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The Arm/Cartridge Matching Myth

When I began my journey in high-end audio 36 years ago….no-one ever wrote about arm and cartridge matching nor tonearm resonant frequency…?
Over the last 10 years or so…this topic has become not only ubiquitous, but has mutated beyond its definition, to THE guiding principle of matching cartridge to tonearm….❓❗️😵
The Resonant Frequency can be calculated using a complex formula relating Tonearm Effective Mass to the cartridge’s Compliance….or it can be simply measured using a Test record of various frequency sweeps.
The RECOMMENDED Resonant Frequency of any tonearm/cartridge combination is between 8-12Hz.
But WHY is this the recommended frequency and WHAT does it really mean…?

The raison d’etre of this Resonant Frequency…is to avoid WARPED records inducing ‘resonance’ into the tonearm…..
Say what…❓😵
WARPED records….❓❗️
Yes…..ONLY warped records❗️😎
But doesn’t it have any meaning for NORMAL records…❓
None whatsoever…..😊👍
Let me explain….🎼

A badly warped record induces the tonearm to rise and fall rapidly on the ‘sprung’ cantilever of the cartridge.
Depending on the severity and frequency of this warping…..a subsonic frequency between 2-5Hz is induced so if your tonearm/cartridge Resonant Frequency dips into this frequency range….it will begin resonating and thus miss-track and/or induce hum through your system.🎤
Keeping the lower limits of your tonearm/cartridge Resonant Frequency to 8Hz simply insures against this possibility.🎶

So what about the 12Hz upper limit…❓
This simply insures against the possibility of any ultra low-level frequency information which MAY be on the record, also inducing this same miss-tracking or hum. For instance if your tonearm/cartridge Resonant Frequency was 18Hz and you had an organ record or one containing synthesised bass going down to 16Hz…..your tonearm may miss-track or you MAY develop a hum❓😢

So how many badly WARPED record do you possess…❓
I have three out of a thousand or so……and have NEVER experienced miss-tracking or hum even on these three…❗️😍

Yet these days….everyone (without exception it seems)…even tonearm and cartridge designers….happily follow the dictum of this Arm/Cartridge MATCH as if it affected sound quality…..❓
This Resonant Frequency has ZERO affect on the sound quality of a particular tonearm/cartridge combination and I have proved it hundreds of times with a dozen different arms and over 40 cartridges.

The best match for ANY cartridge ever made….is simply the very best tonearm you can afford…whatever its Effective Mass…😘
128x128halcro

Showing 5 responses by fleib

fleib
1,124 posts
 
Here's the calculation:
www.luckydog.demon.co.uk/images/EMC.xls

http://www.docstoc.com/docs/111263917/EMC-EMC-Luckydog-s-Tonearm-Effective-Mass-Calculator-Step

Calculate the moment of inertia then divide by the square of the effective length. The MOI is = mass times distance squared. Or use the calculator.

No, I wasn't confusing resonance of the arm tube with low frequency resonance, but they're inextricably linked. The idea is to prevent resonance from increasing into an atomic explosion, while dissipating vibrations.
I'm not advocating resonance outside of the neutral zone, just pointing out a couple of conceptual errors.
Regards,
fleib
1,124 posts
 
Even though there's normally no musical content below 20Hz, there is a variety of noise caused by friction, and the mechanical reality of tracking.
What's the amplitude peak of undamped low frequency resonance? What exactly is it that's resonating, your cantilever perhaps? Ever hear of intermodulation distortion?

This is all well documented for decades now. Imperfect equipment and set-up can allow acoustic and mechanical feedback to wreck havoc that is absent with digital.

If low frequency resonance is near the audio band, say 18Hz, then 2nd harmonic intermodulation is 36Hz.
This is from The Audio Dictionary:
http://books.google.com/books?id=L38MrvScG3gC&pg=PA38&lpg=PA38&dq=low+frequency+resonant+peak+amplitude+in+tonearms&source=bl&ots=L7kNpNUcIL&sig=ux4FxgVPIC1wpe3-WPA3QYKSiYM&hl=en&sa=X&ei=aAQ8VNitOOzbsATX7YLACw&ved=0CDEQ6AEwAw#v=onepage&q=low%20frequency%20resonant%20peak%20amplitude%20in%20tonearms&f=false

Regards,
fleib
1,124 posts
 
Generalizations, half truths, and oversimplification lead to erroneous conclusions even if they work. Rules are made to be broken and it's results that matter. You want to know the resonant frequency of your arm/cart? Buy a test record.

How is it that Halcro can track almost anything with a resonant frequency below the recommended range, magic? It's because his set-up isn't easily excited by acoustic/mechanical impulses and he probably doesn't play severely warped records. They sound like crap anyway, so why?

Resonance doesn't result in near infinite energy out. Even an atomic bomb is finite and we're not converting matter to energy, but the propagation of resonance can be a problem, mimicking oscillation.
Ever see the original Origin Live mod of the Rega arm? They cut two slots along the bottom of the armtube to prevent increased vibration/resonance propagation. The armtube can be sort of like an echo chamber for vibrations.

There are two basic ways to deal with any resonance and vibrations, and the cart will put vibrations into the headshell regardless of resonance. They are damping and dissipation. Over-damping compromises transient response and makes it sound dead, but judiciously applied will mitigate amplitude of resonance and aid tracking. What's the difference between damping and bearing friction? Not much methinks.
Dissipation is channeling energy down the armtube and out, hopefully. The trick is not to have mechanical vibrations go the other way. That's where high quality equipment and set-up comes into play. A well designed table will do this for you if it's set-up right.
Regards,
fleib
1,124 posts
 
Harold NTB,
You mean the Luckydog eff mass calc? Copy the URL:
www.luckydog.demon.co.uk/images/EMC.xls
search and open the document. You should find everything from VTF to counterweight distance. Luckydog is a physicist who happens to like records.
Maybe you should send it to Stephen Hawking for a second opinion. How about a mechanical engineer?
http://www.audioasylum.com/cgi/t.mpl?f=vinyl&m=164890

For some reason I couldn't get either of your URLs to work. It might have something to do with the space-time continuum, or perhaps a glitch in my internet connection or that pesky virus.
Regards,
fleib
1,124 posts
 
VE database has the FR64FX at @ 20g and the 64S @ 35g

Is this is correct?

I'd guess the 12" arms are heavier.
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