[neobop]

"I believe the benefits of potting are due to an increase in the amount of energy that is transferred from needle to body being converted into heat (ie: damped)
The possible negatives with this approach: - the energy that is not converted into heat is returned to the cartridge body, at an altered frequency (refracted) - and usually with a lower amplitude (as part of the energy has been converted to heat) - if the new frequency(ies) is more easily drained off by arm/plinth then thing go real well - but if the new frequency(ies) happen to coincide with a resonance of the arm / headshell / etc... then it may make things worse..... this vibrational stuff is NEVER SIMPLE!!!"

Never looked at it like that.  The potting is in the cart body so vibrations are already there.  The potting material helps keep part of the generator or connecting wires from being affected by the vibrations. This excess mechanical energy should be transferred to the headshell and not reflected back to the generator where the potting material is anyway.  In my limited experiments with potting, it didn't seem to affect the frequency response (although I didn't take measurements) more like focus, and I shudder to use the phrase blacker background.

"The problem is not necessarily the wasted energy... the problem is that the energy drawn off from the signal is not flat in frequency - some frequencies are absorbed more than others.
So the signal then leaving the generator has been altered by the non linear frequency losses."

Once again, isn't this a cart design consideration with excess mechanical energy being predictable or revealed in testing?  Potting MCs has been going on for a long time and is generally considered beneficial and not altering FR.

For those who didn't notice, I edited my post a few back and added a link to an interview of Pierre Lurne.  He talked a lot about energy dissipation and after manufacturing a linear arm, switched to unipivots.  We haven't quite gotten there yet, but his opinion seems quite different from John's.
neo

[dlaloum]

I was actually covering a number of bases shotgun style!

If you look at the latest Ortofon cartridges, one of their primary focuses is damping at the cartridge level... for the 2M's they use damping body compound materials (not to mention the more exotic anna and expression, etc...), but look also at their latest top of the line headshell, the LH10000... an S shaped curve of soft "thermo-plastic elastomer" (sounds like sorbothane to me? - but could be any of a wide range of similar compounds) is embedded in the top of the solid Zinc/Aluminium alloy headshell - clearly not designed for the low mass/high compliance end of the spectrum, although at 14g it is not extreme in its mass.

With regards to potting - yes it minimises wire movement and therefore associated microphony effects - but most of the type of compounds used for potting are also very effective dampers...
The vibrations entering these "softer" materials get reflected and refracted around, and in most cases these materials also tend to convert a larger part of the energy to heat than does the base cartridge body. At areas where the two materials interface there is also shear effect that works to convert further energy to heat.

What magnitude is the damping effect, and what magnitude is the microphony effect? - I am not sure... that would need another study by someone. (I expect it has already been done!)
Based on plinth design principles with differing materials, constrained layer damping principles etc... it is clear that damping would be happening here - and that the effect could be quite substantial at the scales and levels of energy involved. (I suggest visting "cats squirrels" website - http://qualia.webs.com/ he has put together an absolute wealth of information on materials, their properties, how they work in conjunction with each other, and has done extensive measurements of different materials and their behaviour with sound frequencies...)

But this is no mystery - the reason the upper end Clearaudio cartridge MM bodies are fitted with wooden mounts/surrounds is this exact same effect - the wood acts as a cartridge body damper.

Another area of tweaking/moding and optimising - matching cartridge mount materials to headshell materials allows the vibration to transition most easily from cartridge to HS - allowing the HS and Arm to therafter have a greater role in damping the parasitic vibrations coming from the cartridge.
(If the problem is vibrations coming up the arm through the headshell to the cartridge, then you would aim for differing materials and isolation to keep the cartridges vibrations in the cartridge and the arms vibrations in the arm...)
All those who are proponents of tightly bolted/coupled cartridges to headshells are doing exactly this - and for this type of setup, a metal body and mount is usually the preferred construction - so an AT150 body rather than an AT100/120/440 body (as one example) - on the other hand if the headshell is carbon fibre, delrin or some other "plastic" compound, then the AT100/120/440 bodies may be better...
Remembering that all this does is allow the vibrations an easier path out of the cartridge - they then still need to be damped, absorbed and/or handled in some other way.

