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In Reply to: RE: Technics SL-1200 Alignment posted by John Elison on February 19, 2017 at 11:37:56
Must be Common Knowledge that SME 3009 (Series 2 + 3: early arm wand) are based on Stevenson - the SME protactor (and as issued with S2 headshells) is @ inner 60.325 - matched against my ancient HiFi Choice/ELITE gauge.
Follow Ups:
I know that 60.325-mm is the inner null-point for Stevenson's alignment, but what about the outer null-point? I can't find the offset for any of the SME tonearms. However, if I could find the pivot-to-spindle distance of the SME Series II, that would tell me if it's possible for it to have Stevenson's alignment with the outer null-point. The parameter that SME states in the manual is "Distance from Bedplate Center to Turntable Center." If this is pivot-to-spindle mounting distance, then it's not possible for SME II and III tonearms to be Stevenson. Sure, you can align the inner null-point to 60.325-mm, but the outer null-point will not be a Stevenson null-point.
What makes you think the SME II and III use Stevenson geometry. If you're going by the null-points published in the Vinyl Engine, those are erroneous. I don't know how the Vinyl Engine came up with those null-points, but they are wrong. Either the null-points are wrong or else the other listed parameters are wrong.
Best regards,
John Elison
SME's old (92mm long) protractor has the 60.325 'null' - which, with the arm aligned to that, seemingly gives an outer 117.42 (SIC!) - when judged against Max Townshend's 175mm long Gauge.. (Personally I use ~Lofgren A as the choice for LP only)Sorry to intrude; but, as UR a previous SME 3 user, thought the above would be Obvious - unless you foreswore larger/more complex OCD gauges 'back in the day'.
Edits: 02/20/17
Hi Frank,
I don't mind the intrusion at all. I would just like to get the bottom of this.
Normally SME provides more parameters than effective length. Nowadays, SME provides pivot-to-spindle and offset angle in addition to effective length. These three parameters define the tonearm geometry completely. In fact, any three independent parameters defines a unique tonearm geometry for which all other parameters can be determined. I truly believe that "Distance from Bedplate Center to Turntable Center" is pivot-to-spindle distance for the specified effective length. Therefore, here are the numbers directly from the manual of the Early SME Series III:
Effective Length = 229-mm
Pivot-to-Spindle = 215.4-mm
.
I owned the "later" version of the SME III, which was designed for Lofgren A geometry within the IEC modulated groove envelope. It had alignment null-points of 66.00-mm and 120.89-mm.
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I'll take your word for the older Series II tonearm having an outer null-point of 117.42-mm since you measured it. However, if I find any SME published information I'll keep you posted.
Thanks,
John Elison
Just to add (old SME info).3009 templates = spindle/pivot centres: 214mm (original) 217mm (improved) 214.5 (SME 3 - mk.1 supplied with 60.325 protractor, as Series 2).
The later carrying arm (you show) nulls then get re-used (early Series 5 brochure).
The earlier null (can't quote my 1971 protractor..) reflects SME's Classical market - until the mid-60's it would be anticipated to use a mix of LP/45 EP
(NB: THe Series 3 (Mk.1) booklet also quotes 215.4 - but (Steel Rule) the supplied Template is 214.5)
Edits: 02/20/17
> 3009 templates = spindle/pivot centres: 214mm (original) 217mm (improved)We've already addressed the Series III and determined it is not Stevenson's alignment.
Personally, I don't believe the Series II arms are Stevenson's alignment either, but you didn't provide the effective lengths. If you remember from my previous post, we need three independent parameters to define a unique tonearm geometry. For example, we know that Stevenson's alignment includes an inner null-point of 60.325-mm. That's one independent parameter. If we know effective length along with pivot-to-spindle mounting distance, that completes the three independent parameters needed to calculate all other parameters.
Here are the specs from a brochure for the SME 3009 Series II tonearm:
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Effective length is 9-inches or 228.6-mm. Pivot-to-Spindle distance is 8.43-inches or 214.122-mm. If we adjust offset angle until the inner null-point is 60.325-mm, the outer null-point will be 106.253-mm. That's not Stevenson's alignment. I'm not sure any of the SME tonearm's comply with Stevenson's alignment.
