Uni-Protractor Set tonearm alignment

Peter:
Earlier in the thread you asked a question regarding SME and arc protractors (3.11.11)

Surely with arms like these the crucial thing is to determine the effective length as accurately as possible and then set the appropriate pivot-to-spindle distance, again as accurately as possible."

Thom then goes on to miss the point and talk about another issue which fact you then gently draw to his attention.
Then Dertonarm says:

But back to the SME V, which was when introduced anticipated like no other tonearm ever before or ever after.
The SME V is unique in the sense that it's offset and effective length (at least it’s designers thought so and intended it to be that way...) are fixed and pre-determined. Problem is, that SME Ltd. took for granted that each and every cartridge manufacturer would strictly follow IEC standards regarding stylus-mounting slots distance. Which of course they did not.
Now there is the legendary SME slide base to allow sliding the whole tonearm back and forth. That way the arm kind of "moves to the wanted alignment spot".
In theory....
The fact that the fixed offset angle of the fixed headshell isn't really a feature which eases things in any way did not really appeal to the SME engineers in their strive for setting the technical frontier in tonearm design."

Now, apart from the tone (hopefully humorously intended, but easily taken as arrogant and disrespectful) and the assumptions regarding the motivation for the design, there are two very elementary errors:

the first is assuming that the SME has a fixed offset and fixed effective length. It has a nominal offset, and nominal effective length. The misunderstanding here arises from conflating cartridge offset angle and headshell angle. In the SME the headshell angle is fixed and decided by the geometry selected by the designer (Baerwald/LofgrenA IEC). Once this is decided, another dimension follows, namely, linear offset (LO), and this is then a constant for the hardware and given by the effective length times the sine of the cartridge offset angle.

When a cartridge is fitted it retains the headshell angle (within the limits of the mounting hole clearances), and consequently the linear offset remains unchanged. So if you mount a cartridge with say a 12mm mounting hole to Stylus (MH2S) as opposed to one of 9mm MH2S the effective length increases and the cartridge offset decreases, and with a 6mm MH2S the opposite occurs. There is no twisting cartridges unless there is a misalignment within the cartridge (can of worms left unopened...). Only the base needs to be adjusted to supply the correct mounting distance (and therefore overhang) to align the two nulls.

I hope I have explained this well enough. It is something over which even some well respected tonearm designers appear to get confused...try drawing it out on paper.

The second error is assuming that any standard for cartridge mounting hole to stylus distance was implicit in the design. In fact, the opposite could be argued, as this parameter is only relevant in setting up an SME if you use an arc protractor, which is arguably not as universal as a two point, (which can be used with any arm and cartridge) and with the SME is easy to use, owing to its clever sliding base.

To use an arc with the SME V you need to measure the effective length accurately (or as accurately as you can) then obtain and adjust the mounting distance until ideally the two nulls are squared off as per Baerwald/LofgrenA IEC. .

Dertonarm says

"The SME V is a super strict 9"/Baerwald IEC-standard tonearm.

The "super strict" 9"V and the V12 share the same geometry, ie Baerwald/LofgrenA IEC. TPerhaps the V-12 is super strict 12". (I believe the 300 series are actually DIN as opposed to IEC, which should actually appeal to DerTonarm, as he, correctly, in my view, advocates a more general alignment to allow for inner radii less than the IEC standard)

You can't really align him a Loefgren or Stevenson curve with good results."

Lofgren B IEC is simply a matter of sliding the base slightly forward - no fiddling with the cartridge screws.

Dertonarm said in another thread re SME (ironically given the 300 alignment mentioned above)

"The SME 300 series is one of the very few tonearms which does come with a kind of "fixed" geometry in ALL parameters. Given its unability to adjust offset, overhang (we can just move the base - which we shouldn't ... - NOT the cartridge ) and effective length, it surely is a fairly unique sample...

...SME took for granted all industry standards of its day (early 1980ies) and said:

"well, if all cartridge designers do obey to and follow the standards given and if all LPs are cut following the new IEC standard, then evrything will be perfect with our new tonearm - it will be the "best tonearm in the world"............"

