Aligning an SME V-12

[ShawnZH]

SME stopped to sell their arms independantly from their tables recently and I had the chance to acquire an unboxed SME V-12 after the announcemnt. I was quite happy since I always wanted to have one in my system.

The SME V-12 has a lot of good traits to make it a classical arm. It has a bit un-conventional way to adjust its HTA by moving the whole arm base back and forth to align itself to the supplied template. It basically is different from the way to align an arm nowadays. Since the screw holes are fixed (not slotted), the effectively length basically depends on the cart design, the length of the contilver and also the position of the contilever. It is not 308.8mm depending on the specification of the cart. When moving the base, the P2S makes not sense too since it keeps changing.

I usually use the supplied template, which provides an easy, even dummy way to decide the HTA. When I tried to use the Wally Tractor and the Dr. Feickert tractor to align the V-12 with my Lyra Atlas, I found it almost impossible to align to the 2 Baerwald null points, neither the Loefgren null points. I can make it reasonably well aligned to the null points by moving the base outward, thus changing also the P2S, but the sound becames supressed and distorted somehow.

I'd like to get people's opinion of how you align your V-12 on different carts? Any tips and ideas are welcome.

 

[mtemur]

I don’t want to bore you with details but I think it’s best to use supplied Baerwald protractor. alternatively you can draw your own arc protractor using autocad or a dedicated freeware which you can find on the web.
if you can precisely measure your cartridge’s mounting holes to stylus distance you can calculate new effective length. the biggest problem with drawing your own arc protractor is precise printing. I maybe tried 40 times to reach perfectly measured arc protractor (0.05mm error in dimensions)
I used both protractors several times for my sme v and sme v-12 and I think arc protractor is the best option.

if you send me your cartridge’s mounting holes to stylus distance at recommended vtf I can draw and send the arc protractor to you.

 

[mtemur]

f you send me your cartridge’s mounting holes to stylus distance at recommended vtf

normally it’s 9.52mm

 

[PeterA]

Congratulations on your new tonearm. Are used a MINT protractor and it worked very well and is extremely accurate. It has to be custom ordered for the cartridge and the tonearm but he has the SME tonearms on file. You just have to make contact with him via email and then send him the cartridge mounting screw to stylus tip dimension. That has to be accurate. This is an ark type of protractor with two null points. And it is very easy to align the cantilever at the null point.

 

[ShawnZH]

normally it’s 9.52mm

Thanks Mtemur for your advices. I don't have a perfect way to measure the screw holes to stylus distance. Knowing it is a Lyra, according to J. Carr's post on Vinyl Engine, he usually make it 9.52mm as you said. While I was exchanging this with Mr. Boisclair from Wally, he told me that his measurent of an Atlas is 10mm.

 

[mtemur]

Knowing it is a Lyra, according to J. Carr's post on Vinyl Engine, he usually make it 9.52mm as you said.

that’s exactly what I know but it’s better to measure it.
a basic way to measure it mounting on the arm and landing on a ruler with correct vtf and taking a high resolution picture. it’s better to used sme protractor’s ruler lines. in that case cantilever should be 90 degrees to the lines and stylus should land right on the line. after that you can easily measure the distance on a big picture on a computer.

 

[mtemur]

Congratulations on your new tonearm. Are used a MINT protractor and it worked very well and is extremely accurate. It has to be custom ordered for the cartridge and the tonearm but he has the SME tonearms on file. You just have to make contact with him via email and then send him the cartridge mounting screw to stylus tip dimension. That has to be accurate. This is an ark type of protractor with two null points. And it is very easy to align the cantilever at the null point.

you can do it yourself for free.

 

[mtemur]

cartridges I measured:
Kondo: 9.5mm
ZYX: 8.5mm
EMT: 9.5-9.7mm

 

[PeterA]

you can do it yourself for free.

Yes you can. But you have to make some other things into account putting the ark in the right relationship to the spindle is important. The thickness of the glass and which the protractor sits is important. I like the reflective glass and mirror for light. My MINT cost $110 and it took two weeks to get. Some people might consider that too expensive and too much of a hassle but I appreciated the item and I used it with confidence for excellent results.

Certainly there are alternatives, but I was simply responding to the OP and offering my advice.

