Sound Supports (tonearm plates and boards)

[MartinT]

If you remember, Marco, the funk platter on my deck did indeed hide the innards better than my prototype Mike New platter, despite the base plate being installed. Here's my arm plate reversed in the same way as yours:

[Audioman]

Ah, I see... Only problem then is that it may expose the electronics underneath the platter, and look unsightly.

It would depend on whether the 'skirt' of the Funk platter was deep enough to hide the 'innards' of the T/T, once it was raised by bearing base plate... It's one to ponder!

Marco.

Marco if you are settling on the Funk platter there is little point in the base plate as if I remember correctly it is there to strengthen due to the weight of the Mike New platter. As far as the plate orientation goes and from an engineering point of view the step up/down should make no difference.

I am assuming that either way the inner plate is bolted securely to the outer plate which is in turn bolted securly to TT top plate. Nothing is floating over a hole as you put it. Energy transfer from the arm will be the same. Also absolute rigidity may not produce the best sound depending on the arm design. This can only be determined by experimenting and listening tests.

[Marco]

If you remember, Marco, the funk platter on my deck did indeed hide the innards better than my prototype Mike New platter, despite the base plate being installed. Here's my arm plate reversed in the same way as yours:

Martin, can you explain better than me why reversing the orientation of the armboard that we both use on our T/Ts improves the structural rigidity of our respective tonearms?

I've tried, but no-one seems to be getting it

Off out for lunch now, chaps, to our favourite gastro-pub - laters!

Marco.

P.S One other purpose of Mike's bearing base plate was to give the bearing itself something more to 'grip' onto, and thus perhaps improve sonic performance....

[MartinT]

In reversing the plates, I did bond mine together and used nuts and bolts rather than just relying on the threaded holes as before. There is also the benefit of gravity holding them together.

However, most importantly for me is the fact that the arm collar/chuck now sits on a flat surface and is bolted up tight rather than via spacers. This I believe has made a significant improvement.

[YNWaN]

Martin, can you explain better than me why reversing the orientation of the armboard that we both use on our T/Ts improves the structural rigidity of our respective tonearms?

It doesn't.

On a more pedantic note; nothing that one does to the armboard can alter the 'structural rigidity' of your tonearm. The structure of the arm will be the same whether it is welded to a lump of titanium or stuck in a lump of cheese.

In reversing the plates, I did bond mine together and used nuts and bolts rather than just relying on the threaded holes as before. There is also the benefit of gravity holding them together.

Bonding them together will make a difference, but the effect of gravity is negligible in this instance (using nuts instead of relying on the threaded plate isn't inherently better unless one wishes to tighten the screws until the thread is stripped from the aluminium).

In either case, having the board one way up, or the other, will make no difference to the structure or the integrity of that structure. In fact it surprises me that anyone should think that it would.

[Marco]

Lol - yes, sorry, I should've said the structural rigidity of the armboard mounting arrangement, which in my experience is improved by reversing the orientation of armboard I've currently got.

In either case, having the board one way up, or the other, will make no difference to the structure or the integrity of that structure. In fact it surprises me that anyone should think that it would.

I'll show you what I mean when I come round next!

Marco.

[YNWaN]

No, Mark, there is a difference... If you look again at the above pic, you'll see that the inner ring now makes much more contact than before with the outer ring, and the whole armboard structure is more rigid, as a result.

Whereas before, the inner ring was simply 'floating' inside a big hole, mainly being supported by just the edge of the outer ring, which meant that the arm collar, supporting the tonearm, didn't have a rigid surface underneath it, rather just a big hole. It does have a rigid surface underneath it, the way I have it now

No Marco, there is no difference (except visually) - of that I am certain. I will try to explain:

The armboard is made from two parts - an outer ring that bolts to the deck (A) and an inner section that screws to the outer ring (B) - neither of these components have been altered. There is an overlap between the surfaces of component A and component B - this overlap is the same irrespective of which face of component A component B is screwed to. It might look like there is more support, but that is only because you can see component B overlapping component A; but the components are overlapping exactly the same amount if B is screwed to the underside of A as it is when it is screwed to the top side.

[Marco]

See previous post, dahling, we're going round in circles!

Marco.

[Audioman]

The armboard is made from two parts - an outer ring that bolts to the deck (A) and an inner section that screws to the outer ring (B) - neither of these components have been altered. There is an overlap between the surfaces of component A and component B - this overlap is the same irrespective of which face of component A component B is screwed to. It might look like there is more support, but that is only because you can see component B overlapping component A; but the components are overlapping exactly the same amount if B is screwed to the underside of A as it is when it is screwed to the top side.

Agree. Since they are rigidly joined by the same method, irrespective of which way up, they act as the same one piece for transfer of energy. So any energy from cartridge through the arm will be dealt with in the same way. Any difference you hear will be due to more accurate VTA adjustment.

[Mike_New]

Paul,
I think your observations actually sum up the totale of the argument.
However what has not been considered is that the two plates may not have absolutely smooth flat surfaces and most probably will not. Depending on whether the two surfaces are mounted under or over each other then the absolutely matching or touching parts of the surfaces will change. This may be what Marco is experiencing.

Given the excellent sonic quality of arms such as are now being fitted to the SL1200 to matched and indeed to take advantage of the vastly improved quality which my replacement bearing offers; it surely behooves us to examine the mounting for a new arm and to arrive at the most sonically convincing arrangement possible.

The production of a two-piece assembly makes for easier and therefore less costly manufacture. With the outer ring being a standard fitting, and the inner ring being quickly laser cut to the required arm specs and would be available for other turn tables.

With my SME single part copper arm board the mounting slot is actually shorter that recommended by SME, because I am able to optimize the location/angular-orientation, and size of the slot exclusively for use on the SL1200. This provides additional support for the very heavy and rigid arm column across the large hole in the arm well of the SL1200

For other quality arms I believe that the single-piece arm board machined for the specific arm is the ultimate way to go. Machining an inner depression in this board to lower the mounting point is not rocket science, but since it does imply a single-piece component specifically machined for the particular arm on a one-off basis, then the price is going to be a bit higher.