Wooden headshells are another solution - this is the same as the wooden mount CA cartridges - but the damping wood is now in the headshell - people who have experimented with this find that certain types of wood work better with particular cartridges.... which is easily understood given that differing woods having differing damping effects - not just in terms of amplitude but in terms of frequency.... so where one gets a good match of maximum damping amplitude at the frequency that the cartridge puts out the most energy, one gets an optimum headshell/cartridge interaction.

The real charm of these solutions (headshell, cartridge potting) - is they cost almost nothing, and can relatively easily be applied to even the most economical cartridges with audible results....

Much (90%?) of the difference between a budget or mid range TT and TOTL reference tables is down to the work down in the area of vibration control.

The reason there are so many postings, threads, etc... with regards to plinths, turntable mounting, feet, isolation, arm damping etc... etc...  is that in fact many of the vibration control solutions are relatively easy to implement and relatively cheap (in terms of materials)....
But it does take a bit of ingenuity to pull it all together well - and it is very difficult to get really good results without measurement.

Not only that there are an infinite number of possible  effective solutions to the same problem - lots of scope for creativity.

bye for now

David

[Wayner]

Wood dampens things? Maybe, but my Martin guitar is made from wood and it projects sound very well. I think the more important quality of wood is that it doesn't have any resonance frequencies.

Wood is great for cartridge bodies. It's relatively inexpensive to buy, it available almost everywhere, it's a renewable resource, it's non-resonate, it has great machining qualities, and it's an insulator.

The wood arm on my Martin doesn't stop any frequencies. I have a tuning device called a Snark that clamps onto the head of my guitar, that can easily pick out frequencies and, with the help of a LCD display, tune my guitar perfectly.

Wayner

[neobop]

Wood is a preferred headshell material because it doesn't resonate or transmit vibrations like metal, and it's rigid.  Quite different application than the body of a guitar or violin which is a sort of speaker box/sounding board for the instrument.

This is the last of that post on page 2:

"Tonearm Bearings and Coupling

A very important aspect in coupling is giving the energy somewhere to go, and an easy way to transfer it. We all know how things in nature tend to take the path of least resistance. Rivers do this. We all know about this in electricity and electronics in general. The same it true for mechanical energy. In tonearms we want the energy from the cartridge to go somewhere else or simply go away. An important way to accomplish this is by making sure the pivot or bearings be able to transfer the energy down into the mounts. The simplest most direct way to do this is by having rigid bearings (and enough of them) to transfer energy efficiently. However it must do this while offering the least amount of friction in the pivot. This can be difficult. The standard four point gimble bearings is the best type for transfer of energy, however they offer the highest amount of friction. Conversely, Uni-pivots offer the least amount of friction, but are very poor in transferring energy since all that energy must pass through a tiny single point.

So now this begs to ask a question that nobody seems to ask. Which is more important, friction or energy transfer? The answer is clearly energy transfer. Why? Let's look at some basic physics. Uni-pivot bearings are essentially a single point that is held in place by the force of gravity. The actual bearing point of contact is extremely low in mass, relatively speaking. This presents a difficult path for energy to travel through. So, what happens when energy is presented with a high mismatch such as this. Well ... a small portion does get transferred through the bearing. What is left over gets reflected back; to its source which in this case is the stylus. Oddly, this same energy after wiggling the stylus a little bit, now reduced slightly more, gets reflected by the stylus back down the arm again. Back and forth, again and again, until the energy finally does get dissipated by the mass of the arm. In physics this is known as a standing wave.

Now when we look at this mathematically we discover that the difference in friction between the best uni-pivots and the better standard four point gimble designs works out to be about 1% in frictional drag differential. The friction is so low in both designs as to have no negative affect in the working of the arm. However, the energy transfer differences can be as much as 40%, depending on how much damping is used in the uni-pivot design to kill the standing wave. And it is this standing wave of unused energy that creates unnecessary resonances and vibrations in the stylus that do have an significant affect on music.

This is not to say that uni-pivots cannot be designed in such a way to minimize these affects. Bob Graham worked on mitigating these problems for decades and seems to have tackled most of inherent problems in damping these standing waves and making a great sounding uni-pivot. However IMO, all these features that have made his arm famous are designed to correct inherent flaws in the uni-pivot concept. His designs works, but they are much ado about nothing. The problems he solved are problems that simply do not exist in other types of arms, only uni-pivot. The work would have been unnecessary had a more standard bearing design (nearly as frictionless with modern machining techniques) been employed.

