Hi, Bill yes you are correct, I modified an existing SME Series V tone arm by simply removing the existing counterweight, leaving the existing short stub sticking out the rear and attached a new permanent Alnico magnet weighing circa 3 or 4 grams (leaving circa 10 grams mass sticking out from the rear of the arm wand up/ down pivot as residual counterweight).
But you miss the point.
In 2009 GB patent 2459273A was granted to Eric Vant on another tone arm specifically engineered to have minimum possible counterweight, removing in practice all spurious mass from the rear of the arm wand up/ down pivot. This has not been done elsewhere.
Note in order to achieve this, Vant's (pseudo) magnetic levitation assembly is mounted at 90 degrees facing upwards, directly above the gimbal bearing pivot planes. The patent claims this is done to minimise changes in the direction of gravity on the tone arm's geometry / mass whilst it tracks inevitable record warps, thereby minimising oscillations in its moment of inertia. Vant claims this is an improvement on Eckhart's (1978 patent) spring / magnet, and indeed on all counterweighted tone arms.
Vant claims “Superior audio reproduction is possible due to the improvements in stylus trace accuracy and a more constant tracking force”. It employs (pseudo) magnetic levitation, and like all such tone arms, upwards arm movement whilst riding a warp increases the gap between magnets, thereby they “dynamically increase the effective mass (weight) of the tone arm cartridge” to better track warps.
The aim of my starting this thread is to share insights into why and how (pseudo) mag lev tone arms - even crude modifications such as mine on an SME V with only circa 95% of counterweight mass removed - out perform all other geometries offering the best possible sound quality and warp riding from analogue vinyl disc replay.
Voyd Reference Io Ltd. no counterweight SME V - Google Drive
But you miss the point.
In 2009 GB patent 2459273A was granted to Eric Vant on another tone arm specifically engineered to have minimum possible counterweight, removing in practice all spurious mass from the rear of the arm wand up/ down pivot. This has not been done elsewhere.
Note in order to achieve this, Vant's (pseudo) magnetic levitation assembly is mounted at 90 degrees facing upwards, directly above the gimbal bearing pivot planes. The patent claims this is done to minimise changes in the direction of gravity on the tone arm's geometry / mass whilst it tracks inevitable record warps, thereby minimising oscillations in its moment of inertia. Vant claims this is an improvement on Eckhart's (1978 patent) spring / magnet, and indeed on all counterweighted tone arms.
Vant claims “Superior audio reproduction is possible due to the improvements in stylus trace accuracy and a more constant tracking force”. It employs (pseudo) magnetic levitation, and like all such tone arms, upwards arm movement whilst riding a warp increases the gap between magnets, thereby they “dynamically increase the effective mass (weight) of the tone arm cartridge” to better track warps.
The aim of my starting this thread is to share insights into why and how (pseudo) mag lev tone arms - even crude modifications such as mine on an SME V with only circa 95% of counterweight mass removed - out perform all other geometries offering the best possible sound quality and warp riding from analogue vinyl disc replay.
Voyd Reference Io Ltd. no counterweight SME V - Google Drive
This link has descriptions and photos of the Sony turntable you refer to:-
Sony PS-X800 on thevintageknob.org
The PS-X800 series (parallel & pivot racking versions) claims to solve alleged tracking / anti-skate, problems and unspecified “resonance” problems presumably as manifest in cartridge suspension / counterweigh interactions. Nonetheless it still employs a large mass acting as a counterweight.
Users press a button to position the arm, thereby several electric motors and sophisticated sensors are activated.
The photos show a very complicated mechanical mechanism underneath made from non precision metal stampings, with steel pins held in punched holes with nylon wheels and gears. Such a complex, expensive, and prone to failure & user 'mistakes' mechanism is also going to be riddled with spurious operational vibrations. Additional vibrations will come from the two or three motors, mounted on this same mechanism, and to which the cartridge is also attached, which presumably Sony designed to pick up the smallest possible mechanical vibrations in a record groove too.
