Analysis and Summary. These are all about the different options in calculating the arc and the position of the 2 zero-points (together with the maxima and minima of the derivation from the zero-track of course).

I nevertheless got the impression during several threads the past weeks that the BASIC tonearm geometry (all the mentioned links are dealing mostly NOT with the basic geometry, but with the alignment of the stylus) is indeed hardly discussed at all.

Otherwise there wouldn't be that much irritation and confusion about the basic geometry of the tonearm itself - mainly spindle - pivot mounting distance and its ealtions to effective length, offset and overhang.

Baerwald, Stevenson, Bauer, Loefgren - this is all about the aligment of the stylus and the different options of the tracking arc over the LP grooved area.

This is not dealing with the basic geometry of a given tonearm but with its geometrical interaction with the mounted cartridge.

Dear Raul, I agree with you - this is a complex subject. What I am aiming here is the difference between the basic tonearm geometry (for the individual tonearm) and the geometry for the interaction with a stylus (Baerwald, Loefgren, Bauer, Stevenson etc etc.).

I would like to have some light here that there are 2 tonearm geometries - NOT one. We need to fix the 1st - then proceed with any of the mentioned options in the 2nd geometry calculation.

Its this basic TONEARM-geometry I am target on.

Dear Raul, - let me put it in a few "axioms":

1) offset, overhang and effective length do relate to each other and CAN be CHANGED WITHOUT changing the PIVOT-BEARING DISTANCE. Offset, overhang and effective length do change when you align to a different arc-calculation (say - change from Baerwald to Loefgren).

2) If you change the pivot-bearing distance you change the WHOLE GEOMETRY of the given tonearm.

3) you usually get the very best results with the recommended pivot-bearing (= mounting distance) as specified by the manufacturer, because the whole geometry of the given tonearm builds on that one parameter.

4) whether you choose Loefgren, Bauer, Baerwald, Stevenson or whatever calculation for the alignment of the stylus (and these calculations are onyl aiming at the position of the stylus - not at the position of the tonearm !!) is INDEPENDENT from the geometry of the tonearm itself. These alignments can all be done at the headshell alone without moving the base (and thus the pivot-bearing distance). And they should be done without moving the base because that way you can be sure that the basic geometry of your given tonearm is as specified by the manufacturer.

I think we must clearly put a line here between the geometry of the tonearm WITHOUT a cartridge.

This is the basic geometry of the tonearm itself = 1st geometry.
This is step 1.
Then there is the geometry of the stylus in a given tonearm = 2nd geometry. This is step 2.
Here we have the option to align to whatever calculation does fit our needs best (for instance more modern pressings with long run-out-grooves or pressings from the early 1960ies with the inner grooves running close to the label - these need different alignments - one rather Loefgren - one rather IEC). Here we lay the position of the 2 zero-error points and the maxima and minima derivation. This 2nd alignment does have variations in the offset, overhang and effective length (not much, but some) - but NOT in the pivot-bearing (mounting) distance.

Thank you for your direct email. I will put together a few "basics"/standards for LP-quality and will email to you in the next 2 days.

Dear Lewm,
the SME 300 series (including SME V and IV) is one of the very few tonearms which does come with a kind of "fixed" geometry in ALL parameters. Given its unability to adjust offset, overhang (we can just move the base - which we shouldn't... - NOT the cartridge ) and effective length, it surely is a fairly unique sample.

Make no mistake - the SME V was designed for a specific mounting distance spindle to pivot-bearing! The SME sliding base is often mistaken for being an "invitation" to "adjust" the base "freely" to whatever alignment you want.

Not so.

SME does specify a mounting distance of 215.35 mm.
See here:

http://www.sme.ltd.uk/content/Series-V-1330.shtml

They did not give this very precise figure out of the blue........

SME took for granted all industry standards of its day (early 1980ies) and said:

"well, if all cartridge designers do obey to and follow the standards given and if all LPs are cut following the new IEC standard, then evrything will be perfect with our new tonearm - it will be the "best tonearm in the world"............"

But the world is an imperfect one and many people do want to go their own ways.

The new SME surely was the LEAST UNIVERSAL tonearm ever designed .......
It is for sure the one tonearm which gives almost no possibilities to adjust to specific cartridge needs or to different arcs.

