9” vs 12” pick up arms. The mechanics explained minus the anecdotal B.S.

PeterA

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Very interesting discussion and it was great that you got Harry from VPI to discuss the different length arms. He set up and described a legitimate test. Here is a quote from him:

Truth be told I am the only one who has heard 9", 10.5", and 12" Fat Boys mounted on the same Direct Drive Avenger using 3 Ortofon A-95's and can state without a doubt they sound different and I prefer the master tape smoothness of the 12". Besides, I have the same Ampex ATR-102 that Chad uses to make the records, totally rebuilt by ATR Services. I have master tape copies of the music and the 12" sounds more like the master than the 9" or the 10.5".

So, I guess VPI is one of the few manufacturers who did not tell MF privately that they only provide 12" arms to appease customers. Thanks Fsonicsmith for sharing a link to this discussion.
 

PeterA

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I agree with you. Further adding support to this view is that VPI is putting a toe in the water of gimbaled arms.
What makes me feel most uncomfortable with VPI unipivots is that once azimuth is adjusted by means of a Fozgometer, the arm more often than not is significantly canted to one side when at rest. The extent of this leaning ameliorates as the arm travels across the record surface. I think the design of the balancing weights under the pivot point has much to do with this. But the bottom line is that I have never achieved great sound with a VPI arm.
I am heavily influenced by a very knowledgeable person, whom I will leave out of this, that in all likelihood 10.5" is the best all around compromise for tonearm length given all the various compromises and their consequences in the very imperfect world or analogue vinyl playback. But as HW said, a 9" arm may be best for rock and a 12" may have the blackest backgrounds (he didn't say that, but that is what I read into what he did say) and in the middle is....

Harry wrote that the 12" arm sound most like the master tape from which the LP was produced. He compared the sound of the tapes to the various different length arms and concluded that the 12" arm was most like the tape. Also interesting is his comment that he is working on the designs for 14" and 16" arms. If those get developed, perhaps the 12" length will be the best compromise.
 

Fsonicsmith

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Jun 25, 2015
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Harry wrote that the 12" arm sound most like the master tape from which the LP was produced. He compared the sound of the tapes to the various different length arms and concluded that the 12" arm was most like the tape. Also interesting is his comment that he is working on the designs for 14" and 16" arms. If those get SUCCESSFULLY developed, perhaps the 12" length will be the best compromise.

Fixed. :)
 

bonzo75

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I found this by Frank Schroder, on the subject


"All other things being equal, a 12" arm will be superior in terms of max. (and also average)tracing error distorsion. It's the "all other things being equal" part where shorter arms gain ground(or move ahead of their longer bethren), since most other parameters(bearing friction, resonance characteristics-closely linked to bending and torsional armwand stiffness on captured bearing arms,etc.)will yield inferior measurements(and you can hear it, too).
This is not to say that there are no excellent 12"ers in existence. But they too have only two null points and are less forgiving when ever so slightly misaligned. Check out John Elison's Baerwald/Loefgren spreadsheet and alter the figures for overhang or offset angle by the same amount for a 9" and a 12" arm. The resulting graphs will tell the rest of the story.
But off course we all do 100% perfect setups only ... ;-), so the last one is a mute point.
On 12" arms the susceptabilty to cartridge induced resonances is further accentuated by the fact that cartridges that you should ideally partner with longer arms(normally featuring higher eff. mass) have lowish compliances. These typically "feed" more energy into the arm(wand)'s structure than high compliance carts."
 
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Solypsa

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On 12" arms the susceptibility to cartridge induced resonances is further accentuated by the fact that cartridges that you should ideally partner with longer arms(normally featuring higher eff. mass) have lowish compliances. These typically "feed" more energy into the arm(wand)'s structure than high compliance carts."
So get the cart that is a known good match to the arm ( or vice versa ). No need to chart out the moon landing....
 
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DasguteOhr

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Best tonearms are 10.5" with 14-16g eff mass.
a good compromise between dynamic and low distortion. Even mm cartridges still run relatively well.
 

mtemur

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I think it’s pretty clear that 9” tonearm is better on all aspects except tracking error which is to low to be an issue.
 
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theophile

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There was a saying about Angels and heads of pins.
 

ssfas

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Best tonearms are 10.5" with 14-16g eff mass.
a good compromise between dynamic and low distortion. Even mm cartridges still run relatively well.
That's a relief.

I'm just about to buy a 10.3" tonearm with 14g effective mass for a 2.2mV MI SoundSmith cartridge.
 
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DasguteOhr

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That's a relief.

I'm just about to buy a 10.3" tonearm with 14g effective mass for a 2.2mV MI SoundSmith cartridge.
Good choice
This effective mass usually also works with soft-suspended mm pickups. If more effective mass is required, you can easily work with lead or tin plates on the headshell. For me, 10.5 inch tonearms are the best compromise. e.g. TW 10.5, technical EPA 500, Nottingham Anna, all excellent tonearms.
 
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ssfas

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Good choice
This effective mass usually also works with soft-suspended mm pickups. If more effective mass is required, you can easily work with lead or tin plates on the headshell. For me, 10.5 inch tonearms are the best compromise. e.g. TW 10.5, technical EPA 500, Nottingham Anna, all excellent tonearms.
It's a Wand Plus arm.
For those worried about cartridge vibrations/resonance into the tonearm, I use these. About 0.200g of heavenly joy.
 
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Ron Resnick

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I think it’s pretty clear that 9” tonearm is better on all aspects except tracking error which is to low to be an issue.

I think a definitive answer on this topic is pretty far from "clear.":)

Isn't your "exception" actually the main issue? ("Other than that Mrs. Lincoln, how was the show"?)
 

bonzo75

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DasguteOhr

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It's a Wand Plus arm.
For those worried about cartridge vibrations/resonance into the tonearm, I use these. About 0.200g of heavenly joy.
Ohh a cartridge isolator,This doesn't really work great with every cartridge. for Decca cartridge with a sheet metal housing great option. It always helps to just try and see if the result is good, otherwise get rid of the thing P1180648.JPG.f136a4124d3bd300430bd4d1b06c4f4a.jpeg
Exsample to add eff mass.lead between headshell and cartridge 115826-bfece3f6-large.jpg
 

Folsom

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Some carts need something that will compress a little because they don't make good contact. Not sure about that...
 

mtemur

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I think a definitive answer on this topic is pretty far from "clear.":)

Isn't your "exception" actually the main issue? ("Other than that Mrs. Lincoln, how was the show"?)
Actually tracking error is the least important problem regarding tonearm-cartridge setup. All other alignments (SRA, azimuth, anti-skating, zenith) have far more impact on sound quality. The difference in tracking error between 9” and 12” is not too big.
 
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