Such a noisy mechanism will undoubtedly have significantly inferior sound quality compared to what is possible without such a ridiculous marketing department led - or "R&D" as you put it - mechanism constantly whirring and rattling about as records are played.
Wow you have seriously drunk the flat earth society coolaid. It is clear that you think your idea is the best and you are clearly cleverer than the entire engineering department of large companies. As such 'discussion' cannot be had.
You haven't even explained why a counterweight is bad. And 'there is a patent' is not any indication of an engineering problem to be solved. The age of sub 5g effective mass tonearms is long gone so what is left as an issue.
You haven't even explained why a counterweight is bad. And 'there is a patent' is not any indication of an engineering problem to be solved. The age of sub 5g effective mass tonearms is long gone so what is left as an issue.
Hi Bill,
First: Let keep it civil, and please drop the sarcasm, eh?
Second: Yes I have explained why and how a counterweight is "bad" in the attached 7 page essay - I'm guessing you have either not read it or its beyond your comprehension, other wise you'd be explaining here how I've got the mechanical engineering explanations wrong?
Third: its not "my" idea, as I make clear in my essay and in all response here.
Fourth: I'm not in a competition to establish anything. Just offering insights and a little archive history.
Fifth: since about 2000 I've ditched vinyl replay all together, regarding it as an utter waste of time due to sever limits on frequency & dynamic range and noise floor - in built into its specifications.
Sixth: Nonetheless, since my first 'Meccano' record player in 1972, I've built literally dozens of tone arm designs, several turntable designs, various tube amplifiers and power supplies, solid state control and power circuits. Oh and several loudspeakers including several horn loaded designs including Vitavox Thunderbolts.
Seventh: In particular I productionised the then hand built in Japan Audio Note Io & Io Ltd cartridges in the 1990s, which is still in commercial production, and the loudspeaker stands you can see underneath the type 'E' speakers which today features on the opening page of the Audio Note web site.
Music's Finest Conductor | Audio Note (UK) England
Eighth: I've also worked with / for shareholder corporations like Sony (and others). By LAW they obliged to return profits above all else NOT best sound quality or user experiences or whatever. No profit = no product. Period. This is perfectly normal in that realm.
Ninth: If making the above observations means your best response is that I'm "seriously drunk the flat earth society coolaid" and pretend a corporation has anything other than profit as its highest goal, and repeatedly misconstrue my comments and aims, then good sir, I give up on perusing any further conversation with you.
First: Let keep it civil, and please drop the sarcasm, eh?
Second: Yes I have explained why and how a counterweight is "bad" in the attached 7 page essay - I'm guessing you have either not read it or its beyond your comprehension, other wise you'd be explaining here how I've got the mechanical engineering explanations wrong?
Third: its not "my" idea, as I make clear in my essay and in all response here.
Fourth: I'm not in a competition to establish anything. Just offering insights and a little archive history.
Fifth: since about 2000 I've ditched vinyl replay all together, regarding it as an utter waste of time due to sever limits on frequency & dynamic range and noise floor - in built into its specifications.
Sixth: Nonetheless, since my first 'Meccano' record player in 1972, I've built literally dozens of tone arm designs, several turntable designs, various tube amplifiers and power supplies, solid state control and power circuits. Oh and several loudspeakers including several horn loaded designs including Vitavox Thunderbolts.
Seventh: In particular I productionised the then hand built in Japan Audio Note Io & Io Ltd cartridges in the 1990s, which is still in commercial production, and the loudspeaker stands you can see underneath the type 'E' speakers which today features on the opening page of the Audio Note web site.
Music's Finest Conductor | Audio Note (UK) England
Eighth: I've also worked with / for shareholder corporations like Sony (and others). By LAW they obliged to return profits above all else NOT best sound quality or user experiences or whatever. No profit = no product. Period. This is perfectly normal in that realm.
