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Tweakers' Asylum Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ. |
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Tweakers' Asylum Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ. |
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In Reply to: Symposium's concept revisited posted by Len_ on February 18, 2004 at 10:00:44:
You're right about what Symposium is saying, but I think you're making some wrong conclusions.The platforms are a constrained layer isolation device. Vibration entering at one side - either top or bottom - is largely absorbed in the structure of the platform via various mechanisms and is not transmitted to the other side. So a component strongly coupled to the platform will transmit vibration to the platform which will absorb most of it, and little will be passed to the rack. The same thing happens in the reverse direction and little of the rack's vibration will be passed to the component. I say 'little' because no device is perfect.
I don't like the use of the word 'drain' because that implies that the component will have its vibration level reduced significantly. It may not. Depending on how the component is constructed, there may be significant levels of vibration in the chassis/casing, and in the circuit boards, that is not 'removed' by the use of a platform like Symposium platform and a good coupling strategy. All you can really guarantee that you are doing is preventing the greater part of the vibration in the rack and component from passing to each other. In some cases, the chassis and/or circuit board vibration will be reduced but in others it won't. What happens will depend on how the component is constructed, how it is coupled to the platform, and what frequencies of vibration are present. Don't expect uniform results with every component, and definitely don't expect coupling to remove all vibration from the component and leave nothing behind. You can often still gain benefits by applying damping to the case and quite possibly to various internal parts though I've never done that because I simply don't know enough to be able to open a case and tinker safely.
What this does is it still tends to leave the rack vibrating at it'a own rate, and the component at it's own rate, and they will be different rates of vibration. Directly coupling the component to the rack would reduce the difference in vibratory rates between the two. The results will sound different, and a lot of people rely on theory to say that one or the other is inherently better, but the truth is that as I said in my previous message, our preferences don't have to align with theory. Try each and see what you think.
What I have found is best for my CDP and integrated amp is the use of an isolation platform, but both the rack and the component are strongly coupled to the platform. If I was using Symposium products, that would mean using their blocks between the rack and the platform, and between the platform and the component. I would also dispense with the rack's shelves and couple the platform directly to the rack frame.
As for your sorbothane example. The sorbothane is acting like a spring and it needs to be loaded to work correctly. If it isn't loaded sufficiently or if it is too heavily loaded, it will actually be less effective, which means that more vibration will be transmitted than when it is loaded correctly. Springs have a resonant frequency and are only effective isolators at frequencies higher than 1.4 times their resonant frequency. Below that they actually magnify the amount of vibration they transmit due to their own resonance, with the most vibration transmitted at the resonant frequency. At 1.4 time the resonant frequency of the spring, the amount of vibration transmitted is exactly equal to that going into the spring, and from there on as the frequency of vibration increases, the amount of vibration transmitted is reduced making the device a more and more effective isolator.
You can read the theory and see graphs of this behaviour in the Dickson article I referred you too.
I repeat once again, however, that preferences - what we personally think sounds best - do not necessarily correspond to what theory says is best. Take a look at issues like tubes vs SS, and analog vs digital. Opinions are divided as to which sounds best, and the theory gives different plusses and minusses to each 'side' in those areas. It is exactly the same here. Isolation, coupling, and damping each do different things and you will be able to hear differences between those strategies. I doubt there is a single strategy that will work for everyone - that's why there are people supporting every different strategy and product out there. Many claim their approach is more effective than any other but in reality all any of us can really say is which approach 'sounds right' or 'works' for us personally and you will find significant differences in that. You need to find out what works for you and you won't do that in any other way than by trying different options, listening, and choosing the one you prefer.
David Aiken
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Follow Ups
- Re: Symposium's concept revisited - David Aiken 12:37:32 02/18/04 (1)
- Re: Symposium's concept revisited - Len_ 13:29:28 02/18/04 (0)
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