Edits: 02/20/17
I think I know where the problem might be here - bear with me ...the key here is that the SME arms are designed with a fixed linear offset specification and have a fixed angle position for the cartridge. Alignment is achieved by sliding the entire base. The issue here in using the data for effective length in their specs is that there is considerable variability in the cartridge mounting screw centreline to stylus tip (let's call it Tip Distance to reference later) - the main variables of cantilever length and VTA being the determining factors. Typically the tip distance is between 7.5 to 9.5mm although I do have outliers in my collection. An AT440ML is specified at 8.5mm, an AT150MLX is 9mm for example.
Examining the right-angled triangle (for SME) we have already defined the Opposite side (Linear Offset) and the Adjacent (defined in part by Tip Distance in combination with the pipe length). The Hypotenuse (effective length) therefore changes according to the cartridge tip distance since the Linear Offset is predetermined with a specified inner null.
Alignment is achieved by altering arm base which adjusts the overhang and pivot/stylus distance until the stylus hits the correct null point and since the linear offset is defined, you will achieve the second null point where it should be. This is why I think the linear offset jigs are much better because they are completely arm agnostic. You will note that your scan shows "Nominal length" and not Effective Length for the reason I gave about the variable Tip Distance and hence the adjacent. Consequently, the Nominal length should not be used as an input for effective length in your calculations since for a given cartridge other than the one SME designed for, the effective length will always be different.
Would you agree? Or have I forgotten something here!
Regards Anthony
"Beauty is Truth, Truth Beauty.." Keats
Hi Anthony,
I made my first response way too complex. Here is a simple answer.
Linear offset is fixed as you suggested. Linear offset is defined as the sine of the offset angle times the effective length. However, linear offset also happens to be the average of the alignment null-points. Therefore, when you slide the tonearm base to align your cartridge to the inner null-point of 60.325-mm, the outer null-point must always be 106.253-mm because the average doesn't change. I'm referring to the SME Series II tonearm with its constant linear offset of 83.289-mm.
Best regards,
John Elison
Meanwhile, in the Real World, (devoid of 3 decimal-place precision eyesight) this is what an SME 3009 improved/S2R shell (V15/III squarely mounted/78E stylus) looks like when placed on Stevenson 60/117 pinprick-nulls
The SME 3009/S2 Improved has effective length of 231.2-mm and pivot-to-spindle mounting distance of 215.4-mm. When you adjust the inner null-point to 60.325-mm, the outer null-point will be 116.971-mm. This is Stevenson's alignment. The SME 3009/S2 Improved and 3009 Series II Improved tonearms might be the only SME tonearms with Stevenson's Geometry.
Already stated (20 Feb) the SME 3009-Improved Template measured 217mm - which isn't your 215.4 mm (my quoted 214mm 3009 Template essentially was your imperial) - and SME Series 3 (Mk.1 supplied with a 60.325 protractor) had another published/template discrepancy.Only if you can accurately calculate the distances yourself can these various analyses be provable.
NB: The thicker SME S2-R headshell don't even have a particularly straight edge to align by..
NB2: Decca mastered very infrequently to 58mm - one to hand is the first (1G) transfer of s.1 CS7133/Adler 1978 - also probably applies to Elgar 1/Solti first 1972 issue s.2 (not to hand) - high end-velocities in both instances.
Edits: 02/24/17
> Already stated (20 Feb) the SME 3009-Improved Template measured 217mm - which isn't your 215.4 mmJust because your template measured 217-mm doesn't necessarily mean the pivot-to-spindle distance of your tonearm is not 215.4-mm. You can adjust pivot-to-spindle distance as much as +/-12.5-mm. Furthermore, the exact pivot-to-spindle distance depends on the stylus-to-mounting-hole distance of your particular cartridge. You already know that your alignment null-points are approximately 60-mm and 117-mm and the following alignment equations apply to all pivotal tonearms. Therefore, if you can measure either your effective length or your pivot-to-spindle distance, you can plug the numbers into the appropriate equation to determine the remaining variable.
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I've already shown that the early SME III with effective length of 229-mm is not Stevenson's geometry. It's null-points are 60.325-mm and 100.188-mm as shown in the graph below. The later version, which is the one I owned, simply had a longer carrying arm with effective length of 233.2-mm yielding null-points of 66.0-mm and 120.9-mm.