 

[ShawnZH]

I used the SME V-12 supplied template to align a few carts including London Decca Referene and Lyra Atlas. Actually the sound of the alignment is quite good for both cart, better with London Decca somehow. But if I use my 2 protractors (Wally and Feickert) to measure the alignment on the 2 null points, neither can provide a good alignment with the lines at the null points. I used the Baerwald curve which is supposed to be the one used by SME. SME indicated the 2 null points are at 66.04mm and 120.9mm. This is the Baerwald or Loefgren A.

I understand that the different mounting-hole to stylus distance could change the effective length, not anymore 308.8mm. While moving the arm base of the V-12, the P2S keeps changing, not the 295.6mm as stated in the manual of the arm. This is the SME V-12 geometry design. However I am surprised to see the differene between the SME alignment and the more conventional null points alignment. It looks the null points are not 66.04mm and 120.9mm as announced by SME.

 

[mtemur]

It looks the null points are not 66.04mm and 120.9mm as announced by SME.

indeed it is. baerwald, lofgren or stevenson alignments based on constant null points, overhang and offset are calculated according to effective length.
sme v-12 protractor is made for 308.8mm effective length, 13.2mm overhang and 17.62 degrees offset angle. their point is keeping overhang and offset constant for all the variations on effective length due to cartridge differences. that theory may not sound right but changes on stylus to fixing holes center of a cartridge doesn't change effective length much let alone overhang.
for example shortest cartridge in terms of stylus to fixing holes center that I ever come across is zyx. it measures 8.5mm. which is 1.02mm short. lets do the math:
new effective length: 308.8 - (cos 17.62 x 1.02) = 307.828mm
new overhang: 13.25mm
new offset: 17.67 (all the calculations are based on IEC radiuses which sme uses too)
as you can see overhang and offset are almost the same even in this extreme example. so I suggest if you want absolute precision print an arc protractor for specific cartridge or use simply sme protractor.
on the contrary feickert and smartractor are not precision protractors. I know they are advertised that way but that's another story. for non sliding base tonearms the best and the most precise protractor is wally tractor. I recommend it for non sliding base tonearms by using closest effective length cause effective length is not constant as indicated in the manuals. for sliding base tonearms it is better to use arm-cartridge specific arc protractor.

 

[ShawnZH]

indeed it is. baerwald, lofgren or stevenson alignments based on constant null points, overhang and offset are calculated according to effective length.
sme v-12 protractor is made for 308.8mm effective length, 13.2mm overhang and 17.62 degrees offset angle. their point is keeping overhang and offset constant for all the variations on effective length due to cartridge differences. that theory may not sound right but changes on stylus to fixing holes center of a cartridge doesn't change effective length much let alone overhang.
for example shortest cartridge in terms of stylus to fixing holes center that I ever come across is zyx. it measures 8.5mm. which is 1.02mm short. lets do the math:
new effective length: 308.8 - (cos 17.62 x 1.02) = 307.828mm
new overhang: 13.25mm
new offset: 17.67 (all the calculations are based on IEC radiuses which sme uses too)
as you can see overhang and offset are almost the same even in this extreme example. so I suggest if you want absolute precision print an arc protractor for specific cartridge or use simply sme protractor.
on the contrary feickert and smartractor are not precision protractors. I know they are advertised that way but that's another story. for non sliding base tonearms the best and the most precise protractor is wally tractor. I recommend it for non sliding base tonearms by using closest effective length cause effective length is not constant as indicated in the manuals. for sliding base tonearms it is better to use arm-cartridge specific arc protractor.

Thanks a lot Mtemur, you explained very well la rationalité. I tried at least 4 types of protractors, none aligned perfectly with the V-12 arm. The sliding base arms indeed goes best with the customized protractor. Interestingly, I can align the null points by changing quite significantly the P2S distance however the sound was very much distorted. I assume the best for me is to stick to the SME tractor supplied.

 

[mtemur]

Interestingly, I can align the null points by changing quite significantly the P2S distance however the sound was very much distorted.

it's because of improper zenith alignment. I couldn't get rid of distortion no matter what geometry I use until I get Analogmagik. zenith has a big impact on distortion and there is no tool to align it other than computer software. to align cantilever parallel to center line on the protractor may not correctly align zenith.

the problem with sme protractor is centering. when you put the centering plastic on spindle make sure there is no gap. you can use adhesive tape around spindle but make sure it doesn't overlap.
after that do the same thing to centering plastic when putting paper protractor on it. finally check with a magnifier if the stylus lands on dead center of cross. you can use iphone's magnifier with flash on.