SME 3012 Alignment

[Iron]

Ohohooooohhhhh, it seems things are getting more and more complicated.

Actually my (and probably WER's) intention is quite simple: there must be an ideal set up for the SME 3012/II arm, meaning, what was the intention of the SME designers for this arm, therefore what would be the ideal, leaving aside the fact of a fixed hole headshell and the fact of a sliding base. Why is this: by using slotted headshell man can adjust every single cartridge to be mounted, without having to move the arm base.

I originally came from using a Shure V15IV cartridge with original MR needle. This gives me an exact 52.5mm distance from the needle tip to the flange (as shown above, although I simple use a Technics alignment tool, the white headshell stand). An aftermarket HE needle gave me a different (larger) distance already, so this has to be watched. From what I remember, a Denon DL103 has a different distance than the Shure cartridge. I cannot verify this at the moment, as my DL103 sits in an aluminium, aftermarket body.

So, again, for the given SME/EIA Standard (cartridge needle tip 52.5mm from the flange), what is the correct mounting distance (pivot to spindle) for the tonearm? This data is obsolete in every official SME publication. I am looking forward to your replies, as the above causes at least me hassles to get the cartridge tip into the correct position, even when using the original SME protractor. The protractor is not the problem, as it only gives us the required null points at the given distance from the spindle.

Cheers
Marco

[Divedeepdog]

I have limited experience with 2 3012 arms,  the recognised position (centre of the oval) is 296mm, however the 1st plinth I made with this dimension the owner struggled to achieve alignment with an SPU.  The conclusion we came to was  manufacturing vagrancies,  after all this was 60's Britain,  not really known for our precision,  lets not mention the 70's 

[flood2]

Ohohooooohhhhh, it seems things are getting more and more complicated.

Actually my (and probably WER's) intention is quite simple: there must be an ideal set up for the SME 3012/II arm, meaning, what was the intention of the SME designers for this arm, therefore what would be the ideal, leaving aside the fact of a fixed hole headshell and the fact of a sliding base. Why is this: by using slotted headshell man can adjust every single cartridge to be mounted, without having to move the arm base.

Well, the simple explanation is that SME only tell you that the inner null is 2.375" (60.325mm). They don't need to specify any other parameters since that is the only information you need as long as the armboard has been made according to their template. It is reasonable to assume that they may have based the design on Stevenson 1B, but there is no guarantee since the linear offset is not specified and is also dependent on the arm bend tolerance so I would simply use the inner null as your reference. Since they have fixed the offset angle for you...and assuming you have an armboard designed for an SME arm, you simply need a protractor with a null point at 60.325mm and adjust the base until you achieve it. Do NOT use an arc protractor since the SME design is such that the effective length is dependent on your cartridge dimensions - specifically the hole centre to tip distance. When you adjust the arm base you are changing overhang and pivot/spindle distance simultaneously to accomodate the specific tip/hole-centre distance for your specific cartridge which means the arc protractor is useless.

If you are not familiar with the definition of Linear Offset refer to this diagram from VinylEngine:


In my view, adjusting the arm base is a rather clumsy method that has limited accuracy and flexibility to accomodate alternative alignment options or to compensate for cantilever skew which is very common particularly with the original arms since it is hard to make very small adjustments due to the mass of the entire assembly that you are moving. The SME design relies on the cantilever being essentially perfectly located along the centreline of the cartridge which almost never happens even if by luck the cantilever happens to be parallel to the sides of the body.

A slotted headshell is more flexible since the Linear Offset is not pre-determined and you can compensate for any cartridge manufacturing errors as well as achieving any null points you want.

I originally came from using a Shure V15IV cartridge with original MR needle. This gives me an exact 52.5mm distance from the needle tip to the flange (as shown above, although I simple use a Technics alignment tool, the white headshell stand). An aftermarket HE needle gave me a different (larger) distance already, so this has to be watched. From what I remember, a Denon DL103 has a different distance than the Shure cartridge. I cannot verify this at the moment, as my DL103 sits in an aluminium, aftermarket body.

So, again, for the given SME/EIA Standard (cartridge needle tip 52.5mm from the flange), what is the correct mounting distance (pivot to spindle) for the tonearm? This data is obsolete in every official SME publication. I am looking forward to your replies, as the above causes at least me hassles to get the cartridge tip into the correct position, even when using the original SME protractor. The protractor is not the problem, as it only gives us the required null points at the given distance from the spindle.

