Tonearm effective mass??

[ace420]

I have 2 TT's & I've been trying to find out the tonearm effective mass with no success. 1st is a Systemdek IIX with the Profile tonearm (teardrop shaped arm board), I've read everywhere from 10-20g for this tonearm & 2nd is a Denon DP-40F. Any help would be appreciated

 

[hesson11]

Have you checked at vinylengine.com? Click on the "tonearm database" link near the top of the home page.

-Bob

 

[bhundu]

Not sure how accurate the following method is but I've read that if you take off the counter weight and weigh at the headshell end with a TF gauge you may get a good idea. Ideally you would check this method with an arm of a known mass to compare.

 

[fiddlefye]

Have you checked at vinylengine.com? Click on the "tonearm database" link near the top of the home page.

-Bob

Sometimes there's a figure listed, often not. For some arms there seems to be a pretty wide range of figures published in various places as well. Makes it a bigger challenge to do things the "right" way when setting up for a particular cartridge.

 

[gusten]

Over at VE there is a thread " Measuring tonearm effective mass".

Follow that method and You will get an acurrate value.

gusten

 

[hakaplan]

Over at VE there is a thread " Measuring tonearm effective mass".

Follow that method and You will get an acurrate value.

gusten

Fascinating stuff, if you have time to sift through all that and can do the calculations.

Remove the counterweight, remove the stylus. Use a digital pocket scale set at the height of a record. Set the front of the cartridge on body the scale. Take that weight and subtract the weight of the cartridge body. That's a quick and dirty method. I tested using tts of known mass and have gotten withing .5-1g of published mass. To me that's close enough. Especially because if you intend to use this mass to calculate resonant frequency, you're wasting your time there, too. Compliance figures are often inconsistent or inaccurate or published measured at values irrelevant to our needs. Use tracking force as a guide to compliance along with your estimated arm mass and you'll be successful in matching carts to arms.

 

[fiddlefye]

What are the boundaries to low, medium and high mass arms? I've often seen the Jelco SA-750D referred to as a medium mass arm at 20 g effective mass (according to a note on Vinyl Engine sent by a representative of the company), yet a mass that high is called high mass in other places. What's what? I understand that carts with lower compliance cantilevers need lower mass arms etc, but what is the exact co-relation?

Let's say I have a cart which is designed for 1.5 g VTF. How massive an arm will it work with?

The principal is so easy to grasp, the specifics so elusive.....

 

[JohnVF]

Fascinating stuff, if you have time to sift through all that and can do the calculations.

Remove the counterweight, remove the stylus. Use a digital pocket scale set at the height of a record. Set the front of the cartridge on body the scale. Take that weight and subtract the weight of the cartridge body. That's a quick and dirty method. I tested using tts of known mass and have gotten withing .5-1g of published mass. To me that's close enough. Especially because if you intend to use this mass to calculate resonant frequency, you're wasting your time there, too. Compliance figures are often inconsistent or inaccurate or published measured at values irrelevant to our needs. Use tracking force as a guide to compliance along with your estimated arm mass and you'll be successful in matching carts to arms.

Wouldn't the weight of the arm that is still behind the pivot after removing come into play was well? As in, it would still be acting as a counterweight, giving you a lighter arm weight reading? I'm just curious, not trying to nitpick. I agree that matching compliance to arm is very important, but an inexact science given the variables of published figures, etc.

 

[Bob_in_OKC]

What are the boundaries to low, medium and high mass arms? I've often seen the Jelco SA-750D referred to as a medium mass arm at 20 g effective mass (according to a note on Vinyl Engine sent by a representative of the company), yet a mass that high is called high mass in other places. What's what? I understand that carts with lower compliance cantilevers need lower mass arms etc, but what is the exact co-relation?

Let's say I have a cart which is designed for 1.5 g VTF. How massive an arm will it work with?

The principal is so easy to grasp, the specifics so elusive.....

Maybe just a typo, but to clarify...Low-mass arms work better with high-compliance. You also need to consider the mass of the cartridge itself. The Ortofon OM series, with the weight removed, would weigh almost 5 grams less than the 2M series.

 

[fiddlefye]

Maybe just a typo, but to clarify...Low-mass arms work better with high-compliance. You also need to consider the mass of the cartridge itself. The Ortofon OM series, with the weight removed, would weigh almost 5 grams less than the 2M series.

Dozey moment on my part, sorry. I do actually know which way around it goes....

You're right that the mass of the cartridge has an effect, has to. If you know effective mass of the arm, the weight of the shell and add the weight of the cartridge then you'd be on the right track, no? Let's face it, in the end there's always the likelihood of trial and error coming into play as there are too many variables in how and arm/cart/table behave together to get it 100% right just from the numbers (IMO). Having that information can keep the list to things that might possibly work well. From there on it is trying things and learning from the experience of others.

