A Copernican View of the Turntable System

I'm sceptical about all this 'isolation' of the armpod that is being discussed?
Sound is transferred in only two ways:-
Structure-borne transmission
Air-borne transmission
In both these cases, we are interested in transmission in two directions......from armpod to tonearm and from tonearm to armpod.
With the tonearm mounting to the arm pod in the first instance, if there is any 'transmission' from the tonearm base, this indicates 'movement' in the tonearm base which is 'information lost' from the cartridge.
The aim of the tonearm is to have zero friction at the pivot point which means no transfer of any movement to the arm base. The arm itself must
be rigid enough to allow the cartridge to transfer all the stylus movement
to the tonearm wiring only.
In the other direction, the base upon which the armpod sits needs to be stable and immovable. The armpod needs to be 'decoupled' from this base (unless the base itself is acoustically decoupled and levelled) via spikes and the armpod must be absolutely level. With the mass of the armpod (at least in my situation) so large, any structure-borne transmission which somehow transmits across the spikes, is so small and high in frequency, that it is easily absorbed as 'heat' by the armpod.

With the air-borne transmission, please remember that the tonearm and the cartridge assembly themselves, are both directly affected by these same sound waves and are far more susceptible to vibrations (because of their more delicate masses) than the tonearm bases and armpods.
Again if one employs mass-loaded armpods, the amount of sound at varying frequencies which can be reflected and/or absorbed as heat is far more than that of any tonearm or cartridge.
If one wishes to employ a combination of dissimilar materials to counter the transmission of certain frequencies, I see no harm in that as long as visco-elastic ones which allow movement to occur, are avoided?

The above is simply my opinions based on the physics, acoustics and materials science with which I am familiar as well the 'in-field' experience of my Project. As usual YMMV? :-)

Dear Halcro, I can't see even one point in our texts that indicates any dispute. The armpod is by nature isolated once it is free standing & not attached to the TT chassis. Other than this isolation, not me, neither you we were willing to recommend any farther (ie: under the spikes' discs, or even in between the metal layers) as long as we can verify the ability of the shelf to drain the vibrations that intruding from air & floor, and also the effectiveness of the 6x1cm steel discs to drain the resonances coming from up through the spikes. But I feel that we must perceive the spikes as couplers. Theoriticaly we use to refering as decouplers all those viscoelastic materials that we want to avoid. I think as its going till now, this project is promising. Have you noticed any contradiction in the process so far ?

Dear Halcro, Thanks for the lecture reg. 'structure-and air born(sound) transmission'. This is done in the context of the arm pod formulation but, cause of the generality, must also apply to the TT's. We can see, so to speak, two
opposite approches: Raven, Brinkamann, Kuzma XL ,etc. on
one side and ,say, Thorens and Linn-LP12 on the other.
But the last mentioned use springs while the other don't.
Does and how 'mass matter' in this context? BTW this is a
kind of reformulation of my earlier question.

Regards,

Dear Nandric,
the "trumpet" attached to Thuchan's TAD-2002 driver was designed by me and I prepared the technical drawings to have it fine milled from one solid piece in a 3D-CNC-precision milling facility here in Bavaria.
It was not easy.
It is however kind of Thuchan's property now.
Furthermore it only works with the bandpass of his X-over, the TAD-2002 and within and in conjunction with the whole Bavarian Voice-system.
Nothing that can really be copy-paced and transferred to another speaker.
Cheers,
D.
post scriptum: Halcro is right - it shouldn't be all that problem to find tooling-facilities around any major city in europe or the US who can handle milling work on solid metal (or wooden ) pieces to create nice armpods.

Dear Geoch and Henry – thank you for providing very valid points for consideration. My current armpod has served its purpose - it was built to determine if this approach was valid. It was not expensive to make as materials are available and cheap where I live. I am ready to setup up the next one.

It can be done in stages and allow me to use at each stage. I enjoy the DIY approach so would like to continue this way - Thinking of a 4” diameter brass cylinder pod and to mount my Tonearm directly to the top of it with three steel spike couplers on the bottom. This would be the first stage.

I then would make a decision on whether to add a top plate of aluminum to the brass. I need to think more about what has been said here about this.

I was speaking to Bruce of Eminent Technology who informed me that my tonearm uses Cone Point Set screws to level itself to the base. These come in many lengths and diameters.

http://www.radax.com/store.asp?pid=15198

I could mount the top aluminum plate on the brass using the same approach. 3 of these screws close to the perimeter to level it. 2 or 3 bolts would then be placed “just outside of the footprint of the tonearm base” that it will sit on it to secure it to the plate. The plate would ride on air as well as the tonearm. Do you feel this air is an advantage or does it not matter ? Can I get your thoughts on this.

From a DIY point of view - It seems to make more sense if adding this plate to just have it touching the brass at specific touch points with the set screws and bolts and making sure no movement and it is rigid.


I did some research today on materials and pricing.

Metal Supermarkets is located in Canada, the US and the UK.

http://www.metalsupermarkets.com/MetalGuide.aspx?CategoryID=BRASS&ProductID=TUBE_ROUND&ProductSubCategory=360

Prices are for solid brass and SS armpod cylinders. Prices are in Canadian dollars.

4" diameter brass (360 grade) 4 inches high - $152.55 (16 lbs)
3” diameter brass (360 grade) 4 inches high - $79.91 (9 lbs)
4” diameter Stainless Steel 4 inches high - $94.81 (15 lbs)
3” diameter Stainless Steel 4 inches high - $59.71 (8.5 lbs)
3” or 4” (7 mm - approximately ¼ inch) brass top plate is about $10.