But the world is an imperfect one and many people do want to go their own ways.

The new SME surely was the LEAST UNIVERSAL tonearm ever designed .......
It is for sure the one tonearm which gives almost no possibilities to adjust to specific cartridge needs or to different arcs."

I make no claims for SME universality, but all the above is simply laughable, or misleading.

So, Peter, it looks to me like you are setting up the SME correctly. The only issue is that you should use Baerwald/LofgrenA IEC nulls. If you mount your cartridge as accurately as you can in the headshell, then align to the nulls you should be very close. If you have measured your actual effective length, and thereby obtained a mounting distance for the alignment, you can use an arc to check.

Hope all this is of use.
John

Thank you for the clear explanation John. I did supply Yip at Mint with the stylus to mounting hole (MH2S) distance which he used to make the (unique to my arm/cartridge combo) arc-type protractor. The stylus aligns precisely (by 10X loupe standards) at all points of the arc. At the two null points, I adjusted very, very slightly the rotation of the cartridge in the headshell to align with the guide lines at those points. I presume that my MintLP Tractor follows Baerwald/LofgrenA IEC nulls, though I did not know enough to confirm this with Yip when I ordered it. I may email him. Thanks.

John,

In my case, in my #2 paragraph, I reversed DIN and IEC (Dert geometry assumes DIN records, not IEC; and his alignment for the FR-64S creates lower average tracking than using mfr specs for Lofgren A IEC). I will blame it on my lack of morning coffee :^) but I've reversed them before and I am sure I will again.

Thanks for the SME bit. I need some time (and coffee) this morning to wrap my head around one aspect of what you said. May revert.

Dear Geoch,
I know there are still some "fossile guys" out there believing they ( and so everyone) is able to aligne a tonearm by just a small piece of paper. They tell their customers or friends precise alignment is not as important as buying the right tonearm or product. Their customers are usually not very eager learning about proper alignment and its exacetly what they like to hear from 'those gurus' . " you bought the right product, don't worry at all". As long as the (analogue) world will allow herds of followers to believe in such crude philosophies we should not bother about the existance of audio afficinados never being able to distinct good from bad sound.

The (analogue) world is like it is, some good developers and failed ones.
Mostly the failing guys do have a motivation to define the world and tell the succesful developers what they seem to have done in a wrong way.

believe me, I do know producers of tonearms and even turntables who do understand the theoretical implications of proper alignment but they do not really care about it. showing images of inproper alignment may help for a better understanding of the topic - that's all.

best & fun only - Thuchan

T Bone
From your all your posts on this thread, you have obviously thought all this through, and I appreciate your comments. First let me say I ploughed through the thread prior to posting and read all the arguments with all their points, both relevant and off the wall. I also looked at related threads.

I don't have an axe to grind, other than the one called clarity, and I am the first to admit I might not be as clear as I could be at times.

To take your points:

1.

I have seen no vagueness of analysis on 12" versus 9".

Basically he doesn't say why he considers Baerwald/LofgrenA IEC a 9" as opposed to a 12" alignment - the nulls are the same - and confuses the issue with the comments regarding record radii by talking about old records. I'm not saying he's wrong, just that the two things then get connected disproportionately. What I was asking was if he saw a difference between old and new records with full sides - is that a factor.

I have old records with very long run out groove, and new ones with the opposite. What he should have been clear about at the beginning was that the issue is primarily about where the minimum radii are in any particular collection and what each person wants to do about it.

That is as you say, step one, and I agree. Average out the radii in some way, or use a deck as Nandric wittily suggested, with four arms set for different minima, or whatever. In which case there are no standards, but different nulls and you get a protractor to suit each.

You said

Standard geometry using standard assumptions does not always produce lowest possible distortion except in the case when the record has the same dimensions as the standard assumptions AND one does not prioritize low distortion in one part of the record over another.

I don't disagree. I just asked that he should have been specific rather than vague.

