[Seb]

To me, lofgren A or B,
it makes no difference as long as you do thing precisely.

best regards

Seb

[toobluvr]

Oy!  My head is spinning!  Eyes are glassy!

     

The crux and objective of my original question is this.....

Since my mounting distance is 1mm short (according to mfrs spec), can I still use the mfr supplied protractor to properly set offset angle and overhang?  Or is the supplied protractor only valid when the mounting distance is precisely correct?

Arm is Kuzma Stogi Reference
Protractor is Kuzma supplied standard 2 null point system:  66 mm and 121 mm

I think I remember reading in the Kuzma owners manual that if the mount distance is off by a bit, it can be adjusted for by sliding the cartridge in the slotted headshells.  I also recall it saying that that if point B for overhang (121mm) can't be achieved, the pivot / spindle distance error is so great that the arm must be re-mounted. 

So within a certain range, Kuzma says it is OK to be slightly off on the mounting distance, so long as it can be adjusted for with the slotted headshell, and null points can be obtained properly using the protractor.  But I wanted to check with the experts here to see if this is merely a "good enough" solution that is maybe hindering performanc, and if it would be worth my effort and trouble to remount the arm.

Tell you the truth, my query is probably somewhat academic and a bit on the anal side.  I am able to dial in the 2 null points on the Kuzma protractor very precisely, despite my error in mounting distance.  And the performance is very good.  But with this stuff, you always wonder if you truly are "locked in" and getting all that the setup has to offer.       

[Wayner]

To show the "dark side" of what I'm talking about, I took a slightly gross look at arms. I used this as an example, but it gets my point across that you can be "homed in" on the null points, but the results are less then wonderful.

I used the Loefgren B null points of 70.285 and 116.604

Arm Length: 199.520
Overhang: 21.720
Offset angle: 27.927 degrees

Here is the result:


The distortion at the beginning, between null points and end are very bad. But I'm sitting right at the null points.

Perhaps this is an extreme example, but it shows as Doug s. was also getting to that as the arm gets shorter, the problems get worse and worse even if we try our best to fix the problem. All the more reason to smile at John, Thechairguy's comment on longer arm = less distorion and that = to happy listener.

Now, lets please not beat this into a  but I will give you guys a thumbs up on the fact that Leofgren's B curve is the one to go after. But remember that every possible overhang, offset angle and pivot to stylus distance (and they are infinite) all create their own individual distortion curve, of which most of the time should be acceptable.

Editorial: I think most of us realize what is going on here and I am still amazed that very few table manufacturer's don't take advantage of this mathematicageometrical technology. I am also further frustrated by the fact that out of my 6 turntable, 5 have all together different settings (only because 2 of them are Technics with the same specifications.

So I ask  Music Hall, Project, VPI, Thorens, or anybody else with a fixed arm on their table....what up?

Wayner

[Seb]

To show the "dark side" of what I'm talking about, I took a slightly gross look at arms. I used this as an example, but it gets my point across that you can be "homed in" on the null points, but the results are less then wonderful.

I used the Loefgren B null points of 70.285 and 116.604

Arm Length: 199.520
Overhang: 21.720
Offset angle: 27.927 degrees

Here is the result:


The distortion at the beginning, between null points and end are very bad. But I'm sitting right at the null points.

Wayner, this is not the blue curve you should look at. Only the red curve should be considered, since a given tracking error is not producing the same amount of distortion, whatever the radius your on.

see this first graph:



the same tracking error is considered all over the record length (which is impossible) - the tracking distortion is not the same all over the record length. the closer you are from the record spindle, the worse it is.

now, the reverse : I'm supposing a identical amount of distortion across the record length - this is only possible if the tracking error is decreasing.



best regards

Seb

[Seb]

Since my mounting distance is 1mm short (according to mfrs spec), can I still use the mfr supplied protractor to properly set offset angle and overhang?  Or is the supplied protractor only valid when the mounting distance is precisely correct?

Arm is Kuzma Stogi Reference
Protractor is Kuzma supplied standard 2 null point system:  66 mm and 121 mm

A two grids protractor is a UNIVERSAL protractor : you can use it WHATEVER the mounting distance.

best regards

Seb

[toobluvr]

Since my mounting distance is 1mm short (according to mfrs spec), can I still use the mfr supplied protractor to properly set offset angle and overhang?  Or is the supplied protractor only valid when the mounting distance is precisely correct?

Arm is Kuzma Stogi Reference
Protractor is Kuzma supplied standard 2 null point system:  66 mm and 121 mm

A two grids protractor is a UNIVERSAL protractor : you can use it WHATEVER the mounting distance.

best regards

Seb

That's what I thought....but I'm dumb and needed confirmation.

 

Thanks!

