• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Pivot to spinle distance and overhang....

Fishead

Fishead

Gone fishin' Steada just wishin'
Subscriber
Pivot to spindle distance and overhang....

I'm wondering about some things and not quite sure I have a good understanding about the relationship between manufacturer recommended pivot to spindle distance and cartridge overhang.....when using the right protractor for your table, why are either of those factors even necessary considerations, or are they?

When setting the null points, one uses the screws in the cartridge/headshell to either push the cart forward or back in order that the stylus is centered on the null points. The only reason I can imagine the pivot to spindle distance might come into play would be if this adjustment can't be made and the tonearm base needs to be moved either inward or outward to accommodate putting the cartridge in the proper position so that it might be adjusted and fall within the positions of the null points.

So, could it be that the reason for the manufacturer even giving the pivot to spindle and overhang measurements is to make setup possible without a protractor? That seems to me the only plausible explanation but I hope others here can chime in and further illuminate the subject for me. Once you have the stylus hitting the null points dead-on, what importance are overhang and pivot to spindle distances?

Thanks!
 
Last edited:
Register to hide this ad
The P2S distance isn't usually adjustable, except on SME arms. It's the fundamental number that determines where the cartridge will need to go to meet the various alignment methods, Baerwald, etc. If you're making a template, it's very important. If somebody hands you a template, especially a standard 2-point, it's of no concern at all. IMO, overhang isn't a number anyone ever needs to know, and it may complicate things because it can be wrong or for an alignment your'e not using. It's more useful with an arm that can go over center. If you want to really understand this stuff, there's an excellent paper here that compares the various alignment strategies, though it may be TMI for most people.
 
All things considered, It all is important...

Overhang, pivot to spindle, protractor alignment and other issues are ALL important.
I like to tell folks,"NO CHEATING". It all has to align to work.
Each part of the mentioned factors are each just one part of the equation. If any part doesn't work out correctly, the whole setup is not correct.
If the manufacturer supplies an overhang gage, good, but again just one part of the setup. The other factors must be checked and rechecked to get good sound.
I have been a fool way too long trying to get good sound. And I have had some good stuff. AR original TT, Garard Type A, Empire 568III. I would still have them If I had enough intelligence to figure out correct setup. I always blamed the TT, not the person setting it up(me).

Paul
 
There is a specific overhang for each tonearm defined by the bearing to stylus length as defined in the tonearm specs. This presumes that the spindle to bearing distance was measured correctly and that the arm is mounted in the right place. There is also an optimum offset angle.

What all this means is that, if you really want to dial things in, you need to make sure that ALL of these parameters are correct. It also means that you must measure each parameter separately BEFORE you use whichever alignment gauge (Baerwald, etc.) you have chosen.

It is likely that you will end up twisting the cartridge in the headshell to get the offset angle correct after you correctly measure the overhang for the specific tonearm you are using.

Or, after having gone to these very real pain in the a** measures for a lot of years, just use the gauge of your choice and enjoy listening. :music:

YMMV.....
 
Points well-taken.....however, what prompted this post was a recent experience wherein I had just received my Sumiko Blackbird from Soundsmith.

Upon installing in the headshell, I found that the stylus fell far short of the Polaris protractor null points and could not be adjusted far enough forward in the headshell. At that point, I removed the platter from my Nottingham Spacedeck, loosened the allen screw that holds the tonearm base in place, and moved the base inwards towards the spindle from the 210mm manufacturer specification to 204mm, center of pivot to center of spindle. This then allows the cartridge to be moved forward enough to be able to hit the null points. Not sure I could have done it any other way, so that prompted this post and the question posed. Still not sure I understand it correctly, but don't really see how setting the spindle/pivot and then overhang could work in my case because it would not allow me to even get close to the null points on the protractor.....hmmmm.....more information is needed. Thanks.
 
I built a plinth with a 5" aluminum disc in the arm-board, at the arm position (wide of it, but within the p2s arc on a compass). The arm (12" Jelco) is mounted to the disc, and off-center on the disc, to allow rotation, to adjust for varying cart mount requirements. I did this a few years ago, and it has worked out really well.
 
Last edited:
The problem is that not all tonearms are designed correctly and, if you follow their standard set-up instructions, you will not minimize tracking error.

Here is a link to an article by Kessler and Pisha explaining the math and process far better than I can:

http://www.melbourneaudioclub.org.au/pdf/tonearm.pdf

There is an old issue of the Audio Critic that elaborates on the above article. I have not been able to find it online yet but it is worth looking for.
 
Thanks for the link. I'll have a read and report back. Something's not adding up and I'm hoping to get to the bottom of it, as it were, to better understand the technology and hopefully improve my knowledge on the subject. It is, after all, mostly a matter of geometry and that shouldn't be an impossible task. Thanks all for your kind comments, I surely appreciate it.
 
You are most welcome. I may still have a hard copy of the old Audio Critic article. IF ( and that is a very big 'if') I can find it, I'll scan and upload it.

I do remember that several widely used tonearms had incorrect offset angles which required twisting the cartridge in the headshell to dial things in.
 