I personally think we should have our own AK arm/cart/table database where members can input and comment on various combinations they have used or heard. Entries could be for both current set-ups and for those that are of "historical significance". Good idea?

 

[Bob_in_OKC]

Dozey moment on my part, sorry. I do actually know which way around it goes....

You're right that the mass of the cartridge has an effect, has to. If you know effective mass of the arm, the weight of the shell and add the weight of the cartridge then you'd be on the right track, no? Let's face it, in the end there's always the likelihood of trial and error coming into play as there are too many variables in how and arm/cart/table behave together to get it 100% right just from the numbers (IMO). Having that information can keep the list to things that might possibly work well. From there on it is trying things and learning from the experience of others.

I personally think we should have our own AK arm/cart/table database where members can input and comment on various combinations they have used or heard. Entries could be for both current set-ups and for those that are of "historical significance". Good idea?

I'd really like to see a database like that. It would be great especially to see the specs and predicted results compared to subjective evaluation. I saw an old comment here somewhere, where a longtime AK member was surprised at how his M97XE seemed quite happy on a relatively heavy Pioneer S-shaped arm. I don't think he said exactly what the tonearm mass was, though.

I did some fairly careful study on the situation before pulling the trigger on a Goldring 1042. Based on the formula I have and changing the tonearm mass component of the formula, it's pretty difficult to move the resonant frequency outside of the generally accepted preferred ranges. I tried some numbers from SME low-mass arms and found some numbers that didn't work, but everything from 7 grams on up worked.

 

[meggy]

Hey the Tonearm Database lists one only Systemdek arm at 15g.

The Denon 40f isn't listed but the 45f and 47f are.

 

[hakaplan]

Wouldn't the weight of the arm that is still behind the pivot after removing come into play was well? As in, it would still be acting as a counterweight, giving you a lighter arm weight reading?

Yes, but proportionally it's insignificant and the end result is close enough.

 

[Balifly]

Does the Denon DP 40F have a skinny S arm similar to the one on the DP 33F?

 

[ace420]

Does the Denon DP 40F have a skinny S arm similar to the one on the DP 33F?

Yes, that tonearm looks very similar to the one on the DP-40F.

Thanks to all for the tips. I tried the method of removing the cart & counterweight & weighing at the head shell, came up with 12.9g for the Systemdek IIX Profile arm. Some posts I read stated the effective weight for this tonearm at 12-14g so this method seems to be working??
Someone else also asked what the ranges are for low-medium & high mass tonearms, I would also be interested in this info.
Thanks.

 

[hakaplan]

I think I'd call under 10g low mass, above perhaps 15g high mass and 10-15 middle. The Systemdek IIX brochure describes the arm as medium mass which comports with your weighing.

 

[fiddlefye]

I think I'd call under 10g low mass, above perhaps 15g high mass and 10-15 middle. The Systemdek IIX brochure describes the arm as medium mass which comports with your weighing.

So the Jelco SA-750D would be a high mass arm then?

 

[melofelo]

I think I'd call under 10g low mass, above perhaps 15g high mass and 10-15 middle. The Systemdek IIX brochure describes the arm as medium mass which comports with your weighing.

me too..:yes:

 

[gusten]

I agree with Hakaplan, weighing as suggested will mostly be good enough.
The effective mass will be half of the tonearm´s weight. Normally the effective mass strictly calculated will be 1-2g less.

Taking figures of compliance into account, the achievable numbers will have a much larger variation, most of them are just estimations and not so close to real figures.
gusten

 

[pfcs49]

I think I'd call under 10g low mass, above perhaps 15g high mass and 10-15 middle. The Systemdek IIX brochure describes the arm as medium mass which comports with your weighing.

OK-so let's close this circle! For an arm to fall into these categories, what is the assumed cartridge mass? 0g? 5g? (since mfgrs spec excludes cart mass, it needs to be added to mfgrs spec to arrive at total/actual eff mass of tonearm) No one has EVER answered this question unequivocally for me. It seems that in every discussion, the cart weight gets forgotten or assumed, and becomes the elephant in the corner of the room! If under 10g is low, are you including the cart mass in that amount? And are you including the tracking force to be part of the sum (it should be)?

And to keep it simple, what tracking force requirements correlate to low, med, and high mass setups (once we're clear about the above paragraph).

Your expectant admirer, phil

PS: I totally agree about the eff arm mass being VERY close to the measured mass @stylus contact point W/O counterweight-at least in the 2 tonearms I've measured that way. Less than 10% error.