The SME V was a child of its day and was regarded when introduced as the first tonearm which took all (some of them fairly new...) industry standards for record-cutting and cartridge dimensions serious.
Too serious.

Only a cartridge with 100% orientated cantilever and 100% standard horizontal distance mounting holes-stylus can be correctly aligned in a SME V and can only be aligned to ONE standard cuve/arc - the IEC.

Offset can not be aligned in an SME - thats why the SME template does FORCE the user into one possible geometry only.
Thats why the MINT tractor is so very effective with a SME V and a specific cartridge.

In a biological sense the SME V (and its offsprings with fixed headshell and fixed mounting holes) is the very opposite of evolutionary versatile.
It can not "adjust" to any change in the "enviromental conditions".
With the "right" cartridge, it is a VERY serious tonearm.
But there are so very few "right" (read: 100% following IEC standards) cartridges for the SME V around.......

Dear Axel, dear Raul, - I am very familiar with teh AT-180 ML and I want to support Raul's recommendation of thsi particular cartridge. It is outstanding - a very serious contender for most of the $1k to $3k of todays high-flight MCs.
It should work very good in the SME V as should its bigger brothers from AT - why?
Because all AT-cartridges do very precisely hold on to the standards (as do all Ortofons...)in stylus to mounting hole distance and therefor will support the fixed alignment of the SME V.

But - can we discuss the SME V in particular in an individual thread??

Hey Axel - how about starting a thread about the special situation of the SME V in terms of its geometry and design?

I am sure this will get much attention as the SME V is widely owned and I will gladly support it.

Dear Nandric, many quote marks indeed........
I am constantly puzzled how many people do react so anoyed if they are confronted with the pursuit for perfection in technical parameters.
As for the FR-64s I have already made enough comments and already gave the correct and optimzed mounting distance.
Anyone NOT interested in getting the tonearm/stylus geometry as close to perfection as possible has a very good option:

in 1982 the - soon to be history again - audio CD was invented.

This was made for all those countless numbers of music connaisseurs whose smallest unit is the 1mm (which is several hundered times larger than the polished contact area of your stylus).

If you try (try....) to get the perfect geometry, you will not end in the asylum, but maybe end up with no distortion in analog playback and just the sonic results the audio press always promised you.

Leave it to try-and-error is certainly not the way to align a mechanical device.

But - sorry to have created pains in your old wounds with math (also I do not really recall having given any formulas regarding tonearm geometry - I was just displaying geometrical aspects.

BTW - Kessler and Pisha weren't all that correct in their article either and had relativeted most of their "findings" in later years.

Dear Nandric, over the last 5 years I have mounted and aligned about 35 High-end and high-priced cartridges including Lyra Olympus, Lyra Titan and Skala, Kondo IO, Dynavector XRV-1s, Koetsu RSP and Coral Stone, Miyabi Takeda - to name just the more prominent and current ones. Tonearms included all FR-60 family, Da Vinci, Kuzma Airline and P4, Graham Phantom, Micro MAX in all incarnations, SME (all...), even Linn Ekos.

So my practical analog life has its place too aside the theoretical matters.......
The owners asked me to align their high-priced items because I am getting outstanding results in tonearm/cartridge set-up. I do so because of extreme care and because I taking all mechanical and dynamical issues into account and know how to handle them. This is a result of digesting all theoretical background, the skill to use it for practical resuklts and a lot of routine over 30 years.
I am not obssesed with theoretical matters, but I have learned to get practical real world results from digesting the theoretical background and putting all analog handwork on a very solid basis.
To math and geometry it makes no difference whether you like them or not (I didn't liked them in school either...) - the question is rather why not use them for good ?
This is no high math - its all fairly simple 2-dimensional geometry. Drawing on a sheet of paper does very likely clarifies many points - and simplifies them too - which may "sound" theoretical and abstract.
However they aren't.
Putting the mechanical foundations straight and clear just helps getting better sound.
Its that simple.
There are enough areas in our music-systems where it is MUCH more difficult to get things straight and to find the path for sonic improvement (I have built many tube amplifiers and preamps - believe me, they sometimes are a pain far beyond any problems in analog front-end).

The anaolg front-end is all mechanic and dynamic interactions.
I find it fascinating, as this is the one area where we can actually "see" whats going on and can have much more direct influence for the better than in any other part of the chain.