Counter Weight Question

Re: Counter Weight Question

Postby WntrMute » Tue Jan 08, 2019 4:05 pm

Amazon told me to tell you "thank you".
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Re: Counter Weight Question

Postby Johnny » Tue Jan 08, 2019 4:08 pm

WntrMute wrote:Amazon told me to tell you "thank you".

:D I get thank yous from Amazon almost every day.
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Re: Counter Weight Question

Postby Golear » Tue Jan 08, 2019 8:18 pm

I'm not sure I understand the ref to damping. As a general point, I do believe that changing things by a fraction of a millimeter can impact the sound. I'm not sure that extends to the counterweight - but it's the sort of thing that is easier to try out, than to prove on paper. And since no material is infinitely rigid, there will be flexure along the entire length.

As for convincing anyone on "why", perish the thought! That sounds like a terrible job. I just want to contribute to, and benefit from, a "marketplace of ideas" aka an internet forum. (Internet forum!) I want to read posts, then I'll make up my own mind. Everyone else will make up their own mind, too. If I have failed to convince you of something, all I can say is.... erm.... sorry? :-)

I think the reason why there won't be a difference in sound is that the change in counterweight will really only affect the arm/cartridge resonance. And if this changes from 8 Hz to, say, a little more/little less than that, then this change really doesn't matter to the rest of the chain. It's below a threshold so it doesn't change the sound. If there's going to be a difference, it will be in the way the arm processes vibrations, and this would be audible as mistracking. Again, if it is below a threshold, then the change will be inaudible, too. But rather than deduce this, I think it will be easier and quicker to just try it out.

(Apologies in advance, if required.)
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Re: Counter Weight Question

Postby Brf » Wed Jan 09, 2019 9:12 am

Golear wrote:I'm not sure I understand the ref to damping. As a general point, I do believe that changing things by a fraction of a millimeter can impact the sound. I'm not sure that extends to the counterweight - but it's the sort of thing that is easier to try out, than to prove on paper. And since no material is infinitely rigid, there will be flexure along the entire length.

As for convincing anyone on "why", perish the thought! That sounds like a terrible job. I just want to contribute to, and benefit from, a "marketplace of ideas" aka an internet forum. (Internet forum!) I want to read posts, then I'll make up my own mind. Everyone else will make up their own mind, too. If I have failed to convince you of something, all I can say is.... erm.... sorry? :-)

I think the reason why there won't be a difference in sound is that the change in counterweight will really only affect the arm/cartridge resonance. And if this changes from 8 Hz to, say, a little more/little less than that, then this change really doesn't matter to the rest of the chain. It's below a threshold so it doesn't change the sound. If there's going to be a difference, it will be in the way the arm processes vibrations, and this would be audible as mistracking. Again, if it is below a threshold, then the change will be inaudible, too. But rather than deduce this, I think it will be easier and quicker to just try it out.

(Apologies in advance, if required.)


Golear, I believe that you misinterpreted part of my response. When I asked you convince me as to the "why", this was merely a request to elaborate on your theory as to why you believe that moving the c/w will have an impact on sound base on your "node and/or anti node" comment.

Your 3rd paragraph supports exactly what I have been saying all along. Changing the c/w mass and location changes the arm’s effective mass which changes how the tonearm will interacts with the cartridge’s compliance. Tonearm effective mass combined with the cartridge’s compliance can be easily calculated to determine compatibility, therefore, eliminating much of the need and expense of cartridge/tonearm compatibility trials and error.

Sorry if you thought I was being argumentative. I seek to learn also.
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Re: Counter Weight Question

Postby Golear » Wed Jan 09, 2019 11:41 am

Hi Brf

Thanks for your reply. You're right, I did misunderstand. So apologies in advance were very much in order!

We are in agreement about the counterweight. This thread was very helpful to me, as I had not thought of a heavier counterweight lowering the effective mass. My feeling, though, is that there could (and I stress "could") be a difference in the way vibrations from the stylus are processed by the arm. This is, of course, different from the cartridge/arm resonant frequency, which depends on cartridge compliance, tonearm effective mass.