Ninth: If making the above observations means your best response is that I'm "seriously drunk the flat earth society coolaid" and pretend a corporation has anything other than profit as its highest goal, and repeatedly misconstrue my comments and aims, then good sir, I give up on perusing any further conversation with you.
No, anything on the arm that swings around the pivot will contribute to it's moment of inertia. The only way to remove the CW effect is remove the CW.
Effective mass is the Total moment of inertia of the arm / arm effective length^2, m=I/r^2.
Extract from the paper
Gimbal Bearing: All tone arms including the 'Delta Inertia' and the 'Mag Lev' can only
move in 2 degrees of freedom (up and down & side to side)
This is 4 DOF not 2.
I am in the process of building a tonearm and interested in different ideas. How you calculated moment of inertia. Can you show the data and calculations for "I"
I can see by deleting the CW "I" will be lower, but the CW has a small contribution to "I"
For example if we look at the example of a 9" arm with 194g CW, 9g headshell and 7g cartridge with a total effective mass of 18.5g. Removing the CW will only lower EM to 17.2g in this hypothetical example.
Gimbal Bearing: All tone arms including the 'Delta Inertia' and the 'Mag Lev' can only
move in 2 degrees of freedom (up and down & side to side)
This is 4 DOF not 2.
I am in the process of building a tonearm and interested in different ideas. How you calculated moment of inertia. Can you show the data and calculations for "I"
I can see by deleting the CW "I" will be lower, but the CW has a small contribution to "I"
For example if we look at the example of a 9" arm with 194g CW, 9g headshell and 7g cartridge with a total effective mass of 18.5g. Removing the CW will only lower EM to 17.2g in this hypothetical example.
Hi Warrjon,
Thanks for reading my essay / paper. You write: “This is 4 DOF not 2.”
But I don't think it is correct to state this. A standard gimbal tone arm has only two: “pitch” and “yaw”. The six 'degrees of freedom' available are described here:-
Degrees of freedom (mechanics) - Wikipedia)
“For example, the motion of a ship at sea has the six degrees of freedom of a rigid body, and is described as: Translation and rotation:
Moving up and down (elevating/heaving);
Moving left and right (strafing/swaying);
Moving forward and backward (walking/surging);
Swivels left and right (yawing);
Tilts forward and backward (pitching);
Pivots side to side (rolling).”
As such, I think my essay / paper would have been more accurate to describe a gimbal tone arm's two degrees of freedom as “Tilts forward and backward (pitching)” and “Swivels left and right (yawing)” (instead of the colloquial labels I did use: “up and down & side to side” which are both translational degrees, that gimbal bearings do not possess!)
A linear tracking tone arm still has only two, but would presumably be conventionally designated: “Tilts forward and backward (pitching)” and “Moving left and right (strafing/swaying)”.
The main aim of my paper / essay is to show that inertia calculations in tone arms are correct as far as they go, but misleading. They are only for tuning cartridge suspension resonances to be in the so called 'sweet spot' above warp frequencies, but below bass music frequencies (i.e. lower than 20Hz but higher than say 5Hz).
Clearly this is important, but in doing so the 'mechanical impedance' of the cartridges suspension when mounted on a counterweighted tone arm becomes lower than optimal. Groove vibrations cannot be measured if your reference point behaves like a soft sponge. Far better a solid stiff foundation that will not move when vibrations push it about.
Counterweighs and pivots are sponges. Just see how easily the arm wand can fly away when set at zero tracking weight with the slightest puff of air blown out your mouth. Clearly the tracking weight offset (circa 2g) is all that the cartridge suspension can act against.
Compared to a pendulum suspended by (pseudo) magnetic levitation at 90 degrees to gravity (i.e. at greatest potential energy), you always have all the mass of the arm wand (perhaps 100g or more) that the cartridge suspension can act against. This arrangement is far more solid. Go build one and feel how much stiffer it is compared to the flywheel of a standard counterweighed arm. You can't blow it about at all!
