Is a Garrard 401 or 301 "accurate"??

Can you define "damping factor" as it applies to materials of which you might construct a plinth?  I can't imagine there is any single value that would describe that quality except if it has specific reference to a single frequency or set of frequencies, and perhaps other elements of the definition as well.

I use a source of information that has been a reference point within the HiFi community for many years, it is used both by Professional and Amateurs to extract information.

I have used the resourcefulness of the producer of the information further and they have received materials I am using and New to them for testing.

I have made it one of my goals to become quite familiar with materials used for Plinths that are described as having optimum damping, and the result is that I have become very impressed, and have moved away from the Massey Plinth Designs as the mounting methods.

I am keen to maintain the experiences had from being demonstrated the materials with a obove optimum damping measurement, hence my having access to Densified Wood and acquiring a supply of Permali and Panzerholz which carries a considerable expense.

The Polybentonite Resin is in my view a Massey Plinth Design, when produced it has very high measurements compared to other Massey Materials, the Resin measures above optimal damping, but the sonic is different from Densified Wood.

To put a further perspective on the above Materials that are with High Intrinsic Damping, when compared to other regularly mentioned materials such as Slate 0.017 and Aluminium 0.004 it can be seen the divide in the measurements are quite vast and the stone and metal fall way short of optimum damping.

The following is the words of the technician who produces the testing and recording of a wide variety of materials:

When a sample of material is struck, it vibrates, the frequencies at which it vibrates is dependent on its dimensions, its stiffness (Young's modulus), density and how much it deforms when compressed (Poisson ratio).

How long it vibrates for is a function of its damping factor. Have a look at the trace below. My three axis accelerometer was taped to this material, and struck. The sound was captured on a computer, and recorded using Audacity software. You will notice the rate of decay is quite well defined, fast at first, and becoming asymptotic towards the end. The damping factor is calculated by looking at successive peaks, and measuring their heights from the zero line. This gives the 'log decrement', and from this the damping factor is calculated.

The damping factor, Greek letter eta, n , is a dimensionless number which represents the amount of intrinsic damping a material has. The property is like density, it is irrespective of other properties, including dimensions.

 

A material with a damping factor of 0.07, or above, is said to be damping, above 0.1 and it is a good damping material, and as the damping factor is twice the ratio of its damping compared to critical damping, a value of 2 represents critical damping. Most materials encountered in hifi products have a damping factor between 0.01 (or below) and about 0.2, so they are well below the critical damping figure.

 

The trace below shows how a slate tile rings for about a second, when struck, (and they say it makes a good plinth material). Its damping factor is 0.017, very poor!  Amplitude up the y axis, time (seconds) on the x axis.

    

   

@pindac A slate tile is not the same as a 40kg 50mm slab of Pennsylvania state!

The trace below shows how a slate tile rings for about a second, when struck, (and they say it makes a good plinth material). Its damping factor is 0.017, very poor!

Interesting. A few months ago I asked Pindac to define "damping factor" as he applies it to materials used for plinth construction, especially slate, which he dislikes for reasons obvious in the above 2022 post. In the recent exchange he declined to provide the information that he did provide above. Perhaps he did not recall quoting that paragraph describing experiments done by an engineer. I have a dog in the fight, because I own three turntables housed in slate or slate and hardwood plinths. First, I would not argue that panzerholz and the like materials may be superior to slate; I have no way to argue that point, because I do not own a Panzerholz plinth. Albert Porter does or did own an SP10 MK3, like mine, in Panzerholz, and he at least used to sell plinths to others for SP10 Mk2 and Mk3. I have high regard for Albert, so I don’t doubt that P’holz is good.

My thoughts on the experimental results described above are that this may be a classic example of over-interpreting data. Like you said, Noromance, we don’t know much about the slate tile that was used in the experiment. And both of us (apparently) are using very thick (50mm for Lenco and Denon DP80 and 65mm for SP10 Mk3) and very heavy pieces of slate. The engineer says his version of "damping factor" is independent of dimension, but he needs to do an additional experiment to prove that point; I find it hard to believe at face value. In addition, "slate" from different sources is different in density and hardness; Pensylvania slate used by OMA and us is different from slate sourced on the Euro continent; I don't know where the engineer did his work. Another point is that slate is a layered form of stone, so its "damping factor" is likely to be quite different if measured in the plane parallel to the layers vs a plane perpendicular to the layers; this factor is not investigated. In a typical plinth, the layers of a piece of slate are likely oriented in the plane of the TT bearing, where the capacity to absorb vibrational energy is maximal. And finally, who goes around striking a plinth while an LP is in play? I will add one observation: This is completely subjective, but I felt that the SQ from my SP10 Mk3 was slightly enhanced, when I added a base to the slate, composed of solid cherrywood and firmly bolted up into the slate itself, to provide some constrained layer damping. Also, I use the idea I got from Albert, damping the Mk3 bearing housing from below by a heavy metal block. Meantime, my Lenco and DP80 sound wonderful in just plain old slate, the Lenco mounted in the PTP top plate I bought from Peter Reinders.