Fishead said:
Thanks for the link. I'll have a read and report back. Something's not adding up and I'm hoping to get to the bottom of it, as it were, to better understand the technology and hopefully improve my knowledge on the subject. It is, after all, mostly a matter of geometry and that shouldn't be an impossible task. Thanks all for your kind comments, I surely appreciate it.
Click to expand...

I would read the link that ConradH provided. It´s very good.
 
TubeHiFiNut said:
You are most welcome. I may still have a hard copy of the old Audio Critic article. IF ( and that is a very big 'if') I can find it, I'll scan and upload it.

I do remember that several widely used tonearms had incorrect offset angles which required twisting the cartridge in the headshell to dial things in.
Click to expand...

Thanks, that would be great.

Yes, getting the zenith right (twisting the cartridge in the headshell) is readily understandable. It is fairly easy to do this with a good protractor and some magnification in terms of getting close. For a precise setting of both zenith and azimuth along with the VTA, however, I would think something along the lines of a microscope to allow for the measurement of the stylus angle as it interacts with the groove would be ideal rather than alignment of the cantilever, which is what I'm doing for the most part.

I can't see the stylus well enough to be certain it, rather than the cantilever, is perfectly aligned on the protractor grid, and proceed with the assumption that manufacturers get this very close to right, so it should follow that if cantilever is aligned, so should be stylus. The thing is, as many here have talked about, getting it close in this manner and then adjusting by ear is about as good as it gets without the aforementioned microscope. Even then, I would think the ear comes into play.

Drifting a bit from the original question, however, and this comment seems to hit the mark quite well:

If you use a protractor ignore the published overhang spec and vice versa..
Click to expand...

Seems reasonable, provided one has the correct protractor. I have a lot of reading to do (gusten, good advice) given the excellent links provided. I've just been trying to wrap my brain around the whole concept and found myself stumped when I could not get my stylus even close to the null points on the protractor and had to change (shorten) the pivot to spindle distance in order to do so. This then conflicted with the specs Nottingham put forth and I could see no way physically possible to maintain those specs and get the stylus on the null points.....

Thanks again to all....anyone ever wonder, as I do, how we ever listened to records back in the day when all this stuff for most of us never really hit the radar??? Buy a turntable, hook it up and play using the pre-installed cartridge. Boy, how did we ever survive???:scratch2:

I suppose the good news is that if you want to get the best your system is capable of, dialing things in like this will take you closer to that goal! However, considering all the variables, close is really all I expect to get as even the thickness of a record can change everything so I suppose that's just a part of the deal.....albeit a very gratifying deal for the most part!:yes:
 
Last edited:
Overhang determines the radius of the arc the stylus sweeps across the vinyl.
Because it's an arc instead of a line (linear tracking), the angle of the stylus changes across the vinyl in respect to the grooves.
The optimum overhang is about 15mm because that puts your overall distortion minimal with the stylus parallel to the grooves most of the time.
However, some people likes to have less distortion towards the inner groove so they tend to run different overhang and angle.
 
Last edited:
Way back, I think everybody just mounted the cartridge and lived with it, or used whatever plastic mounting aid the turntable maker supplied. I remember getting a Geodisc and that was the bee's knees.

Once the turntable maker drills a hole and plants the arm, the alignments are fixed. Unless you can change the distance, that's that. The math determines where the stylus has to go to achieve a particular strategy. Overhang is a red herring. It's determined by the math and incorporated in whatever template you use, but knowing the number is of no use unless you want to work with one of the alignment spreadsheets. What many people don't appreciate is that the null points are not fixed numbers. The null points come about based on the inner and outer groove radius. IOW, the null points will be different if you optimize Baerwald for a 12" LP vs. a 45. You can cheat a bit by measuring the inner groove radius of the types of records you play. Few records are recorded all the way to the DIN specified minimum. Stevenson places the inner null point at the innermost groove, but 90% of the records you play may never get there.
 
Last edited:
ConradH said:
Way back, I think everybody just mounted the cartridge and lived with it, or used whatever plastic mounting aid the turntable maker supplied. I remember getting a Geodisc and that was the bee's knees.

Once the turntable maker drills a hole and plants the arm, the alignments are fixed. Unless you can change the distance, that's that. The math determines where the stylus has to go to achieve a particular strategy. Overhang is a red herring. It's determined by the math and incorporated in whatever template you use, but knowing the number is of no use unless you want to work with one of the alignment spreadsheets. What many people don't appreciate is that the null points are not fixed numbers. The null points come about based on the inner and outer groove radius. IOW, the null points will be different if you optimize Baerwald for a 12" LP vs. a 45. You can cheat a bit by measuring the inner groove radius of the types of records you play. Few records are recorded all the way to the DIN specified minimum. Stevenson places the inner null point at the innermost groove, but 90% of the records you play may never get there.
Click to expand...

You can tweak things a bit by manually measuring the pivot to stylus length specified for that particular tonearm and then twisting the cartridge in the headshell to align it to the particular protractor you are using BUT.....

As I stated in my earlier post, it is entirely valid and OK to just use the protractor and it is certainly easier on the eyes. ;)
 
You must log in or register to reply here.
Back
Top Bottom