Thanks for reading my essay / paper. You write: “This is 4 DOF not 2.”
But I don't think it is correct to state this. A standard gimbal tone arm has only two: “pitch” and “yaw”. The six 'degrees of freedom' available are described here:-
Degrees of freedom (mechanics) - Wikipedia)
“For example, the motion of a ship at sea has the six degrees of freedom of a rigid body, and is described as: Translation and rotation:
Moving up and down (elevating/heaving);
Moving left and right (strafing/swaying);
Moving forward and backward (walking/surging);
Swivels left and right (yawing);
Tilts forward and backward (pitching);
Pivots side to side (rolling).”
As such, I think my essay / paper would have been more accurate to describe a gimbal tone arm's two degrees of freedom as “Tilts forward and backward (pitching)” and “Swivels left and right (yawing)” (instead of the colloquial labels I did use: “up and down & side to side” which are both translational degrees, that gimbal bearings do not possess!)
A linear tracking tone arm still has only two, but would presumably be conventionally designated: “Tilts forward and backward (pitching)” and “Moving left and right (strafing/swaying)”.
The main aim of my paper / essay is to show that inertia calculations in tone arms are correct as far as they go, but misleading. They are only for tuning cartridge suspension resonances to be in the so called 'sweet spot' above warp frequencies, but below bass music frequencies (i.e. lower than 20Hz but higher than say 5Hz).
Clearly this is important, but in doing so the 'mechanical impedance' of the cartridges suspension when mounted on a counterweighted tone arm becomes lower than optimal. Groove vibrations cannot be measured if your reference point behaves like a soft sponge. Far better a solid stiff foundation that will not move when vibrations push it about.
Counterweighs and pivots are sponges. Just see how easily the arm wand can fly away when set at zero tracking weight with the slightest puff of air blown out your mouth. Clearly the tracking weight offset (circa 2g) is all that the cartridge suspension can act against.
Compared to a pendulum suspended by (pseudo) magnetic levitation at 90 degrees to gravity (i.e. at greatest potential energy), you always have all the mass of the arm wand (perhaps 100g or more) that the cartridge suspension can act against. This arrangement is far more solid. Go build one and feel how much stiffer it is compared to the flywheel of a standard counterweighed arm. You can't blow it about at all!
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The aircraft example has 6 DOF pitch, yaw and roll, a gimbal arm has pitch and yaw which equates to 4 DOF.
You are correct that inertia calculations determine effective mass and this has an effect on the resonant characteristic of the arm/cart system BUT this is only an issue IF this resonance is excited.
What I do not see in the paper is evidence either theoretical (calculations) or testing of the arm. There seems to be a fixture on the headshell is this just for testing or is it required for the system to operate. If it's required for the system to operate it's contribution "I" will be significant. This could put arm/cart resonance far too low.
What I would like to see is more detailed information on tests conducted. Showing the behavior of the arm at the stylus tip. If this system does what you have proposed I could be interested in testing it on my arm.
What most tonearm manufactures fail to do is follow the physics.
Here are a couple of examples of what manufacturers do wrong.
Most tonearms the SME V included, the stylus tip is NOT lined up down the center of the arm wand with the horizontal pivot. This is important as it causes a torque around the vertical pivot. As the arm lifts it will also move sideways due to this torque.
Low slung CW and COG causes the arm to behave like a pendulum. The COG of the arm as a whole should be in the center of the arm wand in the horizontal plane. This is not possible in the vertical plane as the arm wand needs to be higher so the arm does not hit the LP but it can be made close. What I am talking about here is called the ellipsoid of inertia. This is calculated for the bearing housing then moved forward to the stylus tip if the stylus tip is not in the center of this ellipsoid then there will be chaotic behavior.
In simple terms the arm must be able to move in any direction with equal force applied at the stylus tip and come to rest without any erroneous movement.
