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Ikeda IT-407 tonearm geometry

I’ve read all there is to read on this subject and never got satisfaction. It inspired me to ask this question earlier.
“Cartridge alignment with non slotted headshells”. 
The main reason I have a problem with these headshells is with my Ikeda it407 (chrome) tonearm, the cartridge must be twisted quite a bit in towards centre.  I have a vintage audio technica headshell with fixed holes and I don't even need a protractor to see that it won’t work. I don’t think stevenson alignment is this bad? I don't have a protractor with stevenson. My pivot to spindle distance is set perfect using my smartractor. I’m quite sure it is not possible to use an spu headshell in my Ikeda with the tonearm at the recommended distance without being seriously out of alignment. I’ve researched this online and I’ve spoken to Bill Demars at Beauty of Sound.  He said that the recommended pivot to spindle distance is probably wrong and some people position at a further distance. He agreed about spu in spu headshell in the ikeda arm not being ideal. I’ve never heard if anyone has asked Ikeda these questions about their arm. 


I do really like this arm, the way it sounds and the fact that is has a removable headshell, 
I’d just like to have better understanding of it? 



sdrsdrsdr

Showing 3 responses by bukanona

bukanona
174 posts
 
Uni-Din is interesting. But although I am not sure that it's worth the effort.

In most of the records crescendo occurs in the very end (at least in classical and jazz) so with cartridges like SPU which are not the best trackers I do feel more safe to have Stevenson as it less possible that it will damage inner grooves of record.

My proposal is if you do any changes by yourself buy test record and use tracking tests as after trying different alignments you have to be sure that you haven't made some hard errors then aligning cartridge.
bukanona
174 posts
 
It's THD tonearm war and it have roots from nineties followed by small moving mass marketing campaign. 

bukanona
174 posts
 
I was struggling to remember where I have saw the text which have changed my mind about alignment
It’s Stereophille
https://www.stereophile.com/reference/arc_angles_optimizing_tonearm_geometry/index.html
and if to "cut" the core is in the very end so will just copy it:

In all that has gone before, we have assumed that the Löfgren-Baerwald approach of minimizing the maximum LTE distortion across the modulated extent of the groove is indeed the optimal one. But there is good reason to suppose that it isn’t, because lateral-tracking-error distortion is only one form of distortion afflicting vinyl-disc replay. Another source of distortion is tracing error, caused by the replay stylus being unable to follow the same path through the groove as the cutting stylus. In large part this is a function of the shape of the replay stylus, and depends critically on groove curvature. Because of this, tracing distortion worsens toward the end of a record side, as the waveform cut into the disc bunches up.

Although tracking-error and tracing-error distortions are different, there is clearly a case for supposing that, as tracing error increases toward the end of the side, tracking error should decrease. In this case, the optimal arm/cartridge alignment might be one that results in a distortion-vs-groove-radius curve like that in fig.10. But as tracing error differs according to stylus type, this approach also suggests that arm/cartridge alignment should vary accordingly, with a bigger disparity from the conventional alignment for a conical stylus than a line-contact stylus. The concept of a single "right" alignment would then be redundant.


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