Harry has a 14"er ;)

Re: Harry has a 14"er ;)

Postby Johnny » Mon Nov 27, 2017 10:13 am

Gary1955 wrote:Hi Harry, Good to hear from you!

The 14" Longboy looks very interesting. I couldn't tell from the picture if this is a gimbal or unipivot. What sound differences/improvements do you hear versus the 12" 3D Reference?


Looks to be a gimbal.
Johnny
Senior Member
 
Posts: 471
Joined: Mon Sep 29, 2014 7:26 am

Re: Harry has a 14"er ;)

Postby Harry » Mon Nov 27, 2017 12:50 pm

Haven't decided on a gimbal, a yoke, or the unipivot with stabilizer. the yoke lets you change armtubes, the gimbal is very low friction and very stable, and the uni is a uni, it does everything right.

The straight tube with no skating force sounds less mechanical than any arm we have heard with an offset angle. This is most likely due to the fact that the coils have no force moving out of the center of magnetic focus as you will have with any offset headshell. Since there is no skating force the cantilever and coils remain centered without any effort. Yet, we remove all the issues of linear tracking arms and get really clean low bass.

HW
Harry
Admin
 
Posts: 1220
Joined: Mon Aug 25, 2014 10:38 pm

Re: Harry has a 14"er ;)

Postby Letsmakeadeal » Mon Nov 27, 2017 4:36 pm

Sign me up :D
User avatar
Letsmakeadeal
Senior Member
 
Posts: 529
Joined: Fri Aug 29, 2014 3:42 pm
Location: Texas

Re: Harry has a 14"er ;)

Postby Ducky » Wed Dec 13, 2017 5:42 pm

Harry-

This arm looks very interesting, I curious about how it will sound.

I was wondering if you could expand a little on your rationale for going with a straight tone arm, especially at this length? I understand that you wanted to eliminate skating force, but not sure if you can accomplish that given the current set of parameters.

There are a number of on-line calculators for tone-arm geometry (and the formulas are readily available as well). Plugging in 355.6mm for effective length, 370.5mm S2P distance and assuming 63mm for inner radius and 146mm for outer radius, there will be only one null point where there is zero tracking error (104mm center radius) and therefore no skating force and minimum distortion. However, at the inner radius, the tracking error will be -8.8 deg which will create about half of the skating force that a properly offset arm would have, but the distortion will be about 8% or 10x more than the worse case with an offset arm of the same length. :shock:

At the beginning of the record, the tracking error will be +5.7 deg which will cause the stylus to skate away from the spindle and distortion will be more than 4%.

Plugging in the optimum numbers for a 14" arm (17 deg offset angle and 14.1mm overhang), the worst case tracking error is 1.36% and the worst case distortion is 0.8%, with minimum distortion at the beginning and end of the record.

Soooo....what am I missing here?
Ducky
Member
 
Posts: 89
Joined: Tue Jan 12, 2016 6:15 pm

Re: Harry has a 14"er ;)

Postby jonathanb » Wed Dec 13, 2017 5:51 pm

Ducky wrote:Soooo....what am I missing here?

This tonearm does not have an offset headshell. Its primary advantage therefore is that it is subject to zero skating force.
User avatar
jonathanb
Senior Member
 
Posts: 372
Joined: Mon Mar 21, 2016 2:07 pm

Re: Harry has a 14"er ;)

Postby Ducky » Wed Dec 13, 2017 7:33 pm

jonathanb wrote:
Ducky wrote:Soooo....what am I missing here?

This tonearm does not have an offset headshell. Its primary advantage therefore is that it is subject to zero skating force.



Thanks jonathanb, I think I understand that part, but your statement is only true at one point in the playback path.

Skating force is caused by friction working on the stylus at an angle other than perpendicular with the tangent. If the stylus has a tracking angle error, it will also create skating force. With a straight tone arm (no offset angle), the tracking error will be almost 9 deg at the inner track, and exhibit a significant amount of skating force (more than half what it would be with a correct offset angle of 17 deg), not to mention, a lot more distortion 8% vs 0.8% worse case).

At the beginning of the record, the skating force will actually be in the direction towards the outer edge, and again, the distortion will be much higher than a correctly offset headshell.

I was hoping Harry or someone more knowledgeable than myself, could help clarify why this is a good idea?
Ducky
Member
 
Posts: 89
Joined: Tue Jan 12, 2016 6:15 pm

Re: Harry has a 14"er ;)

Postby Brf » Wed Dec 13, 2017 9:25 pm

Ducky wrote:
Skating force is caused by friction working on the stylus at an angle other than perpendicular with the tangent. If the stylus has a tracking angle error, it will also create skating force.


This is a common misconception. Although tracking error will result in more friction, it cannot increase skating force in a tonearm with no head shell offset as the pulling force caused by the friction is in-line with the pivot, therefore, no rotational torque. Side wall tonearm "push" or "pull" due to tracking error is another misnomer.

Tonearm design is all about compromise i.e. the lesser of 2 evils. One of the main challenges with 14"+ tonearms is rigidity, damping and usable effective mass. I assume Harry believes that VPI 3D printing technology solves most of those aforementioned issues, while mitigating a few other at the expense of introducing a few new issues.
User avatar
Brf
Site Admin
 
Posts: 3516
Joined: Tue Aug 26, 2014 9:23 am

Re: Harry has a 14"er ;)

Postby Ducky » Thu Dec 14, 2017 10:26 am

Thanks Brf. I'm still trying to get my head around this, so I drew some simple vector diagrams.

This is what occurs at the single null point where there is zero tracking error:

Skating Force.jpg
Skating Force.jpg (37.29 KiB) Viewed 2308 times




But when the stylus is at the inner radius, it is no longer perpendicular to the tangent and the friction force will not be directly in line with the stylus (and by extension, the tonearm and pivot), so the friction force is split between 2 vectors: stylus force and skating force:


Skating Force1.jpg
Skating Force1.jpg (48.81 KiB) Viewed 2308 times


Is there something wrong with my method?
Ducky
Member
 
Posts: 89
Joined: Tue Jan 12, 2016 6:15 pm

Re: Harry has a 14"er ;)

Postby Brf » Sat Dec 16, 2017 1:19 pm

Ducky, a skating force is a rotational torque around a fixed axis, what you are describing is what causes groove distortion when a stylus is not tangent to the groove.
User avatar
Brf
Site Admin
 
Posts: 3516
Joined: Tue Aug 26, 2014 9:23 am

Re: Harry has a 14"er ;)

Postby Ducky » Sat Dec 16, 2017 2:43 pm

I understand that "normal" skating force is in-line with the cantilever, and the rotation comes from head shell offset causing the drag of the stylus not to be in-line with the tone arm and pivot, but isn't the effect of tracking error and "normal" skating force essentially the same? That is, they both create a vector that would cause the tone arm to attempt to rotate (in my above example, away from the spindle) and create unequal force along the groove walls?

If the inner radius was 14.9mm, the tonearm would be at a right angle to the friction vector as the record passes under the stylus from right to left (90 deg tracking error). Would this not cause the tonearm to attempt to rotate counter-clockwise?

I'm not doubting what you are saying, just having trouble understanding why the 2 scenarios do not create the same affect.
Ducky
Member
 
Posts: 89
Joined: Tue Jan 12, 2016 6:15 pm

PreviousNext

Return to Harry's Corner

Who is online

Users browsing this forum: No registered users and 2 guests

x