Tone arm length

There's much wisdom (and a bit of controversy) in this thread. 

Suffice to say that I fall in the camp that there are many reasons to advocate long arms, but significantly improved tracing distortion is not one of them.

I recently fired up John Ellison's seminal work - his Baerwaald / Löfgren spreadsheet to model various geometries, setups, the relative significance of getting zenith right vs. overhang, and several other scenarios.

If anyone is interested, here's the link:  Modeling Various Setup Parameters

Thom @ Galibier

Dear @thom_at_galibier_design : Nice to see you in Agon again.

I only want to make some comments about the information in that link:

first is that J.Ellison made his spreadsheet geometries named/labeled it in the rigth way ( because he knows very well the Löfgren w.papers. ): Löfgren A and B.

Baerwald has no merit on those alignments other that his solution 4 years latter to Löfgren was exactly the same/similar to Löfgren A. I’m not saying it’s a copy but certainly nothing new or better than Löfgren or a modification.

second is that Stevenson made as Löfgren 2 solutions: Stevenson A and B where the latter is similar to Löfgren A alignment. Not only you but even the tractors manufacturers never specify the correct way: Stevenson A. Are important this issues? well I think it’s. Other issue about is that you named uni-din where this is not a universal alignment an even is not a new equations solution but only a manipulation parameters using Löfgren solution and it’s too what SAT tonearm designer did it ( to set up the cartridge to his tonearm. ) with that kind of manipulations to the original input parameters : innermost groove and outermost groove radius values. These kind of manipulations means that you, me or any one else can have our personal alignment if we want it. You can do it through the Ellison spreadsheet or through the VE alignment calculator. Not big deal as the Löfgren solutions. Btw, VE calculator has the advantage that at the same time gives you both Löfgreen ste up parameters and Stevenson A too and diagrams/charts with the 3 alignments curves to compare visually between them.

in the link I pasted :

" 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). "

Not exactly as you specified it and please let me explain about because I think is way important to any audiophile:

what are the input parameters used in the Löfgren equations that used he?

only 3: effective length, innermost groove radius and outermost groove radius and from those 3 input parameters the Löfgren equations solutions gives/output parameters: both null points ( inner/outer ), off-set angle, overhang and linear offset. The pivot to spindle distance then comes from an atritmetic subtraction: EL - overhang.

Been mathematics we can do whatever we want as could be to have a TT convenience P2S distance and use this parameter in those equations making the changes necessaries but is only a manipulation of the original equations/parameters and not a new alignment. As I said It’s only mathematics.

In reality the Stevenson A is an extreme input parameter change/manipulation ( innermost groove radius. ) but this gentleman made something truly different to what existed and some tonearm designers choosed Stevenson A alignment.

Again good to know from you.

R.

Btw, those ( inner/outer most ) parameters ( radius distances ) are different depending of which Standard values we choose and the alignment cartridge/tonearm is different on each one,

Exist 3 Standards in audio industry for this specific subject: IEC, DIN and JIS where: IEC is the International Electrotechnical Commission ( and it’s the one that comes by default in the Ellison calculator. ), DIN is Deutsches Institute für Normung and JIS is Japanese Industrial Standards. Using either we reach different tracking distortion levels.

Now if we want the whole lower tracking alignment distortions the way to go is with the SAT tonearm choosed parameters that comes in the link I posted in this thread.

I forgot that that " extreme " change that Stevenson made it in his A solution is that he decided that instead to have an innermost groove distance he choiced that there be the inner null point and this " move " is full of compromises ( I think negative trade-offs ) but many Japanese tonearm manufacturers took Stevenson A as their prefered alignment.

R.

I use Stevenson A as my method for Alignment.

I have not been needing to consider any other Alignment Geometry, I am more than content with Stevenson A.

I have not suspected anything negative is present in relation to the effect of the Geometry used for the Cartridge Alignment.   

Hi @rauliruegas,

Long time ;-)

This exercise got me started as I’ve been handling quite a few vintage Japanese tonearms recently, and I’ve been wondering why they specify the same overhang for various effective lengths (15mm for both the 245mm FR 64, and 229mm Jelco for example).

Well, I still don’t know why they fixed the overhang, but when I modeled the FR64 and 9" Jelco, I realized that if you play with the offset angle, you can get reasonably good distortion characteristics with these specifications.

Of course, the problem is that you’ll have difficulty finding a protractor for their geometry (unless you have a factory protractor), which is why I tend to recommend mounting them for Baerwaald or Löfgren when possible ;-)

So down the rabbit hole I went, thinking of various scenarios to model.

After viewing the subtle differences, I don’t want to get into heated discussions about Baerwaald vs. Löfgren vs. Stevenson vs. (dare I say it?) Uni-DIN. Life is too short

Be well!

Thom