Tracking error distortion audibility

Hello to everyone,

A few facts that proove some of the above wrong or, at least, serve as food for thought.

Actual Lyra cartridge measurements, mounting hole to stylus:
Dorian: 10mm
Helikon: 8mm
Titan: 9,5mm
Olympos SL: 9,3mm

Other examples showing that there was never a "norm":
Clearaudio Insider Ref. Wood: 8mm
EMT JSD6: 10mm
Koetsu Black Gold Line. 10,8mm
Decca Maroon: 11mm
Denon DL102: 12mm

I have encountered anything from 6 to 13mm(9,3mm the average so far)...

It is not true that the sonic difference between an arm of 9" vs 12" eff. length is solely attributable to the reduced tracing error related distorsions if the arm cartridge resonance with a specific cartridge is identical.
Simple proof: They will sound different even at the null points.

Some reasons for perceived(and measurable) differences in well known arms:
Higher load(reduced bearing "chatter") on the (knife edge)arm bearings(SME 3009 vs. 3012) due to larger counterweight mass.
Energy storage and release differences due to heavier counterweight on longer arm.
Torsional and bending stiffness reduced on longer arm since most manufacturers maintain the armtube diameter and wall thickness on their 12" arms, i.e. Moerch(likely for aesthetics and/or cost saving).
Consequently, the resonance spectrum(as in "ringing", not fundamental arm cart res.) of the longer arm differs from that of the shorter arm.

It makes no qualitative difference whether one approaches the choice of tonarm geometry from the eff. length or the pivot to spindle distance. The clear advantage of changing the pivot to spindle distance to adjust overhang is simply that one doesn't need to readjust VTF. There is also no risk to accidentally "turn" the cartridge while moving it forward or backward in the slots or while tightening the cartridge screws.
A mechanism allowing for the change of arm position(p-s distance) à la SME, LaLuce or my own is simply harder to produce than a slotted headshell. BUT(!!!), if one chooses this geometry alteration scheme, one also HAS to allow for changing offset angle, albeit within a very small range. Typically there is enough "slack" between cartridge screws and headshell holes for that and a separate, "turning" cartridge mounting plate offers even more room for adjustment.

The best protractor is the one that, for an individual, repeatedly results in an alignment close to perfect. So it is not a question of which protractor, but which person uses it(as long as the protractors are otherwise geometrically correct).

There is no "universally perfect" tonearm alignment. For each record, one perfect alignment exists, defined by the actual used/grooved area. To find the best compromise for YOU, you just need to examine/measure all of your records to come up with an average figure which will differ from IEC or DIN standard.

Many "old school" arms were used to play back singles and transcription discs at broadcast stations. The often questioned choice of an inner Null point near or at the LP "end" groove(r=53mm) makes sense when you want to playback singles(end groove r=48mm) without excessive tracing error related distorsions. Not recommendable if you sold all your singles at a yard sale years ago...

Bob Grahams pivot to spindle jig and hinged overhang gauge work well if you achieved what he wants you to achieve. But if your pivot to spindle distance is off due to poor machining skills(I've seen this more than once)you are repeating the resulting mistake with any new cartridge that you are mounting. Any maybe you have a different idea about the best alignment...

Any cartridge can only perform optimally if the alignment is as close to perfect as possible. In reality cartridge cantilevers/stylii are rarely at 90° angle to a line connecting the mounting holes. Any arm that doesn't allow for at least 2° of offset angle variation/alteration may limit the cart's performance. Don't get me wrong, I don't advocate sloppy cartridge manufacturing, but reality equals imperfection. And as cart suspensions age or with too much skating compensation, the problem gets worse.
Same for Azimuth...

The original question was never addressed. Do linear arm sound better across...
Short answer: yes, but only if you compared two otherwise identical arms. No commercial examples exists, so that debate is pointless.

Let me repeat that it is not correct to say that a tonearm has to have a fixed pivot to spindle distance to be regarded as having a "correct" geometry. If the arm features the required provision to alter the offset angle, it's just as "correct". It will have a "nominal" eff. length, the actual eff. length being a function of the cartridge in use. Arc protractors and Graham style alignment gauges(as good as they are)are therefore out...