Edits: 04/15/17
Have you seen this link before? This gentleman has done a very good job at compiling data for standards and other bits and pieces....
Have a read of the sentence above the table regarding Keith Howard's comment on the SME 309.....and Stevenson 1A! ;)
Imagine how delighted the other inmates are going to be when this is all sorted between us LOL ;)
Regards Anthony
"Beauty is Truth, Truth Beauty.." Keats
I don't believe I've seen this page before. Thanks for the link!
> Have a read of the sentence above the table regarding Keith Howard's comment on the SME 309.....and Stevenson 1A! ;)
I'm not sure I quite understand the sentence:
"Incidentally this sample linear offset length 91.55mm is near to 91.535mm for SME Series 300 arms (1989) which might be based on Stevenson Type 1A for 12inches LP"
The correct linear offset for the SME 300 Series tonearms is 91.535-mm or 91.536-mm. Keith Howard introduced the linear offset of 91.55-mm only because he rounded off the null-point radii to one decimal place and took their average. He is correct about these null-points being based on Lofgren's "A" alignment for a modulated groove envelope in-between 58.00-mm and 146.00-mm. He is also correct that this alignment is close to Stevenson's 1A alignment. However, it's not identical to Stevenson's 1A whereas it is identical to the Lofgren "A" alignment mentioned above. If it were based on Stevenson's 1A alignment I'm sure SME would have gotten it right and not just close. Anyway, that's my opinion.
> Imagine how delighted the other inmates are going to be when this is all sorted between us LOL ;)
I don't think they really care! If you look at the rest of the page, it appears that life continues without us. ;-)
Best regards,
John Elison
"... He is also correct that this alignment is close to Stevenson's 1A alignment. However, it's not identical to Stevenson's 1A whereas it is identical to the Lofgren "A" alignment mentioned above."
I guess this is really down to whether you consider Stevenson a method or a solution. This isn't something that I would debate, because I think that both views are probably valid in the absence of Stevenson himself weighing in! He would be about 77 now. I wonder if he has internet access? LOL
SME's choice of radii doesn't exactly conform to any of the standards (and Stevenson has also exercised similar freedom with his choice of the maximum radius). However, both are applying Lofgren A to values such that an average user will probably achieve virtually identical solutions when you factor in tolerances and repeatibility.
I view the differences to be analogous to taking PI as 22/7 or 3.14 instead of to say 10 dp in a calculation. You get different numbers, but the solution is for all intents and purposes the same. For me, I am more concerned about the "intent" rather than the actual answer perfectly matching to determine equivalency.
For the vast majority of users who aren't going to fuss over whether the templates are a perfect snug fit over the spindle, and the markings have been verified to sufficient accuracy to a traceable standard, the actual difference in the linear offsets achieved by the majority of users doing things by eye would be inconsequential in that 91.54 or 91.55 are effectively the same thing!
Even with the care I took over constructing my LO jig (I verified the accuracy of the laser etchings to within 10um of the target values), I repeated the alignment process multiple times on a single cartridge to determine repeatibility and verify the design. It took several attempts to iron out the errors due to tiny platter rotations and improve repeatibility from ±0.1mm to within 0.05mm (otherwise it was about ±0.1mm allowing for the slight slop in the pivot reference "pin" which sets the correct arc position for the null). Offset angle is another story. In principle I should be able to achieve ±0.3° but in practical terms, with tapered cantilevers and azimuth errors, it is incredibly hard (in my opinion) to determine when the cantilever is perfectly aligned and I suspect the offset error is larger.... Stevenson himself suggested that ±0.25° within the target value for the offset was the goal, but I really don't think this to be achievable in practice - even with a fixed offset design like the SME, you are screwed if the motor assembly of the cartridge is skewed and a large proportion of my MCs are afflicted (particularly the Denon ones - confirmed by Expert Stylus who had complained to Denon about this issue).
Regards Anthony
"Beauty is Truth, Truth Beauty.." Keats
> I guess this is really down to whether you consider Stevenson a method or a solution.You've made it perfectly clear to me that Stevenson is the solution to Lofgren's "A" method for calculating alignment null-points from a modulated groove envelope. In fact, you've proven to me that Lofgren "A" is the method used to find Stevenson's null-point solutions.