[doug s.]

To show the "dark side" of what I'm talking about, I took a slightly gross look at arms. I used this as an example, but it gets my point across that you can be "homed in" on the null points, but the results are less then wonderful.

I used the Loefgren B null points of 70.285 and 116.604

Arm Length: 199.520
Overhang: 21.720
Offset angle: 27.927 degrees

Here is the result:


The distortion at the beginning, between null points and end are very bad. But I'm sitting right at the null points.

Wayner, this is not the blue curve you should look at. Only the red curve should be considered, since a given tracking error is not producing the same amount of distortion, whatever the radius your on.

see this first graph:



the same tracking error is considered all over the record length (which is impossible) - the tracking distortion is not the same all over the record length. the closer you are from the record spindle, the worse it is.

now, the reverse : I'm supposing a identical amount of distortion across the record length - this is only possible if the tracking error is decreasing.



best regards

Seb

this above info explains why some like to optimize the null at the innermost groove, as tracking error equates to smaller distortion the further away from the center of the record you get.  this is what william firebaugh is getting at, w/his set-up ideas, (tho i think his math is off, at his website, as i prewiously noted).

doug s.

[vinylengine]

The distortion at the beginning, between null points and end are very bad. But I'm sitting right at the null points.

Arms as short as 200mm mounting distance can sound bad, although it isn't as bad as it looks as the distortion graph is fairly benign until the very inner grooves and most records don't play that close to the label anyway.

I think most of us realize what is going on here and I am still amazed that very few table manufacturer's don't take advantage of this mathematicageometrical technology.

Around the time of the 'rediscovery' of Baerwald's work SME changed it's geometry from one similar to Stevenson to something closer to Baerwald. Companies like Linn, Kuzma, Manticore and Wheaton have reasonable geometry too.

I think part of the problem is that Japanese arms appear to favour an alignment that favours the DIN inner groove radius? They also seem to like recommending 15mm as the overhang regardless of the dimensions of the rest of the arm. Keep it simple

Rega used the geometry from their old Acos built arm when they designed the RB series and showed their complete lack of interest in alignment by bundling it with the worst protractor on the planet. Luckily they built the arm longer than it's closest competitors so it still sounds good.

Finally you have protractors from the likes of Enjoy the Music and the Guru that have null points chosen by ear. Takes all sorts.

There is also the question of whether you should calculate the null points from inner and outer groove radii more representative of the average record? For example, if you measured all of your collection and found that none started before 145mm or ended after 63mm then the Loefgren B null points would be 72.9 and 117.6mm.

Fun, fun, fun 

Regards,
JaS

[Wayner]

I now understand that null points are ratios between pivot to spindle, overhang and offset data. The 3 elements form a "triangle" if you will to go from one null point set to another (like from Baerwald to Loefgren) the ratios are different between the 2, shifting the null points and distance from null points between the 2 (or 3 if you want to include Stevenson). Geometrically they still end up in the 90 degree position at only 2 positions (demonstrated by vinylengine and my CAD drawings.

This certainly has been a very intense discussion. Perhaps the most "scientific" and "mathematical" ever here at the Audiocircles.

Thanks to everyone who contributed and for keeped their "cool" during some of our more heated discussions. I think everyone learned something.

I think we are all at some mutally agreeable base on our positions and perhaps it's time we turned our attention to others here at the Audiocircles that may need help or have questions regarding the topic.

Wayner

[BobM]

MY HEAD HURTZ

[doug s.]

bob, listen to the accordian for a while, your head will feel better...   

doug s.

[Wayner]

My head hurts too. Vinylengine and Seb are great additions to the Audiocircles and I'm sure other topics will bloom into who knows what.

Someone upstream mentioned that they have trouble going back and forth between the 2 null points, setting the offset angle. If this is the case, then you have something wrong. Your cartridge should dial in perfectly at both null points, so go backwards and try to verify other distances like overhang or pivot to spindle.

I've got lots of new vinyl to listen to so..........time to go.

Wayner

[vinylengine]

Thanks to everyone who contributed and for keeped their "cool" during some of our more heated discussions. I think everyone learned something.

Absolutely, thanks for a fascinating discussion.

Can I also say that I just noticed the alignment tool you showed in the thread while I was away and it looks very interesting.

It's easy to recalculate Loefgren A or B null points for alternative, possibly more optimal, maximum inner and outer groove radii, so a protractor that would allow you to play with different null points and confirm the calculated overhang and offset angle would be a useful tool to own

Regards,
JaS

[Wayner]

Thanks vinylengine,

I think our new cartridge alignment tool offers complete freedom to explore any null point settings a user may want to use. It's the only one of it's kind, I believe that offers this capability.

Have a good day.

Wayner