Eminent Technology ET-2 Tonearm Owners

Slaw
"I do agree with Fremer that this (acrylic) isn't the best material for great transient response, tight, controlled musical bass @ realistic sound that I crave."

Interestingly, last night, I stumbled on the following comment re the VPI Scout 1.1 platter (Joel Salcido, TAS 40th anniversary issue): This one is Not acrylic and to hear Harry (Weisfeld) tell it, acrylic platters are a thing of the past. It's simply easier to machine metal to tighter tolerances, and the fact they sound better ices the cake.

Back in the Goldmund days, I understood their acrylic platter was for optimum impedance matching (with vinyl). Life moves on huh.

Slaw
"I have to say that as regards to using acrylic as a platform for the vinyl record ......"

Further reading, TAS 40th issue.
Wayne Garcia on the new Rega RP8:

"Most notable is a two-piece, 16mm thick flywheel platter made of float glass, a technique wherein molten glass is Floated over molten tin in order to create the flattest possible surface and overall uniformity of thickness. To form the flywheel platter, Rega joins two separate pieces of float glass to the underside .... adding mass to the circumference.

Damn marvellous I say!

Yes, some interesting materials and ideas being used in platters these days. Isn't VPI also making a ceramic one?

Then the Clearaudio, in their Statement and Basis are using plastics.

Take your pick.

John I have owned 3 regas........all digital

Planet, planet2000, my current Saturn of 8 or so years ?, is one of my current digital players.
It sits on 3 symposium rollerblocks

Rega was one of the last companies to enter the digital world.

So I guess I like the company but I have no experience or knowledge of their analog items.

The RP8?

how do you put an ET2 on that ? :^)

I imagine TT designers trash many prototype materials before arriving at what they choose for their product. It should be a requirement imo, especially for some of the higher priced tables to understand the room/gear used to arrived at a turntable design.
This should be published information.

Regarding building turntables and materials used.

Here is a list of materials along with a number beside them. The number indicates the materials ability to pass thru sound (a high number) or hinder sound (a lower number).

The higher the number allows a better pass thru of sound. the lower number deadens, inhibits, absorbs.

Material Z0 [MRayls]

aluminium.........17
brass.............37
copper............42
cast iron.........37
lead..............25
magnesium.........10
steel.............45
tin...............24
tungsten..........101
araldite..........4-13
brick.............15
concrete..........7-10
glass.............10-15
granite...........27
marble............10
slate.............12
all plastics......1-4
all wood..........1-4
except cork.......0.1
carbon fibre......30

This data is informational only and was taken from this site.

http://qualia.webs.com/plinthbuilding.htm

"Another property of materials is the acoustic impedance, that is, how easily sound passes from one material to another. Nearly all the data available is concerned with supersonic frequencies of sound, typically 5 MHz, so not really useful in the audio range. However, it does suggest that getting sound from one material to another seems to be dependent on their respective acoustic impedances, easily calculated as:

Z0 = p x c where Z0 is the acoustic impedance, p is rho, for density, c is the speed of sound through the material [longitudinal wave velocity]
Some acoustic impedances of common materials: Z0 in N•s/m³ /106"

So to transfer sound from one material to another effectively may mean using materials with similar acoustic impedances, or, to hinder transfer, (as in isolation), choosing materials with very different acoustic impedances.

What about rounded edges for the plinth/armpod materials themselves over straight edge; to better deal with resonances? This is done with speakers.