> This isn't something that I would debate, because I think that both views are probably valid in the absence of Stevenson himself weighing in!
Your logic appalls me! Firstly, both views cannot possibly be valid. Secondly, "Stevenson weighing in" cannot possibly resolve anything. The only person that can resolve this issue by "weighing in" is SME.
> SME's choice of radii doesn't exactly conform to any of the standards (and Stevenson has also exercised similar freedom
> with his choice of the maximum radius). However, both are applying Lofgren A to values such that an
> average user will probably achieve virtually identical solutions when you factor in tolerances and repeatibility.Tolerances have nothing to do with this discussion. We are talking about the basis for a specific tonearm geometry---not how accurately a user can achieve an intended alignment.
> I am more concerned about the "intent" rather than the actual answer perfectly matching to determine equivalency.
The only way we have to determine "intent" is to analyze the numbers. I showed you that Lofgren's "A" solution for an innermost and outermost modulated groove of 58.00-mm and 146.00 produces SME's parameters for the 300 Series exactly out to two decimal places. In this respect, Stevenson's number don't even come close.
Parameters ..................... SME .............. Lofgren ................. Stevenson
Effective Length ........... 232.32 ............ 232.320 .................. 232.320
Mounting Distance ....... 215.35 ............ 215.345 .................. 215.448
Offset Angle ................. 23.204 .............. 23.204 .................... 23.124You're off on a tangent now with all your gobbledygook about alignment accuracy. It doesn't pertain to this discussion. The SME Series 300 tonearm parameters are clearly specified by SME and they will not change regardless of whether you and I believe they are influenced by Stevenson or Lofgren. Therefore, it's really not worth arguing anymore, is it?
I will say I've had fun with this discussion, though. I enjoy our interactions in the Asylum. Thank you very much!
Best regards,
John Elison
Edits: 02/25/17 02/25/17
Come come "Appalling logic" and "Gobbledygook" are a little strong John! I know I have difficulty expressing myself clearly at times and VERY occasionally get sidetracked... ;)
Anyway, I agree, we've battered the hell out that topic! I had fun too and I think we had a very productive exchange which will hopefully be seen one day through the archives for anyone questioning the same topic. I always enjoy a good mental "sparring" session like this with you and I thank you as well.
BTW, I don't know if you read this Keith Howard article in Stereophile, but I think you would find this a very interesting read and is right up your/my alley
Regards Anthony
"Beauty is Truth, Truth Beauty.." Keats
> Come come "Appalling logic" and "Gobbledygook" are a little strong John!
You're right! I apologize! I suppose that both views could possibly be valid, but it would require SME to "weigh in" to verify that conclusion with regard to their 300 Series tonearms. With regard to accuracy in the alignment process, what you say is valid; it's just irrelevant to resolving the tonearm geometry issue of the SME 300 Series tonearms.
Thank you for introducing me to Kieth Howard's article on pivotal tonearm geometry. I briefly skimmed it and I will go back and scrutinize it thoroughly when time permits. He makes some very interesting points. Of course, I think his argument for shorter tonearms versus longer tonearms is highly exaggerated. I wrote a post on this very subject some years back. After all, an air-bearing linear tracking tonearm in nothing more than a pivotal tonearm with infinite length. I don't thin anyone would argue in favor of a 9" tonearm versus a linear tracking tonearm on the basis of alignment error.
Another thing Keith forgot to mention is that SME tonearms can be aligned with a one-point protractor as accurately or even more accurately than with any other type of protractor. That's the beauty of the SME design.
Anyway, I have issues with some of his other points, but I think it would be better to leave them for a different thread and a different time. However, it might be fun to discuss this article further when we get a chance.
Interestingly, I met Graeme Dennes in person several years ago and he is the one who convinced me to begin promoting Lofgren as the father of modern tonearm alignment instead of Baerwald. We exchanged many emails discussing tonearm alignment and other audio related topics. I wrote the post at the link below after meeting with Graeme Dennes.
Thanks again,
John Elison
No, I don't agree! However, it's not me that doesn't agree; it's tonearm geometry that doesn't agree. That's the beauty of linear offset. A specific linear offset will always produce the same outer null-point regardless of the stylus-to-mounting hole distance. That's also the beauty of the sliding base principle of alignment. You don't need an arc protractor or even a two point protractor because the outer null-point will always be the same after aligning the inner null-point. SME has chosen the very best method of tonearm alignment. Let me show you.