There are also designs that employ both systems. These are commonly known as dual pivot designs. Basically you have a uni-pivot for your horizontal plane and a standard gimbled bearing for the vertical. Some designs have this reversed. It should give the best of both worlds, lower friction and reasonably good energy transfer. Origin Live uses this system. It seems to work well, IMO.

It should be pointed out that uni-pivot bearings are very easy to make. They also have very low production costs when made in the numbers for commercial distribution. I suspect this is why they are becoming so popular. However, Uni-pivot needs corrective solutions (which include more varied issues than what I so far have mentioned). If these corrective solutions, like those used in the Graham Phantom II, are not utilized then these uncorrected arms do not perform well. The truth is a standard gimbled bearing arm, made well, will outperform a uni-pivot that lacks sophisticated corrective technologies.

Mass, Materials & Physics - A Small Treatise on Absorption

The use of high mass to absorb energy is a well understood fact in physics. The choice of materials that have the right amount of mass and vibrational resistance for a particular type and magnitude of energy is an engineering science, to say the least. In current table designs the physics of this are just apparently being ignored in a vast amount of the designs being offered. However we hear phrases like "massive platter" or "high mass sub-chassis" or "massive bearing" bantered around quite a bit. All the while implying some amount of control over vibration and resonances. When one actually analyzes the materials and amounts of mass being employed, this control is simply either ineffective or inadequate. Some designs do it right.

We have looked at both coupling and damping and explored ways where one can create the other. The two are intrinsically connected in fact. When dealing with energy in turntables the two must always be given equal importance. One cannot control vibration simply with coupling, nor can damping be used exclusively. Mass can do both, it can transfer energy and it can dampen it. But not always at the same time. The choice of material and its inherent properties must be chosen for its combined coupling vs. damping properties. And this based on the function as well the interpretation with a given design aspect. For instance, if you want a plinth that absorbs energy, you simply could use a great deal of mass. However, in this case mass alone involves a surprising large mass to do the job. Large blocks of granite weighing in the high tens of pounds for example. Incidentally, in plinth designs in non-suspension turntables using MDF, the amount of mass required to absorb the same amount of mechanical energy as a block of granite weighing 40lbs works out to be about 240lbs of MDF. Imagine your Rega or VPI weighing in at 250lbs! So you get the idea.

So high mass cannot be seen as some panacea for energy absorption. From a practical perspective very few of us can live in our homes with turntables massive enough to be vibration and resonance free due to mass alone."

It's interesting to note that Pierre Lurne has the opposite view of unipivots.  He has a degree in physics.

"It's the same in tonearm design. An important point of the design is that you must have a path for the vibrations in the arm. I used a unipivot bearing in the Model 1 for that reason. You need to choose a single path for the vibrations to leave the system, in effect to be grounded to earth. If you have two points, it is possible for the vibrations to return by the other one. With just one point, you have a mechanical diode; you say to the vibrations ~'go that way.' And you can then start to control what is happening in your system."
neo

 

[Wayner]

Wood is a preferred headshell material because it doesn't resonate or transmit vibrations like metal, and it's rigid.  Quite different application than the body of a guitar or violin which is a sort of speaker box/sounding board for the instrument.



Did you even read my post? The neck of my Martin guitar is made of maple, and it transmits vibrations the beat hell, hence, the Snark works very well determining what frequency it "feeling", so your transmission theory is out the window. The "doesn't resonate" thing is also iffy, as it depends on how thick the wood is. I said wood doesn't seem to have resonance frequencies (and then the harmonics of them).

Making a headshell out of wood is also an "iffy" idea to me, as wood can expand and contract with temperature and the density may change with humidity changes.

Pretty non-convincing.

Wayner

[neobop]

"Did you even read my post? The neck of my Martin guitar is made of maple, and it transmits vibrations the beat hell, hence, the Snark works very well determining what frequency it "feeling", so your transmission theory is out the window. The "doesn't resonate" thing is also iffy, as it depends on how thick the wood is. I said wood doesn't seem to have resonance frequencies (and then the harmonics of them).

Making a headshell out of wood is also an "iffy" idea to me, as wood can expand and contract with temperature and the density may change with humidity changes.

