A world first? Passive v active isolation platforms test
- Thread starter spiritofmusic
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I’m sure Jarek.
But isolation is one area where even I thought simple justification of going down to 0.5Hz would trump all alternatives.
If it was, the Minus K would have been the no brainer choice.
But isolation is one area where even I thought simple justification of going down to 0.5Hz would trump all alternatives.
If it was, the Minus K would have been the no brainer choice.
If you put the COG of your load at the platform's geometrical center, assuming equal air bladers this creates the same resonance frequency at each support. Although this seems nice and will create a nice feeling of very controlled vertical movement it creates a higher Q global resonance. Do you have different tuning in each chamber? I remember than long ago I tuned an Oracle with different springs using a resonance meter to 3.5 Hz exact in all towers. Although it bounced nicely it sounded a lot better when I detuned two of the towers +/- .3Hz !
Micro, one is free to control the pressure (and hence the resonance point) of each bladder individually.
Cheers
Jarek
Cheers
Jarek
Yes, but unless we are given tables we need some calculus and measurements to master it!
Thanks Jarek. Looking at the photo of your Stacore, it seems to me that the lone footer carries more load than the other two simply because of the way they are located within the platform. Are you saying that without a component on the Stacore that each of the three pneumatic footers is seeing the same load, that is 1/3 of the suspended platform weight?
Looking at it another way, if you were to place a ten pound load in the geometric center of the rectangular top plate of the Stacore, would each footer see 3.333 lbs of that load? It looks to me as if the single footer on the left side would see more that either one of the footers on the right side.
If the platform were an equilateral triangle with one footer at each corner, then I would understand the geometric center also being the center of gravity and the benefit of locating the component's center of gravity at that precise geometric center point. But your platform is a rectangle with three feet which complicates matters. Could you clarify this for me?
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Micro, we need to listen
I leave this fine tuning to each customer's taste. We have the load-pressure-fres tables of the bladders but I would not trust them down to 0.3Hz and besides platform has more complicates movement patterns than a single bladder (with all the consequences).Cheers,
Jarek
Peter, I'm sorry but that would require sharing more details of our design than I would like to share. I hope you understand.
Cheers,
Jarek
Yes Jarek, I understand.
So, to you and to Theophile, if you are both suggesting that the customer locate the center of gravity of his component and then place that in proximity to the center of gravity of the isolation platform/device but the customer is not told where that is or how to locate it, how would you suggest the customer proceed in order to achieve optimal performance of your product?
Is this what you meant earlier when you wrote to just place the component's COG in proximity, which would mean directly above, the geometric center of the top plate of your Stacore? If so, then that can be determined following Theophile's suggestion with the half round dowels and simply locating the center of your platform by noting the intersection of two straight lines.
I will try to discuss this with Kinetic Systems, the manufacturer of Vibraplane.
EDIT: It also seems to me that placing a component on the standard Stacore is considerably different that placing it on the Advanced Model Stacore because of the change in load distribution because of the three ball/cup assemblies. In the latter case, the load of that top slate shelf plus component is distributed directly over the three pneumatic footers while in the standard model platform, the load is distributed over the entire surface of the platform's top plate and differently distributed to each of the pneumatic footers. I would think that is why placement of those three ball/cup assemblies is so critical.
Yes yes. And then move around if possible to see if there is any change. We are also talking here about a rather very fine tuning of very sensitive devices like top flying TT's. Besides, our big mass masks any COG offset to some extent.
Cheers,
You forget the equipment feet. The weight of the equipment can never be evenly distributed to the entire surface of the platform unless the bottom of equipment is completely in contact with the platform. Symposium recommends to use 3 footers under equipment for best sound. Is there some special on 3 footers arrangement? Maybe we can also use Symposium Rollerblocks on the Basic platform to mimic Advanced platform
Excellent point. Yes, I forgot about the equipment feet and their effect on load distribution. Thank you for pointing that out.
Remember that the Stacore has three cups and balls. These are designed to directly contact the underside of the component. Read that again: Directly contact. Consider that.
That’s not corrrect Theo.
The second slate platform sits on these ball bearings and the component on this.
It’s reasonably easy to approximate the component to fit the footprint of these ball bearings.
The second slate platform sits on these ball bearings and the component on this.
It’s reasonably easy to approximate the component to fit the footprint of these ball bearings.
Theo, in our case it is not so. We use a slate CLD plate (with the racings fitted into it) on top of the bearing balls. It helps to damp the bearings.
Cheers,
Excuse me Jarek. Your mention of Barry Diament as an inspiration led me to conclude that. Barry is an advocate of the ball being in direct contact with the underside of the component. I have applied Barry's method. Extrapolating that across to your platform was an assumption on my part.
My apologies to any others who were misled by my post.
No need to apologize Theo, not a big deal
Actually IIRC Barry was using a marble tile as the upper race at some point.
The problem I see with a direct supporting of the component (through racing plates) is that there is no direct control over the damping
of the upper races. And IMHO this is absolutely *critical* with the roller bearings.
Not sure if it proves anything, but not a single time we heard
the typical for suboptimal bearings comment of HF harshness or artificial vividness. Never!
To the opposite actually. People used to artificial and harsh HF in their systems,
first find something lacking with our platform in action.
Cheers,
Attending many classical music concerts, I found the live sound is darker and warmer. People are so used to bright sound of the system, they don’t realize the live sound is darker and warmer in my opinion.
+100 Anthony, or wait, +1000! I applaud you for saying this loud and clear - live sound is darker than our imagination about it based on reproduced music.
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