Firstly, I don't need to do anything but I did. 

Secondly, My first venture into Alternate Plinth Materials with a intention to make a New Improved Design for a Plinth, resulted in my ending up with  9 Stone in weight Monolith Granite Plinth. A real feat  of One Mans expression of a Dominance over Nature. I'm Older and not so silly, well a little bit less, as the Back Screams at such ideas, where handling is still to follow. 

Thirdly, Not too far on in following years of having the Granite Plinth. The Engineer I refer to who carries out Materials measurements was becoming a contributor on a forum, and was becoming more frequent in being vociferous for using Polybentonite Resin as the material to substitute other materials used for producing Mass Plinths for a TT. As the main market for Mass Plinths both DIY and Commercial was aimed at Idler Drive TT's, the alternate ideas for Plinth Types got my attention. 

I would say it was at this time my interest in Plinth Materials took hold in a similar way mechanical interfaces on a TT Platter Bearing Assembly had become an established area of interest.. I would suggest I was beginning to recognise a TT / Plinth - TT / Chassis / Plinth as another mechanical Interface needing a careful condideration.  This has evolved over numerous years and many demonstrations of Plinth Designs being used., as well as rethink on how a TT interfaces with a Plinth Design. 

As a Mass Plinth alternative, I heavily rate Polybentonite Resin as a Plinth Material on a Idler Drive, there is something extra to the End Sound in comparison to a Mass Plinth. 

I also know of Polybentonite Resin users who have now adopted Densified Wood as their alternative material of choice. 

Additionally I have not too long ago strongly suggested a High Compression Bamboo Board used a Plinth on Garrard 401, when mounted on Densified Wood Sub plinths has been the best experience recollected of  being in the company of a 401 being demo'd. 

I ended up going down the Densified Wood route as a result of seeing the attractive measurements for Polybentonite Resin as a Plinth Material being Superseded with Densified Wood. 

I also at a similar time was being able to be demo'd my own 401 by the New Owner, in a selection of New Wood Based Designs, using MM Cart's on SME 3009 Tonearm with removable Headshells. 

All demon's using the non-Granite Plinths were more attractive as a end sound in the new owners system. 

Similar was also done with GL 75 vs my PTP Solid Nine mounted on Corian. There were Saucepan Style GL75's mounted into a bedding Co. Pompound on a Timber Design Plinth that was seemingly inseparable to the PTP. 

Hence Timber Materials become the main interest. Which led to Penultimately Compressed Boards  and Ultimately Densified Wood Boards. 

Moving over to a different  DD TT Drive Type, a OEM Resin Type Plinth, possibly having a Similar Function to a Polybentonite Resin?, has been compared to Marine Plywood, MU25 and Phenolic Resin Impregnated Wood Board  Densified Wood (Panzerholz}, using same TT >Tonearm > Cart' and Support Structure. 

I've done my footwork made my choices, initially influenced by a individual who publishes information on Materials and have also had other material types used measured for my own learning. 

The final choices made through a process of ilimination, where Traditional Mass Plinth Types, using Granite has been Superseded. 

Having experienced Resin Plinths as a Mass Alternative and Wood as a Mass alternative and Wood as  design to create a Structure with Cabinet Making Skills and adding materials to control energies, the use of Wood Superseded other option available. 

In the use of Wood for demo's  of Wood Types for a Plinth, the experiences had, showed a Wood Type claimed to have attractive properties for use as Plinth Structure proved the most attractive in use as a Board only serving the  Purpose of a Plinth.

This Phenolic Resin Impregnated Wood Board has also been the best Sub plinth Material experienced in use under a broad range of Audio Devices. 

Other experiments undertaken with this material has shown it's Value above other materials typically accepted to be used for the role. 

It is no surprise Brands of Wood Board such as Panzerholz or Brands producing a Wood Board as a very similar product are finding these products encroaching into Audio Equipment  use. 

Linn are the latest I know of using this Board Type on their latest $60K TT. 

My route adopted is much much cheaper as means to experience this material type. 

I have no discussion left on this material, I am only willing to share my experience and impression made.

I am an advocate of Densified Wood Board Material.  As a result of Trials  undertaken and Experiencing the material in comparison to alternate options.

For myself in all things Audio Related, Math alone is not the convincing influence for my choices considered to be made or choice made and realized.