VPI 12" 3DR confirmed NO Carbon Fiber in design

Re: VPI 12" 3DR confirmed NO Carbon Fiber in design

Postby tom collins » Fri Sep 01, 2017 7:08 am

i did not buy either of the arms, but it seems to me that a gesture from the company of some type may be in order for those that bought the carbon fiber version prior to the confusion being cleared up. Just a suggestion.
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Re: VPI 12" 3DR confirmed NO Carbon Fiber in design

Postby Marc » Fri Sep 01, 2017 9:54 am

cbl117 wrote:This is marketing at its finest. I see no real improvement...only variation in noise floor.

Please keep in mind this is just showing the different resonances between the tonearm as requested from the forum. This does not show how each tonearm sounds in comparison to the others. I am having Mike write a more detailed response about the graphs. This way he can guide how to read them and what differences you should be looking for.
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Re: VPI 12" 3DR confirmed NO Carbon Fiber in design

Postby Mat » Fri Sep 01, 2017 10:21 am

Hey all, no marketing BS at play here, we couldn't do a gloss finish, it was not possible 3 years ago. With the Prime Signature it became possible and then requested. With enough requests it became the norm (actually you can request either or). Lets also keep in mind at this level we are at diminishing returns and we are talking about a $200 difference without factoring in the cost of the Nordost Reference wire so each improvement is not as head and shoulders different as the difference between a Prime Scout and Prime (or Prime Signature).

To put things in perspective, my Grandma just got into a car accident (she is fine) and the body work is projected between $200 and $300 but the paint will cost her $800 for a pearl gloss finish to paint a space that is smaller than one of these tonearms. And the finish doesn't do anything for the performance of the car she just likes it ;)

Both sound great, and sound better than without the finish. We have listened to the different arms/different finishes with the same wire and there are differences between each arm. This test takes out all of the personal listening opinions and shows the additional dampening provided by a finish, wrap, or gloss. This does not show the sonic signature or musical preference just the resonance of the material.

I hope this post and the measurements help clear this up so we can get back to spinning and enjoying our tables :)
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Re: VPI 12" 3DR confirmed NO Carbon Fiber in design

Postby MichaelBettinger » Fri Sep 01, 2017 12:50 pm

Hi all,
Marc has asked me to respond as there is some misinterpretation of what the information displayed in the graphs means. But first a bit of background about the test itself.

Any experienced audiophile that has auditioned various tonearms knows they sound different. The differences in sound has to be attributed to the various physical geometries and materials used in its construction.

When a record is playing the rotation of the record and the friction of the stylus in the groove supplies vibrational energy to the tonearm. Applying vibrational energy to any object will vibrate and resonate at whatever frequencies the physical geometry and the materials it is constructed from allow it to; regardless of the frequency of the energy applied to it. Best example: a bell. One hit to the side and it vibrates at a frequency related to its physical characteristics.

A tonearm will resonate (vibrate) due to energy being supplied to it by the rotation of the record and the dynamics of the stylus in the groove being transferred into the tonearm. This vibration is added or subtracted from the output of the cartridge during playback (normally at very low levels).
Our test involves supplying a known vibration source to the arm base. This is accomplished using the primarily 120 Hz vibration from a synchronous motor that is bolted to the base, very effectively transmitting this vibration to the tonearm through the uni-pivot

The test applies this vibrational energy to the tonearm while placing the stylus on an unmoving record there by constraining its motion. Any and all relative motion between the uni-pivot and the record is picked up by the cartridge and can be measured and is displayed in the graphs in a frequency spectrum form.

We have found this test to be a good approach in that it provides a clearer picture of the tonearms response without the effects of groove noise; warped surfaces; skating forces and more, induced into the output signal making interpreting the output quite confusing. Quite cool!

