Help me understand cartridge alignment

Clearthinker earlier brought up a great point about zenith errors in the fastening of the stylus tip to the cantilever, which of course is done by the manufacturer. This came up in the other long thread on the Viv Float tonearm. Apparently, Ogura, and Namiki, who make the cantilever/stylus assemblies for most new cartridges, have a tolerance of +/-5 degrees in zenith. Even an error of a few degrees will throw off even the most carefully done alignment. So I imagine that many of us who think our cartridges are near perfectly aligned are laboring under a delusion. This was demonstrated to me graphically and computationally in my own home with actual measurements. When my cartridge was then twisted in the headshell to compensate for zenith error, three of us in the room heard a massive improvement in clarity. Sorry to Clearthinker that I did not recognize the importance of his remark when he first mentioned it here.  I am not sure what dentdog is describing, but it does sound as if he had the same epiphany regarding zenith adjustment.  Unfortunately, probably none of us has the tools needed to correct for aberrant zenith by actual measurement at home.  For one thing, mine was done with a special test LP that enabled measuring IM distortion.

Goodbye, R.

Raul, in that interaction you were per usual arguing the superiority of Baerwald vs Stevenson. We were not discussing the importance of very accurate alignment. Perhaps it is you who have the faulty memory. Also back then I was reporting a problem that arose when I used Baerwald with my 505, which requires twisting the cartridge with respect to the headshell. Again, that had nothing to do with the anal approach to alignment. I won’t rehash the whole issue here.

You are wrong about my "opinion". For most of my audiophile life, I went along with the idea that very precise alignment is important. Only in the last few years have I begun to seriously question that proposition. And the key word is "question". I am not about to say that alignment is NOT important. And I do align my cartridges carefully. But I don’t fret over a mm or 2, just because of my own experience with underhung tonearms and the fact that once or twice I have discovered that my alignment of overhung tonearms was way off (only because I periodically check with a protractor) without any audible associated deficit in SQ. This may be because, even based on your own data above, the associated distortion (which I still do not understand the nature of) is low compared to the sum total of all the other distortions associated with vinyl.

The reason I am still in the dark as to the nature of the distortion associated with minor misalignment of an overhung cartridge is that your response, "Were measured through the Löfgren A-B equations in reference to cartridge/tonearm alignment and under IEC, DIN or JIS standards." suggests to me that you misunderstood my question or I misunderstand your response. Do you mean to say that (someone) measured actual distortion of the audio signal in relation to IEC, DIN, or JIS standards?  If that is what you mean to say, what sort of distortion was being measured?  To say the standards used is not to describe the nature of the distortion.  What I am asking cannot be answered by any equation, because an equation will give you a theoretical answer only, and my real question is whether reality conforms to theory.  Lofgren, Baerwald, and maybe even Stevenson all did their work around 1940, so far as I can find out.  Way before stereo or any high fidelity home audio.

Raul, I just saw your post. What is "tracking distortion"? Are you talking about harmonic distortion, IM distortion, or what? Can you refer me to the source of your data, or have you yourself made these measurements? I am certainly willing to believe there is a relationship between tracking angle error and distortion of some kind, but I have not seen the data, until now possibly. My private hypothesis is that stylus overhang and headshell offset angle taken together are examples of the cure (for TAE) being worse than the disease. Invented 80 years ago by a few guys, who were more mathematicians than audio engineers, to drive us crazy. I realize that my view is not the norm, so I am not anxious to argue about it. But tell me how "tracking distortion" was measured, please. And thanks.

Clearthinker, Your remark about parallel tracking tonearms is totally beside the point, but someone will always bring up parallel tracking tonearms in a discussion about alignment, so you cannot be blamed. But it doesn’t help us or the OP to understand why he is happy with his SQ despite being 5mm off in alignment. My point is that tracking angle error (TAE), while it is best minimized, does not so obviously manifest itself as "distortion" in the electrical sense. For my evidence, I give you underhung tonearms with zero headshell offset angle. Such underhung tonearms can only achieve a single null point on the surface of the LP, where also the skating force is zero, and deliver gobs of TAE at the extremes of the arc across the LP surface, much more TAE than almost any "properly aligned" overhung tonearm with an offset headshell. And yet, my experience with two different examples suggests their TAE is relatively harmless to SQ.  I admit this is subjective evidence, and I have not made measurements.  But neither have the alignment police.

Everyone who’s responded is correct except everyone equates tracking angle error (the degrees by which the cantilever is not tangent to the groove) with “distortion”. Where are the data that confirm a linear relationship between the two?

This is the kind of thing that good little vinylphiles don’t mention. Rigorous alignment is a sine qua non, except when it isn’t.