Isolation vs. Absorbtion

Hi Sean. My view is that mass loading of components has pluses and minuses. I hold to my view that mass in general is a bad thing (for reasons both you and I have referred to above), but is a necessary evil in the pursuit of rigidity and damping. So therefore you are best to only add mass when it has a significant pay-off in terms of damping or rigidity. Mass-loading a component does nothing for rigidity, so the benefits can only come in terms of damping. Arguably, adding a ziplock bag of sand on top of a component is doing three things; it is damping the ringing of the top plate (and to a degree the whole structure) with a substance that is unlikely to feed energy back into the top plate (this should be good); the extra weight will also lower the frequency that the top plate will vibrate at and will cause it to release its energy a little more slowly (this is not so good but is part of the inevitable consequences of damping); the added weight, as you ptu it, "will increase the energy transfer from the rack into the component". Personally I don't think adding weight in this way is the best way to go. It can appear to have beneficial consequences in terms of smoothing out peakiness and can appear to add bass weight (when all it is really doing is smearing the bass). But I shouldn't be so dismissive - it is just that with my overall strategy to the vibration issue, mass loading does not have benefits. If I followed a different overall strategy, such as the "massive" structure approach some take, or the clamp-rack approach that others take then mass loading may make more sense. Using my approach of light, rigid and damped, I believe I can get the good parts of mass loading without the bad parts by using another strategy. Essentially I modify the component by damping it - usually internally. While this is too intrusive an approach for many people, I just see it as good sense when most components are just not put together well. If you have a chance, have a look at a Sonic Frontiers component one day - while I don't particularly like their electronics, the boxes they put them in are brilliant. Much thicker steel panels than you usually find, able to be very securely fastened, judicious use of panel damping and good use of damping/isolation of the electronics from the box. It is poor attention to these details that I reckon using sandbags can ameliorate, but at too high a cost.

To Redkiwi. If I recall correctly you have a Theta Data III. If so, what isolation approach do you use?

Thanks for the follow-up Redkiwi. I know others that use a similar approach as to what you do and they too are quite satisfied with it. While i have never ventured down that path myself, i might end up trying it soon enough. In terms of using the sandbags, my main use of them is primarily for lightweight items like tuners, some cd players, etc.. or components with thin and flimsy lids that tend to resonate , ring or rattle. I think that you get the basic idea. As far as damping components internally goes, does anyone know who the first company was to do this on a production model ? I already know the answer but am curious to see if anyone else does. Any takers ? If so, please be as specific as possible : ) Sean >

Plsl, I am still trying things, but like something light and rigid, not just because that is what I am trying right now, but discovered some time ago that the Theta worked better that way. I would want to keep trying things for another week or so before I am too definitive but so far the Neuance shelf with E-A-R large feet in between component and shelf sound pretty good. I will also be trying oil filled bladders (but air bladders were not good) and Maple Butchers Block. None of these are shabby, but will take a bit more time to try out fully. The time consuming part is of course that you can only ever listen to the whole system, not parts of it, and different components may benefit from different supports.

Thanks. I also have a Theta Data III. The cabinet is quite susceptible to air induced vibration at mid bass frequencies. I have mine on a Zoethicus stand which sits on an oak plank base seperated from the floor by air bladders. On the stand the Data III currently sits on a lead shot tray and is mass loaded across the entire top (except the vents) with a thin bag of lead shot. I like the sound and by lightly touching the cabinet before and after it is quite clear that the cabinet vibrations are gone, However, I'm always looking for what might be a better alternative.