The stylus moves in the groove, and produces a lot of mechanical energy that has to be channelled via the cartridge body, bolts, arm tube, bearing and base, into the turntable itself. There's a fair bit of energy here - as you found via your experiments on how much load should be put on the Dual Pivot.

I wouldn't ignore the counterweight when it comes to the vibrations. I think some people have reported better sound by using the half-moon shaped counterweight. This is a very different shape, and I think is made of brass (or bronze?). That was all I was trying to say. As for why that counterweight might sound different - I don't have any good info. May be it's the mass, may be the material, may be that it happens to be at a node for a particular frequency of vibration which happens to help the cartridge.
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Re: Counter Weight Question

Postby Mr_Putty » Thu Jan 10, 2019 1:55 am

Re: Counterweight effect on sound. I am of the opinion that the weight arm interface is important. My 3D arm and VPI weight has more clearance than desirable. That said, I found that a single wrap of blue painters tape on the arm was a good snug fit and improved sound. I also found I no longer needed the locking screw which I thought had negative effects in my particular setup. ( the screw adds a pressure point to the arm which I think makes it less “relaxed”) I also use two spiral wraps (not layered) of Friction tape on the arm tube. I know this seems weird but visually it’s barely noticeable. I have been using this combination for several months so I am pretty confident in the sonic benefits. Brf s comment about effective arm mass has me wondering if I stumbled on an improvement because of that as well. One of my speakers is close to my TT (no other option) so maybe the tape is just adding some needed dampening? In general I agree with Golear about arm resonant importance in a system to get the most performance. Or maybe it’s nonresonance of the arm integration that is more revealing to music.
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Re: Counter Weight Question

Postby Brf » Thu Jan 10, 2019 10:48 am

Good discussion.

Tonearm resonance is an important factor when designing a tonearm. One of the main reasons VPI went with the 3D technology is that it provided superior (across all audible frequencies) damping when compared to their metal arms.

I remember a while back, VPI’s electrical engineer Mike Bettinger posted frequency spectrum plots of their 3D tonearm (plot posted below). He used an out of phase motor to generate various vibrations that were picked up by the cartridge itself, thus duplicating a more real world experience.

The plot below is very flat with little amplitude. This demonstrates that when the tonearm is presented with a parasitic frequency, it dampens (reduces) the oscillations in the tonearm/cartridge system and dissipates/decays that energy after a disturbance as quickly as possible without coloration (addition or subtraction).

In addition, tonearm designer typically place more emphasis on resonance control/damping from the transducer to the pivot/bearing than they do aft of the pivot/bearing. This is why you will see some manufactures offer various arm wand materials, shapes, etc. to appeal to a wider compatibility with cartridges of varying weight and compliance. The shape of the c/w will have more an affect on the mechanical function of the tonearm i.e. tracking etc. Some users have reported favourable results using the after market half moon under slug c/w.

Having said the above, tonearm designers are attempting to produce a tonearm that is neutral as possible. Just like a well-prepared filet minion, prepared by a world-class chef, some users will still season to taste, and that is where audio tweaking comes into play. In the end, the only person you need to satisfy is your self.
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Re: Counter Weight Question

Postby Golear » Fri Jan 11, 2019 1:37 am

The good thing about VPI equipment is that the tonearm and turntable come from the same manufacturer so we can expect a good match between the two. However, there are many different cartridges out there, and each will interact with the tonearm differently. So some adjustment, to taste, may be in order.

And very interesting discovery, Mr Putty! I think you provided a very good example for what I was trying to say. I had not thought about some tape between the counterweight and the armtube. When my arm was set up by my dealer, he mentioned that he had torqued the counterweight screw quite tightly. So I guess he had noticed that the screw was impacting the sound, too. This sort of thing would need to be figured out by trial and error.
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