Cheers
Marco

Have a read of my original explanation again. It might make more sense now. You have seen for yourself that the cartridge mounting hole centre to tip distance is NOT standardised. Where does this "52.5mm" distance come from? SME don't publish this dimension in any of the 3009/3012 manuals. If you know that the flange tip distance is EXACTLY 52.5mm by design (and not from anecdotal evidence), then you could shim the flange for shorter cartridges to put the tip back to the same reference position as your Shure V15. However, you are stuck if the distance is greater!



SME do not need to tell you the effective length/overhang or offset since you do not actually need to know this as long as the arm has been made sufficiently accurately to achieve the specified inner null at 60.3mm

[Iron]

I believe this distance came from an SPU in a G-Headshell. Anyone to confirm that?

Greets from the lake of Zürich
Marco

[flood2]

I believe this distance came from an SPU in a G-Headshell. Anyone to confirm that?

Greets from the lake of Zürich
Marco

I thought I had already given you all the information and answers you needed and even included a pretty picture!
Do you still not understand what I wrote? Too many words perhaps...

Manufacturing tolerances mean that using a fixed headshell/flange distance will not give you consistent geometry.
"52.5mm" may have been what someone measured, but it isn't what Ortofon define for the 2M PnP or Concorde and I doubt was what the SPU was meant to be originally either.

Using a fixed distance assumes three things: the cantilever lies exactly on the centreline (which is almost never the case despite what you might assume), the arm base was perfectly adjusted to the correct position initially to make the fixed distance valid and finally that the arm bend and length are exactly the nominal value to make the 52mm the correct distance to shim your stylus/flange distance. None of those things are necessarily true and very unlikely to all be correct simultaneously.

There is at least a 3.5mm variation for mounting hole to tip distance for Ortofon (https://www.ortofon.com/support/support-hifi/cartridges-dimensions-chart). Realistically, you can't use shims to accomodate this range so sliding the base and adjusting the cartridge offset using the inner null of 60.3mm are the only ways to get consistent geometry for a given cartridge in an SME arm.

[Iron]

I believe this distance came from an SPU in a G-Headshell. Anyone to confirm that?

Greets from the lake of Zürich
Marco

Found the answer myself, by re-reading the thread: thank you @ be.audiophil!

BTW, what Pivot-to-Spindle distance do you guys have, when using an SPU, just to finish things off and have a reference?

Cheers
Marco

[flood2]

Found the answer myself, by re-reading the thread: thank you @ be.audiophil!

BTW, what Pivot-to-Spindle distance do you guys have, when using an SPU, just to finish things off and have a reference?

Cheers
Marco

That isn't what Ortofon themselves quote for the SPU. It is 52mm.
However, if you want to assume 52.5mm go right ahead!

What null points have you got on your SME template?

[Iron]

I use the old one point SME protractor for my SME 3012/II.

Further I have a new Feickert protractor, the Aura Protractor (Dennessen copy), an AAA full record strobe and protractor round thing, a simple Audio Magazine (Germany) cut out protractor, which actually is sufficient to check the null points, an all mirror AVID protractor for my Audiomods tonearm (where I do not have any problems), a later SME 2 point protractor, which I do not trust as I do not know to which tonearm it truly belongs, etc. I did never manage to get both null points as quoted, which is frustrating. Additionally, I have a feeling, that my cartridge (Denon DL103 with Aluminium body) is not ideally tracking the records. Therefore the geometry of the arm seems to be slightly wrong. I have read what has been written, and I believe to understand most (at least) of it, but still: mine is not perfect.

So all I want to know is: what distance should the tonearm be mounted (pivot to spindle) to have a standard set up which conforms with what the designers intended to be the ideal set up for this arm. I expected it to be the standard set up with an Ortofon SPU pickup mounted. Nevertheless, if it turns out to me a flange-to-needle distance of 52mm instead of 52,5mm, fine. I do not care. I just want to know, what mounting distance others are using, as I intended not to use the normal SME headshells but slotted ones to standardize this variable.

As nobody as given me the answer yet, to me this arm still remains somewhat of a mystery. All we got here was theory, but I asked for live/practice data. I might show a bit of an emotional overreaction here, but it's close to 40degr. Celcius here, so please excuse this, folks.