All of that said, what the graphs show is the sum of all energy being supplied to the arm. I am going to simplify here to keep us on the rails… First you see spikes at 60Hz; 120Hz; 180Hz; and 240Hz, all harmonics of the vibration source. These will vary in height based on the physical elements of the arm design (and by how the total supplied energy is distributed throughout the rest of the spectrum). Once again this is very simplified.

The thing to understand about these harmonic peaks (60;120; etc.) is that they are an attribute of the strong 120Hz vibration source and they are not really present at these levels when actually playing a record. During playback the vibration source is the rotation of the record, groove noise and stylus drag. The height of these peaks is not a solid quality indicator. In my experience the non-harmonically related energy present in the graphs is of more interest. Although the presence of the harmonics in the test and how they change depending on the arm is an indicator of sorts.

Two other aspects of the graphs I personally find more interesting. First is the sidebands peaks on either side of the harmonic peaks. You’ll note that these are more pronounced on some and reduced on other graphs. My jury is still out on these so I won’t comment much other than to say sonically the tonearms where these are minimized articulate detail better but I feel more experimenting on our part is need to clear this up.

The second item of note is the spikes rising from the noise floor between the harmonics. These I have found these to be related to the damping of arm. They subjectively correlate with an arms ability to resolve subtle decays, room reflections and the ability to sort more complex parts of dynamic recordings. Our interpretation of these is that the less spikes present and the more consistent the noise floor is, the more confident we are in the quality of a tonearm’s design.

To summarize: these measurements, and our interpretation of them, is that they are just one of the tools that we use to guide our tonearm and turntable designs. Applying these test indicates VPI’s growth in trying to quantify what our ears have been telling us over the years. We included them in this thread for the sole purpose of sharing them for you own interpretation and understanding.

As for any questions for me about any this, they will have to wait until next week as I am currently off of work for the holiday weekend. I have tried my best to avoid engineer speak and hope that my explanations help.

Regards, Mike
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Re: VPI 12" 3DR confirmed NO Carbon Fiber in design

Postby Brf » Fri Sep 01, 2017 1:47 pm

Letsmakeadeal wrote:Marc or BRF - Will you please explain what we are looking at here.


I am by no means an expert in this area, but I can try and help with how to read the graph and give some general impressions.

The graph is merely an amplitude vs. frequency plot. Amplitude is expressed in db which is a logarithmic scale based on orders of magnitude, rather than a standard linear scale. Mike used a 1kz test tone to create a repeatable reference point which is plotted as 0db on the y-axis. All subsequent measurements are referenced to 0db.

An out of phase motor is used to generate vibrations. These vibrations include various frequencies which are plotted on the x-axis of the graph.

Motor vibrations (frequencies) travel from the arm board, through the pivot spike, down the arm tube and then excites the MC stylus which creates an electronic signal which is feed to a broad band frequency analyzer. The output is then displayed in the graphs above.

I found Mike’s use of a cartridge as the transducer to produce an electrical signal to be both unique and interesting. My initial thought was why not use a piezoelectric accelerometer to read the vibrations that feeds the output to the broad band frequency analyzer? Mike did mention that his test and conclusions are subjective and based as much on experience and personal biases, therefore, I can only assume that Mike wanted to recreate a more real world resonance test that would include the mass of a cartridge and the compliance of the suspension, all combined with the tonearm. It should be noted that output results “could” vary based on the cartridge employed as the cartridge is now part of the tonearm.

What does a perfect tonearm resonance spectrum look like? The plot should be flat and consistent with little amplitude as possible. This means 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 addition or subtraction.

Based on my experience and understanding, the three graphs presented by VPI illustrates three (3) well-designed and well implemented tonearms. IMHO, the resonance peak at 120 hz can “possibly” be attributed to the pivot point bearing interface or a secondary harmonic distortion of the 60hz line frequency of the motor. Since we are talking about the 100-150hz range, the ear would have a difficult time discerning the difference in magnitude. Personally, I am not concerned.

