The Arm/Cartridge Matching Myth

Very interesting Halcro. Thanks for the post.

I suppose another approach is to try to find out which arms the cartridge designers used while developing your cartridge. Then you would at least get closer to what those designers like.

The problem is that there is the whole rest of the system and even the room that plays a role in the overall sound and that will certainly be different from one's own set up.

I have not read anywhere which arms Lyra uses to develop its cartridges, but I did read that the AirTight Supreme was in part developed on an SME arm, for instance.

I would only place upper and lower limits on Halcro's proposition; it would not be a great idea to use a very high mass tonearm with a very high compliance cartridge, simply because of the resulting flexing of a very compliant cantilever which might cause physical damage, never mind resonance. Let say, an ADC XLM with an FR66S.

Of greater concern and something that is not easy to measure are the secondary arm and cartridge resonances that are excited by the energy put back into the arm.

An interesting point Viridian…and one that I’ve been wrestling with over five years or so….😖
Many people have mentioned both cartridge resonances and “energy transference” into tonearms over the years…..yet no-one (to my knowledge) has provided any scientific data or evidence to support such claims…?
If cartridge resonances OUTSIDE of the cartridge body really exist (and if they did I can’t help but think this would indicate information loss?)….they would be easily measurable and the data should be available for all the cartridges in the market place…❓
I am unaware of any such data and until some is provided…it seems presumptuous to base an argument or philosophy on this…😵

Energy transference into the tonearm is more easily understood I believe, as it is a purely structural phenomenon….⏄
The tonearm is a counter-weighted propped cantilevered beam as a structural description….
In its neutral balanced state (before any tracking weight is applied)….it is a purely counterweighted cantilever with the total weight of the arm and counterweight transferred vertically through the pivot to the arm bearing.
The stress (or force or reaction) at the headshell in this state is zero…..0️⃣
The bending-moment diagram from this point towards the pivot then increases in a curved catenary slope (because of the arm’s uniformly distributed self weight) until it reaches its maximum bending moment (and shear stress by the way)…at the pivot..😎
Every single stress, bending moment and deflection can be calculated knowing the length of the arm, the material and cross-sectional configuration.
Incidentally….the Resonant Frequency of the tonearm in this ‘balanced’ condition is wayyy below that of the arm on its ‘sprung’ cantilever…😋
Once the VTF is dialed in…the reaction (or force) at the headshell is whatever the VTF is…1.5 Gm-2.0 Gm etc..
From here it becomes less clear cut….😢
There is a constant reaction 1.5 Gm at the headshell as it traverses the record (otherwise VTF would be changing)…but it is a dynamically changing propped cantilever now with the arm moving both sideways and also up and down…😱
If the bearings are truly frictionless…it should induce no extra stresses into the arm other than the ones previously in existence as a propped counterweighted cantilever as far as I can see…😴❓
But it would require a computer run simulation to analyse exactly what was occurring…and the only tonearm manufacturer that has done that to my knowledge is Continuum Audio Labs with their Cobra and Copperhead tonearms…

Beginning with Finite Element Analysis using NASTRAN, PATRAN, and DYTRAN from www.mscsoftware.com finalising in the complex process of Gradient Shape Optimisation using Reshape from www.advea.com. The wand is eggshell thin with special contours and compound curves to “shape” the resonant behavior of the arm. These behaviours are only visible with specialized software tools but clearly audible to experienced listeners.

As it so happens….my Copperhead tonearm is the very best performer with every single one of my cartridges be they high-compliance MMs or low-compliance LOMCs…😘
Very closely behind the Copperhead in matching with multiple cartridge types and designs….are the 35 year-old (high mass) Fidelity Research designed FR-64s/66s and (medium mass) SAEC WE-8000/ST...😍

On the other hand Viridian….I agree with Larryi’s advice to never tap on the arm when in the playing position….😰
Apart from possible damage to the cantilever as he points out….dynamic (or impact) loading on a material bears little relationship to the transfer of sound waves propagated through structure or air and thence into the material…👎
In architecture…when we test a wall for its sound-proofing properties or a theatre wall for its reverberant characteristics…we never ‘hit’ it with any implement..👀
In acoustic theory….sound is propagated through materials by Reflection, Transmission and Absorption and the amount of each of these is able to be calculated by the materials’ properties and thicknesses and the frequencies and SPL (volume) of the sound.
When designing a parquet timber or tile or stone clad floor for minimizing the ‘impact’ sound of stiletto footsteps…..different design solutions are required…😕

What we all seem to agree on though…. Boofer included….is that the notorious arm/cartridge Resonant Frequency Calculator is no indication of a tonearm’s ‘matching’ ability to a cartridge….😎✋

I would only place upper and lower limits on Halcro's proposition; it would not be a great idea to use a very high mass tonearm with a very high compliance cartridge, simply because of the resulting flexing of a very compliant cantilever which might cause physical damage, never mind resonance. Let say, an ADC XLM with an FR66S.

That's interesting.....I've never heard of anyone destroying a cantilever with a high-mass arm...😱❓
I understand how confusing it must be for most audiophiles to understand esoteric structural principles....😴
In normal playing conditions....the cartridge has no idea about the tonearm's Effective Mass...😎
The only 'mass' it sees is the VTF of 1.5Gm...😛
When I balance my six arms to 'neutral' (before applying VTF)....they ALL pivot freely when pushed towards the spindle....despite their differing Effective Masses 👍
Imagine a huge tonearm weighing two tons on perfectly frictionless pivots..👀
You could easily push it with one finger to start it pivoting...👅
The problem comes when you try to STOP it once it is pivoting...😵
It is only THEN that the Effective Mass becomes an issue...😱
So it is only a change in RELATIVE movement which brings into play Effective Mass...hence its role in the UP and DOWN movement of tracking a warp...☺️
If you play a record with a seriously off-centre hole...you will notice the tonearm moving back and forth while it tracks the groove...😫
This again will bring into play the Effective Mass...👀

So the only times Effective Mass plays a role is when playing a warped or off-centre record...😏
At all other times....the 'mass' that the stylus and cantilever sees is the VTF...😘

I suppose another approach is to try to find out which arms the cartridge designers used while developing your cartridge. Then you would at least get closer to what those designers like.

I'm not sure about this Peterayer.....❓
If I were designing a tonearm, I'd want to test it with as many different cartridges (and TYPES of cartridges) as I could..😎
However...I suspect that nowadays most designers of high-end arms test them predominantly with MC cartridges as they believe that most buyers will be using this type of cartridge....😢
A well-known and much-aclaimed tonearm I once owned....sounded fine with LOMCs yet performed poorly with every MM I tried...😩⁉️
In fact the interesting discovery with my many arms and cartridges......was that the poor arms were exposed...not with different LOMC cartridges...but with different MM cartridges...😵❓
So the common audiophile belief that LOMCs require better arms than MMs...is simply another myth IMO...👀😎❓