Well, in Tonearm Geometry two Problems have to be solved, the complicated ones and the simple ones.. the complicated ones for example Mass in correlation to Cartridge Compliance, standing waves in the Arm and what to do to avoid them,
The Bearing, Damping, skating compensation, the used wire inside, soldering....but nobody talks about the "simple" Problems like Geometry (the right Geometry!), the interaction from that in combination to tracking distortions...the modern Audiophile thinks, when he has the money to buy a tonearm he automatically gets a perfect Product..well, this is probably the mistake of his audiophile Life. Most today is copied from something, made cheap, sometimes wrong but always served with a high price and a nice finish. Arch Angle is for most "Designers" much too complicated, a top bearing much to expensive and "dynamically balanced Design" is in general a big question mark...but it is important enough that minimizing Tracking Errors is mainly based on that.
The "secret" is in reality no secret, B. Bauer and Dr. Seagrave analyzed the influence between Arm Geometry and resulting distortion of it in 1941, it is valid until today.
Another important view is, for what "Nulls" is the Arm calculated? Close to the last track, far away from it, or even close to the last grooves in the last track? There also also huge differences which shows the user that his modern Arm works great with reissues or records after 1990...but get problems when listening to old Mercury Living Presence LP's. Some Arms simply can't be adjusted properly, but the User will never discover it (the only judgement he can or will do is based on "when I like what I hear then it is good") Doing right geometry is same from costs than doing wrong but when the knowledge is simply not existing what can we expect? The Diamond touches both side walls from the groove, when there is something not absolutely precise, you get a time shifting in the channel reproduction, result is, the details are smearing. you hear that not with a female singer in the middle, but you can hear that easily with older classical records which have huge dynamic swings in parts of a second. And you can't correct it with Azimuth adjustments or similar, the error is in the geometry. This is the reason why some Arms sail through everything and some not.
Some Arms are calculated that they only work with cartridges which have a cantilever length based on that Design, some Arms have nothing, they have a so called "Do-whatever-you-want-Geometry" and all have their Fangroups.
Another interesting chapter is the development from vibration removal and what the result of that is...lot of knowledge is gone (real knowledge, not blabbering), today we have wood tubes which can be bought for $65 in music shops and the drill for it is another 15,--. Cocobolo, Cherry or whatever, nice polish, touched from a Music "enthusiast", kissed before sending it...For some this is good enough. The grail.
For some. Not all.
But even when done all right, do we hear it?
A good question, after 15 years I think, hardly or no. The real money or brain from the Designer is in the reproduction of high frequencies (the ultra silent signals which can open another window in the sonic puzzle). Most Phonostages can't do that anyway (they need a damping to avoid pain in the ears of the listner), most Turntables are not good enough from isolation and most Speakers go into clipping with higher frequencies based on mediocre chassis. This is one reason why average units become a rating to be a Standard. Even when you compare it, it is possible you will never detect it. It is like a bottleneck. This shifting of overall balance (idler fans call it PRaT) is in reality a loss, which is compensated in a different frequency areas (Bass for example). And that is what we have today. The compensation from something "weak" with this or that. At the end of day you can roll a dice, too.