One could derive a question from this thread's headline which is directly related to the original post:

What is the threshold for the audibility of tracing error related distorsions? - and: How "tolerant" are the various stylus profiles as tracing error increases?

Time for dinner...

Cheerio,

Frank

Hells Bells,

here comes a man that actually makes the stuff (Frank) and tells me what I was arguing for 101 questions and answers with DerTonarm i.e. the spindle-to-pivot distance is not of this ultimate importance to be even close to 0.1 mm according to some geometry decided spec.
You just compensate with the off-set (turn the cart some more left or right) someone must have heard me cry for help.

So now you have it from an arm designer and manufacturer. Very nice Frank, thank you for sharing, time for bed.

Greetings,
Axel

Hi Axel and the rest of the "gang",

Here are the figures relevant for an SME V:

Let's say cart A has a mounting hole to stylus distance of 9,5mm, cart B is unusually "short" and features 6,5mm mh-s distance and finally, we have cart C, the Jaguar E-type of cartridges with 12,5mm mh-s distance

Required for Baerwald alignment(other alignments possible too):

A: 233,15mm eff., offset angle: 23,63°, pivot to spindle distance: 215,35mm, overhang: 17,79mm

B: 230,15mm eff., offset angle: 23,96°, pivot to spindle distance: 212,11mm, overhang: 18,04mm

C: 236,15mm eff., offset angle: 23,31°, pivot to spindle distance: 218,61mm, overhang: 17,55mm

So all that is required is enough slack to rotate the cartridge by little more than 0,3° either way and slide the base forward or backward about 3,5mm, both of which are easily achieved.
Even the "tightest" headshell holes leave enough room and before anyone takes out a reamer to mess with his SME, just reduce(every household needs a small lathe ;-) the diameter of ONE cartridge mounting screw towards the head, leave the bottom part where the thread engages with the cart alone and you have enough leeway for even badly skewed cantilevers(better just send such carts back to the manufacturer).

And many cartridges have cantilevers that are off by more than the above mentioned 0,3°.

Have fun guys...

Frank

Frank,
That suggestion to file down ONE cartridge mounting screw at the top is pure elegance. Simple, effective, and no damage to the arm. Why didn't I think of that? There was enough play in my mounting holes to allow me to rotate my cartridge in the SME V slightly to achieve the proper offset angle according to my protractor.

I'm curious. You mention in your earlier post that an arc-type protractor will not work if effective length has changed. This should not hold true for a protractor that was designed with a specific cartridge and arm in mind, or am I missing something?

You seem to describe perfectly what I have experienced with my SME arm and cartridge. Thank you.

Dear Frank: Welcome a-board.

+++++ " What is the threshold for the audibility of tracing error related distorsions? "+++++

IMHO the " start " subject here is to define/identified first which are and how we hear those related tracing error distortions over the frequency range, certainly we can but is not an easy task especially if we want to define the threshold/limit.

There are some " difficulties/obstacles " other than system quality performance: the wide differences on the velocity recording through the LP, certainly the tracing error related distortions are different at outer grooves than at medium or inner grooves and we have to identified over the whole record, as you point out we have additional " problems " because of stylus shape, different tonearm/cartridge combinations could be more or less " tolerant " about, our ears and know-how level is important too, there is other subject: there are distortions that are incorrect but we like it ( many of us do not like low distortion sound, many people likes higher distortions/colorations. That's why we have to identified the incorrect distortions due to bad geometry tonearm/cartridge set-up. ), etc, etc

Of course that we can do it in a scientific way making measures and then listening till we find for specific grooves the limit to start/begin to hear " distortions " related to tracing error due to bad geometry set-up.

From my mistakes/errors ( like the one I posted elsewhere with the FR702. ) experiences and due that we live in an analog imperfect world it seems to me that that threshold is wider than what we imagine and cmplex to be absolute precise by ear only.

In the mid-time we have to take care on every single step on the tonearm/cartridge rigth and " precise " set-up.

The 90% of what the people ask in this forum, one way or the other, are related with distortions ( everywhere and any kind ) due to an incorrect audio items set-up.
I repeat again, we have to take care on a precise audio link set-up on the audio chain.

Anyway, I know that there are other tonearm designers that are reading this and other related threads, I hope they want and can joint us to share their thoughts and experiences about.

Regards and enjoy the music.
Raul.