Here is the alignment of the SME Series II tonearm I presented in my previous post.
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Now, suppose we use a cartridge with stylus-to-mounting hole distance that produces an effective length that is 5-mm longer than spec. We will still use a protractor that sets the inner null-point to 60.325-mm by sliding the base farther away from the spindle. The cartridge remains squarely mounted in the headshell and the linear offset remains the same.
.
Now, let's use a cartridge with stylus-to-mounting hole distance that produces an effective length 5-mm shorter than the original. We now slide the base closer to the spindle to align our cartridge to 60.325-mm inner null-point. The outer null-point remains the same as before because the linear offset has not changed.
Forgive me for saying this, but I'm not sure you are reading my (admittedly wordy) messages in detail as you appear to be repeating back the same information I wrote in my original message as though I need an explanation! I believe I had already covered the advantage of linear offset based jigs many times before and how the arm base slide is adjusting the overhang to the new effective length defined by the cartridge in use. Would I be wrong in interpreting this as a retreat from your previous advocation for arc protractors? The archives will show that I have repeatedly stated that Linear Offset jigs were arm agnostic and able to achieve higher accuracy in alignment.
In fact I would argue that the use of a Linear Offset jig with an arm utilising headshell slots combined with interchangeable headshells gives an even more versatile and accurate solution than SME - recall I made a jig that provides me with 4 different alignments which I can swap between at will with a simple change of the headshell mounted cartridge and achieve whatever alignment I deem to be most appropriate at the time!
Anyway back to your post - I tried to point this out gently in my previous message, but I'm afraid your linear offset calculation is incorrect because you are taking the "nominal length" as an actual specification. Your calculated offset angle is too low for the length of the arm; There is no way 83.29mm would be the correct linear offset. Your previous screen shot clearly indicated that SME have designed the arm for an inner null of 60.325mm (2.375"). Anything less than 88.65mm is no longer applicable to an LP as it puts the nulls too close together so they no longer satisfy the minimum peak weighted distortion solution of Lofgren A for typical LP radii unless you dramatically reduce the modulation envelope to an Xmax of <126mm or so with Xmin of somewhere around 56mm. You have previously stated that SME do not make mistakes and I am inclined to agree (although the 2.75" inner null for the 3009 Series 1 would perhaps suggest otherwise and they made subsequent corrections).
Frank's information on the null points he achieves with said arm would tend to confirm my view that there is a mistake in your calculation of the linear offset.
Sorry, I must respectfully disagree with your assertions based on your calculations as they are inconsistent with the evidence and data available.
Regards Anthony
"Beauty is Truth, Truth Beauty.." Keats
I'm sorry! I probably do not understand everything you're writing. My mind is a bit foggy with all the pain medication I'm taking currently.
It just dawned on me what you mean by "linear offset protractor." It's the type of protractor that you point at the tonearm pivot like a Dennesen Soundtractor. Yes, it appears that you have constructed a very nice one. I have no doubt it is accurate.
On the other hand, I prefer an arc protractor for tonearms with fixed mounting distance and variable effective length. For tonearms like SME with variable mounting distance and fixed effective length, a single point protractor is all that is necessary for utmost accuracy. In other words, I'm sure your linear offset protractor is just as accurate as any arc protractor, but I still prefer an arc protractor for tonearms other than SME.
> I'm afraid your linear offset calculation is incorrect because you are taking the "nominal length" as an actual specification.
I believe the "nominal length" is an actual specification for a cartridge with the right stylus-to-mounting-hole distance. In that case, I believe the two lengths provided represent effective length and pivot-to-spindle distance. If these numbers do not represent those two independent parameters, then you might be right about my calculations. If you can find any SME literature that provides three independent tonearm parameters, I would be very interested in seeing it.
I apologize, but I'm too tired to continue tonight. Please show me any SME data you have to support your position. If you've already done this, then I apologize again. I'm just too foggy at the moment to discuss this further.
Thanks,
John Elison
Thank you - you beat me to it!
Regards Anthony
"Beauty is Truth, Truth Beauty.." Keats
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