One turntable with two arms, or two turntables with one each - which would you prefer?

I prefer having 2 turntables and two arms over one TT 2 arms.

Why, because when I had multiple arms on one turntable I wiped out my Koetsu reaching over the back of the TT to lower the arm.

On the second TT I have a tonearm with headshell so it is easy to swap cartridges.

My main TT is my reference which I like to keep with best arm & cartridge.

I have built several TT plinths - here are my observations 

Panzerholz is not stable -it can warp and I would only use it in conjunction with another material that is dimensionally stable.

Granite - rings - no matter how thick.

Slate is ok, doesn't ring like granite due to its stratafied structure.

2 Materials that  I have had very good results with are

Engineered Stone ( high quality euro ) 95% quartz. Relatively easy to cut, you can source it cheaply from kitchen bench manufacturers ( offcuts ). Some have CNC facilities which makes it a doddle.

Compressed high density Bamboo ply. It is 50% more dense than Maple, and dimensionally very stable. I use this with my modified Garrard 301 and the result is exceptional. Even my mate with a Kuzma M/4point combo was gobsmacked when he heard my modded Garrard 301 with my compressed bamboo ply/birch ply hybrid plinth - medium mass, rigid, inert.

Beech B25 Panzerholz, are you talking about the same thing

Never used these words - have no idea what you are referring to.

I find that Pz warps only when left unsealed. Is your experience otherwise? Thanks!

Yes. Panzerholz is hard to get in New Zealand.

I purchased from the importer, checked the flatness of the raw material and found the sheets were not dead flat.

Basically I had to laminate 2 pieces, choosing adjacent material and inverting one so that when I laminated the 2 pieces the warp was eliminated. We are talking half a mm across 12 inches, but for me thats too much - I want the arm and bearing to be precisely on the same plain. And I would not want to machine the material flat and disturb the surface - hence the lamination process seemed the best option for me to resolve the warp issue.

Soundwise used as an armboard it damped resonances very well compared to my usual gunmetal armbands. for example it worked well with my FR64S, but these results can be very much dependent on the turntable itself and how the armbands are terminated. For example on my reference TT the armboards are terminated with a 60kg SPZ ( superplastic zinc alloy ) plinth that is as dead as a dodo - on this specific TT the panzerholz armboard is inferior to the gunmetal.

B25 was what I used.

The 40mm compressed bamboo ply I used was dead flat - really impressed with the quality and easy to refinish the surface if required. I used a 60ft bed CNC router used for yacht manufacturing and it knackered the cutter - its a tough material.

Very dead plinth the liveliness that the metal brings would be missed by some so balance is a key here. Its a valid point one must be wary of over deadening in this application where one surface meets another for preference.

or the deadness of Panzerholz could be missed.

My reference TT was specifically designed in the 70’s as an energy dissipation device.

The primary material used, SPZ, was a specially formulated engineering supermaterial, developed in the 1970’s in Japan for earthquake proofing buildings, that has superplasticity at room temperature - any vibration or energy between 10hz to 100hz entering the material disappears through grain sliding at a molecular level. It is no longer available - too expensive to produce.

The secondary material gunmetal is a high lead content naval bronze and was specifically chosen to encourage the transmission of unwanted energy from the arm to the SPZ slab with minimal backward reflection. Having a propagation speed of 2 materials close together improves damping ( sometimes referred to as bi-metallic damping ) and more importantly minimises backward reflection of energy at the material junction - in this case minimises backward reflection into the arm/stylus.

In layman’s terms the greater the disparity between 2 conjoint materials in terms of energy transfer and propagation speeds of any disturbances, the worse the damping and backward reflection is. Something to remember when you are combining different materials in a turntable structure.

Soft material like Panzerholz can absorb a lot of surplus energy, but at some stage that energy has to go somewhere, eventually the unwanted energy will be released in an.uncontrolled manner in terms of time - leading to a smearing of the leading edge in replay.

Ideally you really want a path to ground for the unwanted energy rather than a temporary sink.

I am also an owner of Manufactured Stone as a Plinth, which has the Brand Name Corian. 

Corian is about 1/3 resin 2/3 mineral.

Engineered quartz stone is 95% quartz  / 5% resin.

These materials are quite different. I would never describe corian as a manufactured stone.

@syntax 

Why are you posting here - this is the thread for those who think a bit of floobydust and magic material will turn their Thorens 160, Garrard sp25, Teac into the best TT on the planet - bar none.

Some wag here thinks panzerholz is hard - on my CNC machine it is so soft it cuts like butter. Engineered quartz cuts like butter too - these materials are epoxy in reality. 

But what do I know - I've machined, drilled, cut, tapped,  CNC'd both.

Corian was trialled by a few TT guru's back in the 80's and never took off. Maybe this is for the baby boomers who want the 80's back along with their bell bottomed jeans and paisley Viyella shirts.

Now compare this to $16000 pounds for a phono cable from LFD that has a lovely electrostatic inducing plastic shroud, big chunky metal connectors so those micro wires know what a real man looks like and contains an assortment of different wires based on listening over 30 years, and of course they can voice them for you - you can have Freddy Mercury on helium, or Dolly Parton sound like Nat King Cole - now thats a real audio high end product.