If the LP was perfectly flat and concentric what you are proposing could work, the issue is no LP is flat or concentric. The arm must be able to move freely in all 4 DOF the lower the starting torque and inertia the better the stylus can track off center pressings and warps.
You are correct that inertia calculations determine effective mass and this has an effect on the resonant characteristic of the arm/cart system BUT this is only an issue IF this resonance is excited.
What I do not see in the paper is evidence either theoretical (calculations) or testing of the arm. There seems to be a fixture on the headshell is this just for testing or is it required for the system to operate. If it's required for the system to operate it's contribution "I" will be significant. This could put arm/cart resonance far too low.
What I would like to see is more detailed information on tests conducted. Showing the behavior of the arm at the stylus tip. If this system does what you have proposed I could be interested in testing it on my arm.
What most tonearm manufactures fail to do is follow the physics.
Here are a couple of examples of what manufacturers do wrong.
Most tonearms the SME V included, the stylus tip is NOT lined up down the center of the arm wand with the horizontal pivot. This is important as it causes a torque around the vertical pivot. As the arm lifts it will also move sideways due to this torque.
Low slung CW and COG causes the arm to behave like a pendulum. The COG of the arm as a whole should be in the center of the arm wand in the horizontal plane. This is not possible in the vertical plane as the arm wand needs to be higher so the arm does not hit the LP but it can be made close. What I am talking about here is called the ellipsoid of inertia. This is calculated for the bearing housing then moved forward to the stylus tip if the stylus tip is not in the center of this ellipsoid then there will be chaotic behavior.
In simple terms the arm must be able to move in any direction with equal force applied at the stylus tip and come to rest without any erroneous movement.
If the LP was perfectly flat and concentric what you are proposing could work, the issue is no LP is flat or concentric. The arm must be able to move freely in all 4 DOF the lower the starting torque and inertia the better the stylus can track off center pressings and warps.
It is possible to have a counterweight that has no effect on the inertial mass, if it is placed on the horizontal pivot.
If the music in the groove is represented by horizontal and vertical modulation, you have to have strict 2DOF in your arm, not 4.
2wice, It is impossible by definition to have mass without inertia. Hold a counterweight in your hand. It has inertia in all six degree of freedom. However the tone arm's bearings confine the effects of the counterweight's inertia - with reference to the tone arm and record player - to only two degrees of freedom. Colloquially 1. up/down & 2. left/right - or horizontal as you put it.
Also, what's the point of a counterweight on the horizontal (left/right) pivot anyway?
The “fixture on the headshell” was an active version one off prototype employing a fibre optic cantilever position sensor. It worked just as well without all this active electronics. The effects on inertia of the fibre optic gear on the head shell in (pseudo) magnetic levitation system are well below record warp resonant frequencies. That's part of the whole point of removing the counterweigh and replacing with (pseudo) magnetic levitation.
What I am “proposing” is a passive (pseudo) magnetic levitation instead of a counterweigh, which works in the real world. Detailed mechanics calculation are beyond my range of skills. I build stuff and test it that way. See the movies of a Voyd turntable suspension being wobbled with the Mag-lev keeping the cartridge 'glued' to the record without its suspension wobbling at all.
Voyd Reference Io Ltd. no counterweight SME V - Google Drive
The tone arm / tracking geometry issues you raise are insignificant on final music signal integrity / distortion compared to arranging for the highest mechanical impedance at the cantilever suspension. All forms of counterweighs on pivots have lower mechanical impedance at audio frequencies than pendulums suspended at maximum potential energy (90 degrees to gravity) by a passive (pseudo) magnetic levitation system.
Also until we agree on mechanical science definitions that a tone arm has only two degrees of freedom, not four, discussing “ellipsoid of inertia” issues will be moot.
Build one and try it yourself, you'll be amazed! Good luck!
What happens to "I" in your formula if r=0?