From 225hz and up, all three arms demonstrate an on average of -80db flat response with very little change in amplitude. This means that the tone arm will not impart a sonic signature regardless to the frequency band. Using Mike’s Bell analogy, you do not want to see a resonance peak where a certain frequency is emphasized over the expense of the entire frequency band.

Which tonearm is the best? From the data presented, I cannot draw a definitive answer as I do not possess the technical analytic wherewithal to make an informed opinion, plus there are a lot of “other” variables than just resonance that determines a tonearm’s overall performance. BUT, after seeing the graphs, my perspective has changed. I was expecting the “reference” arms to demonstrate superior test results, but what I wasn’t expecting is how excellent the standard arm measured! IMHO, the reference arms deliver the results as expected, but the standard 12-3D over achieves.

I’ve owned a 12-3DR arm longer than most on this forum, and I can tell you based on my personal experience and listening, the 12-3dR is the real deal!
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Re: VPI 12" 3DR confirmed NO Carbon Fiber in design

Postby MichaelBettinger » Fri Sep 01, 2017 3:25 pm

Excellent commentary BRF. Just two comments.

I have accelerometers but find they do not recreate a realistic scenario nor do mine have the low level resolution needed for this type of measurement. The cartridge does create a more realistic test setup. Also the same cartridge (A Lyra Dorian) was used in all of the tests and the setup was consistent from arm to arm.

The second is that the 120hz peak is the primary vibration frequency of the out of phase motor and not due to a tonearm resonance, only affected by it. It will be the most dominant peak as it is the driving frequency.

And yes, all of the arms tested were excellent performers to start with.

Thanks for helping shape this into a more understandable form.

Regards, Mike
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Re: VPI 12" 3DR confirmed NO Carbon Fiber in design

Postby Johnny » Fri Sep 01, 2017 7:19 pm

Thanks Mike for the test results. I must admit, this subject matter is out of my wheel house and I want to express my appreciation to Brf for taking the time and effort to explain in lay person terms what we are seeing. He has a way of taking complex technical topics and explaining them in a manner that an accountant can understand :D

I believe that I now have a rudemenatry understanding of what the graphs present although I still don't fully grasp the "db" scale. Yes, this topic got me wound up as I just dropped $20k on the Avenger Reference and I was having second thoughts. My own personal conclusion is to stop second guessing the science and sit back, trust my ears, and relax. Thanks for talking me off the ledge.
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Re: VPI 12" 3DR confirmed NO Carbon Fiber in design

Postby teenage diplomat » Sat Sep 02, 2017 2:02 pm

What a read! Many thanks to VPI for doing this. Here are my takeaways, from a consumer's standpoint. First, VPI wasn't trying to sell snake oil when it offered a wrapped version of the 3D arm. Its use of the term "carbon fiber" may have been somewhat unfortunate, but not intentionally misleading. Next, the differences noted in the tests are small both absolutely and relatively. Moreover, they will vary with the cartridge utilized. Therefore, I wouldn't expect major audible differences to arise directly from the wrap. In fact, the resonant differences created by different cartridge body materials, suspensions, and styli almost certainly would change the overall resonant signature of the wrapped tone arm much more than swapping an unwrapped arm for the wrapped version while employing the same cartridge. As the owner of two first generation 12" 3D arms (integral finger lift, complex armtube shape - not constant diameter tube - Discovery wire) I feel no need to change. Having said that, I don't think owners of the wrapped arm should feel that they've been taken for a marketing ride - they haven't been. Just my $.02, YMMV.
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Re: VPI 12" 3DR confirmed NO Carbon Fiber in design

Postby JRM » Sat Sep 02, 2017 5:00 pm

brf,

What do you define as a standard arm, the regular JMW arm (non 3d)? Thanks,

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Re: VPI 12" 3DR confirmed NO Carbon Fiber in design

Postby Guss2 » Sat Sep 02, 2017 7:47 pm

JRM wrote:brf,

What do you define as a standard arm, the regular JMW arm (non 3d)? Thanks,

JRM

No offense , but this thread is about the 12" 3D arm.
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