Cheers

Marco

[flood2]

As nobody as given me the answer yet, to me this arm still remains somewhat of a mystery. All we got here was theory, but I asked for live/practice data. I might show a bit of an emotional overreaction here, but it's close to 40degr. Celcius here, so please excuse this, folks.

Cheers

Marco

The mystery here is that you have a Feickert and several other similar tools haven't managed to work it out !? 

 
You can leave the arm where it is, use your Feickert with the Stevenson 1B option since the SME was designed to have a null at 60.3mm.

Now measure the flange/tip distance...... Duplicate that for the other cartridges you want to align. With a slotted headshell you can now correct for cantilever skew errors better and change the alignment nulls to whatever you need/want.

It is irrelevant to know what the effective length is - it is no use to rely on since manufacturing tolerances mean that it will vary from arm to arm very slightly and that is why they don't publish it.

Also, I don't know why you think using the default SME alignment is the "best to use". It isn't if you are playing LPs and given that you are using a slotted headshell, you can optimise for whatever you want as I have explained countless times now.

Do you understand it now?

[stratokaster83]

It seems I am another victim of this mystery.

My SME 3012 is mounted on a plinth which was specifically made for 12-inch SME tonearms. I am able to adjust the spindle to pivot distance from ~286mm to ~304mm.

If the cartridge is mounted at 52mm stylus to headshell collar, I can achieve proper alignment only with the tonearm all the way back on its sliding base. (Verified using a high quality copy of the original one-point protractor.)

Frankly, this is a bit 

[Tomcat1969]

This is why I use a slotted headshell with my SME arm.  (3009)

[flood2]

It seems I am another victim of this mystery.

My SME 3012 is mounted on a plinth which was specifically made for 12-inch SME tonearms. I am able to adjust the spindle to pivot distance from ~286mm to ~304mm.

If the cartridge is mounted at 52mm stylus to headshell collar, I can achieve proper alignment only with the tonearm all the way back on its sliding base. (Verified using a high quality copy of the original one-point protractor.)

Frankly, this is a bit 

Have you seen this link? https://www.vinylengine.com/turntable_forum/viewtopic.php?t=122105
The magnitude of the shift you are talking about is similar to what this person had observed and he found his "effective length" was some 6 to 7mm longer than expected for a reference Spindle/Pivot distance of 294mm

[stratokaster83]

Have you seen this link? https://www.vinylengine.com/turntable_forum/viewtopic.php?t=122105
The magnitude of the shift you are talking about is similar to what this person had observed and he found his "effective length" was some 6 to 7mm longer than expected for a reference Spindle/Pivot distance of 294mm

Thanks Anthony. Frankly, this is all a bit confusing...

[flood2]

Thanks Anthony. Frankly, this is all a bit confusing...

Hi Pavel
As the previous poster (Tomcat) suggested, perhaps a slot headshell would be the best option! I know that the "Sliding Base" method is favoured by some, but I always found it surprising that SME would publish an "effective length" specification when it is clearly inappropriate given the variations in cartridge mounting hole to stylus distance which results in a change in effective length and overhang set for any cartridge not matching the design value. Far simpler to specify the offset angle and linear offset and provide a guide for a nominal centre for the mounting.

What is the inner null for the reference SME one-point protractor you have? Does it match the 2.375"/60.3mm null that manual quotes? The only other possible explanation is that the arm linear offset parameter/offset is different to that for which the protractor is intended?

[stratokaster83]

Hi Pavel
As the previous poster (Tomcat) suggested, perhaps a slot headshell would be the best option! I know that the "Sliding Base" method is favoured by some, but I always found it surprising that SME would publish an "effective length" specification when it is clearly inappropriate given the variations in cartridge mounting hole to stylus distance which results in a change in effective length and overhang set for any cartridge not matching the design value. Far simpler to specify the offset angle and linear offset and provide a guide for a nominal centre for the mounting.

What is the inner null for the reference SME one-point protractor you have? Does it match the 2.375"/60.3mm null that manual quotes? The only other possible explanation is that the arm linear offset parameter/offset is different to that for which the protractor is intended?

Hi Anthony,

Aha! My protractor apparently is not a copy of the original SME protractor (even if it was sold as such) but something else entirely - the null point is at 66mm which suggests Baerwald alignment. Maybe I should ditch it and get the Tracking Wizard arc protractor — I have one for my Fidelity Research and it's a joy to use.