Nope,
Code:
Moment of inertia I is defined as the ratio of the net angular momentum L of a system to its angular velocity ω around a principal axisA mass suspended in space with no velocity has no inertia.
r=0
This is not true. The stylus (and not the cartridge) suspension 'acts' against the effective mass.
Originally Posted by hend1n1
Counterweighs and pivots are sponges. Just see how easily the arm wand can fly away when set at zero tracking weight with the slightest puff of air blown out your mouth. Clearly the tracking weight offset (circa 2g) is all that the cartridge suspension can act against.
Hi alighiszem, If I am wrong and what you say were true, then on an arm with say 10g (typical) effective mass with the tracking weight to zero grams, a cartridge would happily track the record grooves.
But of course it won't. So it can only be acting against the pivot balance offset of 2 grams (or whatever) not the 10g effective mass, which remember is arranged as a flywheel to easily store and recover potential energy, not be a firm foundation to act against at all frequencies. Hence why you can blow it about with your breath so easily.
So there has to be more going on than inertia calculations to arrive at a proxy "effective mass" and call that the sum of mass against which vibrations act at the cartridge suspension, i.e. the mechanical impedance of the electro-mechanical side of the transducer.
Also frames of reference are often forgotten when doing inertia though experiments. Yes 10g (or whatever) of effective mass is available but only outside the closed circuit of the record player itself.
Counterweighs and pivots are sponges. Just see how easily the arm wand can fly away when set at zero tracking weight with the slightest puff of air blown out your mouth. Clearly the tracking weight offset (circa 2g) is all that the cartridge suspension can act against.
Hi alighiszem, If I am wrong and what you say were true, then on an arm with say 10g (typical) effective mass with the tracking weight to zero grams, a cartridge would happily track the record grooves.
But of course it won't. So it can only be acting against the pivot balance offset of 2 grams (or whatever) not the 10g effective mass, which remember is arranged as a flywheel to easily store and recover potential energy, not be a firm foundation to act against at all frequencies. Hence why you can blow it about with your breath so easily.
So there has to be more going on than inertia calculations to arrive at a proxy "effective mass" and call that the sum of mass against which vibrations act at the cartridge suspension, i.e. the mechanical impedance of the electro-mechanical side of the transducer.
Also frames of reference are often forgotten when doing inertia though experiments. Yes 10g (or whatever) of effective mass is available but only outside the closed circuit of the record player itself.
You appear to be confusing momentum with inertia. It may have no relative momentum but it always has its inertia - let's consult Newton's first law:-
"A body at rest remains at rest, or, if in motion, remains in motion at a constant velocity unless acted on by a net external force."
Newton’s First Law of Motion: Inertia | Physics
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Apologies, you are correct, perhaps I explained it incorrectly.
I'll rather get someone else to do it then.
CW over horizontal pivot will do this.
Yes it will, you are correct, but this explanation is exactly the reason we don't want the "moment of inertia [i.e. momentum] will be zero" (or some whatever number like 10g "effective mass") by employing a "CW over horizontal pivot" !
Zero "moment of inertia" = zero mechanical impedance = zero signal.
An electro-mechanical transducer requires a high mechanical impedance on one side of it sensing mechanism - a mechanical ground. This acts as a mechanical reference point to measure movements induced by grooves into the relatively low mechanical impedance of the cantilever's attachment to its suspension (i.e. the opposite side of the pivot point's ground side).
An ideal mechanical ground has a so called 'high mechanical impedance' which typical c10g effective mass / moment of inertia can provide.
This means increases increases of moment of inertia at the transducers mechanical ground = increases in signal to noise ratio i.e. better sound quality (all other factors being equal such as cartridge suspension resonances - which in CW arm are problematic, hence the "effective mass" chase curing the wrong problem, throwing the baby out with bath water etc... ).
Hence why (pseudo) magnetic levitation which provides all the arm wand's c100g of mass as mechanical ground - ten times better than a counterweighed arm's typical c10g "effective mass".