2. In other words, is he just saying:
"use a minimum radius of 55mm", (say, or 57 or whatever),
or is he effectively saying: "I played around with the spreadsheet and found nulls which work best with both DIN and IEC",
or is he saying
"I have a theory which says that the existing weightings are inappropriate because there is D% more distortion due the added effects of X and Y and Z, and here is what I think the weighting should be.to compensate - use this to insert into the Lofgren equations to calculate the best alignment for your record collection".

That to me, is being vague, or obtuse, deliberately or not.
I'm not looking for "new math", just asking for clarity regarding the existing old math. I have looked through the thread and admire your persistence in bringing some sort of sense to the scene, and I take all your points regarding Darkling Dert's alignment being the way it is. I don't disagree with him, or say he is wrong in what he is taking as his parameters and objectives, but until your intervention it appears that he wasn't up for clarifying things. Presumably, he had reasons for that, personal, commercial, legal "foral", who knows.

3. You said

I think all of us, including the dastardly Dertonarm, get that minute changes and ball-busting accuracy requirements for one or two of the parameters will necessitate the same accuracy requirements for ALL the geometric inputs (though inner-most groove by its very nature must have some flexibility because one does not newly align (or set up a new headshell) for every particular length).

I wasn't talking about being so anal as to change alignment for every record, nor saying that DerT wasn't concerned with accuracy, but drawing attention to the fact that he didn't share any measure of that concern in terms of how accurate was his offset angle adjustment method. As you well know, if the angle is off by half a degree, never mind more, all that precision will leave your alignment different from what was intended, and generally not in a nice way.

You said:

As an aside, as far as I can tell, the supplied lengths and angle for your signature tonearm don't match the null points noted in the manual.

The null points for all my RP1 arms as I recall, were 63.5 and 119.5. with a minimum radii of 58/146 - basically Baerwald Din, rather than IEC, as I had more records with that characteristic, and it seemed a good option - in that regard I concur with DerT. I think he is correct. And I would agree that a different alignment approach can pay dividends.

Not having seen the supplied protractor, I can only presume it was in fact like a jig so that people could set their cart perfectly straight without deviating from appropriate offset angle, and then the overhang would fall into place shown on the protractor.

I don't get this, T Bone.
No jig was supplied. The protractor was a two point, and the effective length was a nominal 230mm, the offset, a nominal 23.5degrees, with a linear offset of 91.5. Mounting distance was therefore variable as it would depend on the effective length with cartridge (see SME comments to Peterayer above)

Using the accuracy as stated, one would not have come up with the same null points as you did, which means that anyone using a protractor other than yours would have been off Baerwald by a decent bit, even if they had managed to get the offset angle and mounting distance perfect.

Could you be more specific? I'd have thought that would be more applicable to arc protractors... as long as there is play in the cartridge mount you can get a Baerwald IEC or Lofgren without any problem -just adjust angle and mounting distance as necessary. You'd need a two point protractor, though.

4.
I don't know Dertonarm, and perhaps I could dig up some info on him, if I had to (the internet is a wonderful thing, but time consuming). My point was that I don't think I should have to.

If I was selling something, I'd be happy for people to know who I was, and where I was - it's not an issue for me - although perhaps I'm just a bit behind the times and it's more acceptable now, in a forum, on ebay etc. Anyway, you knew exactly who I was, without any digging, and, by now, anyone else who wishes will know a great deal.

As to the protractor, other people challenged him on the subject, and rather than complain about being attacked, he made it. He is now offering it out.

Good for him, I hope he makes his money back, but he isn't doing anything different from a host of others who try their luck at the hifi business.

Is it more expensive than a laminated piece of cardboard? Yes. Is it for everyone or is necessary for achieving good sound? No. But neither is a gold-plated tonearm with diamonds on the headshell.

A slightly cheap shot - I don't know you and, with you, I have no beef, T Bone, but perhaps I deserve it. If I have been a bit too critical in some areas and if I've caused offence, I apologise, But reading the thread, there were some obvious things that needed to be said.

And I agree that gold plate and diamonds aren't obligatory, however, you may have given our man, Diamante Dert, an idea for a more limited edition...