Pretty non-convincing."

Did you read my post?  I said it doesn't resonate or transmit vibrations like metal. 
neo

[Wayner]

By the way, if your going to post pages and pages of some bla, bla, bla by "some dude", I believe it would be nice if you referenced the author.

Just sayin'

Have a nice day.

Wayner

[Jeff K]

I followed the V.E. thread when it was current. The OP started out saying, in so many words, that he was the smartest person in the room and was going to set everyone straight. At least that was the impression it gave me. Nevertheless, it was a very interesting read.

Some other very smart people then began to question some of his assertions. John's last post was June 19, when he indicated he was off to prepare his next post. The thread continued for a few weeks with posts by others with mechanical engineering and practical backgrounds with equally compelling arguments.

I'm still waiting for LeVasseur0's next response.   

[dlaloum]

Wayner,

leather is a great damper, and stretched across an open container, becomes an excellent resonating surface ... (aka old fashioned drum!) the two are not mutually exclusive...

Wood panelled rooms tend to be quiet - well damped - as the wood panelling absorbs sound....


Wood has a number of interesting properties - Directional fibres - this leads to differing  speed of sound when moving with as opposed to across the grain, also the differing density of wood within the fibre (dense) and between the fibre (less dense) also makes for interesting properties....

As waves traverse the material across the fibres they need to enter and exist differing densities of matter - each of these interfaces causes heat generating shear effects which absorb a small part of the energy, energy travelling the other way - along the fibre - does not need to traverse material boundaries and therefore travels both faster and more efficiently.

If you look at many wooden plinth building designs, you usually see laminated layers with the wood grain in each layer placed across the previous one to maximise the damping value of the wood. (at its simplest, two layers at 90 degrees to each other, more complex setups will have a range of differing angular differences as it goes down layers)

The differing densities and other material properties of different wood types also provides further scope for adjustment.

Instrument makers use these same properties to enhance the resonance of an instrument - the direction of the grain in an instrument is essential to its sound, as is the type of wood used....
A solid bodied guitar has negligible sound (without amplification) when compared to a traditional resonating cavity design - yet they are both wood - resonating cavities are best avoided with turntables, unless you want them to act as a musical instrument!

With regards to the author of the substantive quotations - his name is in the title of the thread...

bye for now

David

[neobop]

This thread was started specifically by xsb7244 about the thread on VE.  There's a link to it on page 1 of this thread, a few posts down.  On VE turntable forum it's now around page 16.

Given the subject matter I don't think it's inappropriate to quote the body of the posts, and it saves everyone the trouble of finding/sorting it out.   I think much of what he says is right, but like the unipivot opinion, some is obviously controversial and IMO, wrong.  It is a good basis for discussion though.

To be honest, I find the interviews with Pierre Lurne more interesting.

http://www.stereophile.com/interviews/pierre_lurne_audiomecas_turntable_designer/index.html

http://www.enjoythemusic.com/magazine/manufacture/0208/

http://www.tnt-audio.com/intervis/lurne_e.html

neo

[xsb7244]

I read about Pierre Lurne.  He made some outstanding stuff.  How do you contact him?  Where is he? 

[neobop]

Somewhere in France I suspect.  His name is actually Lurne'.  His company is Audiomeca, and seems to be unreachable lately. 

The last project he worked on was a CD transport that was talked about in the magazines a few years ago.

neo

[Wayner]

I just think it's proper to always recognize the author of a quote (probably a legal requirement as well) otherwise some may think it's plagiarism. Enough of that.

Sure, wood is probably better then concrete or even sheet rock as buffer for a room, but that's a different application then using it for tonearm components. There have been several wood tonearms, like the Grado for example, and the current Marantz has an ebony arm, but it doesn't get that good of reviews, and the Grado arm is all but extinct.

And then to top it all off, the old cheapie AR-XA(XB) turntable, with it's aluminum arm and cheap plastic head shell probably can sonically beat a very expensive VPI table. This is where theorys by PHD guys gets all muddied up. The AR table is almost a contradiction of everything discussed here, but there it is (properly set up of course), playing records like it's nobodies business, pissing off some PHD guy cause it's not supposed to sound that good.

In our world of infinite possibilities, there is more then one way to "skin a cat". Like in the show, the Big Bag Theory, they like to "do the math" on stuff like this, and good for them. But in another, more practical way, others like the real world of trial and error. While this process may take longer, the results can have big rewards.

Wayner

[RSG]

There are several companys that use a wooden armwand in their designs, Teres (Illius), Durand (Talea), and Schroder (Reference) come to mind. I have heard the Schroder and it is one of the most musical sounding tonearms I have ever encountered. My table is made entirely of exotic hardwoods, both the base and the platter, but caries a more traditional arm/cartridge (Origin Live/Shelter). I would love to hear one of these wooden arms on my table but I am quite happy with my current rig. Also, I could not afford the upgrade  .

Cheers,
RG

[tomytoons]

The Marantz Satisfy tonearm is NOT wood, although they do make one.
"Anodized (black) Aluminum Straight Type Tone Arm" From the description on the site.
I looked close at that that table when purchasing. The reviews were good. That table has been out for some time noow without changes.
Nice table for the $$$

Sorry for the off topic just a correction.

Pete Riggle's arm looks interesting though.

[Wayner]

The Music Direct catalog says it's ebony, "a sophisticated ebony tonearm" found on page 11.

Sorry for the correction on the correction. And the table has not always received good reviews.

Wayner

[woodsyi]

The Music Direct catalog says it's ebony, "a sophisticated ebony tonearm" found on page 11.

Sorry for the correction on the correction. And the table has not always received good reviews.

Wayner

From what I can gather, there are aluminum and ebony versions of the Satisfy arm.  The Marantz Satisfy is aluminum but Clearaudio does make Ebony Satisfy arm. 

[Wayner]

I'm just going by what the catalog says. It's really not important to the discussion anyway.

Wayner

[woodsyi]

It's really not important to the discussion anyway.

Wayner

I agree. That's why I wanted to put it to rest. 

[dlaloum]

I just think it's proper to always recognize the author of a quote (probably a legal requirement as well) otherwise some may think it's plagiarism. Enough of that.

Sure, wood is probably better then concrete or even sheet rock as buffer for a room, but that's a different application then using it for tonearm components. There have been several wood tonearms, like the Grado for example, and the current Marantz has an ebony arm, but it doesn't get that good of reviews, and the Grado arm is all but extinct.

And then to top it all off, the old cheapie AR-XA(XB) turntable, with it's aluminum arm and cheap plastic head shell probably can sonically beat a very expensive VPI table. This is where theorys by PHD guys gets all muddied up. The AR table is almost a contradiction of everything discussed here, but there it is (properly set up of course), playing records like it's nobodies business, pissing off some PHD guy cause it's not supposed to sound that good.

In our world of infinite possibilities, there is more then one way to "skin a cat". Like in the show, the Big Bag Theory, they like to "do the math" on stuff like this, and good for them. But in another, more practical way, others like the real world of trial and error. While this process may take longer, the results can have big rewards.

Wayner

Many Many ways to skin this cat! totally agree!

The downside to (pure) trial and error (as someone who has spent many an hour using T&E methods) is that it lacks a methodical system with which to eliminate possible solutions that are unlikely to work.

That is to say, working within a practical theoretical framework, with measurements, allows one to try something, and then based on the results, deduce that a whole branch of the trial and error tree is a dead end, and prune it from the next series of iterative tests - saving an enormous amount of time in the process.

Without the rigour of a logical structure system around that T&E, you can easily end up at the optimal end of a dead end branch of tests, thinking this is the best alternative, not realising that there is another easy alternative in a branch of experimentation that you have not tried (and one with possibly greater performance upside!)

I don't know whether my analogy is clear....

The point is T&E is essential, but so is a theoretical and systemic structure within which you use that T&E, otherwise you are playing the performance lottery, and each change is mere pot-luck as to whether it will be better or worse than the last. And without measurement you can also be trapped by the psycho acoustic fog.... something that sounds better in the evening may sound worse in the morning (when that single malt has worn off....).

The scientific method - hypothesis followed by T&E with methodical systemic measurement and notes has become the gold standard in all fields (outside theology) for good reason.

On the other hand, many people approach turntables as a form of religion, and far be it from me to interfere with your theology.

(an analogy here between flat earthers and flat platters is tempting, were it not for the fact that a non-flat platter really does not work very well...  )

bye for now

David